Cleistanthus collinus poisoning affects mitochondrial respiration and induces oxidative stress in the rat kidney.

Cleistanthus collinus is a poisonous shrub used for deliberate self-harm in rural areas of South India and intake of boiled decoction of leaves is a common method of self-harm. Distal renal tubular acidosis (dRTA) is an important clinical symptom observed in C. collinus poisoning, and renal V-ATPases may be potential targets of damage. However, a lack of understanding of molecular mediators involved hampers medical management, which is mainly supportive. We hypothesized that C. collinus poisoning induces renal oxidative stress; probably by inducing mitochondrial uncoupling, which compromises V-ATPase activity to ultimately produce dRTA. This was tested by exposing renal BBMV, kidney cells in culture, and Wistar rats to C. collinus poisoning. Exposure to C. collinus aqueous extract resulted in significant elevations in the lipid peroxidation marker, conjugated dienes, in cell culture and in vivo. A significant decrease in mitochondrial respiratory control ratio was observed in kidneys from C. collinus-treated animals suggesting that mitochondrial oxidative phosphorylation is uncoupled. This was accompanied by significant increase in ADP levels and a decrease in proton pump activity. Thus, these results demonstrate that C. collinus poisoning induces oxidative stress which influences proton pump activity, probably due to feedback inhibition by elevated ADP levels because of mitochondrial dysfunction in the rat kidney.

A renal cell carcinoma tumorgraft platform to advance precision medicine.

Renal cell carcinoma (RCC) encompasses a heterogenous group of tumors, but representative preclinical models are lacking. We previously showed that patient-derived tumorgraft (TG) models recapitulate the biology and treatment responsiveness. Through systematic orthotopic implantation of tumor samples from 926 ethnically diverse individuals into non-obese diabetic (NOD)/severe combined immunodeficiency (SCID) mice, we generate a resource comprising 172 independently derived, stably engrafted TG lines from 148 individuals. TG lines are characterized histologically and genomically (whole-exome [n = 97] and RNA [n = 102] sequencing). The platform features a variety of histological and oncogenotypes, including TCGA clades further corroborated through orthogonal metabolomic analyses. We illustrate how it enables a deeper understanding of RCC biology; enables the development of tissue- and imaging-based molecular probes; and supports advances in drug development.

Mechanisms of toxicity of Cleistanthus collinus: vacuolar ATPases are a putative target.

Ingestion of Cleistanthus collinus, a shrub native to South India, either intentionally or accidentally, is a common cause of death in the area. Consumption of a boiled decoction of leaves is highly toxic, but medical management of patients is mainly supportive because the molecular mechanisms of toxin action are unknown. Distal renal tubular acidosis is one of the symptoms of poisoning in patients and adenosine triphosphate (ATP) requiring proton pumps is important for acid secretion in the kidney. Hence, we hypothesized that these may be putative targets for C. collinus action and we tested this by exposing rat renal brush border membrane (BBM) as well as cultured kidney cells to a boiled decoction of C. collinus. Exposure to the C. collinus decoction resulted in significant inhibition of vacuolar type H(+)-ATPase (V-ATPase) activity in renal BBM as well as blocking of the proton pump in renal BBM vesicles. C. collinus decoction was also found to inhibit acidification of intracellular organelles in cells in culture, similar to the effect seen with either bafilomycin or concanamycin - specific inhibitors of the V-ATPase. This was accompanied by a decrease in V-ATPase activity, but an increase in protein levels. These results demonstrate that the V-ATPase in renal cells is a putative target for the toxins in C. collinus and the inhibition of this important proton pump probably plays a role in the development of distal renal tubular acidosis and subsequent renal failure seen in poisoned patients.