Effects of Remote Ischaemic Preconditioning on the Internal Thoracic Artery Nitric Oxide Synthase Isoforms in Patients Undergoing Coronary Artery Bypass Grafting

Remote ischaemic preconditioning (RIPC) is a medical procedure that consists of repeated brief periods of transient ischaemia and reperfusion of distant organs (limbs) with the ability to provide internal organ protection from ischaemia. Even though RIPC has been successfully applied in patients with myocardial infarction during coronary revascularization (surgery/percutaneous angioplasty), the underlying molecular mechanisms are yet to be clarified. Thus, our study aimed to determine the role of nitric oxide synthase (NOS) isoforms in RIPC-induced protection (3 × 5 min of forearm ischaemia with 5 min of reperfusion) of arterial graft in patients undergoing urgent coronary artery bypass grafting (CABG). We examined RIPC effects on specific expression and immunolocalization of three NOS isoforms — endothelial (eNOS), inducible (iNOS) and neuronal (nNOS) in patients’ internal thoracic artery (ITA) used as a graft. We found that the application of RIPC protocol leads to an increased protein expression of eNOS, which was further confirmed with strong eNOS immunopositivity, especially in the endothelium and smooth muscle cells of ITA. The same analysis of two other NOS isoforms, iNOS and nNOS, showed no significant differences between patients undergoing CABG with or without RIPC. Our results demonstrate RIPC-induced upregulation of eNOS in human ITA, pointing to its significance in achieving protective phenotype on a systemic level with important implications for graft patency.

Mitochondrial Dysfunction in Cardiorenal Syndrome 3: Renocardiac Effect of Vitamin C

Cardiorenal syndrome (CRS) is a pathological link between the kidneys and heart, in which an insult in a kidney or heart leads the other organ to incur damage. CRS is classified into five subtypes, and type 3 (CRS3) is characterized by acute kidney injury as a precursor to subsequent cardiovascular changes. Mitochondrial dysfunction and oxidative and nitrosative stress have been reported in the pathophysiology of CRS3. It is known that vitamin C, an antioxidant, has proven protective capacity for cardiac, renal, and vascular endothelial tissues. Therefore, the present study aimed to assess whether vitamin C provides protection to heart and the kidneys in an in vivo CRS3 model. The unilateral renal ischemia and reperfusion (IR) protocol was performed for 60 min in the left kidney of adult mice, with and without vitamin C treatment, immediately after IR or 15 days after IR. Kidneys and hearts were subsequently collected, and the following analyses were conducted: renal morphometric evaluation, serum urea and creatinine levels, high-resolution respirometry, amperometry technique for NO measurement, gene expression of mitochondrial dynamic markers, and NOS. The analyses showed that the left kidney weight was reduced, urea and creatinine levels were increased, mitochondrial oxygen consumption was reduced, NO levels were elevated, and Mfn2 expression was reduced after 15 days of IR compared to the sham group. Oxygen consumption and NO levels in the heart were also reduced. The treatment with vitamin C preserved the left kidney weight, restored renal function, reduced NO levels, decreased iNOS expression, elevated constitutive NOS isoforms, and improved oxygen consumption. In the heart, oxygen consumption and NO levels were improved after vitamin C treatment, whereas the three NOS isoforms were overexpressed. These data indicate that vitamin C provides protection to the kidneys and some beneficial effects to the heart after IR, indicating it may be a preventive approach against cardiorenal insults.

Placental Ischemia Says “NO” to Proper NOS-Mediated Control of Vascular Tone and Blood Pressure in Preeclampsia

In this review, we first provide a brief overview of the nitric oxide synthase (NOS) isoforms and biochemistry. This is followed by describing what is known about NOS-mediated blood pressure control during normal pregnancy. Circulating nitric oxide (NO) bioavailability has been assessed by measuring its metabolites, nitrite (NO2) and/or nitrate (NO3), and shown to rise throughout normal pregnancy in humans and rats and decline postpartum. In contrast, placental malperfusion/ischemia leads to systemic reductions in NO bioavailability leading to maternal endothelial and vascular dysfunction with subsequent development of hypertension in PE. We end this article by describing emergent risk factors for placental malperfusion and ischemic disease and discussing strategies to target the NOS system therapeutically to increase NO bioavailability in preeclamptic patients. Throughout this discussion, we highlight the critical importance that experimental animal studies have played in our current understanding of NOS biology in normal pregnancy and their use in finding novel ways to preserve this signaling pathway to prevent the development, treat symptoms, or reduce the severity of PE.

