Sirtuins in macrophage immune metabolism: A novel target for cardiovascular disorders

Sirtuins (SIRT1-SIRT7), as a family of NAD+-dependent protein modifying enzymes, have various catalytic functions, such as deacetylases, dealkalylases, and deribonucleases. The Sirtuins family is directly or indirectly involved in pathophysiological processes such as glucolipid metabolism, oxidative stress, DNA repair and inflammatory response through various pathways and assumes an important role in several cardiovascular diseases such as atherosclerosis, myocardial infarction, hypertension and heart failure. A growing number of studies supports that metabolic and bioenergetic reprogramming directs the sequential process of inflammation. Failure of homeostatic restoration leads to many inflammatory diseases, and that macrophages are the central cells involving the inflammatory response and are the main source of inflammatory cytokines. Regulation of cellular metabolism has emerged as a fundamental process controlling macrophage function, but its exact signaling mechanisms remain to be revealed. Understanding the precise molecular basis of metabolic control of macrophage inflammatory processes may provide new approaches for targeting immune metabolism and inflammation. Here, we provide an update of studies in cardiovascular disease on the function and role of sirtuins in macrophage inflammation and metabolism, as well as drug candidates that may interfere with sirtuins, pointing to future prospects in this field.

Oxidative stress and inflammation regulation of sirtuins: New insights into common oral diseases

Sirtuins are a family of nicotinamide adenine dinucleotide (NAD)⁺-dependent histone deacetylases, comprising seven members SIRT1-SIRT7. Sirtuins have been extensively studied in regulating ageing and age-related diseases. Sirtuins are also pivotal modulators in oxidative stress and inflammation, as they can regulate the expression and activation of downstream transcriptional factors (such as Forkhead box protein O3 (FOXO3a), nuclear factor erythroid 2-related factor 2 (Nrf2) and nuclear factor-kappa B (NF-κB)) as well as antioxidant enzymes, through epigenetic modification and post-translational modification. Most importantly, studies have shown that aberrant sirtuins are involved in the pathogenesis of infectious and inflammatory oral diseases, and oral cancer. In this review, we provide a comprehensive overview of the regulatory patterns of sirtuins at multiple levels, and the essential roles of sirtuins in regulating inflammation, oxidative stress, and bone metabolism. We summarize the involvement of sirtuins in several oral diseases such as periodontitis, apical periodontitis, pulpitis, oral candidiasis, oral herpesvirus infections, dental fluorosis, and oral cancer. At last, we discuss the potential utilization of sirtuins as therapeutic targets in oral diseases.

OPN N-glycosylation Promoted Bone Destruction

OBJECTIVES

Exploring the role of OPN N-glycosylation in osteoblasts and osteoclasts.

METHODS

Immunohistochemistry was used to detect the expression of OPN in mice with apical periodontitis. The asparagine at position 79 of the OPN protein was mutated to glutamine, and the above plasmids were transfected into osteoblasts and osteoclasts. The effect of OPN N-glycosylation on proliferation of osteoblasts and osteoclasts was detected by CCK8 assays. Western blotting was used to detect the expression of OPN N-glycosylation on osteoclasts and osteoblasts. Detection of N-glycosylation of OPN activated the NF-κB signaling pathway to regulate osteoblasts and osteoclasts.

RESULTS

OPN increased expression in a mice model of apical periodontitis. The expression curve of OPN resembled a reverse V shape. The OPN N-glycosylation site was identified as 79 by MS. N-glycosylation of OPN promoted the proliferation of osteoclasts. But the N79 glycosylation site of mutant OPN couldn't increase the proliferation of osteoblasts. OPN N-glycosylation modulated the expression of osteoclast- and osteoblast-associated factors through the NF-κB signaling pathway. N-glycosylation of OPN promoted nuclear translocation of NF-κB in osteoclasts and osteoblasts.

CONCLUSIONS

The N-glycosylation site of OPN is 79. N-glycosylation of OPN played an important role in the biological function of OPN protein.

Artemisinin Alleviates Cerebral Ischemia/Reperfusion Injury via Regulation of the Forkhead Transcription Factor O1 Signaling Pathway

