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1.
Reasons for performing study: There is a need to assess the laminar inflammatory response in a laminitis model that more closely resembles clinical cases of sepsis‐related laminitis than the black walnut extract (BWE) model. Objectives: To determine if a similar pattern of laminar inflammation, characterised by proinflammatory cytokine expression, occurs in the CHO model of laminitis as has been previously reported for the BWE model. Methods: Sixteen horses administered 17.6 g of starch (85% corn starch/15% wood flour)/kg bwt via nasogastric (NG) tube were anaesthetised either after developing a temperature >38.9°C (DEV group, n = 8) or at onset of Obel grade 1 lameness (OG1 group, n = 8). Control horses (CON group, n = 8) were anaesthetised 24 h after NG administration of 6 l of deionised water. Laminar tissue was collected from horses while under anaesthesia, followed by humane euthanasia. Real time‐quantitative PCR was used to assess laminar mRNA concentrations of genes involved in inflammatory signalling. Results: Increased mRNA concentrations (P<0.05) for IL‐1β, IL‐6, IL‐12p35, COX‐2, E‐selectin and ICAM‐1 were present in laminae from horses with OG1 lameness but not at the DEV time, when compared to the CON horses. No differences between the groups were found for IL‐2, IL‐4, IL‐10, TNF‐α, IFN‐γ or COX‐1 at either the DEV or OG1 time points. Conclusions: There was a notable difference in the temporal pattern of inflammatory events between the BWE and CHO models, with the majority of laminar inflammatory events appearing to occur at or near the onset of lameness in the CHO model, whereas many of these events peak earlier in the developmental stages in the BWE model. This suggests that, in addition to circulating inflammatory molecules, there may be a local phenomenon in the CHO model resulting in the simultaneous onset of multiple laminar events including endothelial activation, leucocyte emigration and proinflammatory cytokine expression. Potential relevance: The similar (although somewhat delayed) inflammatory response in the CHO model of laminitis indicates that inflammatory signalling is a consistent entity in the pathophysiology of laminitis.  相似文献   

2.
Reasons for performing study: A significant proinflammatory response is known to occur in the forelimb lamina after carbohydrate administration. As the hindlimbs are often less affected by laminitis compared with the forelimbs, we assessed hindlimb inflammatory response in the early stages of carbohydrate‐induced laminitis to determine whether differences in the response existed. Objective: To determine whether a similar proinflammatory response occurs in the hindlimb laminae to that previously reported for the forelimb. Methods: Archived laminar samples from 12 horses administered 17.6 g of starch (85% corn starch, 15% wood flour)/kg bwt via nasogastric tube that were anaesthetised either after developing a temperature >38.9°C (DEV; n = 6) or at the onset of Obel grade 1 lameness (OG1; n = 6) were used in addition to 6 control horses (CON) that were anaesthetised 24 h after administration of water. Real‐time quantitative polymerase chain reaction for selected proinflammatory mediators and MAC387 immunohistochemistry were performed. The data were analysed nonparametrically to compare groups. Results: Increases in laminar MAC387‐positive leucocytes and laminar messenger ribonucleic acid (mRNA) concentrations (P<0.05) for interleukin‐1β, interleukin‐6, cyclo‐oxygenase‐2, chemokine (C‐X‐C motif)ligand (CXCL)1 and CXCL8 were present in both fore‐ and hindlimb laminae from horses with OG1 lameness. Both CXCL1 and CXCL8 were also increased in forelimb and hindlimb laminae in the DEV horses. Conclusions: Administration of carbohydrate resulted in a similar inflammatory response in the hindlimb laminae to that previously reported for the forelimb laminae. These findings suggest that other factors, such as weightbearing, may play an important role in the development of laminitis after a systemic inflammatory condition develops. Potential relevance: Evidence of inflammation in the hindlimb laminae suggests that the hindfeet should be addressed in the septic horse at risk for laminitis; however, laminitis is often less severe in the hindlimbs due to other factors, such as weightbearing and hoof angle.  相似文献   

3.

Background

Although continuous digital hypothermia (CDH) protects lamellae from injury in the oligofructose (OF) model of sepsis‐related laminitis (SRL), conflicting results exist from these studies regarding effects of CDH on lamellar inflammatory events.

