NLRP6 inflammasome-mediated dysbiosis augments acetaminophen induced acute liver injury

Background & Aims:

Acetaminophen (APAP) poisoning represents the leading cause of acute liver failure (ALF) in western countries. Whereas the link between intestinal dysbiosis and chronic liver disease is well established, insight into the role of gut-liver crosstalk for drug induced liver injury (DILI) remains scarce. Here, we hypothesized that intestinal microbiota may affect the outcome of APAP induced liver failure.

Methods:

Male 6 – 8 week old wildtype (WT) and Nlrp6 ^-/- mice were injected with a sublethal dose of APAP to induce DILI. 12 hours after injection, a comprehensive analysis of liver injury was performed based on liver functions tests (LFTs), histology, flow cytometry immunophenotyping (FACS) and 16S rRNA-based microbiota profiling. Moreover, microbiota of WT and Nlrp6 ^-/- mice was modulated by fecal microbiota transfer (FMT).

Results:

APAP administration induced significantly increased liver injury in Nlrp6 ^-/- mice compared to WT controls as evidenced by LFTs and histological assessment, which revealed necrosis as the predominant form of cell death. Enhanced DILI in Nlrp6 ^-/- mice was associated with markedly increased infiltration of Ly6C^hi monocyte derived macrophages (MoMFs) as demonstrated by FACS analysis. Interestingly, microbiota of Nlrp6 ^-/- mice was less diverse and did not undergo a major change upon DILI. In contrast, acute liver injury in WT mice prompted a massive change in microbiota composition and a reduction of microbial diversity. These changes were associated with an expansion of colonic mucus layers in WT mice. This potentially protective response did not appear in Nlrp6 ^-/- mice, which presented significantly increased serum endotoxin levels after APAP administration. Strikingly, WT mice gavaged with microbiota from Nlrp6 ^-/- mice displayed significantly increased liver injury upon APAP treatment and resembled the inflammatory phenotype of Nlrp6 ^-/- mice. Specifically, FMT skewed MoMF polarization in WT mice toward a Ly6C^hi inflammatory phenotype suggesting a critical function of MoMF as sensors of gut-derived signals orchestrating the inflammatory response.

Conclusions:

Our data suggest an important, yet unknown function of intestinal microbiota and gut-liver crosstalk during acute liver injury. Intestinal dysbiosis – as seen in Nlrp6 ^-/- mice and transferrable to healthy WT controls via FMT – aggravated liver injury upon APAP administration by promoting pro-inflammatory Ly6C^hi macrophage polarization.