The Functional Diversity of Nitric Oxide Synthase Isoforms in Human Nose and Paranasal Sinuses: Contrasting Pathophysiological Aspects in Nasal Allergy and Chronic Rhinosinusitis

The human paranasal sinuses are the major source of intrinsic nitric oxide (NO) production in the human airway. NO plays several roles in the maintenance of physiological homeostasis and the regulation of airway inflammation through the expression of three NO synthase (NOS) isoforms. Measuring NO levels can contribute to the diagnosis and assessment of allergic rhinitis (AR) and chronic rhinosinusitis (CRS). In symptomatic AR patients, pro-inflammatory cytokines upregulate the expression of inducible NOS (iNOS) in the inferior turbinate. Excessive amounts of NO cause oxidative damage to cellular components, leading to the deposition of cytotoxic substances. CRS phenotype and endotype classifications have provided insights into modern treatment strategies. Analyses of the production of sinus NO and its metabolites revealed pathobiological diversity that can be exploited for useful biomarkers. Measuring nasal NO based on different NOS activities is a potent tool for specific interventions targeting molecular pathways underlying CRS endotype-specific inflammation. We provide a comprehensive review of the functional diversity of NOS isoforms in the human sinonasal system in relation to these two major nasal disorders’ pathologies. The regulatory mechanisms of NOS expression associated with the substrate bioavailability indicate the involvement of both type 1 and type 2 immune responses.

The role of NO system in low back pain chronicity

Low back pain (LBP) is an important interdisciplinary medical problem, in the development of which various molecular genetics, pathomorphological and pathobiomechanical mechanisms play a role. Intervertebral disc degeneration (IVDD), facet joints arthrosis and myofascial syndrome are the most important pathological processes associated with chronic lower back pain in adults. The nitric oxide (NO) system may play one of the key roles in the development of LBP and its chronicity. (1): Background: The review of publications which are devoted to changes in the NO system in patients with LBP. (2): Materials: We have carried out a search for Russian-language and English-language full-text articles published in e-Library, PubMed, Oxford Press, Clinical Case, Springer, Elsevier, Google Scholar databases. The search was carried out using keywords and their combinations. The search depth was 10 years (2011-2021). (3): Results: Role of NO and various NOsynthase (NOS) isoforms in LBP process demonstrated primarily from animal models to humans. The most studied are the neuronal NOS (nNOS). The role of inducible nose (iNOS) and endothelial (eNOS) - continues to be studied. Associative genetic studies have shown that single nucleotide variants (SNV) of genes encoding all three NOS isoforms (nNOS, NOS1 gene; iNOS, NOS2 gene; eNOS, NOS3 gene) may be associated with chronic LBP. Prospects for the use of NOS inhibitors to modulate the effect of drugs used to treat back pain are discussed. (4): Conclusion: Associative genetic studies of SNV NOS1, NOS2, NOS3 genes are important for understanding genetic predictors of LBP chronicity and development of new personalized pharmacotherapy strategies.

Abstract P51: Temporal Changes In Nitric Oxide Synthase Isoform Expression And Function In Spontaneously Hypertensive Stroke Prone Rats