Hypothesis/Objectives

To determine the effect of CDH on lamellar inflammatory events in normal and OF‐treated horses when instituted at a clinically relevant time point (onset of clinical signs of sepsis in this model).

Animals

Standardbred geldings (n = 15) aged 3–11 years were used.

Methods

In a randomized, controlled discovery study, animals were administered either OF (OF group, n = 8) or water (CON group, n = 8) by nasogastric tube and CDH was initiated in one forelimb (ICE) 12 hours later. Lamellar tissue samples were collected 24 hours after initiation of CDH (ICE and ambient [AMB] forelimbs). Lamellar mRNA concentrations of inflammatory mediators and lamellar leukocyte numbers were assessed using qPCR and immunohistochemistry, respectively; values from four sample groups (CON AMB, OF AMB, CON ICE, and OF ICE) were analyzed using mixed model linear regression.

Results

Although lamellar mRNA concentrations of multiple inflammatory mediators (IL‐1β, IL‐6, CXCL1, MCP2, COX‐2) were increased after OF administration (OF AMB group versus CON AMB; P < 0.05), only 2 inflammatory mediators (IL‐6 and COX‐2) and lamellar leukocyte numbers were decreased with CDH (OF ICE versus OF AMB; P < 0.05).

Conclusions and Clinical Importance

Continuous digital hypothermia initiated at a time point similar to that commonly used clinically (clinical onset of sepsis) resulted in a more focused inhibition of inflammatory signaling.  相似文献   

4.
Chemokines play a vital role in leukocyte activation and emigration that reportedly plays a central role in laminar injury in equine laminitis. The purpose of this study was to evaluate the pattern of laminar chemokine expression in horses in the classical carbohydrate overload (CHO)-model of laminitis. Laminar samples were obtained 24h following water administration in the control group (CON, n=8), and at the onset of fever (≥ 102°F, 12-22 h post CHO, DEV group, n=8) and at the onset of lameness (20-48 h post CHO, LAM group, n=8) in induced horses. Real time quantitative PCR was performed on all samples in order to determine laminar mRNA concentrations of both CXC chemokines (CXCL1, CXCL6, CXCL8) and CC chemokines (CCL2 [MCP-1], CCL3 [MIP-1α], and CCL8 [MCP-2]). Data were subjected to ANOVA followed by Student-Newman-Keuls (P<0.05). Laminar mRNA concentrations for all CXC chemokines were increased (P<0.05) at both the DEV and LAM horses when compared to the control horses, whereas mRNA concentrations of CCL2 and CCL8 were only increased in the LAM horses when compared to controls and the DEV horses. When taken in context with our previous studies, CXCL1, CXCL6 and CXCL8 increases precede peak laminar leukocyte accumulation. Additionally, CCL2 and CCL8 expression corroborate previous reports of monocyte/macrophage accumulation in affected laminae. Compared with previous studies, our findings demonstrate that increased laminar CXC chemokine expression consistently precedes peak leukocyte accumulation and onset of lameness in CHO laminitis models. Chemokine antagonists may be considered as possible therapeutic targets to decrease the influx of leukocytes that occurs during the development of equine laminitis.  相似文献   

5.
REASONS FOR PERFORMING STUDY: Recent research has indicated that inflammation plays a role in the early stages of laminitis and that, similar to organ failure in human sepsis, early inflammatory mechanisms may lead to downstream events resulting in lamellar failure. Characterisation of the type of immune response (i.e. innate vs. adaptive) is essential in order to develop therapeutic strategies to counteract these deleterious events. OBJECTIVES: To quantitate gene expression of pro-inflammatory cytokines known to be important in the innate and adaptive immune response during the early stages of laminitis, using both the black walnut extract (BWE) and oligofructose (OF) models of laminitis. METHODS: Real-time qPCR was used to assess lamellar mRNA expression of interleukins-1beta, 2, 4, 6, 8, 10, 12 and 18, and tumour necrosis factor alpha and interferon gamma at the developmental stage and at the onset of lameness. RESULTS: Significantly increased lamellar mRNA expression of cytokines important in the innate immune response were present at the developmental stage of the BWE model, and at the onset of acute lameness in both the BWE model and OF model. Of the cytokines characteristic of the Th1 and Th2 arms of the adaptive immune response, a mixed response was noted at the onset of acute lameness in the BWE model, whereas the response was skewed towards a Th1 response at the onset of lameness in the OF model. CONCLUSIONS: Lamellar inflammation is characterised by strong innate immune response in the developmental stages of laminitis; and a mixture of innate and adaptive immune responses at the onset of lameness. POTENTIAL RELEVANCE: These results indicate that anti-inflammatory treatment of early stage laminitis (and the horse at risk of laminitis) should include not only therapeutic drugs that address prostanoid activity, but should also address the marked increases in lamellar cytokine expression.  相似文献   

