Mechanism of hepatotoxicity due to black cohosh (Cimicifuga racemosa): histological, immunohistochemical and electron microscopy analysis of two liver biopsies with clinical correlation

Abstract

Background: Consumption of herbal supplements in the developed world remains high. Cimicifuga racemosa (C. racemosa) extract, or black cohosh, is widely used as a hormone replacing and an anti-inflammatory agent, and has been shown to cause idiosyncratic hepatitis. The mechanism of acute liver injury in those cases is unclear. To date, hepatotoxic effects of C. racemosa have been studied mostly in vitro and in animal models. Data on human tissue is extremely limited, and mostly confined to histological findings of explanted livers.

Methods: We evaluated clinical data and examined surgical diagnostic liver biopsy specimens obtained from two female patients, who developed acute submassive liver necrosis, following consumption of C. racemosa. Both patients presented with acute elevation of liver enzymes, cholestasis, absence of reactivity to hepatitis A, B and C antibodies, and weak non-specific positivity for autoimmune serological markers. Initial histological interpretation of the biopsies, with focus on hepatic parenchyma and portal tracts, was done by light microscopy, followed by special stain series and immunohistochemical studies, including Cam 5.2, AE1/AE3, reticulin, α-actin, sirius red, and PAS with diastase. Areas of prominent lymphocytic infiltration of the periportal liver plate, observed microscopically, were further evaluated by electron microscopy (EM). 4HNE adduction study, an immunofluorescent assay, was performed to detect products of the oxidative damage and their localization in the liver parenchyma.

Results: Oxidative damage was evident by accumulation of 4HNE protein adducts in the cytoplasm of hepatocytes, secondary lysosomes and macrophages. We hypothesize that the adducted proteins, accumulated in the liver parenchyma, serve as autoantigens, which provoke an autoimmune response, and cause migration of lymphocytes to the affected regions. The formation of immunological synapses between hepatocytes and lymphocytes, predominantly T-lymphocytes, is demonstrated by electron microscopy. The autoimmune response induces piecemeal, or troxis necrosis of hepatocytes, a well described biological phenomenon, where lymphocytes gradually remove hepatocytes in a piecemeal fashion, slowly consuming them and leaving fragments of liver cells, or nubbins of anuclear cytoplasm of liver cell, at the interface between lymphocytes and hepatocytes.

Conclusion: The pattern of pathological injury of liver cells in both patients, following consumption of black cohosh, is identical to troxis necrosis, seen during autoimmune hepatitis. Recognition of the possibility of the acute hepatic injury by the herbal supplement black cohosh is essential for early accurate diagnosis, and timely patient management.

Keywords: Acute hepatitis; Autoimmune hepatitis; Cimicifuga racemosa (black cohosh); Piecemeal necrosis; Troxis necrosis.