Tissue concentrations of 4-HNE in the black walnut extract model of laminitis: indication of oxidant stress in affected laminae.

In the septic horse prone to laminitis, a similar activation of the innate immune system appears to occur as reported in the septic human prone to organ failure. Because oxidant injury plays a central role in organ failure occurring due to an overzealous innate immune response in human sepsis, this study was performed to determine whether there was evidence of oxidant stress in the laminar tissue in the early stages of laminitis. 4-Hydroxy-2-nonenal (4-HNE), a lipid aldehyde that forms due to lipid peroxidation occurring during episodes of oxidant stress, readily forms adducts with cellular proteins; these adducts can be assessed as a marker of oxidant stress in the form of lipid peroxidation. In this study, a slot blot technique was used to assess 4-HNE adduct concentrations in the laminae, lung, liver, and intestinal tract in the black walnut extract (BWE) model of laminitis. Significant increases in laminar 4-HNE adduct concentrations were identified at two early stages in the BWE model, in the absence of such changes in the other tissues. These data indicate that oxidant stress may play an important role in the laminar failure in laminitis, and further support the concept that a poor antioxidant response in the laminae relative to other equine tissues may be responsible for failure of the laminae in the septic horse. In contrast, tissues such as the lung and liver that undergo oxidant injury in human sepsis appear to be relatively protected in horses.