6.
Reasons for performing study: Laminitis is a serious complication of horses suffering from sepsis/endotoxaemia‐related events. Laminitis in horses and organ injury in human sepsis are both reported to involve inflammatory injury to the laminae/organs including early activation of endothelium and leucocytes leading to emigration of neutrophils into the tissue interstitium. In the black walnut extract (BWE) model, systemic inflammatory events coincide with marked increase in laminar mRNA concentrations of inflammatory genes including proinflammatory cytokines (i.e. IL‐1β, IL‐6), COX‐2, chemokines (i.e. IL‐8) and endothelial adhesion molecules (i.e. ICAM‐1 and E‐selectin). In models of human sepsis, i.v. lidocaine has been reported to decrease leucocyte and endothelial activation, and the expression of proinflammatory cytokines and chemokines. Objectives: To evaluate the effect of i.v. lidocaine therapy on the inflammatory processes documented to occur in the BWE model of laminitis. Methods: Twelve horses were administered BWE and treated immediately with either lidocaine (1.3 mg/kg bwt bolus, followed by 0.05 mg/kg bwt/min CRI, n = 6) or saline (n = 6) for 10 h. At 10 h post BWE administration, laminar samples were obtained under general anaesthesia for assessment of proinflammatory gene expression (using RT‐qPCR) and leucocyte emigration (via CD13 immunohistochemistry). At 0, 3 and 10 h post BWE administration, skin samples were obtained for assessment of leucocyte emigration (via calprotectin immunohistochemistry). Results: No significant differences between groups were noted for inflammatory gene mRNA concentrations (IL‐1β, IL‐6, IL‐8, COX‐2) or for number of leucocytes present within the laminar interstitium or skin dermis. Increased (P<0.05) laminar E‐selectin mRNA concentrations were present in the LD group (vs. SAL group). Conclusions: Continuous administration of i.v. lidocaine does not inhibit inflammatory events in either the laminae or skin in the horse administered black walnut extract. Potential relevance: This work questions the use of continuous i.v. administration of lidocaine as an effective anti‐inflammatory therapy for systemic inflammation.  相似文献   

7.
REASONS FOR PERFORMING STUDY: Light microscopical studies show that the key lesion of laminitis is separation at the hoof lamellar dermal-epidermal interface. More precise knowledge of the damage occurring in the lamellar basement membrane zone may result if laminitis affected tissue is examined with the transmission electron microscope. This could lead to better understanding of the pathogenesis of lesions and the means of treatment or prevention. OBJECTIVES: To investigate the ultrastructure of acute laminitis as disease of greater severity is induced by increasing oligofructose (OF) dosage. METHODS: Three pairs of normal horses, dosed with OF at 7.5, 10 and 12.5 g/kg bwt via nasogastric intubation, developed laminitis 48 h later. Following euthanasia, their forefeet were processed for transmission electron microscopy. Lamellar basal cell hemidesmosome (HD) numbers and the distance between the basal cell plasmalemma and the lamina densa of the basement membrane were estimated and compared to control tissue. RESULTS: Increasing OF dosage caused greater HD loss and more severe laminitis. The characteristic separation of the basement membrane, cytoskeleton failure and rounded basal cell nuclei results from combined HD dysassembly and anchoring filament failure. CONCLUSIONS: Without properly assembled HDs, dysadhesion between the lamina densa of the basement membrane (BM) and epidermal basal cells occurs, emphasising the fundamental importance of HDs in maintaining attachment at the lamellar interface. Medical conditions that trigger lamellar matrix metalloproteinase (MMP) activation and/or compromise entry of glucose into lamellar basal cells appear to promote loss and failure of HDs and, therefore, laminitis development. POTENTIAL RELEVANCE: A correlation between lameness severity and escalating loss of lamellar HDs now exists. Therapy aimed at protecting the lamellar environment from haematogenous delivery of MMP activators or from glucose deprivation may control laminitis development.  相似文献   

