The mitochondrial inner membrane anion channel is inhibited by DIDS

Abstract

The mitochondrial inner membrane anion channel (IMAC) is a channel, identified by flux studies in intact mitochondria, which has a broad anion selectivity and is maintained closed or inactive by matrix Mg2+ and H+. We now present evidence that this channel, like many other chloride/anion channels, is reversibly blocked/inhibited by stilbene-2,2'-disulfonates. Inhibition of malonate transport approaches 100% with IC50 values of 26, 44, and 88 mu M for DIDS, H2-DIDS, and SITS respectively and Hill coefficients < or = 1. In contrast, inhibition of Cl- transport is incomplete, reaching a maximum of about 30% at pH 7.4 and 65% at pH 8.4 with an IC50 which is severalfold higher than that for malonate. The IC50 for malonate transport is decreased about 50% by pretreatment of the mitochondria with N-ethylmaleimide. Raising the assay pH from 7.4 to 8.4 increases the IC50 by about 50%, but under conditions where only the matrix pH is made alkaline the IC50 is decreased slightly. These properties and competition studies suggest that DIDS inhibits by binding to the same site as Cibacron blue 3GA. In contrast, DIDS does not appear to compete with the fluorescein derivative Erythrosin B for inhibition. These findings not only provide further evidence that IMAC may be more closely related to other "Cl-" channels than previously thought, but also suggest that other Cl- channels may be sensitive to some of the many regulators of IMAC which have been identified.

The mitochondrial origin of postischemic arrhythmias

“…Similarly, the agonist FGIN-1-27 (2-aryl-3-indoleacetamide) binds with high affinity to the mBzR but not to the central BzR (23). The mBzR inhibitors are known to block mitochondrial IMAC, as originally described in swelling assays of isolated mitochondria (24,25), and were later shown to block anion channels in single-channel patch clamp studies of isolated mitoplasts (26). We have also confirmed that 5-50 µM concentrations of PK11195 and 4′-Cl-DZP block mitochondrial inner membrane ion channels in cardiac mitoplasts (data not shown).…”

Lung Surfactant Gelation Induced by Epithelial Cells Exposed to Air Pollution or Oxidative Stress

“…The mitochondrial electron transport chain generates ROS, which are then transported into the cytoplasm through voltage-dependent anion channels. The mitochondrial anion channel inhibitor, DIDS, protects cells from oxidative injury by blocking the egress of mitochondrial ROS into the cytoplasm (30). We show that DIDS substantially decreases ROFA-AEC surfactant gelation, implicating mitochrondrial ROS in surfactant gelation.…”

“…We next characterized the contribution of mitochondrial-derived ROS to ROFA-AEC surfactant gelation by coincubating A549 cells with the mitochondrial anion channel inhibitor, 4,4Ј diisothiocyanatostilbene-2, 2Јdisulfonic acid (DIDS) (10 M) during ROFA exposure (30)(31)(32). A549 cells treated with DIDS alone showed no increase in surfactant gelation ( Figure 3B, filled squares).…”

Redox regulation of p53 during hypoxia

“…Anion channels have been described in both the inner and outer mitochondrial membranes (Ballarin and Sorgato, 1996;Colombini et al, 1996). An inhibitor of these channels such as 4,4'-diisothiocyanato-stilbene-2,2'-disulfonate (DIDS) can suppress the egress of superoxide from the mitochondria (Beavis et al, 1996). Figure 1a shows that DIDS abolished the increase in DCF¯uorescence observed during hypoxia.…”