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Zidovudine (AZT) inhibits HIV-1 replication in AIDS. A limiting side effect is AZT-induced toxic myopathy. Molecular changes in a rat model of AZT-induced toxic myopathy in vivo helped define pathogenetic molecular, biochemical, and ultrastructural toxic events in skeletal muscle and supported clinical and in vitro findings. After 35 d of AZT treatment, selective ehanges in rat striated muscle were localized ultrastructurally to mitochondria, and included swelling, cristae disruption, and myelin figures. Decreased muscle mitochondrial (mt) DNA, mtRNA, and decreased mitochondrial polypeptide synthesis in vitro were found in parallel. Mitochondrial molecular changes occurred in absence of altered abundance of cytosolic glyceraldehyde-3-phosphate dehydrogenase, or sarcomeric mitochondrial creatine kinase mRNAs. Quadriceps mitochondrial DNA polymerase gamma activity was similar in both AZT-treated and control rats. In vivo findings with rats support the hypotheis that AZT-induced inhibition of mtDNA replication has an tT. of depressing the abundance of striated muscle mtDNA,

The FDA has approved 31 small-molecule kinase inhibitors (KIs) for human use as of November 2016, with six having black box warnings for hepatotoxicity (BBW-H) in product labeling. The precise mechanisms and risk factors for KI-induced hepatotoxicity are poorly understood. Here, the 31 KIs were tested in isolated rat liver mitochondria, an in vitro system recently proposed to be a useful tool to predict drug-induced hepatotoxicity in humans. The KIs were incubated with mitochondria or submitochondrial particles at concentrations ranging from therapeutic maximal blood concentrations (Cmax) levels to 100-fold Cmax levels. Ten endpoints were measured, including oxygen consumption rate, inner membrane potential, cytochrome c release, swelling, reactive oxygen species, and individual respiratory chain complex (I–V) activities. Of the 31 KIs examined only three including sorafenib, regorafenib and pazopanib, all of which are hepatotoxic, caused significant mitochondrial toxicity at concentrations equal to the Cmax, indicating that mitochondrial toxicity likely contributes to the pathogenesis of hepatotoxicity associated with these KIs. At concentrations equal to 100-fold Cmax, 18 KIs were found to be toxic to mitochondria, and among six KIs with BBW-H, mitochondrial injury was induced by regorafenib, lapatinib, idelalisib, and pazopanib, but not ponatinib, or sunitinib. Mitochondrial liability at 100-fold Cmax had a positive predictive power (PPV) of 72% and negative predictive power (NPV) of 33% in predicting human KI hepatotoxicity as defined by product labeling, with the sensitivity and specificity being 62% and 44%, respectively. Similar predictive power was obtained using the criterion of Cmax ≥1.1 µM or daily dose ≥100 mg. Mitochondrial liability at 1–2.5-fold Cmax showed a 100% PPV and specificity, though the NPV and sensitivity were 32% and 14%, respectively. These data provide novel mechanistic insights into KI hepatotoxicity and indicate that mitochondrial toxicity at therapeutic levels can help identify hepatotoxic KIs.Electronic supplementary materialThe online version of this article (doi:10.1007/s00204-016-1918-1) contains supplementary material, which is available to authorized users.

The characteristics and pathogenesi s of the cardiovascula r toxicity induced by the type III selective phosphodiesteras e inhibitor SK&F 95654 were examined in 2 studies. Sprague-Dawley rats received either a single sc injection of 50, 100, or 200 mg/kg SK&F 95654 and were euthanized at 24 hours after administration of the drug (Study 1), or were given a single subcutaneou s (sc) injection of 100 mg/kg SK&F 95654 and euthanized at 1, 2, 4, 6, 8, 12, 24 hours, or 2 weeks after treatment (Study 2). Control rats received either DMSO or saline. Myocardial lesions and vascular lesions of the mesentery, spleen, and pancreas were seen 24 hours after dosing with either 50, 100, or 200 mg/kg SK&F 95654. The frequency and severity of these lesions (evaluated after the 100 mg/kg dose) increased with time over a period of 1 to 24 hours. By 2 weeks, the lesions subsided. Cardiac lesions consisted of myocyte necrosis with hypercontraction bands, in ammatory cell in ltration, interstitial hemorrhage, and interstitial edema. Vascular lesions of the mesentery were most prominent and consisted of vasodilatation and in ammation in the small-sized vessels, arterial medial necrosis and hemorrhage , and venous thrombosis. The vascular lesions included: leukocyt e adhesion to endothelial cells, transendothelia l migration of leukocytes, and in ammatory cell in ltration into vessel walls. Affected vessels included arteries, terminal arterioles, capillaries, postcapillary venules, and veins. Apoptosis of endothelial and smooth muscle cells was detected in the mesenteric vasculature by both TUNEL assay and electron microscopy. Evidence of endothelial cell activation in the mesenteric arteries and veins was also observed by electron microscopy. Immunohistochemica l staining detected enhanced endothelial cell expression of intercellular adhesion molecule-1 (ICAM-1) and von Willebrand factor (vWF) in the mesenteric arteries and veins. Mast cells were noted to be more prevalent in affected mesenteric tissue from drug-treated animals. The present ndings suggest that apoptosis of endothelial and smooth muscle cells, activation of endothelial cells, recruitment of mast cells, and increased expression of adhesion molecules are important factors to the overall pathogenesi s of SK&F 95654-induce d vasculitis.Keywords. Myocardial necrosis and in ammation; drug-induce d vasculitis; vasodilatation; endothelial cell activation; endothelial and smooth muscle cell apoptosis; intercellular adhesion molecule-1 (ICAM-1); von Willebrand factor; mast cell degranulation . INTRODUCTIONType III phosphodiesterase (PDE) belongs to the cyclic 3 ,5 -adenosine guanosine monophosphate (cGMP)-inhibited PDE family of enzymes that hydrolyze intracellular cAMP (40). Selective inhibitors of PDE III possess bronchodilator activity (40), which offers these agents potential for treating patients with asthma. However, in nonclinical studies, PDE III inhibitors have been reported to cause cardiac and vascular alterations (10, 17, 21-23, 32, 36-38, 44). SK&F 95654, a s...

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