• B cells;
  • bipolar disorder;
  • ion channels;
  • oxidative stress;
  • TRPC3;
  • TRPM2

Roedding AS, Gao AF, Au-Yeung W, Scarcelli T, Li PP, Warsh JJ. Effect of oxidative stress on TRPM2 and TRPC3 channels in B lymphoblast cells in bipolar disorder. Bipolar Disord 2012: 14: 151–161. © 2012 The Authors. Journal compilation © 2012 John Wiley & Sons A/S.

Objectives:  Recent findings implicate the calcium-permeable nonselective ion channels transient receptor potential (TRP) melastatin subtype 2 (TRPM2) and canonical subtype 3 (TRPC3) in the pathogenesis of bipolar disorder (BD). These channels are involved in calcium and oxidative stress signaling, both of which are disrupted in BD. Thus, we sought to determine if these channels are differentially affected by oxidative stress in cell lines of BD patient origin.

Methods:  B lymphoblast cell lines (BLCLs) from bipolar I disorder (BD-I) patients (n = 6) and healthy controls (n = 5) were challenged with the oxidative stressor rotenone (2.5 μM and 10 μM) or vehicle for acute (24 hours) and chronic (four days) intervals. Cell viability was measured using propidium iodide, while TRPM2- and TRPC3-mediated calcium fluxes were measured in the presence of their respective activators (H2O2 and 1-oleoyl-2-acetyl-sn-glycerol) using Fluo-4. Changes in TRPM2 and TRPC3 expression levels were determined by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) and Western blotting.

Results:  Cell viability decreased with increasing dose and duration of rotenone treatment, with BD-I patient BLCLs more susceptible than controls acutely (p < 0.001). A dose-dependent decrease in TRPC3 protein expression occurred after chronic (24%, p = 0.008) but not acute rotenone treatment. Interestingly, H2O2-provoked TRPM2-dependent calcium fluxes revealed an interaction between the effects of stressor addition and diagnostic subject group (p = 0.003).

Conclusions:  These data support an important role for TRPM2 and TRPC3 in sensing and responding to oxidative stress and in transducing oxidative stress signaling to intracellular calcium homeostasis and cellular stress responses, all of which have been implicated in the pathophysiology of BD.