Introduction: Nitric oxide (NO) has been implicated in the pathogenesis of cerebral small vessel disease (cSVD). NO is produced by three NO synthase (NOS) isoforms including endothelial (eNOS), neuronal (nNOS), and inducible (iNOS). While eNOS has been implicated in cSVD pathologies that occur in Spontaneously Hypertensive Stroke Prone Rats (SHRSP), cSVD model, the mechanistic role and temporal changes of NOS isoform expression including eNOS in relation to cSVD development in SHRSP remains unknown. We aimed to characterize the temporal changes of NOS isoforms expression in SHRSP from the asymptomatic stage until the development of cSVD lesions. Methods: 20 SHRSP and 20 Wistar Kyoto (WKY) male rats were studied. Systolic blood pressure (SBP) was measured weekly using tail-cuff plethysmography. Half of the groups were euthanized at 7 weeks of age and the remaining rats were followed until 24 weeks of age. Routine histology and immunohistochemistry were performed for eNOS, nNOS, iNOS, superoxide radicals (DHE), NO (DAF) and Iba1 for microglia activation. Results: At 7 weeks, SBP was not significantly different between the groups (WKY 106.6±5.4 vs SHRSP 120.8±5.4, P=0.06). SHRSP developed hypertension between 9-11 weeks and maintained it throughout the experiment (SBP (21 weeks): WKY 134.8±5.4 vs 168.9±5.4, P<0.0001). Brain histology was largely negative for cSVD lesions at 7 weeks. At 24 weeks, histology showed areas of demyelination, microbleed formation, arteriosclerosis and hemosiderin deposits in SHRSP. At 7 weeks, compared to WKY, eNOS and nNOS expression were 50% and 30% lower in SHRSP (P=0.0038 and 0.0211, respectively). iNOS expression was 93% higher in SHRSP (P=0.0068). Superoxide levels were 133% higher in SHRSP (P<0.0001) and NO was 40% lower in SHRSP (P<0.0008). At 24 weeks, all of these differences became larger. Iba-1 expression was 25% higher at 7 weeks and became 97% higher in SHRSP at 24 weeks (P<0.0001). Conclusions: SHRSP show significant differences in NOS isoform expression with loss of NO and gain of superoxide production early in life prior to development of cSVD lesions. Superoxide overproduction and related oxidant stress may lead to NOS dysfunction and uncoupling which may trigger cSVD onset and point towards potential future therapies.

Rapid, Nitric Oxide Synthesis-Dependent Activation of MMP-9 at Pericyte Somata During Capillary Ischemia in vivo

Nitric oxide serves essential roles in normal vascular physiology, but paradoxically contributes to vascular pathology in disease. During brain ischemia, aberrant nitric oxide levels can cause cellular injury through induction of nitrosative/oxidative stress and post-translational activation of matrix-metalloproteinase-9 (MMP-9). We recently demonstrated that brain pericyte somata were associated with very early and localized MMP-9 activation along capillaries during cerebral ischemia, leading to focal blood-brain barrier disruption. Here, we tested whether this effect was dependent upon nitric oxide production. In vivo two-photon imaging was used to directly visualize MMP9 activity using a FITC-gelatin probe and leakage of intravenous dye during photothrombotically induced capillary ischemia. Results showed that the NOS inhibitor, L-NIL, at concentrations affecting both iNOS and constitutive NOS isoforms, attenuated capillary leakage at pericyte soma-specific locations and substantially reduced FITC-gelatin cleavage. We also found that combined administration of L-NIL and anisomycin, an inhibitor of protein synthesis, led to near complete elimination of FITC-gelatin cleavage and vascular leakage. These results indicate that both nitric oxide synthase and new protein synthesis are involved in the rapid activation of MMP-9 at somata of capillary pericytes during ischemia.

Human Nitric Oxide Synthase—Its Functions, Polymorphisms, and Inhibitors in the Context of Inflammation, Diabetes and Cardiovascular Diseases

In various diseases, there is an increased production of the free radicals needed to carry out certain physiological processes but their excessive amounts can cause oxidative stress and cell damage. Enzymes play a major role in the transformations associated with free radicals. One of them is nitric oxide synthase (NOS), which catalyzes the formation of nitric oxide (NO). This enzyme exists in three forms (NOS1, NOS2, NOS3), each encoded by a different gene. The following work presents the most important information on the NOS isoforms and their role in the human body, including NO synthesis in various tissues and cells, intercellular signaling and activities supporting the immune system and regulating blood vessel functions. The role of NOS in pathological conditions such as obesity, diabetes and heart disease is considered. Attention is also paid to the influence of the polymorphisms of these genes, encoding particular isoforms, on the development of these pathologies and the role of NOS inhibitors in the treatment of patients.

