35kDa hyaluronan ameliorates ethanol driven loss of anti-microbial defense and intestinal barrier integrity in a TLR4-dependent manner

Acute and chronic alcohol exposure compromise intestinal epithelial integrity, due to reduced expression of anti-microbial peptides (AMP) and loss of tight junction integrity. Ameliorating gut damage is beneficial in pre-venting associated distant organ pathologies. Orally administered purified hyaluronan (HA) polymers with an average size of 35 kDa have multiple protective effects in the gut and are well-tolerated in humans. Therefore, we tested the hypothesis that HA35 ameliorates ethanol-induced gut damage. Specifically, mechanisms that restore epithelial barrier integrity and normalize expression of the Reg3 class of C-type lectin AMPs (i.e. Reg3b and Reg3g) were investigated. Chronic ethanol feeding to mice reduced expression of C-type lectin AMPs in the proximal small intestine (jejunum), reduced expression of tight junction proteins and increased bacterial translocation to the mesenteric lymph node. Oral consumption of HA35 during the last 6 days of eth-anol exposure ameliorated the effects of chronic ethanol. Similarly, in vitro challenge of isolated intestinal organoids from murine jejunum with ethanol reduced the expression of C-type lectin AMPs and impaired bar-rier integrity; these ethanol-induced responses were prevented by pre-treatment with HA35. Importantly, HA receptor null jejunum-derived organoids demonstrated that the HA receptor Tlr4, but not Cd44 nor Tlr2, was required for the protective effect of HA35. Consistent with the data from organoids, HA35 did not protect Tlr4- deficient mice from chronic ethanol-induced intestinal injury. Together, these data suggest therapeutic admin-istration of HA35 is beneficial in restoring gut epithelial integrity and defense during the early stages of etha-nol-driven intestinal damage.(c) 2022 Elsevier B.V. All rights reserved.