In proteinuric nephropathies of chronic kidney disease, the epithelial cells of the nephron including the collecting duct are exposed to high concentrations of luminal albumin. Albumin is taken up from collecting duct cells by endocytosis causing excessive reactive oxygen species (ROS) production and a proinflammatory response. Curcumin used in the traditional medicine possesses anti-inflammatory and antioxidant effects. ROS and ADP-ribose (ADPR) activate the cation channel TRPM2. We hypothesize, that albumin-induced cell stress and proinflammatory response are mediated by Ca²⁺ and can be reduced by curcumin. The cortical collecting duct (CCD) cells mpkCCD_c14 exhibit spontaneous and inducible Ca²⁺ oscillations, which can be blocked by pre-treatment with curcumin. Curcumin accumulates in plasma membrane and intracellular vesicles, where it interferes with TRPM2 and decreases the influx of Ca²⁺. Albumin reduces cell viability and increases apoptosis, NF-κB activation, and mitochondrial membrane depolarization via Ca²⁺-dependent signaling, which results in increased ROS production. Albumin-induced cell stress is diminished by the inhibition of TRPM2 after administration of curcumin and ADPR (PARP1) inhibitors. Curcumin did not reduce the Ca2+ elevation induced by thapsigargin in Ca²⁺-free medium, but it reduced the function of store-operated Ca²⁺ channels and ATP-evoked Ca²⁺ response. In conclusion, albumin-induced oxidative stress is mediated by Ca²⁺-dependent signaling via TRPM2 and leads to cell damage and a proinflammatory response, strengthening the role of CCD cells in the progression of chronic kidney disease.

Diabetes, which causes oxidative stress-induced neuronal damage, is still one of the most important chronic health problems in the world. It can cause serious cellular loss and damage throughout the course of the disease. It is hypothesized that increased oxidative stress in this process increases free reactive oxygen species (ROS) and apoptotic markers and causes diabetic damage. Alpha-Lipoic acid (α-LA), which has a direct antioxidant effect in ROS reduction reactions, is also among the main components of the antioxidant system that works for free radical control and apoptosis. To understand the role of α-LA in reducing diabetes-induced oxidative damage, we examined the production of ROS in the brain cortex and erythrocytes of rats and their effects on markers of apoptosis. Forty adult Wistar albino rats were divided into four groups as control, α-LA, diabetic (DIA), and DIA+α-LA. For the induction of diabetes, the intraperitoneal injection of a dose of streptozotocin (STZ) (45 mg/kg) was used. α-LA (50 mg/kg) was applied to the groups of α-LA and DIA+α-LA for 14 days. At the end of the experiment, the brain cortex tissue and erythrocyte samples were taken from the rats. The levels of apoptosis, caspase 3, caspase 9, mitochondrial membrane potential, intracellular ROS, and lipid peroxidation were increased in the STZ group, although their levels were decreased in the DIA+α-LA group by the injection of α-LA. The STZ treatmentinduced decreases of cell viability, reduced glutathione, and glutathione peroxidase were increased in the brain and erythrocytes by the treatment of α-LA. In conclusion, diabetes acted a role in neuronal damage caused by increased ROS and apoptosis. We observed that α-LA induced a modulatory role on the apoptotic, oxidant, and antioxidant parameters in the brain and erythrocyte. The neuroprotective role of α-LA treatment may be explained by its modulating activity against increased oxidative stress and apoptosis.