Comparison of Cytotoxicity of Cysteine and Homocysteine for Renal Epithelial Cells

Abstract

Background: Although the cytotoxic effects of cysteine (Cys) on renal cells have been established, the effects of homocysteine (Hcy), which causes endothelial cell dysfunction, have not been well tested. We compared the direct toxicity of Hcy on renal tubular cells to that of Cys and examined the mechanism of cell toxicity. Methods: LLC-PK1 cells were incubated with test media containing 500 µM Cys or Hcy in the presence or absence of 100 µM copper. Lactate dehydrogenase release and thiobarbituric acid reactive substance were measured for estimating cytolysis and lipid peroxidation, respectively. The generation of hydrogen peroxide and hydroxyl radical, and the cell redox state were analyzed using the scopoletin method, salicylate-trap method, and glutathione (GSH) content, respectively. Superoxide dismutase, catalase, and vitamin E also were used for clarifying the mechanism of toxicity. Results: In the presence of copper (+ Cu), cytolysis at 16 h was more prominent in cells exposed to Cys than Hcy. In accordance with cytotoxicity, lipid peroxidation at 4 h of incubation, as well as hydrogen peroxide and hydroxyl radical formation in a shorter incubation, were remarkably greater in Cys + Cu than Hcy + Cu. The addition of Hcy, but not Cys, decreased GSH content significantly. Conclusion: In the presence of copper, Cys was extraordinarily more cytotoxic to renal cells than Hcy. Cytotoxicity from Hcy may be dependent upon depletion of cellular GSH, while Cys cytotoxicity is primarily dependent upon the generation of reactive oxygen species and lipid peroxidation.

Cell culture media for recombinant protein expression in Chinese hamster ovary (CHO) cells: History, key components, and optimization strategies

“…A drop in cysteine concentration below 0.1 mM in the production medium can result in a 40% loss of titer in monoclonal antibody production. Meanwhile, cysteine concentration of >1 mM can be toxic for mammalian cells, possibly due to lipid peroxidation and formation of hydroxyl radicals, which can be further accelerated in the presence of copper . In mammals, the cysteine pool is regulated by the liver .…”

“…Meanwhile, cysteine concentration of >1 mM can be toxic for mammalian cells, 92 possibly due to lipid peroxidation and formation of hydroxyl radicals, which can be further accelerated in the presence of copper. 93 In mammals, the cysteine pool is regulated by the liver. 94 Without such a regulating mechanism in CHO cells, cysteine concentration in the medium should be carefully designed and controlled for cell culture processes.…”

Tumor Necrosis Factor-α–Induced Iron Sequestration and Oxidative Stress in Human Endothelial Cells

“…21 HUVEC were reseeded in 6-well cell culture clusters with modified MCDB131 medium containing 2% fetal calf serum, and allowed to adhere for 2 hours. After treatment, cells were incubated with reaction buffer containing 10 mmol/L Na salicylate, 1.2 mmol/L MgCl 2 , and 1.2 mmol/L CaCl 2 in PBS for 30 minutes.…”

Neuroprotective Effects of Polysaccharides from Wolfberry, the Fruits of Lycium barbarum, Against Homocysteine-induced Toxicity in Rat Cortical Neurons

“…Folate deficiency and hyperhomocysteinemia precede the onset of dementia [7], further suggesting the causal role of Hcy in AD development. The underlying mechanisms of its toxicity remain elusive, but evidence shows that high levels of Hcy can induce direct toxicity to different types of tissues [16][17][18]. Some scientists proposed that Hcy-lowering therapy with vitamin B may be beneficial to health [19], while others conduct research on agents with direct protective effects against Hcy toxicity [20].…”