In vitro activity: Azathioprine suppresses the activation of Rac1 target genes such as mitogen-activated protein kinase kinase (MEK), NF-kappaB, and bcl-x(L), leading to a mitochondrial pathway of apoptosis in primary human CD4+ T lymphocytes. Azathioprine thus converts a costimulatory signal into an apoptotic signal by modulating Rac1 activity. Azathioprine-generated 6-Thio-GTP thus prevents the development of an effective immune response via blockade of Vav activity on Rac proteins. Azathioprine (1 mM) restores ATP levels and arrests cell injury, while culture in glucose-enriched media augments ATP levels and ameliorates cell death. Azathioprine reduces viability 5-34% at day 1 and 42-92% by day 4. Azathioprine decreases the viability of hepatocytes and induces the following events in primary culture of isolated rat hepatocytes: intracellular reduces glutathione (GSH) depletion, metabolic activity reduction, and lactate dehydrogenase release. Azathioprine effect on hepatocytes is associated with swelling and increased oxygen consumption of intact isolated rat liver mitochondria.

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