Effects of aging on isoflurane-induced and protein kinase A-mediated activation of ATP-sensitive potassium channels in cultured rat aortic vascular smooth muscle cells

Comparison of ketamine/xylazine and isoflurane anesthesia on the establishment of mouse middle cerebral artery occlusion model

The middle cerebral artery occlusion model (MCAO) is one of the most common stroke models in neuroscience research. The establishment of the mouse MCAO model in terms of animal survival depends on anesthesia, which is an important part of the entire surgical process. The 7-day survival rate of the MCAO model under isoflurane (ISO) anesthesia (35%) was lower than ketamine/xylazine (KX) anesthesia (70%), which demonstrated that the success rate of the MCAO model under KX anesthesia would be significantly higher than that under ISO anesthesia. As confirmed by TTC staining and MRI, the cerebral infarction area of mice successfully modeled under ISO anesthesia was significantly smaller than that of KX anesthesia. The diameter of cerebral blood vessels under ISO anesthesia was significantly larger than that under KX, and the blood perfusion volume was also significantly increased in the same area. ISO has proven to delay the coagulation time and affect the activation of coagulation factors. ISO anesthesia may cause bleeding, vasodilation, respiratory depression, and other phenomena that affect the success rate and death of diseased animal models. In conclusion, compared with ISO anesthesia, KX anesthesia is a safer and more suitable method for the establishment of a mouse MCAO model. The data will inform safer and more detailed anesthesia recommendations forthe establishment of animal models of vascular-related major injury diseases.

Activation of Inward Rectifier K+ Channel 2.1 by PDGF-BB in Rat Vascular Smooth Muscle Cells through Protein Kinase A

Platelet-derived growth factor-BB (PDGF-BB) can induce the proliferation, migration, and phenotypic modulation of vascular smooth muscle cells (VSMCs). We used patch clamp methods to study the effects of PDGF-BB on inward rectifier K⁺ channel 2.1 (Kir2.1) channels in rat thoracic aorta VSMCs (RASMCs). PDGF-BB (25 ng/mL) increased Kir2.x currents (−11.81 ± 2.47 pA/pF, P < 0.05 vs. CON, n = 10). Ba²⁺(50 μM) decreased Kir2.x currents (−2.13 ± 0.23 pA/pF, P < 0.05 vs. CON, n = 10), which were promoted by PDGF-BB (−6.98 ± 1.03 pA/pF). PDGF-BB specifically activates Kir2.1 but not Kir2.2 and Kir2.3 channels in HEK-293 cells. The PDGF-BB-induced stimulation of Kir2.1 currents was blocked by the PDGF-BB receptor β (PDGF-BBRβ) inhibitor AG1295 and was not affected by the PDGF-BBRα inhibitor AG1296. The PDGF-BB-induced stimulation of Kir2.1 currents was blocked by the protein kinase A inhibitor Rp-8-CPT-cAMPs; however, the antagonist of protein kinase B (GSK690693) had marginal effects on current activity. The PDGF-BB-induced stimulation of Kir2.1 currents was enhanced by forskolin, an adenylyl cyclase (AC) activator, and was blocked by the AC inhibitor SQ22536. We conclude that PDGF-BB increases Kir2.1 currents via PDGF-BBRβ through activation of cAMP-PKA signaling in RASMCs.

Gastrodin causes vasodilation by activating KATP channels in vascular smooth muscles via PKA-dependent signaling pathway

Gastrodin, one of the major components extracted from the Chinese herb Gastrodia elata Bl., has been widely used as an anticonvulsant, sedative, analgesic and hypotensive. In our study, we aimed to investigate the effects and possible mechanisms of gastrodin on vascular K_ATP channels. Tension experiments were used on rat mesenteric artery rings without an endothelium. Patch clamp experiments were executed to investigate the influences of gastrodin on the membrane current in mesenteric artery smooth muscle cells. Gastrodin induced vasorelaxation in a concentration dependent manner when rat mesenteric artery rings were pre-contracted with Phenylephrine. The vasorelaxation effect was partially diminished by pre-treating with a K_ATP channel inhibitor, or a PKA inhibitor. With whole-cell patch-clamp recording techniques, we found that gastrodin is a activator of K_ATP in rat mesenteric artery smooth muscle cells, and this effect was eliminate by pre-treating with H89or PKI, PKA inhibitor. In addition, when rat vascular smooth muscle cells were treated with 100 μM gastrodin for 24 h, maximum K_ATP current density increased by 28.1%. The results indicate that gastrodin exerts vasorelaxation effect through activation of PKA and subsequent opening of smooth muscle K_ATP channels.

Cardiovascular KATP channels and advanced aging

With advanced aging, there is a decline in innate cardiovascular function. This decline is not general in nature. Instead, specific changes occur that impact the basic cardiovascular function, which include alterations in biochemical pathways and ion channel function. This review focuses on a particular ion channel that couple the latter two processes, namely the K_ATP channel, which opening is promoted by alterations in intracellular energy metabolism. We show that the intrinsic properties of the K_ATP channel changes with advanced aging and argue that the channel can be further modulated by biochemical changes. The importance is widespread, given the ubiquitous nature of the K_ATP channel in the cardiovascular system where it can regulate processes as diverse as cardiac function, blood flow and protection mechanisms against superimposed stress, such as cardiac ischemia. We highlight questions that remain to be answered before the K_ATP channel can be considered as a viable target for therapeutic intervention.

ABCC9/SUR2 in the brain: Implications for hippocampal sclerosis of aging and a potential therapeutic target

The ABCC9 gene and its polypeptide product, SUR2, are increasingly implicated in human neurologic disease, including prevalent diseases of the aged brain. SUR2 proteins are a component of the ATP-sensitive potassium ("KATP") channel, a metabolic sensor for stress and/or hypoxia that has been shown to change in aging. The KATP channel also helps regulate the neurovascular unit. Most brain cell types express SUR2, including neurons, astrocytes, oligodendrocytes, microglia, vascular smooth muscle, pericytes, and endothelial cells. Thus it is not surprising that ABCC9 gene variants are associated with risk for human brain diseases. For example, Cantu syndrome is a result of ABCC9 mutations; we discuss neurologic manifestations of this genetic syndrome. More common brain disorders linked to ABCC9 gene variants include hippocampal sclerosis of aging (HS-Aging), sleep disorders, and depression. HS-Aging is a prevalent neurological disease with pathologic features of both neurodegenerative (aberrant TDP-43) and cerebrovascular (arteriolosclerosis) disease. As to potential therapeutic intervention, the human pharmacopeia features both SUR2 agonists and antagonists, so ABCC9/SUR2 may provide a "druggable target", relevant perhaps to both HS-Aging and Alzheimer's disease. We conclude that more work is required to better understand the roles of ABCC9/SUR2 in the human brain during health and disease conditions.