M1 Polarization Bias and Subsequent Nonalcoholic Steatohepatitis Progression Is Attenuated by Nitric Oxide Donor DETA NONOate via Inhibition of CYP2E1-Induced Oxidative Stress in Obese Mice

Abstract

Activation of M1 macrophages in nonalcoholic steatohepatitis (NASH) is produced by several external or endogenous factors: inflammatory stimuli, oxidative stress, and cytokines are known. However, any direct role of oxidative stress in causing M1 polarization in NASH has been unclear. We hypothesized that CYP2E1-mediated oxidative stress causes M1 polarization in experimental NASH, and that nitric oxide (NO) donor administration inhibits CYP2E1-mediated inflammation with concomitant attenuation of M1 polarization. Because CYP2E1 takes center stage in these studies, we used a toxin model of NASH that uses a ligand and a substrate of CYP2E1 for inducing NASH. Subsequently, we used a methionine and choline-deficient diet-induced rodent NASH model where the role of CYP2E1 in disease progression has been shown. Our results show that CYP2E1 causes M1 polarization bias, which includes a significant increase in interleukin-1b (IL-1b) and IL-12 in both models of NASH, whereas CYP2E1-null mice or diallyl sulfide administration prevented it. Administration of gadolinium chloride (GdCl 3 ), a macrophage toxin, attenuated both the initial M1 response and the subsequent M2 response, showing that the observed increase in cytokine levels is primarily from macrophages. Based on the evidence of an adaptive NO increase, the NO donor administration in vivo that mechanistically inhibited CYP2E1 catalyzed the oxidative stress during the entire study in NASHabrogated M1 polarization and NASH progression. The results obtained show the association of CYP2E1 in M1 polarization, and that inhibition of CYP2E1 catalyzed oxidative stress by an NO donor (DETA NONOate [(Z)-1-[N-(2-aminoethyl)-N-(2-ammonioethyl) amino]diazen-1-ium-1,2-diolate]) can be a promising therapeutic strategy in NASH.

Diets rich in fructose, fat or fructose and fat alter intestinal barrier function and lead to the development of nonalcoholic fatty liver disease over time

“…These findings support the hypothesis that an increased formation of reactive oxygen species -be it through endotoxin-dependent signaling cascades or other mechanisms -is critical in the development of NAFLD. It was further suggested that an endotoxin-dependent activation of Kupffer cells in the liver leads to an M1 polarization of these cells, which in turn further contributes to the onset and progression of inflammatory processes in the liver [18,46,47]. In the present study, elevated endotoxin and TLR-4 levels found in mice fed fructose, fat or a combination of both were associated with a reduced expression of Arg-1 and induction of MCP-1 in liver, suggesting that the development of NAFLD in these mice was associated with a change in polarization of Kupffer cells and infiltrating macrophages in liver.…”

Nitric oxide in liver diseases

“…Simvastatin [3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor], which is known to increase eNOS activity and thus NO production, was also shown to mitigate NASH-related liver fibrosis by inhibiting HSC activation [74]. NO donors also showed preventive roles in hepatic steatosis by facilitating fatty acid β-oxidation [75] and by blocking cytochrome P450 2E1 enzyme (CYP2E1)-mediated oxidative stress [76]. …”

Role of CYP2E1 in Mitochondrial Dysfunction and Hepatic Injury by Alcohol and Non-Alcoholic Substances

“…As mentioned earlier, CYP2E1 has been reported to be markedly induced following HFD or under diabetes, and obesity whereas CYP2E1 -null mice have been protected, at least partially but significantly, from the CYP2E1-mediated deleterious effects of NAFLD [38, 110, 111, 120–122]. In addition, over-expression of hepatic CYP2E1 both in vitro and in vivo promotes the development of hepatic insulin resistance, partly through the activation of c-Jun N-terminal protein kinase (JNK) [116, 123].…”