The mammalian brain is highly vulnerable to oxygen deprivation, yet the mechanism underlying the brain's sensitivity to hypoxia is incompletely understood. Hypoxia induces accumulation of hydrogen sulfide, a gas that inhibits mitochondrial respiration. Here, we show that, in mice, rats, and naturally hypoxia-tolerant ground squirrels, the sensitivity of the brain to hypoxia is inversely related to the levels of sulfide:quinone oxidoreductase (SQOR) and the capacity to catabolize sulfide. Silencing SQOR increased the sensitivity of the brain to hypoxia, whereas neuron-specific SQOR expression prevented hypoxia-induced sulfide accumulation, bioenergetic failure, and ischemic brain injury. Excluding SQOR from mitochondria increased sensitivity to hypoxia not only in the brain but also in heart and liver. Pharmacological scavenging of sulfide maintained mitochondrial respiration in hypoxic neurons and made mice resistant to hypoxia. These results illuminate the critical role of sulfide catabolism in energy homeostasis during hypoxia and identify a therapeutic target for ischemic brain injury.

/pdf/sulfide-catabolism-ameliorates-hypoxic-brain-injury-mfqdckkiz9.pdf

Sulfide catabolism ameliorates hypoxic brain injury

-etheno-8-bromoguano-sine-3 ,5 ulated guanylyl cyclases and can bind to and modulate the-cyclic monophosphorothioate, Rp-isomer) is cur-rently considered one of the most permeable, selective, andpotentcGKIinhibitorsavailableforintactcellstudies.Here,wehaveevaluatedthepropertiesofRp-PETusingcGKI-expressingand cGKI-deficient primary vascular smooth muscle cells(VSMCs), purified cGKI isozymes, and an engineered cGMPsensorprotein.cGKIactivityinintactVSMCswasmonitoredbycGMP/cGKI-stimulated cell growth and phosphorylation ofvasodilator-stimulatedphosphoprotein.Unexpectedly,Rp-PET(100 prising an N-terminal regulatory domain with two cGMP-

The Commonly Used cGMP-dependent Protein Kinase Type I (cGKI) Inhibitor Rp-8-Br-PET-cGMPS Can Activate cGKI in Vitro

Mechanisms that limit thrombosis are poorly defined. One of the few known endogenous platelet inhibitors is nitric oxide (NO). NO activates NO sensitive guanylyl cyclase (NO-GC) in platelets, resulting in an increase of cyclic guanosine monophosphate (cGMP). Here we show, using cGMP sensor mice to study spatiotemporal dynamics of platelet cGMP, that NO-induced cGMP production in pre-activated platelets is strongly shear-dependent. We delineate a new mode of platelet-inhibitory mechanotransduction via shear-activated NO-GC followed by cGMP synthesis, activation of cGMP-dependent protein kinase I (cGKI), and suppression of Ca2+ signaling. Correlative profiling of cGMP dynamics and thrombus formation in vivo indicates that high cGMP concentrations in shear-exposed platelets at the thrombus periphery limit thrombosis, primarily through facilitation of thrombus dissolution. We propose that an increase in shear stress during thrombus growth activates the NO-cGMP-cGKI pathway, which acts as an auto-regulatory brake to prevent vessel occlusion, while preserving wound closure under low shear.

/pdf/a-shear-dependent-no-cgmp-cgki-cascade-in-platelets-acts-as-54yu4pvdwf.pdf

A shear-dependent NO-cGMP-cGKI cascade in platelets acts as an auto-regulatory brake of thrombosis

Diabetes mellitus (DM) is one of the principal manifestations of metabolic syndrome and its prevalence with modern lifestyle is increasing incessantly. Chronic hyperglycemia can induce several vascular complications that were referred to be the major cause of morbidity and mortality in DM. Although several therapeutic targets have been identified and accessed clinically, the imminent risk of DM and its prevalence are still ascending. Substantial pieces of evidence revealed that histone deacetylase (HDAC) isoforms can regulate various molecular activities in DM via epigenetic and post-translational regulation of several transcription factors. To date, 18 HDAC isoforms have been identified in mammals that were categorized into four different classes. Classes I, II, and IV are regarded as classical HDACs, which operate through a Zn-based mechanism. In contrast, class III HDACs or Sirtuins depend on nicotinamide adenine dinucleotide (NAD+) for their molecular activity. Functionally, most of the HDAC isoforms can regulate β cell fate, insulin release, insulin expression and signaling, and glucose metabolism. Moreover, the roles of HDAC members have been implicated in the regulation of oxidative stress, inflammation, apoptosis, fibrosis, and other pathological events, which substantially contribute to diabetes-related vascular dysfunctions. Therefore, HDACs could serve as the potential therapeutic target in DM towards developing novel intervention strategies. This review sheds light on the emerging role of HDACs/isoforms in diabetic pathophysiology and emphasized the scope of their targeting in DM for constituting novel interventional strategies for metabolic disorders/complications.

