Elementary calcium signaling in arterial smooth muscle

Vascular smooth muscle cells (VSMCs) of small peripheral arteries contribute to blood pressure control by adapting their contractile state. These adaptations depend on the VSMC cytosolic Ca(2+) concentration, regulated by complex local elementary Ca(2+) signaling pathways. Ca(2+) sparks represent local, transient, rapid calcium release events from a cluster of ryanodine receptors (RyRs) in the sarcoplasmic reticulum. In arterial SMCs, Ca(2+) sparks activate nearby calcium-dependent potassium channels, cause membrane hyperpolarization and thus decrease the global intracellular [Ca(2+)] to oppose vasoconstriction. Arterial SMC Ca(V)1.2 L-type channels regulate intracellular calcium stores content, which in turn modulates calcium efflux through RyRs. Ca(V)3.2 T-type channels contribute to a minor extend to Ca(2+) spark generation in certain types of arteries. Their localization within cell membrane caveolae is essential. We summarize present data on local elementary calcium signaling (Ca(2+) sparks) in arterial SMCs with focus on RyR isoforms, large-conductance calcium-dependent potassium (BK(Ca)) channels, and cell membrane-bound calcium channels (Ca(V)1.2 and Ca(V)3.2), particularly in caveolar microdomains

Local regularity for fractional heat equations

We prove the maximal local regularity of weak solutions to the parabolic problem associated with the fractional Laplacian with homogeneous Dirichlet boundary conditions on an arbitrary bounded open set $\Omega\subset\mathbb{R}^N$. Proofs combine classical abstract regularity results for parabolic equations with some new local regularity results for the associated elliptic problems.Comment: arXiv admin note: substantial text overlap with arXiv:1704.0756

Vasodilation of rat skeletal muscle arteries by the novel BK channel opener GoSlo is mediated by the simultaneous activation of BK and Kv7 channels

BACKGROUND AND PURPOSE: BK channels play important roles in various physiological and pathophysiological processes and thus have been the target of several drug development programs focused on creating new efficacious BK channel openers, such as the GoSlo-SR compounds. However, the effect of GoSlo-SR compounds on vascular smooth muscle has not been studied. Therefore, we tested the hypothesis that GoSlo-SR compounds dilate arteries exclusively by activating BK channels. EXPERIMENTAL APPROACH: Experiments were performed on rat Gracilis muscle, saphenous, mesenteric and tail arteries using isobaric and isometric myography, sharp microelectrodes, digital droplet PCR and the patch-clamp technique. KEY RESULTS: GoSlo-SR compounds dilated isobaric and relaxed and hyperpolarized isometric vessel preparations and their effects were abolished after (i) functionally eliminating K channels by pre-constriction with 50 mM KCl or (ii) blocking all K channels known to be expressed in vascular smooth muscle. However, these effects were not blocked when BK channels were inhibited. Surprisingly, the K(V)7 channel inhibitor XE991 reduced their effects considerably, but neither K(V)1 nor K(V)2 channel blockers altered the inhibitory effects of GoSlo-SR. However, the combined blockade of BK and K(V)7 channels abolished the GoSlo-SR-induced relaxation. GoSlo-SR compounds also activated K(V)7.4 and K(V)7.5 channels expressed in HEK 293 cells. CONCLUSIONS AND IMPLICATIONS: This study shows that GoSlo-SR-compounds are effective relaxants in vascular smooth muscle and mediate their effects by a combined activation of BK and K(V)7.4/K(V)7.5 channels. Activation of K(V)1, K(V)2 or K(V)7.1 channels or other vasodilator pathways seem not to be involved

Myogenic vasoconstriction requires canonical Gq/11 signaling of the angiotensin II type 1a receptor in the murine vasculature

