S-Nitrosylation of Histone Deacetylase 2 by Neuronal Nitric Oxide Synthase as a Mechanism of Diastolic Dysfunction

BACKGROUND

Although the clinical importance of heart failure with preserved ejection fraction has been extensively explored, most therapeutic regimens, including nitric oxide (NO) donors, lack therapeutic benefit. Although the clinical characteristics of heart failure with preserved ejection fraction are somewhat heterogeneous, diastolic dysfunction (DD) is one of the most important features. Here we report that neuronal NO synthase (nNOS) induces DD by S-nitrosylation of HDAC2 (histone deacetylase 2).

METHODS

Two animal models of DD-SAUNA (SAlty drinking water/Unilateral Nephrectomy/Aldosterone) and mild transverse aortic constriction mice-as well as human heart samples from patients with left ventricular hypertrophy were used. Genetically modified mice that were either nNOS-ablated or HDAC2 S-nitrosylation-resistant were also challenged. N(ω)-propyl-L-arginine, an nNOS selective inhibitor, and dimethyl fumarate, an NRF2 (nuclear factor erythroid 2-related factor 2) inducer, were used. Molecular events were further checked in human left ventricle specimens.

RESULTS

SAUNA or mild transverse aortic constriction stress impaired diastolic function and exercise tolerance without overt systolic failure. Among the posttranslational modifications tested, S-nitrosylation was most dramatically increased in both models. Utilizing heart samples from both mice and humans, we observed increases in nNOS expression and NO production. N(ω)-propyl-L-arginine alleviated the development of DD in vivo. Similarly, nNOS knockout mice were resistant to SAUNA stress. nNOS-induced S-nitrosylation of HDAC2 was relayed by transnitrosylation of GAPDH. HDAC2 S-nitrosylation was confirmed in both DD mouse and human left ventricular hypertrophy. S-nitrosylation of HDAC2 took place at C262 and C274. When DD was induced, HDAC2 S-nitrosylation was detected in wild-type mouse, but not in HDAC2 knock-in mouse heart that expressed HDAC2 C262A/C274A. In addition, HDAC2 C262A/C274A mice maintained normal diastolic function under DD stimuli. Gene delivery with adenovirus-associated virus 9 (AAV9)-NRF2, a putative denitrosylase of HDAC2, or pharmacological intervention by dimethyl fumarate successfully induced HDAC2 denitrosylation and mitigated DD in vivo.

CONCLUSIONS

Our observations are the first to demonstrate a new mechanism underlying DD pathophysiology. Our results provide theoretical and experimental evidence to explain the ineffectiveness of conventional NO enhancement trials for improving DD with heart failure symptoms. More important, our results suggest that reduction of NO or denitrosylation of HDAC2 may provide a new therapeutic platform for the treatment of refractory heart failure with preserved ejection fraction.

Association Analysis of Neuronal Nitric Oxide Synthase 1 Gene Polymorphism With Psychopathological Symptoms in Chronic Ketamine Users

Objective: We previously found that chronic ketamine usages were associated with various psychotic and cognitive symptoms mimicking schizophrenia. The blockade of the NMDA receptor and subsequent nitric oxide synthase 1 (NOS1) dysfunction were found to be closely correlated with schizophrenia including NOS1 gene polymorphisms. We examined the allelic variants of the gene coding neuronal nitric oxide synthase 1 (NOS1) in chronic ketamine users in the Chinese population and analyzed the association between NOS1 gene polymorphism and psychopathological symptoms in chronic ketamine users. The association between the NOS1 polymorphism and ketamine use characteristics was also examined. Methods: One hundred ninety seven male chronic ketamine users and 82 controls were recruited. Four common SNPs of the NOS1 gene, rs6490121, rs41279104, rs3782206, and rs3782219, were examined by real-time PCR with the TaqMan® assay system. Psychopathological symptoms were assessed using the Positive and Negative Syndrome Scale (PANSS), Beck Depression Inventory (BDI), and the Beck Anxiety Inventory (BAI). Results: The genotype distribution of rs6490121 and rs41279104 in chronic ketamine users was significantly different from that in the control (p = 0.0001 and p = 0.002). The G allele frequency of rs6490121 in ketamine users was higher than that in the control (p = 2.23 * 10^-6, OR = 3.07, 95% CI = 1.93-4.90). The T allele frequency of rs41279104 in chronic ketamine users was higher than that in the control (p = 0.01, OR = 1.76, 95% CI = 1.14-2.72). The BAI score was significantly different among the three genotypic groups of rs6490121 (F = 6.21, p = 0.002) in ketamine users; subjects of genotype AG and GG had a lower score than subjects of genotype AA. The score of the negative symptom subscale of PANSS was significantly different among the three genotypic groups of rs41279104 (F = 5.39, p = 0.005); in ketamine users, subjects of genotype CT and TT had a higher score than subjects of genotype CC. There was no difference in drug use characteristics in different genotypes of the four NOS1 gene polymorphisms tested in ketamine users (p > 0.05).

