Investigation of Ca 2+ signaling induced by the flavonoid diosmin in glioblastoma cells and its potential implications in the treatment using the Ca 2+ chelating agent BAPTA-AM

Flavonoids, found in fruits and vegetables, can potentially prevent brain diseases. Diosmin (diosmetin-7-O-rutinoside), a flavonoid, exhibits various pharmacological activities, but its impact on calcium ion (Ca²⁺) signaling and the associated mechanisms in human glioblastoma cells remain unclear. This study investigated the effect of diosmin on intracellular Ca²⁺ levels ([Ca²⁺]_i), cell viability, and the participation of Ca²⁺-related pathways in DBTRG-05MG human glioblastoma cells. It also investigated the connection between Ca²⁺ signaling and toxicity in cells treated with diosmin and the Ca²⁺ chelator BAPTA-AM. Research indicates that diosmin (20-60 μM) caused an increase in [Ca²⁺]_i and induced cytotoxicity in a concentration-dependent manner. Furthermore, pre-treating the cells with the BAPTA-AM can intensify the cytotoxic effect. The removal of extracellular Ca²⁺ suppressed the entry of Ca²⁺. Agents that modulate store-operated Ca²⁺ channels, SKF96365 and 2-APB, can inhibit the entry of Ca²⁺ induced by diosmin. Treatment with the endoplasmic reticulum Ca²⁺ pump inhibitor thapsigargin in a Ca²⁺-free environment inhibited the increase in [Ca²⁺]_i caused by diosmin; conversely, treatment with diosmin reduced the increase in [Ca²⁺]_i caused by thapsigargin. Moreover, inhibiting phospholipase C (PLC) with U73122 eliminated the increase in [Ca²⁺]_i triggered by diosmin. In DBTRG-05MG cells, diosmin-induced cell death is associated with Ca²⁺, a process involving the entry of Ca²⁺ through store-operated Ca²⁺ channels and the release of Ca²⁺ from the endoplasmic reticulum, which relies on the PLC. Additionally, BAPTA-AM, a compound with Ca²⁺-chelating properties, shows promise in enhancing diosmin-induced cytotoxicity, and this could represent a significant development in glioblastoma research.