8.
Background: Insulin resistance has been associated with risk of laminitis in horses. Genes coding for proinflammatory cytokines and chemokines are expressed more in visceral adipose tissue than in subcutaneous adipose tissue of insulin‐resistant (IR) humans and rodents. Hypothesis/Objectives: To investigate adipose depot‐specific cytokine and chemokine gene expression in horses and its relationship to insulin sensitivity (SI). Animals: Eleven light breed mares. Methods: Animals were classified as IR (SI = 0.58 ± 0.31 × 10?4 L/min/mU; n = 5) or insulin sensitive (IS; SI = 2.59 ± 1.21 × 10?4 L/min/mU; n = 6) based on results of a frequently sampled intravenous glucose tolerance test. Omental, retroperitoneal, and mesocolonic fat was collected by ventral midline celiotomy; incisional nuchal ligament and tail head adipose tissue biopsy specimens were collected concurrently. The expression of tumor necrosis factor‐α (TNF‐α), interleukin (IL)‐1β, IL‐6, plasminogen activator inhibitor‐1 (PAI‐1), and monocyte chemoattractant protein‐1 (MCP‐1) in each depot was measured by real‐time quantitative polymerase chain reaction. Data were analyzed by 2‐way analysis of variance for repeated measures (P < .05). Results: No differences in TNF‐α, IL‐1β, IL‐6, PAI‐1, or MCP‐1 mRNA concentrations were noted between IR and IS groups for each depot. Concentrations of mRNA coding for IL‐1β (P= .0005) and IL‐6 (P= .004) were significantly higher in nuchal ligament adipose tissue than in other depots. Conclusions and Clinical Importance: These data suggest that the nuchal ligament depot has unique biological behavior in the horse and is more likely to adopt an inflammatory phenotype than other depots examined. Visceral fat may not contribute to the pathogenesis of obesity‐related disorders in the horse as in other species.  相似文献   

9.
REASONS FOR PERFORMING STUDY: The hypometabolic and vasoconstrictive effects of cryotherapy could prevent the development of laminitis. OBJECTIVES: To use distal limb cryotherapy to prevent laminitis induced by alimentary carbohydrate overload. METHODS: Laminitis was induced in 6 Standardbred horses that had one front limb continuously cooled in an ice/water mixture. Lameness evaluation, blinded lamellar histological grading and analysis for lamellar matrix metalloproteinase-2 (MMP-2) mRNA expression were used to evaluate the severity of laminitis. RESULTS: Cryotherapy was well tolerated and effective in cooling the feet. In each horse no lameness was observed in the treated limbs. Laminitis histology scores in the treated limbs were significantly less than those of the corresponding untreated forelimbs (P < 0.05). Laminitis histology scores in the treated limbs were also significantly less than those of the untreated limbs (fore- and hind) as a group (P < 0.05). Expression of MMP-2 mRNA in the iced feet was significantly (P < 0.05) less than that detected in the untreated feet. CONCLUSIONS: Cryotherapy, when applied to one foot, markedly reduced the severity of acute laminitis in this study. We propose that vasoconstriction (preventing delivery of haematogenous trigger factors) and hypometabolism (reduction in lamellar MMP activity) were the primary therapeutic mechanisms. POTENTIAL RELEVANCE: Although further research is needed, we suggest cryotherapy as a potentially effective prophylactic strategy in horses at risk of developing acute laminitis.  相似文献   