The contribution of collecting duct NOS1 to the concentrating mechanisms in male and female mice

The collecting duct (CD) concentrates the urine, thereby maintaining body water volume and plasma osmolality within a normal range. The endocrine hormone arginine vasopressin acts in the CD to increase water permeability via the vasopressin 2 receptor (V2R)-aquaporin (AQP) axis. Recent studies have suggested that autocrine factors may also contribute to the regulation of CD water permeability. Nitric oxide is produced predominantly by nitric oxide synthase 1 (NOS1) in the CD and acts as a diuretic during salt loading. The present study sought to determine whether CD NOS1 regulates diuresis during changes in hydration status. Male and female control and CD NOS1 knockout (CDNOS1KO) mice were hydrated (5% sucrose water), water deprived, or acutely challenged with the V2R agonist desmopressin. In male mice, water deprivation resulted in decreased urine flow and increased plasma osmolality, copeptin concentration, and kidney AQP2 abundance independent of CD NOS1. In female control mice, water deprivation reduced urine flow, increased plasma osmolality and copeptin, but did not significantly change total AQP2; however, there was increased basolateral AQP3 localization. Surprisingly, female CDNOS1KO mice while on the sucrose water presented with symptoms of dehydration. Fibroblast growth factor 21, an endocrine regulator of sweetness preference, was significantly higher in female CDNOS1KO mice, suggesting that this was reducing their drive to drink the sucrose water. With acute desmopressin challenge, female CDNOS1KO mice failed to appropriately concentrate their urine, resulting in higher plasma osmolality than controls. In conclusion, CD NOS1 plays only a minor role in urine-concentrating mechanisms.

NOS1 upregulates ABCG2 expression contributing to DDP chemoresistance in ovarian cancer cells

Nitric oxide synthase 1 (NOS1) has been reported to promote various cancer processes including chemoresistance. However, the role of NOS1 in chemoresistance has remained unclear. ATP-binding cassette, subfamily G, member 2 (ABCG2) has been identified as a molecular cause of multidrug resistance in a number of cancer types, including ovarian cancer. The present study observed that in ovarian cancer cells, the expression of ABCG2 was significantly upregulated in response to cis-diamminedichloroplatinum (cisplatin/DDP) treatment, in addition the expression of NOS1 exhibited an increasing trend. Additionally, the levels of NOS1 and ABCG2 in chemoresistant ovarian cancer profiles in Gene Expression Omnibus datasets (GSE26712 and GSE51373) were higher than in chemosensitive profiles. Furthermore, overexpression of NOS1 could upregulate ABCG2 expression, and expression of ABCG2 was inhibited by NOS1 selective inhibitor (N-PLA). In assays of cell survival, NOS1 appeared to increase the potential for DDP resistance, and this effect was reversed by addition of ABCG2 inhibitor (verapamil). The present study indicated that NOS1-induced chemoresistance was partly mediated by the upregulation of ABCG2 expression. This result suggests a link between the expression of NOS1 and the ABCG2-associated chemoresistance in ovarian cancer.