Effect of digital hypothermia on lamellar inflammatory signaling in the euglycemic hyperinsulinemic clamp laminitis model.

Abstract

BACKGROUND: Continuous digital hypothermia (CDH) prevents lamellar failure in the euglycemic hyperinsulinemic clamp (EHC) model of laminitis, but the protective mechanisms are unclear. HYPOTHESIS/OBJECTIVES: To determine if CDH inhibits lamellar inflammatory signaling in the EHC model of laminitis. ANIMALS: Eight Standardbred horses. METHODS: Prospective experimental study. Horses underwent an EHC, with 1 forelimb treated with CDH and the other kept at ambient temperature (AMB). Horses were euthanized 48&#x2009;hours after initiation of the EHC and lamellar tissue was analyzed via polymerase chain reaction (pro-inflammatory cytokine and chemokine genes-CXCL1, CXCL6, CXCL8, IL-6, MCP-1, MCP-2, IL-1&#x3b2;, IL-11, cyclooxygenase 1 and 2, tumour necrosis factor-alpha [TNF-&#x3b1;], E-selectin, and intercellular adhesion molecule-1 [ICAM-1]) and immunoblotting (phosphorylated and total signal transducer and activator of transcription 1 [STAT1] and STAT3). RESULTS: Compared to AMB, lamellar messenger ribonucleic acid (mRNA) concentrations of CXCL6 (P =.02), CXCL8 (P = .008), IL-6 (P = .008), IL-1&#x3b2; (P = .008), IL-11 (P = .008), and cyclooxygenase-2 (P = .008) were decreased in CDH. Cyclooxygenase-1 (P =&#x2009;.008) was increased in CDH, while CXCL1 (P = .15), MCP-1 (P = .05), MCP-2 (P = .46), TNF-&#x3b1; (P = .05), E-selectin (P = .15), and ICAM-1 (P = .15) mRNA were not significantly different. Compared to AMB, lamellar concentration of total STAT3 protein was decreased in CDH (P&#x2009;< .001), but there was no change in phosphorylated STAT3 (P-STAT3 [S727] P = .19; P-STAT3 [Y705] P =&#x2009;.05). There was no change in lamellar concentrations of total STAT1 (P =&#x2009;.75) or phosphorylated STAT1 (P-STAT1 [S727], P = .25; P-STAT1 [Y701], P = .64). CONCLUSIONS AND CLINICAL IMPORTANCE: These data add further support for the use of CDH as a first aid treatment for severe acute laminitis associated with hyperinsulinemia in horses.