10.
Reason for performing study: The role of matrix metalloproteases (MMPs) and the timeline of proteolysis during laminitis development are incompletely understood. Objectives: To determine the temporal progression of selected MMPs and protease regulators during laminitis development. Methods: Five clinically normal Standardbred horses received, via nasogastric intubation, an oligofructose (OF) bolus (10 g/kg bwt). Laminitis induction proceeded for 48 h followed by euthanasia. Lamellar biopsies were obtained prior to dosing and at intervals during the treatment period for analysis (12, 18, 24, 30 and 36 h and at 48 h following euthanasia). Tissue samples were analysed by real‐time PCR, zymography and western blotting. Results: Activation of proMMP‐2 occurs either simultaneously or at least 12 h following lamellar basement membrane (BM) damage, while no activation of proMMP‐9 is seen during OF laminitis induction. Aggrecanase gene expression increased initially at 12–18 h post OF dosing, similar to BM changes. Gene expression of TIMP‐2, a MMP regulator, decreases during laminitis development. Conclusions: The MMP‐2/MT1‐MMP complex may not play a major role in initiating lamellar BM damage. Aggrecanase and TIMP‐2 gene expression appear related to BM lamellar changes. Potential relevance: MMPs, historically thought to cause laminitis, do not appear to play an initiating role in the lamellar lesion. Other host derived proteases and degradation of alternative lamellar matrix components need to be considered.  相似文献   

11.
Background: C-X-C motif ligand 1 (CXCL1) is an important chemokine of epithelial origin in rodents and humans.
Objectives: To assess in vivo and in vitro the regulation of CXCL1 in equine laminitis.
Animals: Twenty adult horses.
Methods: Real-time quantitative polymerase chain reaction (PCR) was used to assess expression of CXCL1 in samples of laminae, liver, skin, and lung from the black walnut extract (BWE) model of laminitis, and in cultured equine epithelial cells (EpCs). Tissue was obtained from control animals (CON, n = 5), and at 1.5 hours (early time point [ETP] group, n = 5), at the onset of leukopenia (developmental time point [DTP] group, n = 5), and at the onset of lameness (LAM group, n = 5) after BWE administration. EpCs were exposed to Toll-like/Nod receptor ligands, oxidative stress agents, and reduced atmospheric oxygen (3%). In situ PCR was used to localize the laminar cell types undergoing CXCL1 mRNA expression.
Results: Increases in laminar CXCL1 mRNA concentrations occurred in the ETP (163-fold [ P = .0001]) and DTP groups (21-fold [ P = .005]). Smaller increases in CXCL1 expression occurred in other tissues and organs. In cultured EpCs, increases ( P < .05) in CXCL1 mRNA concentration occurred after exposure to lipopolysaccharide (LPS [28-fold]), xanthine/xanthine oxidase (3.5-fold), and H2O2 (2-fold). Hypoxia enhanced the LPS-induced increase in CXCL1 mRNA ( P = .007). CXCL1 gene expression was localized to laminar EpCs, endothelial cells, and emigrating leukocytes.
Conclusion and Clinical Importance: These findings indicate that CXCL1 plays an early and possibly initiating role in neutrophil accumulation in the BWE laminitis model, and that laminar keratinocytes are an important source of this chemokine. New therapies using chemokine receptor antagonists may be indicated.  相似文献   

12.
Reasons for performing study: A previous preliminary study demonstrated the potential of distal limb cryotherapy (DLC) for preventing laminitis. Clinically, DLC must be effective for periods longer than 48 h and the preventive effect must extend beyond its discontinuation. Objectives: To evaluate the effect of DLC, applied during the developmental phase of induced laminitis, on the severity of clinical laminitis and lamellar histopathology 7 days after dosing. Methods: Eighteen normal Standardbred horses were divided into 3 groups of 6. Continuous cryotherapy was applied for 72 h to the distal limbs of the first group. The second and third groups were administered laminitis inducing doses of oligofructose and 72 h of cryotherapy applied (immediately after dosing) to the second group. After clinical assessment all horses were subjected to euthanasia 7 days after dosing and hoof lamellar tissues were harvested and analysed. Results: In the laminitis induced horses clinical lameness and laminitis histopathology was significantly reduced in horses that underwent 72 h of DLC compared with untreated controls. Cryotherapy alone produced no significant lameness or other ill effect. Conclusions: Continuous, medium‐ to long‐term (72 h) cryotherapy applied to the distal limbs of horses safely and effectively ameliorates the clinical signs and pathology of acute laminitis. Potential relevance: Pre‐emptive distal limb cryotherapy is a practical method of ameliorating laminitis in ill horses at risk of developing the disease.  相似文献   

