Redox Switches Controlling Nitric Oxide Signaling in the Resistance Vasculature and Implications for Blood Pressure Regulation: Mid-Career Award for Research Excellence 2020

Regulatory effects of curcumin on nitric oxide signaling in the cardiovascular system

The continuously rising prevalence of cardiovascular disease (CVD) globally substantially impacts the economic growth of developing countries. Indeed, one of the leading causes of death worldwide is unfavorable cardiovascular events. Reduced nitric oxide (NO) generation is the pathogenic foundation of endothelial dysfunction, which is regarded as the first stage in the development of a number of CVDs. Nitric oxide exerts an array of biological effects, including vasodilation, the suppression of vascular smooth muscle cell proliferation and the functional control of cardiac cells. Numerous treatment strategies aim to increase NO synthesis or upregulate downstream NO signaling pathways. The major component of Curcuma longa, curcumin, has long been utilized in traditional medicine to treat various illnesses, especially CVDs. Curcumin improves CV function as well as having important pleiotropic effects, such as anti-inflammatory and antioxidant, through its ability to increase the bioavailability of NO and to positively impact NO-related signaling pathways. In this review, we discuss the scientific literature relating to curcumin's positive effects on NO signaling and vascular endothelial function.

COMMD5 is involved in the mechanisms of hypotension after parathyroidectomy in patients receiving hemodialysis

BACKGROUND

Secondary hyperparathyroidism (SHPT) is a common complication of end-stage renal disease. Parathyroidectomy (PTx) is often employed for treatment of severe SHPT. However, PTx may cause hypotension via unknown mechanisms. COMM domain-containing protein 5 (COMMD5) in the parathyroid glands has been linked to blood pressure regulation of spontaneously hypertensive rats.

OBJECTIVE

To explore the relationship between COMMD5 levels and reduced BP after PTx in patients receiving hemodialysis (HD).

METHODS AND RESULTS

(1) The study cohort included 31 patients receiving HD who underwent PTx. Serum COMMD5 levels were higher post-PTx vs. pre-PTx. (2) Sprague-Dawley rats (n = 22) were assigned to a 5/6 nephrectomy group or sham surgery group, vascular rings of the thoracic aorta from rats with CKD were incubated with COMMD5, and changes in vascular tension were compared. COMMD5 inhibited vasoconstriction of vascular rings with intact endothelium, but had no effect on vascular rings without the endothelium. (3) Human umbilical vein endothelial cells were stimulated with COMMD5 or small interfering RNA (siRNA). The expression levels of atrial natriuretic peptide (ANP) and endothelial nitric oxide synthase (eNOS) were up-regulated and down-regulated, respectively.

CONCLUSIONS

Serum COMMD5 levels were increased after PTx in SHPT patients. COMMD5 promoted high expression of ANP and eNOS in endothelial cells, leading to vasodilation and resulting in hypotension.

S1P (Sphingosine-1-Phosphate)-Induced Vasodilation in Human Resistance Arterioles During Health and Disease

BACKGROUND

Preclinical studies suggest that S1P (sphingosine-1-phosphate) influences blood pressure regulation primarily through NO-induced vasodilation. Because microvascular tone significantly contributes to mean arterial pressure, the mechanism of S1P on human resistance arterioles was investigated. We hypothesized that S1P induces NO-mediated vasodilation in human arterioles from adults without coronary artery disease (non-coronary artery disease) through activation of 2 receptors, S1PR1 (S1P receptor 1) and S1PR3 (S1P receptor 3). Furthermore, we tested whether this mechanism is altered in vessels from patients diagnosed with coronary artery disease.

METHODS

Human arterioles (50-200 µm in luminal diameter) were dissected from otherwise discarded surgical adipose tissue, cannulated, and pressurized. Following equilibration, resistance vessels were preconstricted with ET-1 (endothelin-1) and changes in internal diameter to increasing concentrations of S1P (10-12 to 10-7 M) in the presence or absence of various inhibitors were measured.

