Long non-coding RNA Gm15441 attenuates hepatic inflammasome activation in response to metabolic stress

Chad N. Brocker; Donghwan Kim; Tisha Melia; Kritika Karri; Thomas J. Velenosi; Shogo Takahashi; Jessica A. Bonzo; David J. Waxman; Frank J. Gonzalez

PPARA plays a role in attenuating inflammation in many tissues and disease models (Kono et al., 2009; Schaefer et al., 2008; Yoo et al., 2013; Yoo et al., 2011) . In the liver, PPARA ameliorates inflammation by reducing ER stress in hepatocytes (Zhang et al., 2016) . TXNIP is known to facilitate ER stress-induced NLRP3 inflammasome activation (Anthony and Wek, 2012; Lee et al., 2014b; Lerner et al., 2012; Oslowski et al., 2012) . By regulating TXNIP levels, Gm15441 could serve as a link between PPARA and the NLRP3 inflammasome. To ascertain whether lncRNA Gm15441 attenuates inflammasome activation by regulating TXNIP levels, mice were treated with WY-14643 for 48 hours, and weight loss, liver index, ALT, AST, and serum glucose levels were measured. There was no discernable difference in weight loss between Gm15441 +/+ and Gm15441 LSL mice on a WY-14643 diet ( Figure 5A ). Serum ALT and AST levels were unchanged by genotype or following WY-14643 treatment. Serum glucose levels were significantly decreased by WY-14643 in both Gm15441 +/+ and Gm15441 LSL mice, but the decrease was significantly greater in Gm15441 LSL mice ( Figure 5A ). Furthermore, upon gross liver examination, pronounced hepatomegaly was induced by WY-14643 treatment in both Gm15441 +/+ and Gm15441 LSL mice ( Figure 5B ). Pronounced swelling of hepatocytes was noted in livers of WY-14643-treated Gm15441 +/+ and Gm15441 LSL mice ( Figure 5B) . Expression of the PPARA target genes acyl-CoA dehydrogenase medium chain (Acadm) and Cyp4a14 was significantly increased by WY-14643 in both Gm15441 +/+ and Gm15441 LSL mice. Gm15441 was strongly upregulated in livers of wild-type mice but was not detected in Gm15441 LSL mice. Txnip mRNA was significantly decreased by WY-14643 in livers of wild-type animals, consistent with Figure 2 , but was significantly induced in Gm15441 LSL livers ( Figure 5C ). Basal expression of the inflammasome-related proteins TXNIP, cleaved caspase 1 (CASP1), and cleaved interleukin 1β . CC-BY-NC-ND 4.0 International license is made available under a The copyright holder for this preprint (which was not peer-reviewed) is the author/funder. It . https://doi.org/10.1101/675785 doi: bioRxiv preprint (IL1B) was elevated in livers of Gm15441 LSL mice compared to wild-type mice, and significant further increases were seen following WY-14643 treatment (Figure 5D, 5E) . Overall, levels of all three proteins were much higher in livers of WY-14643-treated Gm15441 LSL mice than wild-type mice ( Figure 5E ). Thus, ablation of Gm15441 increases the expression of TXNIP and two other proteins associated with NLRP3 inflammasome activation, namely, cleaved CASP1 and IL1B.