13.
Background: Oxidative stress reportedly plays a role in sepsis‐induced organ dysfunction and failure in many species. In septic horses, laminae are targeted; evidence of laminar oxidative stress has been reported experimentally in the black walnut extract (BWE) model. Carbohydrate (CHO)‐induced laminitis may be more similar to clinical sepsis‐related laminitis than the BWE model in that animals with CHO‐induced disease commonly develop laminar failure. The role of oxidative stress in the CHO model remains unknown. Hypothesis/Objectives: Markers of oxidative stress will be increased in laminae from horses with BWE‐ and CHO‐induced laminitis. Animals: Banked laminar tissue from various time points from animals subjected to BWE (n = 15) and CHO (n = 20) protocols. Methods: Laminar 4‐hydroxynonenal (4‐HNE) and protein carbonyl content were evaluated by slot blot analysis. Laminar 3‐nitrotyrosine (3‐NT) immunohistochemistry was performed. Results: The number of laminar 3‐NT (+) cells was increased at developmental and Obel grade 1 (OG1) time points in the BWE model (versus control [CON]; P= .013) and lower in OG1 tissues than CON in the CHO model (P= .04). No change in 4‐HNE content was observed in the CHO model, and no increase in laminar protein carbonyl content was present in either model (P > .05). Conclusions and Clinical Importance: These results do not support a prominent role for oxidative stress at examined time points in CHO‐overload laminitis and support transient oxidative stress in the BWE model. Tissue oxidation does not appear to be a central early pathophysiologic event in CHO‐associated laminitis.  相似文献   

14.
Systemic inflammation is a risk factor for laminitis in horses and precedes the onset of lameness in experimental models. We therefore hypothesized that whole-blood inflammatory cytokine expression would increase during the development of laminitis in a carbohydrate overload model. Blood samples were obtained from 14 horses undergoing laminitis induction with 10 g/kg oligofructose as part of another study. Samples were collected at 0, 8, 12, 16, 20, and 24 hours, and lameness evaluations were performed every 4 hours. Expression levels of interleukin-1β (IL-1β), IL-6, IL-8, IL-10, and tumor necrosis factor-α were measured in whole blood by using real-time PCR. IL-1β, IL-8, and IL-10 expression increased above baseline from 8 to 24 hours (P < .001), and IL-6 expression increased at 16 and 20 hours (P = .005). Expression of tumor necrosis factor-α did not change over time. All horses developed clinical laminitis between 12 and 24 hours. Increased mean IL-1β, IL-8, and IL-10 expression detected at 8 hours therefore preceded the onset of lameness. We conclude that peripheral leukocyte cytokine expression increases as systemic inflammation develops in an alimentary carbohydrate overload model of laminitis, and this precedes detection of lameness. Results support current recommendations to control the systemic inflammatory response in order to lower the risk of laminitis in horses.  相似文献   

15.
Reasons for performing study: The timing of lamellar basement membrane (BM) changes occurring during laminitis development is incompletely understood. Objectives: To determine the temporal progression of lamellar BM changes and whether laminin‐332 (Ln‐332) γ2 cleavage products are generated during laminitis development. Methods: Eight clinically normal Standardbred horses were allocated into treatment (n = 5) or sham (n = 3) groups. The treatment group received, via nasogastric intubation, an oligofructose (OF) bolus (10 g/kg bwt) while the sham group was given water. Laminitis induction proceeded for 48 h followed by euthanasia. Lamellar biopsies were obtained prior to dosing and at intervals during the treatment period for analysis (at 12, 18, 24, 30 and 36 h and at 48 h following euthanasia). Results: Changes in lamellar collagen type IV and Ln‐332 were first observed at 12 h post dosing. A unique pattern of reactivity for the Ln‐332 γ2 antibody D4B5 occurred, in which reactivity was observed only in lamellar tissue affected by laminitis. No bioactive Ln‐332 γ2 proteolytic fragments were detected in lamellar samples. Conclusions: Basement membrane changes occurred early during the laminitis process. Direct Ln‐332 γ2 cleavage to release biologically active products did not appear to occur. Thus loss of stability or protein interaction of the BM is probably responsible for the γ2 specific reactivity observed. Potential relevance: Basement membrane changes may a first step in lamellar failure occurring prior to detection with conventional methods. Thus, more sensitive detection methods of BM changes are required to study laminitis development.  相似文献   