RESULTS

S1P resulted in significant dilation that was abolished in vessels treated with S1PR1 and S1PR3 inhibitors and in vessels with reduced expression of each receptor. Dilation to S1P was significantly reduced in the presence of the NOS (NO synthase) inhibitor Nω-nitro-L-arginine methyl ester and the NO scavenger 2-4-(carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide. Interestingly, dilation was also significantly impaired in the presence of PEG-catalase (polyethylene glycol-catalase), apocynin, and specific inhibitors of NOX (NADPH oxidases) 2 and 4. Dilation in vessels from patients diagnosed with coronary artery disease was dependent on H2O2 alone which was only dependent on S1PR3 activation.

CONCLUSIONS

These translational studies highlight the inter-species variation observed in vascular signaling and provide insight into the mechanism by which S1P regulates microvascular resistance and ultimately blood pressure in humans.

Soluble guanylyl cyclase mediates noncanonical nitric oxide signaling by nitrosothiol transfer under oxidative stress

Soluble guanylyl cyclase (GC1) is an α/β heterodimer producing cGMP when stimulated by nitric oxide (NO). The NO-GC1-cGMP pathway is essential for cardiovascular homeostasis but is disrupted by oxidative stress, which causes GC1 desensitization to NO by heme oxidation and S-nitrosation (SNO) of specific cysteines. We discovered that under these conditions, GC1-α subunit increases cellular S-nitrosation via transfer of nitrosothiols to other proteins (transnitrosation) in cardiac and smooth muscle cells. One of the GC1 SNO-targets was the oxidized form of Thioredoxin1 (oTrx1), which is unidirectionally transnitrosated by GC1 with αC610 as a SNO-donor. Because oTrx1 itself drives transnitrosation, we sought and identified SNO-proteins targeted by both GC1 and Trx1. We found that transnitrosation of the small GTPase RhoA by SNO-GC1 requires oTrx1 as a nitrosothiol relay, suggesting a SNO-GC1→oTrx1→RhoA cascade. The RhoA signaling pathway, which is antagonized by the canonical NO-cGMP pathway, was alternatively inhibited by GC1-α-dependent S-nitrosation under oxidative conditions. We propose that SNO-GC1, via transnitrosation, mediates adaptive responses triggered by oxidation of the canonical NO-cGMP pathway.

Mitochondrial Dysfunction: An Emerging Link in the Pathophysiology of Cardiorenal Syndrome

The crosstalk between the heart and kidney is carried out through various bidirectional pathways. Cardiorenal syndrome (CRS) is a pathological condition in which acute or chronic dysfunction in the heart or kidneys induces acute or chronic dysfunction of the other organ. Complex hemodynamic factors and biochemical and hormonal pathways contribute to the development of CRS. In addition to playing a critical role in generating metabolic energy in eukaryotic cells and serving as signaling hubs during several vital processes, mitochondria rapidly sense and respond to a wide range of stress stimuli in the external environment. Impaired adaptive responses ultimately lead to mitochondrial dysfunction, inducing cell death and tissue damage. Subsequently, these changes result in organ failure and trigger a vicious cycle. In vitro and animal studies have identified an important role of mitochondrial dysfunction in heart failure (HF) and chronic kidney disease (CKD). Maintaining mitochondrial homeostasis may be a promising therapeutic strategy to interrupt the vicious cycle between HF and acute kidney injury (AKI)/CKD. In this review, we hypothesize that mitochondrial dysfunction may also play a central role in the development and progression of CRS. We first focus on the role of mitochondrial dysfunction in the pathophysiology of HF and AKI/CKD, then discuss the current research evidence supporting that mitochondrial dysfunction is involved in various types of CRS.

Tri-iodide and vanadium chloride based chemiluminescent methods for quantification of nitrogen oxides

Nitric Oxide (NO) is an important signaling molecule that plays roles in controlling vascular tone, hemostasis, host defense, and many other physiological functions. Low NO bioavailability contributes to pathology and NO administration has therapeutic potential in a variety of diseases. Thus, accurate measurements of NO bioavailability and reactivity are critical. Due to its short lifetime in vivo and many in vitro conditions, NO bioavailability and reactivity are often best determined by measuring NO congeners and metabolites that are more stable. Chemiluminescence-based detection of NO following chemical reduction of these compounds using the tri-iodide and vanadium chloride methods have been widely used in a variety of clinical and laboratory studies. In this review, we describe these methods used to detect nitrite, nitrate, nitrosothiols and other species and discuss limitations and proper controls.