Captopril and the liver

Establishment of a mouse model of enalapril-induced liver injury and investigation of the pathogenesis

Drug-induced liver injury (DILI) is a major concern in drug development and clinical drug therapy. Since the underlying mechanisms of DILI have not been fully understood in most cases, elucidation of the hepatotoxic mechanisms of drugs is expected. Although enalapril (ELP), an angiotensin-converting enzyme inhibitor, has been reported to cause liver injuries with a low incidence in humans, the precise mechanisms by which ELP causes liver injury remains unknown. In this study, we established a mouse model of ELP-induced liver injury and analyzed the mechanisms of its hepatotoxicity. Mice that were administered ELP alone did not develop liver injury, and mice that were pretreated with a synthetic glucocorticoid dexamethasone (DEX) and a glutathione synthesis inhibitor l-buthionine-(S,R)-sulfoximine (BSO) exhibited liver steatosis without significant increase in plasma alanine aminotransferase (ALT). In mice pretreated with DEX and BSO, ALT levels were significantly increased after ELP administration, suggesting that hepatic steatosis sensitized the liver to ELP hepatotoxicity. An immunohistochemical analysis showed that the numbers of myeloperoxidase-positive cells that infiltrated the liver were significantly increased in the mice administered DEX/BSO/ELP. The levels of oxidative stress-related factors, including hepatic heme oxygenase-1, serum hydrogen peroxide and hepatic malondialdehyde, were elevated in the mice administered DEX/BSO/ELP. The involvement of oxidative stress in ELP-induced liver injury was further supported by the observation that tempol, an antioxidant agent, ameliorated ELP-induced liver injury. In conclusion, we successfully established a model of ELP-induced liver injury in DEX-treated steatotic mice and demonstrated that oxidative stress and neutrophil infiltration are involved in the pathogenesis of ELP-induced liver injury.

Drug-induced cholestasis

Drugs may cause several overlapping syndromes of cholestasis, the pathophysiological syndrome resulting from impaired bile flow. These reactions comprise approximately 17% of all hepatic adverse drug reactions (ADRs) and they may be severe. Causes of 'pure' (bland) cholestasis include oestrogens and anabolic steroids; rarer associations are with antimicrobials and NSAIDs. 'Cholestatic hepatitis' is a common drug reaction in which liver injury and inflammation cause significant elevation of serum alanine aminotransferase (ALT) as well as cholestasis. Chlorpromazine and ketoconazole are classic examples, but it is now exemplified by amoxycillin-clavulanate and other oxy-penicillins. Chronic cholestasis results from small bile duct injury leading to the vanishing bile duct syndrome (VBDS), a disorder mimicking primary biliary cirrhosis, or from injury to larger bile ducts causing secondary sclerosing cholangitis. Whilst there is increasing evidence of a genetic predisposition to cholestatic drug reactions, there are currently no pretreatment tests to predict drug safety. Prevention of severe reactions therefore relies on early detection of liver injury and prompt drug withdrawal. Symptomatic management includes relief of pruritus and correction of fat-soluble vitamin deficiency. In small cohort studies, ursodeoxycholic acid (UDCA) arrested progressive cholestasis in two-thirds of cases, but evidence for use of corticosteroids is anecdotal. This review considers diagnosis, pathogenesis, prevention and management of drug-induced cholestasis, with particular reference to frequently- and newly-described causes.

Captopril-induced jaundice: report of 2 cases and a review of 13 additional reports in the literature

Two elderly patients, treated with captopril for left ventricular dysfunction and diabetes, developed severe cholestatic jaundice for which no alternative explanation could be found. The jaundice resolved completely after discontinuation of the drug. A review of the literature identifies a highly similar and distinctive clinical pattern in another 13 cases reported and suggests that hepatotoxicity is a well-established yet rare adverse effect of captopril. However, the very common use of this drug, together with the severity of the liver injury it may cause, calls for a high index of suspicion and increased awareness of this phenomenon.