BACKGROUND: The myogenic response is an inherent vasoconstrictive property of resistance arteries to keep blood flow constant in response to increases in intravascular pressure. Angiotensin II (Ang II) type 1 receptors (AT1R) are broadly distributed, mechanoactivated receptors, which have been proposed to transduce myogenic vasoconstriction. However, the AT1R subtype(s) involved and their downstream G protein- and β-arrestin-mediated signaling pathways are still elusive. OBJECTIVE: To characterize the function of AT1aR and AT1bR in the regulation of the myogenic response of resistance size arteries and possible downstream signaling cascades mediated by G(q/11) and/or β-arrestins. METHODS: We used Agtr1a(-/-), Agtr1b(-/-) and tamoxifen-inducible smooth muscle-specific AT1aR knockout mice (SM-Agtr1a mice). FR900359, [Sar1, Ile4, Ile8] Ang II (SII) and TRV120055 were used as selective G(q/11) protein inhibitor and biased agonists to activate non-canonical β-arrestin and canonical G(q/11) signaling of the AT1R, respectively. RESULTS: Myogenic and Ang II-induced vasoconstrictions were diminished in the perfused renal vasculature of Agtr1a(-/-) and SM-Agtr1a mice. Similar results were observed in isolated pressurized mesenteric and cerebral arteries. Myogenic tone and Ang II-induced vasoconstrictions were normal in arteries from Agtr1b(-/-) mice. The G(q/11) blocker FR900359 decreased myogenic tone and Ang II vasoconstrictions while selective biased targeting of AT1R β-arrestin signaling pathways had no effects. CONCLUSION: The present study demonstrates that myogenic arterial constriction requires G(q/11)-dependent signaling pathways of mechanoactivated AT1aR but not G protein-independent, noncanonical alternative signaling pathways in the murine mesenteric, cerebral and renal circulation

The PPAR-gamma agonist pioglitazone protects cortical neurons from inflammatory mediators via improvement in peroxisomal function

<p>Abstract</p> <p>Background</p> <p>Inflammation is known to play a pivotal role in mediating neuronal damage and axonal injury in a variety of neurodegenerative disorders. Among the range of inflammatory mediators, nitric oxide and hydrogen peroxide are potent neurotoxic agents. Recent evidence has suggested that oligodendrocyte peroxisomes may play an important role in protecting neurons from inflammatory damage.</p> <p>Methods</p> <p>To assess the influence of peroxisomal activation on nitric oxide mediated neurotoxicity, we investigated the effects of the peroxisomal proliferator activated receptor (PPAR) gamma agonist, pioglitazone in primary cortical neurons that were either exposed to a nitric oxide donor or co-cultured with activated microglia.</p> <p>Results</p> <p>Pioglitazone protected neurons and axons against both nitric-oxide donor-induced and microglia-derived nitric oxide-induced toxicity. Moreover, cortical neurons treated with this compound showed a significant increase in the protein and gene expression of PPAR-gamma, which was associated with a concomitant increase in the enzymatic activity of catalase. In addition, the protection of neurons and axons against hydrogen peroxide-induced toxicity afforded by pioglitazone appeared to be dependent on catalase.</p> <p>Conclusions</p> <p>Collectively, these observations provide evidence that modulation of PPAR-gamma activity and peroxisomal function by pioglitazone attenuates both NO and hydrogen peroxide-mediated neuronal and axonal damage suggesting a new therapeutic approach to protect against neurodegenerative changes associated with neuroinflammation.</p

PD-1 Regulates Neural Damage in Oligodendroglia-Induced Inflammation

We investigated the impact of immune regulatory mechanisms involved in the modulation of the recently presented, CD8+ lymphocyte mediated immune response in a mouse model of oligodendropathy-induced inflammation (PLPtg-mutants). The focus was on the role of the co-inhibitory molecule PD-1, a CD28-related receptor expressed on activated T- and B-lymphocytes associated with immune homeostasis and autoimmunity. PLPtg/PD-1-deficient double mutants and the corresponding bone marrow chimeras were generated and analysed using immunohistochemistry, light- and electron microscopy, with particular emphasis on immune-cell number and neural damage. In addition, the immune cells in both the CNS and the peripheral immune system were investigated by IFN-gamma elispot assays and spectratype analysis. We found that mice with combined pathology exhibited significantly increased numbers of CD4+ and CD8+ T-lymphocytes in the CNS. Lack of PD-1 substantially aggravated the pathological phenotype of the PLPtg mutants compared to genuine PLPtg mutants, whereas the PD-1 deletion alone did not cause alterations in the CNS. CNS T-lymphocytes in PLPtg/PD-1-/- double mutants exhibited massive clonal expansions. Furthermore, PD-1 deficiency was associated with a significantly higher propensity of CNS but not peripheral CD8+ T-cells to secrete proinflammatory cytokines. PD-1 could be identified as a crucial player of tissue homeostasis and immune-mediated damage in a model of oligodendropathy-induced inflammation. Alterations of this regulatory pathway lead to overt neuroinflammation of high pathogenetic impact. Our finding may have implications for understanding the mechanisms leading to the high clinical variability of polygenic or even monogenic disorders of the nervous system