Liver microRNA-21 is overexpressed in non-alcoholic steatohepatitis and contributes to the disease in experimental models by inhibiting PPARα expression

OBJECTIVE

Previous studies suggested that microRNA-21 may be upregulated in the liver in non-alcoholic steatohepatitis (NASH), but its role in the development of this disease remains unknown. This study aimed to determine the role of microRNA-21 in NASH.

DESIGN

We inhibited or suppressed microRNA-21 in different mouse models of NASH: (a) low-density lipoprotein receptor-deficient (Ldlr^-/-) mice fed a high-fat diet and treated with antagomir-21 or antagomir control; (b) microRNA-21-deficient and wild-type mice fed a methionine-choline-deficient (MCD) diet; (c) peroxisome proliferation-activator receptor α (PPARα)-deficient mice fed an MCD diet and treated with antagomir-21 or antagomir control. We assessed features of NASH and determined liver microRNA-21 levels and cell localisation. MicroRNA-21 levels were also quantified in the liver of patients with NASH, bland steatosis or normal liver and localisation was determined.

RESULTS

Inhibiting or suppressing liver microRNA-21 expression reduced liver cell injury, inflammation and fibrogenesis without affecting liver lipid accumulation in Ldlr^-/- fed a high-fat diet and in wild-type mice fed an MCD diet. Liver microRNA-21 was overexpressed, primarily in biliary and inflammatory cells, in mouse models as well as in patients with NASH, but not in patients with bland steatosis. PPARα, a known microRNA-21 target, implicated in NASH, was decreased in the liver of mice with NASH and restored following microRNA-21 inhibition or suppression. The effect of antagomir-21 was lost in PPARα-deficient mice.

CONCLUSIONS

MicroRNA-21 inhibition or suppression decreases liver injury, inflammation and fibrosis, by restoring PPARα expression. Antagomir-21 might be a future therapeutic strategy for NASH.

[Lyell syndrome in Senegal: responsibility of thiacetazone]

INTRODUCTION

Toxic epidermal necrolysis is a severe disease often leading to death or to mucosal, particularly ocular, after effects. The principle drugs responsible are antibacterial sulfonamides, anti-epileptics, non-steroid anti-inflammatories, allopurinol and chlormezanone. We report a series of 38 cases of toxic epidermal necrolysis, observed in Dakar, imputable to thiacetazone and lethal in 60 percent of cases.

PATIENTS AND METHODS

Our study was retrospective. Diagnosis of toxic epidermal necrolysis was made in patients presenting more than 30 p. 100 of the epidermis of their total body surface stripped off, multi-orificial mucosal damage and epidermal necrosis revealed on histological examination. Drug imputability was established on classical criteria. Treatment was composed of reanimation and antibiotics.

RESULTS

Among the 38 cases of toxic epidermal necrolysis counted, 24 were imputable to thiacetazone. All the patients presented typical clinical features, confirmed histologically. Evolution was lethal in 60 p. 100 of cases. The causes of death were frequently hypovolemic shock during the first week and septic shock during the second. The deceased were generally aged over 50, had more than 50 p. 100 of total epidermis stripped off, presented evolving tuberculosis at the time of the accident and HIV infection at the AIDS stage. After effects were vaginal synechia and 2 cases of blindness.

COMMENTS

Our series is exceptional in that a) the drug responsible: thiacetazone, an economic tuberculostatic of minor efficacy, was systematically introduced after 2 months of intensive treatment with 4 major anti-tuberculosis agents; b) the 60 percent mortality rate, two-fold greater that that usually observed. Other than the known elements of poor prognosis in our patients, the treatment conditions of this dermatological emergency explain this high rate of mortality.