16.
OBJECTIVE: To determine whether a unique dihydropyridine (BAYTG 1000) would be beneficial in preventing laminitis in horses. ANIMALS: 16 clinically normal adult horses. PROCEDURE: 8 pairs of horses were used in a controlled double-blind study, using sex- and age-matched horses randomly assigned to treatment or control groups. Horses were subjected to carbohydrate overload to induce laminitis. Treated horses were administered BAY TG 1000 (30 mg/kg, PO, q 24 h) for 3 days. Hoof wall surface temperature (HWST) and lameness were recorded at 4-hour intervals. The HWST was adjusted on the basis of time of onset of lameness and evaluated, using a repeated-measures ANOVA. Lameness 8 hours after onset and clinical status 72 hours after onset of lameness were evaluated, using Mann-Whitney procedures. RESULTS: Analysis revealed that BAYTG 1000 did not decrease the incidence of lameness but significantly ameliorated prodromal hypothermia, lessened the severity of lameness 8 hours after onset of lameness, and improved the clinical status of horses 72 hours after onset of lameness. CONCLUSION AND CLINICAL RELEVANCE: Results support the conclusion that BAYTG 1000 was protective when used in prevention of laminitis. The drug decreased severity and improved clinical status (recovery) of induced lameness, which was interpreted to mean that the drug's actions were on mechanisms important but secondary to primary causal mechanisms of laminitis. Therefore, drugs that enhance digital perfusion via alteration of rheologic activity may have potential use in the prevention and management of laminitis in horses.  相似文献   

17.
Reasons for performing study: Further knowledge of equine keratinocyte physiology and keratinocyte response to various stimuli is important in developing a better understanding of disease states involving the epidermis. Objectives: To assess the inflammatory cytokine response of cultured equine keratinocytes to various pathogen‐associated molecular pattern molecules (PAMPs) from both Gram‐negative and positive bacteria likely to be present in equine sepsis. Methods: Keratinocytes were isolated from skin of 2 horses and primary cultures performed. Keratinocytes were harvested for RNA extraction after exposure to lipopolysaccharide (LPS), lipoteichoic acid (LTA), peptidoglycan (PGN), bacterial DNA (CpG), flagellin or maintained in medium (controls) for 4 or 24 h. Real time‐quantitative PCR was used to quantify interleukin‐1β (IL‐1β), interleukin‐6 (IL‐6) and CXCL8 mRNA concentrations. Results: Increases (P<0.05) in IL‐1β, IL‐6 and CXCL8 mRNA concentrations were induced by LPS exposure compared to controls. Increased mRNA concentrations of both IL‐6 and CXCL8 were also noted (vs. controls) upon exposure to flagellin. Overall, responses were greater at 4 h. No increases (P>0.05) in cytokine expression by keratinocytes were present after LTA, PGN or CpG exposure. Conclusions: Increased proinflammatory cytokine expression in response to LPS and flagellin indicate that equine keratinocytes have functional TLR4 and TLR5 receptor signalling. However, the lack of keratinocyte stimulation by PGN, LTA or CpG provides no evidence for functional TLR2, TLR9 or NOD receptor signalling. These results suggest that equine keratinocytes are more responsive to PAMPs usually associated with Gram‐negative sepsis and unresponsive to PAMPs most commonly associated with Gram‐positive sepsis. Potential relevance: The increased incidence of injury of epidermal structures in clinical cases of Gram‐negative (vs. Gram‐positive) sepsis in the horse may be due to a lack of functional TLR signalling for Gram‐positive PAMPs in the equine keratinocyte.  相似文献   

18.
BACKGROUND: Recent reports indicate increased amounts of mRNA from inflammation-related genes in the prodromal stage of laminitis. HYPOTHESIS: Cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) undergo distinct patterns of expression in equine laminae in the developmental stage (DEV) and acute clinical stage (LAM) of laminitis. ANIMALS: Horses selected from an outbred population were placed into 1 of 4 groups: DEV (n = 5), CON-3h (control group for DEV, n = 5), LAM (n = 5) and CON-10h (control group for LAM, n = 5). METHODS: Laminar and skin samples were obtained from (1) animals either undergoing leukopenia (DEV) or the onset of clinical signs of laminitis (LAM) after black walnut extract (BWE) administration and (2) animals either 3 (CON-3h) or 10 (CON-10h) hours after administration of water. Real-time quantitative polymerase chain reaction (RT-qPCR), immunoblotting, and immunohistochemical analysis were performed for COX-1 and COX-2. RESULTS: Upon immunohistochemical analysis of all 4 groups, COX-2 was expressed by most viable epithelial cells in both laminae and skin. COX-1 exhibited similar epithelial expression to COX-2 in skin epidermis, but was expressed exclusively in the basal layer of laminar epidermis. COX-1 protein was not detectable in dermal vasculature of equine skin or laminae, whereas COX-2 was present in endothelial and vascular smooth muscle cells of dermal vasculature in both skin and laminae in all groups. A marked increase in laminar COX-2 protein concentrations was detected on immunoblotting in the DEV group, although a lesser increase was observed in the LAM group. CONCLUSIONS AND CLINICAL IMPORTANCE: COX-2 protein expression is markedly increased in the resident laminar cell types in the developmental stage of BWE-induced laminitis.  相似文献   

