Excess phosphate promotes SARS­CoV­2 N protein­induced NLRP3 inflammasome activation via the SCAP­SREBP2 signaling pathway.

Hyperphosphatemia or severe acute respiratory syndrome coronavirus 2 (SARS­CoV­2) infection can promote cardiovascular adverse events in patients with chronic kidney disease. Hyperphosphatemia is associated with elevated inflammation and sterol regulatory element binding protein 2 (SREBP2) activation, but the underlying mechanisms in SARS­CoV­2 that are related to cardiovascular disease remain unclear. The present study aimed to elucidate the role of excess inorganic phosphate (PI) in SARS­CoV­2 N protein­induced NLRP3 inflammasome activation and the underlying mechanisms in vascular smooth muscle cells (VSMCs). The expression levels of SARS­CoV­2 N protein, SREBP cleavage­activating protein (SCAP), mature N­terminal SREBP2, NLRP3, procaspase­1, cleaved caspase­1, IL­1ß and IL­18 were examined by western blotting. The expression levels of SREBP2, HMG­CoA reductase, HMGCS1, low density lipoprotein receptor, proprotein convertase subtilisin/kexin type 9 (PCSK9), SREBP1c, fatty acid synthase, stearyl coenzyme A desaturase 1, acetyl­CoA carboxylase α and ATP­citrate lyase were determined by reverse transcription­quantitative PCR. The translocation of SCAP or NLRP3 from the endoplasmic reticulum to the Golgi was detected by confocal microscopy. The results showed that excess PI promoted SCAP­SREBP and NLRP3 complex translocation to the Golgi, potentially leading to NLRP3 inflammasome activation and lipogenic gene expression. Furthermore, PI amplified SARS­CoV­2 N protein­induced inflammation via the SCAP­SREBP pathway, which facilitates NLRP3 inflammasome assembly and activation. Inhibition of phosphate uptake with phosphonoformate sodium alleviated NLRP3 inflammasome activation and reduced SREBP­mediated lipogenic gene expression in VSMCs stimulated with PI and with SARS­CoV­2 N protein overexpression. Inhibition of SREBP2 or small interfering RNA­induced silencing of SREBP2 effectively suppressed the effect of PI and SARS­CoV­2 N protein on NLRP3 inflammasome activation and lipogenic gene expression. In conclusion, the present study identified that PI amplified SARS­CoV­2 N protein­induced NLRP3 inflammasome activation and lipogenic gene expression via the SCAP­SREBP signaling pathway.

SARS-CoV-2 nucleocapsid protein promotes TMAO-induced NLRP3 inflammasome activation by SCAP-SREBP signaling pathway.

The sterol regulatory element-binding protein (SREBP) activation and cytokine level were significantly increased in coronavirus disease-19. The NLRP3 inflammasome is an amplifier for cellular inflammation. This study aimed to elucidate the modulatory effect of SARS-CoV-2 nucleocapsid protein (SARS-CoV-2 NP) on trimethylamine N-oxide (TMAO)-induced lipogenesis and NLRP3 inflammasome activation and the underlying mechanisms in vascular smooth muscle cells (VSMCs). Our data indicated that SARS-CoV-2 NP activates the dissociation of the SREBP cleavage activating protein (SCAP) from the endoplasmic reticulum, resulting in SREBP activation, increased lipogenic gene expression, and NLRP3 inflammasome activation. TMAO was applied to VSMC-induced NLRP3 inflammasome by promoting the SCAP-SREBP complex endoplasmic reticulum-to-Golgi translocation, which facilitates directly binding of SARS-CoV-2 NP to the NLRP3 protein for NLRP3 inflammasome assembly. SARS-CoV-2 NP amplified the TMAO-induced lipogenic gene expression and NLRP3 inflammasome. Knockdown of SCAP-SREBP2 can effectively reduce lipogenic gene expression and alleviate NLRP3 inflammasome-mediated systemic inflammation in VSMCs stimulated with TMAO and SARS-CoV-2 NP. These results reveal that SARS-CoV-2 NP amplified TMAO-induced lipogenesis and NLRP3 inflammasome activation via priming the SCAP-SREBP signaling pathway.

Hydrogen sulfide attenuates TMAO­induced macrophage inflammation through increased SIRT1 sulfhydration.

