Laminar regulation of STAT1 and STAT3 in black walnut extract and carbohydrate overload induced models of laminitis.

Background: STAT1 and STAT3 are important signaling molecules in disorders of systemic inflammation and are likely to be involved in laminitis, as laminar and systemic inflammation have been well documented in experimental models of laminitis.

Hypothesis: The STAT1 and STAT3 activation (via phosphorylation of tyrosine and serine moieties) is occurring in the laminar tissue during the developmental and onset of lameness time points in both the black walnut extract (BWE) and carbohydrate overload (CHO) models of laminitis.

Animals: Archived laminar tissue from horses.

Methods: Experimental studies of induced laminitis (BWE and CHO administration) in horses were conducted and laminar tissue samples archived. Western hybridization was performed to determine concentrations of Tyr- and Ser-phosphorylated STAT1 and STAT3 from these archived samples. The RT-qPCR was also performed to assess mRNA concentrations of target genes of STAT1 and STAT3.

Results: Increases (P < .05) in phosphorylation of tyrosine705 and serine727 of STAT3, demonstrated by band intensity ratios, are present in laminar tissue from both the BWE and CHO models at the DEV and OG1 time points. No change in phosphorylation of tyrosine701 or serine727 of STAT1 was present in the laminar tissue from either the BWE or the CHO models. The SOCS3 mRNA concentrations were increased at the onset of lameness in both the CHO and BWE models.

Conclusions and clinical relevance: The STAT3 activation likely plays a role in equine laminitis, similar to its reported involvement in organ injury/failure in human sepsis. Regulation of JAK-STAT, through STAT3 inhibitors, might serve as potential therapeutic target for controlling the inflammatory response in the septic horse.