Calcium Oxalate Monohydrate is Associated with Endothelial Cell Toxicity But Not with Reactive Oxygen Species Accumulation.

One characteristic of ethylene glycol overdose is a cardiopulmonary syndrome including hypertension and pulmonary edema with pathology indicating damage to the endothelium of heart, lung and brain vessels. The mechanism of the cardiopulmonary toxicity is unknown, but has been linked with accumulation of the metabolite calcium oxalate monohydrate (COM) in the endothelium. These studies have evaluated the hypothesis that COM or the oxalate ion produces endothelial damage in vitro and that damage is linked with induction of reactive oxygen species (ROS). In cultured human umbilical vein endothelial cells (HUVEC), COM, but not the oxalate ion, produced cytotoxicity in a dose- and time-dependent manner. Using three ROS-sensitive dyes, HUVEC exposed to COM did not significantly increase ROS production. Additionally, co-treatment with three antioxidants that operate by different mechanisms did not reduce COM cytotoxicity. As such, an increase in ROS production does not explain cell death in endothelial cells. Aluminum citrate, uniquely among citrate compounds, significantly reduced COM cytotoxicity to endothelial cells and thus may act as an adjunct therapy for ethylene glycol poisoning to reduce endothelial damage. These results imply that accumulation of COM in endothelial cells is an important aspect of the cardiopulmonary toxicity from ethylene glycol.

Effects of HIV drug combinations on endothelin-1 and vascular cell proliferation.

Pulmonary arterial hypertension (PAH) is a progressive disease of the pulmonary vasculature involving endothelial and vascular smooth muscle cell (VSMC) proliferation, vasoconstriction, right ventricular hypertrophy, and eventually, right heart failure and death. PAH occurs 1000-fold more frequently in HIV patients than in the general population. Although conventional HIV therapy with nucleoside reverse transcriptase inhibitors (NRTIs) leads to regression of PAH, highly active antiretroviral therapy (HAART; two NRTI plus a protease inhibitor) increases the incidence of HIV-associated PAH as much as twofold. Although there are relatively few models for PAH, previous reports indicate the disease can be initiated by endothelial injury and release of the mitogen endothelin-1 (ET-1). ET-1, in turn, stimulates VSMC proliferation. To determine whether HAART induces endothelial injury and release of cytokines like ET-1, we treated human umbilical vein endothelial cells with micromolar amounts of AZT (3'-azido-3'-deoxythymidine), the protease inhibitor indinavir, or AZT plus indinavir, and measured cell viability, mitochondrial function, and ET-1 release. Both AZT and indinavir induced marked decreases in cellular oxygen uptake, as well as increases in ET-1 release. Although the drugs had no apparent effect on proliferation in VSMCs alone, in cocultures of VSMCs plus endothelial cells, the drugs increased proliferation of both endothelial cells and VSMCs. Finally, when cocultures of endothelial cells and VSMCs were treated with BQ-123 and BQ-788, selective antagonists for ET(A) and ET(B) receptors, respectively, drug-induced proliferation of both VSMCs and endothelial cells was attenuated. These data thus suggest that HIV drug cocktails may exacerbate preexisting HIV-associated PAH by inducing endothelial mitochondrial dysfunction, in turn stimulating the release of ET-1, and ultimately, vascular cell proliferation.