https://www.mdpi.com/2073-4409/10/6/1340/pdf

The Emerging Role of HDACs: Pathology and Therapeutic Targets in Diabetes Mellitus

Secondary structural and functional abnormalities of the neurovascular unit are important pathological mechanisms following traumatic brain injury (TBI). The neurovascular unit maintains blood–brain barrier and vascular integrity through interactions among glial cells, pericytes and endothelial cells. Trauma-induced neuroinflammation and oxidative stress may act as initiating factors for pathological damage after TBI, which in turn impairs cerebral microcirculatory function. Studies have shown that the tumor necrosis factor α (TNF-α)/nuclear factor-κB (NF-κB) pathway regulates inflammation and oxidative damage, but its role in pericyte-mediated cerebral microcirculation are currently unknown. Herein, we assessed TNF-α/NF-κB signaling and inducible nitric oxide synthase (iNOS), and the effects of the TNF-α inhibitor infliximab after TBI. Whether pericyte damage is dependent on the TNF-α/NF-κB/iNOS axis was also evaluated to explore the mechanisms underlying disturbances in the microcirculation after TBI. Microglia are activated after TBI to promote inflammatory factors and free radical release, and upregulate NF-κB and iNOS expression. After lipopolysaccharide treatment, the activity of TNF-α/NF-κB/iNOS in BV2 cells was also upregulated. Inhibition of TNF-α using infliximab reduced NF-κB phosphorylation and nuclear translocation and downregulated iNOS expression, which attenuated the inflammation and oxidative damage. Meanwhile, inhibition of TNF-α reversed pericyte marker loss, and improved pericyte function and microcirculation perfusion after TBI. In conclusion, our study suggests that microglia released TNF-α after TBI, which promoted neuroinflammation and oxidative stress by activating downstream NF-κB/iNOS signals, and this led to pericyte-mediated disturbance of the cerebral microcirculation. 

/pdf/tnf-a-impairs-pericyte-mediated-cerebral-microcirculation-2ssmtqn5.pdf

TNF-α Impairs Pericyte-Mediated Cerebral Microcirculation via the NF-κB/iNOS Axis after Experimental Traumatic Brain Injury

Recent works highlight the therapeutic potential of targeting cyclic guanosine monophosphate (cGMP)-dependent pathways in the context of brain ischemia/reperfusion injury (IRI). Although cGMP-depen...

cGMP-dependent protein kinase I in vascular smooth muscle cells improves ischemic stroke outcome in mice.

Background: Sirt1 is a NAD+ dependent deacetylase that is known as an important metobolic regulator for type 2 diabetes mellitus. To determine the role of Sirt1 in ischemic stroke induced metabolic imbalance, we generated the neuronal specific Sirt1 knock-in (nSirt1 KI) and knock-out (Sirt1 KO) mice and examined its effect and mechanism. Methods: To determine the role of Sirt1 in ischemic stroke induced impaired metabolic actions including insulin and glucose abnormality, we tested the pharmacological effects of metformin and sirtinol. To determine the genetic role of neuronal Sirt1 in the brain, we generated the nSirt1 KI mice. We used the Ischemia/Reperfusion (I/R: 1h MCAO/23h reperfusion) injury model to induce the abnormal metabolic changes. Infarction volume was measured by TTC staining and we determined neurological deficit score (NDS) at 23h after 1h MCAO. The level of glucose was measured by a drop of tail blood using test-strip before, during (every 10 minutes interval), and after MCAO. Results: Metformin reduced infarction volume and sirtinol worsened the infarction volume via Sirt1 signaling pathway. Heterozygous Sirt1 KO (Sirt1+/-) mice showed decreased relative cerebral blood flow and worsen infarction volume in ischemic areas, whereas nSirt1 KI mice exhibited increased rCBF, improved NDS, regulating abnormal blood glucose, and reduced infarction volume by 42% compare to that of littermate control in I/R injury model (n=7, p Conclusion: These findings indicate that the important neuroprotective effect of neuronal cells is mediated by Sirt1 overexpression and suggest that upregulation of neuronal Sirt1 may be an important therapeutic target for ischemic stroke via regulating metabolic imbalance. Disclosure G. Li: None. H. Kim: None. Funding Jeongseon County

Ge Li

Papers

cGMP-dependent protein kinase I in vascular smooth muscle cells improves ischemic stroke outcome in mice.

201-LB: The Neuronal Sirt1 Regulate the Metabolic Imbalance in Ischemic Stroke