Chronic inflammation is a key factor that accelerates the progression of inflammatory vascular disease. Hydrogen sulfide (H2S) has potent anti­inflammatory effects; however, its underlying mechanism of action has not been fully elucidated. The present study aimed to investigate the potential effect of H2S on sirtuin 1 (SIRT1) sulfhydration in trimethylamine N­oxide (TMAO)­induced macrophage inflammation, and its underlying mechanism. Pro­inflammatory M1 cytokines (MCP­1, IL­1ß, and IL­6) and anti­inflammatory M2 cytokines (IL­4 and IL­10) were detected by RT­qPCR. CSE, p65 NF­κB, p­p65 NF­κB, IL­1ß, IL­6 and TNF­α levels were measured by Western blot. The results revealed that cystathionine γ­lyase protein expression was negatively associated with TMAO­induced inflammation. Sodium hydrosulfide (a donor of H2S) increased SIRT1 expression and inhibited the expression of inflammatory cytokines in TMAO­stimulated macrophages. Furthermore, nicotinamide, a SIRT1 inhibitor, antagonized the protective effect of H2S, which contributed to P65 NF­κB phosphorylation and upregulated the expression of inflammatory factors in macrophages. H2S ameliorated TMAO­induced activation of the NF­κB signaling pathway via SIRT1 sulfhydration. Moreover, the antagonistic effect of H2S on inflammatory activation was largely eliminated by the desulfhydration reagent dithiothreitol. These results indicated that H2S may prevent TMAO­induced macrophage inflammation by reducing P65 NF­κB phosphorylation via the upregulation and sulfhydration of SIRT1, suggesting that H2S may be used to treat inflammatory vascular diseases.

Role of PCSK9 in lipid metabolism and atherosclerosis.

Elevated plasma low-density lipoprotein cholesterol (LDL-C) is an important risk factor for cardiovascular diseases. Statins are the most widely used therapy for patients with hyperlipidemia. However, a significant residual cardiovascular risk remains in some patients even after maximally tolerated statin therapy. Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a new pharmacologically therapeutic target for decreasing LDL-C. PCSK9 reduces LDL intake from circulation by enhancing LDLR degradation and preventing LDLR recirculation to the cell surface. Moreover, PCSK9 inhibitors have been approved for patients with either familial hypercholesterolemia or atherosclerotic cardiovascular disease, who require additional reduction of LDL-C. In addition, PCSK9 inhibition combined with statins has been used as a new approach to help reduce LDL-C levels in patients with either statin intolerance or unattainable LDL goal. This review will discuss the emerging anti-PCSK9 therapies in the regulation of cholesterol metabolism and atherosclerosis.

Molecular mechanisms of autophagy in cardiac ischemia/reperfusion injury (Review).

Autophagy is a maintenance process for recycling long-lived proteins and cytoplasmic organelles. The level of this process is enhanced during ischemia/reperfusion (I/R) injury. Autophagy can trigger survival signaling in myocardial ischemia, whereas defective autophagy during reperfusion is detrimental. Autophagy can be regulated through multiple signaling pathways in I/R, including Beclin­1/class III phosphatidylinositol­3 kinase (PI­3K), adenosine monophosphate activated protein kinase/mammalian target of rapamycin (mTOR), and PI­3K/protein kinase B/mTOR pathways, which consequently lead to different functions. Thus, autophagy has both protective and detrimental functions, which are determined by different signaling pathways and conditions. Targeting the activation of autophagy can be a promising new therapeutic strategy for treating cardiovascular disease.

Production and identification of haploid dwarf male sterile wheat plants induced by corn inducer.

BACKGROUND: Using the cross of wheat and maize is a very useful way to produce wheat haploid plants by chromosome elimination. Dwarf male sterile wheat (DMSW) and corn inducer are potential important germplasm for wheat breeding by recurrent selection and doubled haploid strategies. There is no report yet to achieve the haploid plants from DMSW induced by maize inbred line and especially the corn inducer. RESULTS: Haploid plants of DMSW were successfully obtained in this study induced by both maize pollens of inducer line and normal inbred line. The efficiencies for wheat embryos formation and plantlets production induced by the two corn lines had no significant difference. All the eleven haploid wheat plants derived from the male sterile material were identified by botanic appearance, cytology, cytogenetics, and molecular markers. They were all haploid based on their guard cell length of 42.78-42.90 µm compared with the diploid control of 71.52 µm, and their chromosome number of 21 compared with the diploid control of 42. In addition, according to anthers, plant height, and molecular markers, the haploid plants were divided into two types. Eight of them showed dwarf, having no anthers, and the special band of Rht10, and the other three plants displayed normal plant height, having anthers, and not containing the special band of Rht10, indicating that they were originated from the MS2/Rht10 and ms2/rht10 female gametes, respectively. CONCLUSIONS: MS2/Rht10 haploid plants were successfully obtained in this study by using corn inducer and inbred line, and will be employed as candidate materials for the potential cloning of MS2 dominant male gene.