Chronic L-Name-Treatment Produces Hypertension by Different Mechanisms in Peripheral Tissues and Brain: Role of Central eNOS

The goal of our study was to analyze the time course of the effect of NG-nitro-L-arginine methyl ester (L-NAME) on nitric oxide synthase (NOS) isoforms and nuclear factor–κB (NF-κB) protein expression, total NOS activity, and blood pressure (BP) in rats. Adult 12-week-old male Wistar rats were subjected to treatment with L-NAME (40 mg/kg/day) for four and seven weeks. BP was increased after 4- and 7-week L-NAME treatments. NOS activity decreased after 4-week-L-NAME treatment; however, the 7-week treatment increased NOS activity in the aorta, heart, and kidney, while it markedly decreased NOS activity in the brainstem, cerebellum, and brain cortex. The 4-week-L-NAME treatment increased eNOS expression in the aorta, heart, and kidney and this increase was amplified after 7 weeks of treatment. In the brain regions, eNOS expression remained unchanged after 4-week L-NAME treatment and prolonged treatment led to a significant decrease of eNOS expression in these tissues. NF-κB expression increased in both peripheral and brain tissues after 4 weeks of treatment and prolongation of treatment decreased the expression in the aorta, heart, and kidney. In conclusion, decreased expression of eNOS in the brain regions after 7-week L-NAME treatment may be responsible for a remarkable decrease of NOS activity in these regions. Since the BP increase persisted after 7 weeks of L-NAME treatment, we hypothesize that central regulation of BP may contribute significantly to L-NAME-induced hypertension.

Abstract 12692: Overexpression of Myocardial Inducible Nitric Oxide Synthase Exacerbates Cardiac Dysfunction and Beta-Adrenergic Desensitization in Streptozotocin-Induced Diabetic Mice

Background: Recent evidence links impaired nitric oxide (NO) signaling pathway in the pathogenesis of diabetes-induced cardiac dysfunction. However, the different nitric oxide synthases (NOS) isoforms involved in this pathology are controversial. Recent reports have shown that in failing myocardium, increased inducible NOS (iNOS) contributes to the attenuation of β-adrenergic receptor (AR)-mediated inotropic effect. The alteration and functional significance of cardiac iNOS in diabetic cardiomyopathy (DCM) are unclear. We assessed the hypothesis that increased cardiomyocyte iNOS expression and stimulation may inhibit myocyte contraction, relaxation, [Ca 2+ ] i transient ([Ca 2+ ] iT ), and depress its response to β-AR stimulation, thereby directly contributing to the functional impairment in DCM. Methods: Left ventricular (LV) myocyte protein levels of 3 NOS and myocyte functional responses were evaluated in 2 groups of wild-type female mice (11/group): control and DCM-induced by streptozotocin (STZ) (at 10 weeks after receiving 200 mg/kg STZ, ip). In DCM, we further assessed myocyte contractile and ([Ca 2+ ] iT ) responses to β-AR stimulation by isoproterenol (ISO, 10 -8 M) with and without pretreatment of myocytes with a selective iNOS inhibitor, 1400W (10 -5 M). Results: Compared with controls, DCM myocytes had significantly increased iNOS (1.76 vs 1.03) with decreased eNOS (0.29 vs 0.34), but relatively unchanged nNOS (0.17 vs 0.18). These changes were followed by significantly reduced basal cell contraction (dL/dt max , 73.8 vs 140.7 μm/s), relaxation (dR/dt max , 61.5 vs 121.1 μm/s) and [Ca 2+ ] iT (0.17 vs 0.20). ISO-stimulated increases in dL/dt max (32% vs 59%), dR/dt max (30% vs 55%) and [Ca 2+ ] iT (17% vs 31%) were also significantly reduced. Moreover, in DCM myocytes, pretreatment with 1400W markedly improved myocyte basal contraction (128.0 μm/s) and relaxation (111.7 μm/s). The ISO-induced increases in dL/dt max (55%), dR/dt max (52%), and [Ca 2+ ] iT (29%) were also significantly augmented. Conclusions: Our findings indicate that myocardial iNOS is activated in diabetic mice and suggest that increased iNOS expression contributes to depressed myocardial contractility, impaired [Ca 2+ ] i regulation and β-adrenergic hyporesponsiveness.