The effect and mechanism of artemisinin therapy on cerebral ischemia-reperfusion injury (CIRI) was analyzed in this work. 100 healthy male C57BL/6 mice were selected and randomly divided into the sham group (no treatment), CIRI model group (IR), IR + artemisinin posttreatment group (IR + Arte), EX527 + IR group (EX527 + IR), and EX527 + IR + artemisinin posttreatment group (EX527 + IR + Arte), with 20 mice in each group. The cerebral infarct volumes of mice in different groups were measured by the 2,3,5-triphenyltetrazolium chloride (TTC) staining method. The neurological function scores and oxidative stress levels of mice in different groups were measured and compared. In addition, the expressions of silent information regulator 1 (SIRT1), forkhead transcription factor O1 (FOXO1), and p53 protein in brain tissue were detected. The results showed that the contents of reactive oxygen species (ROS) and malondialdehyde (MDA) in the EX527 + IR group and EX527 + IR + Arte group were significantly higher than those in the IR + Arte group (P < 0.05). The expressions of SIRT1 protein in the brain tissue of the IR group and EX527 + IR group were much lower than that of the sham group (P < 0.01); compared with the IR + Arte group, the expression of the X527 + IR group in the brain tissue was greatly reduced (P < 0.05). The expression levels of FOXO1 protein and p53 protein in the brain tissue of mice in the IR group and EX527 + IR group were higher than those in the sham group (P < 0.01). It was concluded that artemisinin treatment can reduce oxidative stress damage and alleviate CIRI through the SIRT1/FOXO1 signaling pathway, thereby achieving neuroprotective effects.

Epstein-Barr virus reactivation by persistent apical periodontal pathogens

AIM

To assess whether Epstein-Barr virus (EBV) reactivation is triggered by persistent apical periodontitis-related microbes using in vitro and ex vivo methodologies.

METHODOLOGY

Surgically removed human periapical granulomas (n = 50) and healthy gingival tissues (n = 10) were analysed to determine the presence of EBV and seven persistent apical periodontitis-related microbes. In addition, real-time polymerase chain reaction was used to detect the mRNA expression of BZLF-1, an immediate-early gene of EBV. Expression of latent membrane protein (LMP)-1 and ZEBRA, an early lytic protein of EBV encoded by BZLF-1, was also examined using triple-colour immunofluorescence staining. n-Butyric acid produced by the microbes was quantified, and luciferase assays were performed in association with bacterial lysates. In addition, Daudi cells were cultured with bacterial lysates, and the expression levels of BZLF-1 mRNA and ZEBRA protein were determined.

RESULTS

EBV DNA and BZLF-1 mRNA were detected in 47 out of 50 periapical granulomas, but not in healthy gingival tissues. The EBV DNA copy number and the number of Fusobacterium nucleatum were significantly positively correlated with BZLF-1 expression in periapical granulomas. The number of Prevotella intermedia was slightly correlated with BZLF-1 expression; however, the other microbes were not. CD79a-positive B cells in periapical granulomas, but not those in healthy gingival tissues, expressed both LMP-1 and ZEBRA. n-Butyric acid production was the highest in F. nucleatum and the lowest in P. intermedia. Enterococcus faecalis, Candida albicans and the other tested microbes did not produce n-butyric acid. An F. nucleatum lysate exhibited significantly increased BZLF-1-luciferase activity in the same manner of commercial butyric acid, whereas P. intermedia did not. F. nucleatum also induced the expression of BZLF-1 mRNA and ZEBRA protein by Daudi cells, indicating that EBV reactivation was induced.

CONCLUSION

Among the persistent apical periodontitis-related bacteria that were tested, F. nucleatum most strongly reactivated latent EBV, whereas E. faecalis and C. albicans as well as the other microbes did not.

Modulatory Role of SIRT1 and Resistin as Therapeutic Targets in Patients with Aortic Valve Stenosis

BACKGROUND

Inflammatory is one of the main cause of aortic valve stenosis (AS), so discovering novel biomarkers for the targeted therapy of inflammation could be an attractive strategy in AS prevention. The objectives of our study were to clarify the modulatory role of resistin and silent information regulator 1 (SIRT1) before and after surgery and also to evaluate the therapeutic effects of resveratrol.

METHODS

Nineteen AS patients and 15 healthy subjects were studied as the case and control groups, respectively. Peripheral blood mononuclear cells (PBMCs) were isolated and cultured to determine the levels of resistin and SIRT1 and the effects of resveratrol on them.

RESULTS

Significant increase in resistin expression was observed in the patients compare to the control (p ≤0.01), and this upregulation was augmented 72 h following surgery (p ≤0.01). The SIRT1 expression decreased in the AS group compare to the control but this reduction was not significant. Aortic valve replacement caused a higher decrease in the protein (p ≤0.01) and mRNA level (p ≤0.05) of SIRT1. Resveratrol in the AS group significantly diminished the resistin level (p ≤0.05) but increased the SIRT1 level (p ≤0.001).

CONCLUSIONS

In our patients with AS, the resistin level was increased, whereas the expression of SIRT1 was reduced and surgery augmented these alterations. Resveratrol improved inflammation in the PBMCs of the patients through the SIRT1/resistin pathway. These findings suggest that pharmacological therapy with resveratrol might be a novel approach to alleviating inflammation in patients with AS.