title: Mechanisms of toxicity of Cleistanthus collinus: vacuolar ATPases are a putative target.
abstract: 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.
authors.affiliation: The Wellcome Trust Research Laboratory, Department of Gastrointestinal Sciences, Christian Medical College, Vellore, India.
authors.forename: Kavitha Priya
authors.initials: KP
authors.lastname: Kettimuthu
authors.forename: A Amala
authors.initials: AA
authors.lastname: Lourthuraj
authors.forename: A Soosai
authors.initials: AS
authors.lastname: Manickam
authors.forename: Sathya
authors.initials: S
authors.lastname: Subramani
authors.forename: Anup
authors.initials: A
authors.lastname: Ramachandran
mesh_terms: D000143:Acids / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D019665:Euphorbiaceae / Q000737:chemistry / Q000506:poisoning*; D006801:Humans; D007194:India; D007668:Kidney / Q000187:drug effects / Q000201:enzymology; D008566:Membranes / Q000187:drug effects / Q000201:enzymology / Q000473:pathology; D008861:Microsomes / Q000378:metabolism; D008871:Microvilli / Q000187:drug effects / Q000201:enzymology / Q000473:pathology; D009840:Oligomycins / Q000494:pharmacology; D010936:Plant Extracts / Q000737:chemistry / Q000506:poisoning; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D054328:Proton Pump Inhibitors / Q000633:toxicity; D017494:Proton Pumps / Q000378:metabolism; D051381:Rats; D014475:Uncoupling Agents / Q000494:pharmacology; D025262:Vacuolar Proton-Translocating ATPases / Q000037:antagonists & inhibitors*; D014617:Vacuoles / Q000187:drug effects* / Q000201:enzymology*
chemical_list: D000143:Acids; D009840:Oligomycins; D010936:Plant Extracts; D011500:Protein Synthesis Inhibitors; D054328:Proton Pump Inhibitors; D017494:Proton Pumps; D014475:Uncoupling Agents; D025262:Vacuolar Proton-Translocating ATPases