Comparative cytotoxicity of angiotensin-converting enzyme inhibitors in cultured rat hepatocytes

Captopril and enalapril, angiotensin-converting enzyme inhibitors (ACEIs), have been associated with idiosyncratic hepatotoxicity. Such drug reactions may be caused by the formation of reactive metabolites by cytochrome P450 isozymes, which can then cause direct or immune-mediated toxicity. Previously, we have demonstrated that enalapril cytotoxicity in primary cultures of rat hepatocytes was due, at least in part, to cytochrome P450-dependent metabolism, and that glutathione was involved in the detoxification process. In the present study, we extended our investigations into mechanisms of cytotoxicity, using rat hepatocyte cultures, to captopril and three recently marketed ACEIs: fosinopril, lisinopril and quinapril. After 24 hr of exposure to lisinopril or enalaprilat (the deesterified metabolite of enalapril), hepatocytes did not show any evidence of cytotoxicity, measured by lactate dehydrogenase leakage, even at 10 mM drug concentrations. The other ACEIs were toxic to the liver cells, with the rank order of toxicity as quinapril (LC50 = 0.28 mM) > fosinopril (LC50 = 0.4 mM) > enalapril (LC50 = 2.0 mM) > captopril (LC50 = 20 mM). In vivo pretreatment of rats with pregnenolone-16 alpha-carbonitrile to induce isozymes of the P450 3A subfamily significantly enhanced the cytotoxicities of quinapril, fosinopril and enalapril but did not affect captopril cytotoxicity. Pretreatment with P450 inducers selective for other isozyme subfamilies (ethanol, beta-naphthoflavone and phenobarbital) did not alter the in vitro toxicity of any of the ACEIs. Co-incubation with SKF525-A (15 microM) or troleandomycin (0.1 mM) reduced the hepatocidal toxicities of quinapril, fosinopril and enalapril. Preincubation with buthionine sulfoximine (2 mM) enhanced the cytotoxicities of quinapril, fosinopril, enalapril and captopril. The results of this study indicate that like enalapril, quinapril and fosinopril can also undergo P450 3A-dependent bioactivation and require maintenance of glutathione status for detoxification, and that captopril causes cytotoxicity independent of cytochrome P450 metabolism.

Hepatotoxicity associated with angiotensin-converting enzyme inhibitors

OBJECTIVE

To review published reports of hepatotoxicity associated with angiotensin-converting enzyme (ACE) inhibitors and to explore possible mechanisms of injury.

DATA SOURCES

Published reports of hepatotoxicity associated with use of ACE inhibitors and investigations that suggest potential mechanisms of injury.

DATA SYNTHESIS

Nineteen cases of ACE-inhibitor-associated hepatotoxicity are presented. Early theories regarding mechanisms are reviewed. Laboratory investigations of hepatic effects of eicosanoids on hepatic function are reviewed and a novel mechanism by which ACE inhibitors may cause hepatic injury is postulated.

CONCLUSIONS

Hepatotoxicity, usually cholestatic in nature, has been reported with captopril, enalapril, and lisinopril use. Apparent cross-reactivity has been reported twice. Potential mechanisms of injury include idiopathic hypersensitivity and modulation of eicosanoid metabolism by inhibition of kininase II and subsequent increased hepatic bradykinin activity. Mediation via altered eicosanoid metabolism provides a plausible explanation for cross-reactivity among ACE inhibitors. Hepatotoxicity resolves if ACE inhibitors are stopped but may progress to liver failure if treatment is continued.

Cholestatic jaundice associated with captopril therapy

Captopril has attained widespread use as an effective agent in the treatment of heart failure and hypertension. Dermatological, renal and haematological toxicity associated with its use has been widely described and is usually well recognized. There have been comparatively few reports implicating it as causing hepatic drug reactions. Most descriptions have emphasized strongly cholestatic features, although a mixed hepatocellular cholestatic picture and predominant hepatocellular reactions have been reported. Between November 1972 and June 1990 only five cases of possible Captopril-associated hepatic dysfunction were reported to the Australian Adverse Drug Reaction Advisory Committee. Cases reported suggest equal sex distribution, latent period to development of abnormality between 1 week and 20 months, with slow resolution of jaundice and biochemical abnormality from 1 week to 6 months after withdrawal of the drug. One case of hepatic coma and death with massive acute hepatic necrosis on biopsy has been reported. Not uncommonly the accompanying systemic features suggest a syndrome of drug hypersensitivity. We report a case of Captopril-induced cholestatic jaundice in which the abnormality occurred 2 weeks after commencement of the drug and resolved slowly upon discontinuation. The case illustrates two important points: first, the importance of taking a full history, obtaining detailed information about previous drug administration in patients admitted with jaundice; and second, in the case of Captopril-induced liver disease, the jaundice may persist for many weeks after drug withdrawal.