Important role of proinflammatory cytokines/other endogenous substances in drug-induced hepatotoxicity: depression of drug metabolism during infections/inflammation states, and genetic polymorphisms of drug-metabolizing enzymes/cytokines may markedly contribute to this pathology.

Analysis of literature data on drug-induced hepatotoxicity reveals that often upper respiratory febrile illnesses and/or inflammation states precede liver injury/diseases related to administration of drugs or hepatotoxicity associated with administration of therapeutic doses of acetaminophen in some genetically predisposed subjects. The goals of this paper are to review the potential role of alterations in the balance between TH1 cells producing cytokines associated with a cell-mediated response and TH2 cells associated with an antibody response, as well as other endogenous substances, eg, growth factors, leading to a shift in immune response to one that may participate in the liver cells injury during administration of certain drugs, especially in subjects with genetic polymorphisms in drug-metabolizing enzymes. The papers cited in this review were selected to illustrate specific issue related to how profuse and dysregulated production of cytokines, growth factors, and/or other endogenous substances during viral/bacterial infections and inflammation states play a role in the development of drug-induced liver injury. Several cases of liver injury related to administration of drugs appear to be initiated or intensified by upper respiratory febrile illnesses and/or inflammation states, which stimulate sometimes dysregulated production of interferon gamma and/or other proinflammatory cytokines/growth factors. This, in turn, results in down-regulation of various induced and constitutive isoforms of cytochromes P-450, and other enzymes involved in the metabolism of several exogenous (eg, drugs) and endogenous lipophilic (eg, steroids) substances, thus having an important impact on the alterations in bioactivation and detoxication processes in the body and on the balance between production, utilization, and elimination of endogenous bioproducts of these reactions. Activation of systemic host defense mechanisms results in down-regulation of various enzymes involved in drug metabolism and elimination, as well as in production, utilization, and excretion of many endogenous substances that have beneficial effects on vital processes in the body. It seems that treatment of acute and chronic infections and/or inflammations with, for example, antibacterials not metabolized in the liver, and use of medications that decrease proinflammatory cytokine levels (eg, pentoxifylline, a TNF-alpha synthesis inhibitor, directed against TNF-alpha-induced priming of human neutrophils, immunotherapy with IL-4, IL-1 receptor antagonists or factors inducing IL-1ra, dietary supplementation with long-chain n-3 fatty acids, and other antioxidant agents) may perhaps, in some cases, be helpful in the prevention and management of drug-induced hepatotoxicity. Drug-mediated injuries may eventually be prevented by screening methods that can identify genetic polymorphism of drug-metabolizing enzymes and gene polymorphisms or RNA-expression profiles of some proinflammatory cytokines before a patient uses a drug.