19.
REASONS FOR PERFORMING STUDY: The mediators and signalling cascades important in the initiation of laminitis remain unclear. We therefore wanted to explore the genes and overall signalling mechanisms that play an important role in the developmental stage of laminitis. OBJECTIVE: To use a broad genomic screening technique to identify novel genes that are differentially regulated in the equine lamellae during the developmental period of laminitis. METHODS: Differential mRNA display (DRD) was performed to discover regulated genes, and real-time quantitative polymerase chain reaction (RT-qPCR) was then used to evaluate lamellar mRNA levels of a regulated gene (MAIL) and mediators related to that gene (IL-1beta and IL-6) in control horses (n = 5) and horses administered black walnut extract (BWE; n = 5). RESULTS: Using DRD, MAIL was identified as a regulated gene. RT-qPCR indicated a 4-fold increase in expression of the MAIL mRNA in BWE lamellae compared to controls. A 30-fold increase in IL-1beta, and a 160-fold difference in IL-6 mRNA expression was present in BWE lamellae. Differences in MAIL, IL-1beta and IL-6 mRNA expression were statistically significant between groups (P < 0.05). CONCLUSIONS AND POTENTIAL RELEVANCE: The data strongly support a role for inflammatory cytokines in the developmental stages of laminitis, possibly inducing the vascular and metabolic alterations reported to occur in the affected digit. These results potentially support the use of anti-inflammatory drugs in horses at risk of laminitis, and warrant further investigation of the link between systemic disease processes associated with laminitis and the reported digital inflammation.  相似文献   

20.
Reasons for performing study: Several conditions associated with laminitis in horses are also associated with insulin resistance, which represents the failure of glucose uptake via the insulin‐responsive glucose transport proteins in certain tissues. Glucose starvation is a possible mechanism of laminitis, but glucose uptake mechanisms in the hoof are not well understood. Objectives: To determine whether glucose uptake in equine lamellae is dependent on insulin, to characterise the glucose transport mechanism in lamellae from healthy horses and ponies, and to compare this with ponies with laminitis. Methods: Study 1 investigated the effects of insulin (300 µU/ml; acute and 24 h) and various concentrations of glucose up to 24 mmol/l, on 2‐deoxy‐D‐[2,6‐3H]glucose uptake in hoof lamellar explants in vitro. Study 2 measured the mRNA expression of GLUT1 and GLUT4 transport proteins by PCR analysis in coronary band and lamellar tissue from healthy horses and ponies, ponies with insulin‐induced laminitis, and ponies suffering from chronic laminitis as a result of equine Cushing's syndrome. Results: Glucose uptake was not affected by insulin. Furthermore, the relationship between glucose concentration and glucose uptake was consistent with an insulin‐independent glucose transport system. GLUT1 mRNA expression was strong in brain, coronary band and lamellar tissue, but was weak in skeletal muscle. Expression of GLUT4 mRNA was strong in skeletal muscle, but was either absent or barely detectable in coronary band and lamellar tissue. Conclusions: The results do not support a glucose deprivation model for laminitis, in which glucose uptake in the hoof is impaired by reduced insulin sensitivity. Hoof lamellae rely on a GLUT1‐mediated glucose transport system, and it is unlikely that GLUT4 proteins play a substantial role in this tissue. Potential relevance: Laminitis associated with insulin resistance is unlikely to be due to impaired glucose uptake and subsequent glucose deprivation in lamellae.  相似文献   

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