SAH-Induced MMP Activation and K V Current Suppression is Mediated Via Both ROS-Dependent and ROS-Independent Mechanisms

Abstract

Summary Voltage-gated potassium (KV) channels regulate cerebral artery tone and have been implicated in subarachnoid hemorrhage (SAH)-induced pathologies. Here, we examined whether matrix metalloprotease (MMP) activation contributes to SAH-induced KV current suppression and cerebral artery constriction via activation of epidermal growth factor receptors (EGFRs). Using patch clamp electrophysiology, we observed that KV currents were selectively decreased in cerebral artery myocytes isolated from SAH model rabbits. Consistent with involvement of enhanced MMP and EGFR activity in SAH-induced KV current suppression, we found that: 1) OxyHb and/or the exogenous EGFR ligand, HB-EGF, failed to induce further KV current suppression after SAH and 2) gelatin zymography detected significantly higher MMP-2 activity after SAH. The removal of reactive oxygen species (ROS) by combined treatment with superoxide dismutase (SOD) and catalase partially inhibited OxyHb-induced KV current suppression. However, these agents had little effect on OxyHb-induced MMP-2 activation. Interestingly, in the presence of a broad spectrum MMP inhibitor (GM6001), OxyHb failed to cause KV current suppression. These data suggest OxyHb suppresses KV currents through both ROS-dependent and ROS-independent pathways involving MMP activation. The ROS-independent pathway involves activation of MMP-2, whereas the ROS-dependent pathway involves activation of a second unidentified MMP or ADAM (a disintegrin and metalloprotease domain).

Derepression of co-silenced tumor suppressor genes by nanoparticle-loaded circular ssDNA reduces tumor malignancy

“…The gel was stained with Coomassie Brilliant Blue. MMP activity was detected as unstained bands against the background of bluestained gelatin (36).…”

“…After vacuum freezedrying and coating with gold, cells were photo graphed using a scanning electron microscope (JEOL6000). At 12,24,36,48,60, and 72 hours after transfection, cell culture medium was removed and 100 l of methylthiazolyldiphenyltetrazolium bromide (MTT) (1 mg/ml) was added to each well of a 96well plate. Afterward, the cells were incubated for 5 hours at 37°C in 5% CO 2 .…”

The yin and yang of KV channels in cerebral small vessel pathologies

“…Given the role of K + efflux through K V channels in opposing pressure‐induced membrane depolarization and vasoconstriction, the prediction is that increased (CADASIL) or decreased (SAH) K V channel numbers would alter the degree of negative feedback control, resulting in hyperpolarization (CADASIL) or depolarization (SAH) of PA SMCs. Consistent with this prediction, experimentally measured V m was hyperpolarized (−45 mV) and depolarized (−28 mV) in pressurized (40 mm Hg) PAs obtained from CADASIL mice and SAH model animals, respectively, compared to CTL groups (−35 mV).…”

Cerebral artery myogenic reactivity: The next frontier in developing effective interventions for subarachnoid hemorrhage

“…90,164,165 Experiments using oxyhemoglobin to mimic the effect of the subarachnoid blood provide solid corroborating evidence. [166][167][168] The precise channels affected, however, are less clear: K v 1.5, K v 2.1 and K v 2.2 transcripts and protein levels are reduced in SAH, 169 although functional measures suggest that K v 2 and K v 7 family members are the pertinent functional targets. 164,170 The involvement of BK channels is contradictory: Koide and co-workers showed that SAH causes a distinct reduction in calcium sparkinduced transient BK currents, 92 while Jahromi and co-workers found that virtually all BK channel characteristics are unaffected in SAH.…”