Effect of Lipopolysaccharides (LPS) and Lipoteichoic Acid (LTA) on the Inflammatory Response in Rumen Epithelial Cells (REC) and the Impact of LPS on Claw Explants

SIMPLE SUMMARY: Endotoxins, often referred to as lipopolysaccharides (LPS), are bacterial toxins and play an essential role in several diseases in ruminants. One of the most common disorders in dairy cows, sub-acute rumen acidosis (SARA), is associated with a substantial increase of ruminal and intestinal endotoxin load. Other potentially harmful substances, e.g., lipoteichoic acid (LTA), derived from the cell wall of Gram-positive bacteria, might play an essential role during SARA as well. Besides the potential local effect of LPS, translocation to the blood can induce a strong immune response in cattle. Furthermore, LPS might reach the claw tissue after translocation. In our study, we used a cell culture model with epithelial cells isolated from rumen tissue to assess the effects of LPS and LTA. Furthermore, we evaluated the effects of LPS on claw tissue with an explant model. LPS and LTA could induce an inflammatory response in rumen epithelial cells. However, the effect of LPS was more substantial and seen at an earlier time point compared to LTA. Furthermore, in claw explants, LPS negatively affected the separation force, an indicator for tissue integrity, which decreased with increasing LPS concentrations. Overall, our data suggest that especially endotoxins can impact local inflammatory response in the rumen. Furthermore, if endotoxins reach the claw tissue, it might affect claw health. ABSTRACT: Endotoxins play a crucial role in ruminant health due to their deleterious effects on animal health. The study aimed to evaluate whether LPS and LTA can induce an inflammatory response in rumen epithelial cells. For this purpose, epithelial cells isolated from rumen tissue (REC) were stimulated with LPS and LTA for 1, 2, 4, and 24 h. Thereafter, the expression of selected genes of the LPS and LTA pathway and inflammatory response were evaluated. Furthermore, it was assessed whether LPS affects inflammatory response and structural integrity of claw explants. Therefore, claw explants were incubated with LPS for 4 h to assess the expression of selected genes and for 24 h to evaluate tissue integrity via separation force. LPS strongly affected the expression of genes related to inflammation (NFkB, TNF-α, IL1B, IL6, CXCL8, MMP9) in REC. LTA induced a delayed and weaker inflammatory response than LPS. In claw explants, LPS affected tissue integrity, as there was a concentration-dependent decrease of separation force. Incubation time had a strong effect on inflammatory genes in claw explants. Our data suggest that endotoxins can induce a local inflammatory response in the rumen epithelium. Furthermore, translocation of LPS might negatively impact claw health.