Survival of glioblastoma cells in response to endogenous and exogenous oxidative challenges: possible implication of NMDA receptor-mediated regulation of redox homeostasis.

Abstract

Cancer cells are highly metabolically active and produce high levels of reactive oxygen species (ROS). Drug resistance in cancer cells is closely related to their redox status. The role of ROS and its impact on cancer cell survival seems far from elucidation. The mechanisms through which glioblastoma cells overcome aberrant ROS and oxidative stress in a milieu of hypermetabolic state is still elusive. We hypothesize that the formidable growth potential of glioma cells is through manipulation of tumor microenvironment for its survival and growth, which can be attributed to an astute redox regulation through a nexus between activation of N-methyl-d-aspartate receptor (NMDAR) and glutathione (GSH)-based antioxidant prowess. Hence, we examined the NMDAR activation on intracellular ROS level, and cell viability on exposure to hydrogen peroxide (H2 O2 ), and antioxidants in glutamate-rich microenvironment of glioblastoma. The activation of NMDAR attenuated the intracellular ROS production in LN18 and U251MG glioma cells. MK-801 significantly reversed this effect. On evaluation of GSH redox cycle in these cells, the level of reduced GSH and glutathione reductase (GR) activity were significantly increased. NMDAR significantly enhanced the cell viability in LN18 and U251MG glioblastoma cells, by attenuating exogenous H2 O2 -induced oxidative stress, and significantly increased catalase activity, the key antioxidant that detoxifies H2 O2 . We hereby report an unexplored role of NMDAR activation induced protection of the rapidly multiplying glioblastoma cells against both endogenous ROS as well as exogenous oxidative challenges. We propose potentiation of reduced GSH, GR, and catalase in glioblastoma cells through NMDAR as a novel rationale of chemoresistance in glioblastoma.