Caspase-1 Deficiency Modulates Adipogenesis through Atg7-Mediated Autophagy: An Inflammatory-Independent Mechanism.

Obesity stands as a significant risk factor for type 2 diabetes, hyperlipidemia, and cardiovascular diseases, intertwining increased inflammation and decreased adipogenesis with metabolic disorders. Studies have highlighted the correlation between Caspase-1 and inflammation in obesity, elucidating its essential role in the biological functions of adipose tissue. However, the impact of Caspase-1 on adipogenesis and the underlying mechanisms remain largely elusive. In our study, we observed a positive correlation between Caspase-1 expression and obesity and its association with adipogenesis. In vivo experiments revealed that, under normal diet conditions, Caspase-1 deficiency improved glucose homeostasis, stimulated subcutaneous adipose tissue expansion, and enhanced adipogenesis. Furthermore, our findings indicate that Caspase-1 deficiency promotes the expression of autophagy-related proteins and inhibits autophagy with 3-MA or CQ blocked Caspase-1 deficiency-induced adipogenesis in vitro. Notably, Caspase-1 deficiency promotes adipogenesis via Atg7-mediated autophagy activation. In addition, Caspase-1 deficiency resisted against high-fat diet-induced obesity and glucose intolerance. Our study proposes the downregulation of Caspase-1 as a promising strategy for mitigating obesity and its associated metabolic disorders.

IFN-γ deficiency in the rostral ventrolateral medulla contributes to stress-induced hypertension by impairing microglial synaptic engulfment.

BACKGROUND: Dysfunctional neurons and microglia in the rostral ventrolateral medulla (RVLM) have been implicated in the pathogenesis of stress-induced hypertension (SIH). Functional perturbation of microglial synaptic engulfment can induce aberrant brain circuit activity. IFN-γ is a pleiotropic cytokine that plays a role in regulating neuronal activity. However, existing research on the exploration of the effects of microglia on synapses in the RVLM is lacking, particularly on the function of IFN-γ in microglial synaptic engulfment involved in SIH. METHODS: A SIH rat model was established by electric foot shocks combined with noise stimulation. The underlying mechanism of IFN-γ on synaptic density and microglial synaptic engulfment was investigated through in-vivo and in-vitro experiments involving gain of function, immunofluorescence, quantitative real-time PCR, western blot, and morphometric analysis. Furthermore, the function of IFN-γ in neuronal activity, renal sympathetic nerve activity (RSNA), and blood pressure (BP) regulation was determined through in-vivo and in-vitro experiments involving Ca 2+ imaging, immunofluorescence, platinum-iridium electrode recording, ELISA, the femoral artery cannulation test, and the tail-cuff method. RESULTS: The BP, heart rate, RSNA, plasma norepinephrine, and the number of c-Fos-positive neurons in SIH rats increased compared with those in control rats. Pre and postsynaptic densities in the RVLM also increased in SIH rats. IFN-γ and CCL2 expression levels were significantly reduced in the RVLM of the SIH group, whose microglia also exhibited an impaired capacity for synapse engulfment. IFN-γ elevation increased CCL2 expression and microglial synaptic engulfment and decreased synaptic density in vivo and in vitro . However, CCL2 inhibition reversed these effects. Moreover, the reduction of neuronal excitability, RSNA, plasma norepinephrine, and BP by IFN-γ was abrogated through CCL2 expression. CONCLUSION: IFN-γ deficiency in the RVLM impaired the microglial engulfment of synapses by inhibiting CCL2 expression and increasing synaptic density and neuronal excitability, thereby contributing to SIH progression. Targeting IFN-γ may be considered a potential strategy to combat SIH.

Microglia-derived TNF-α contributes to RVLM neuronal mitochondrial dysfunction via blocking the AMPK-Sirt3 pathway in stress-induced hypertension.

BACKGROUND: Neuroinflammation in the rostral ventrolateral medulla (RVLM) has been associated with the pathogenesis of stress-induced hypertension (SIH). Neuronal mitochondrial dysfunction is involved in many pathological and physiological processes. However, the impact of neuroinflammation on neuronal mitochondrial homeostasis and the involved signaling pathway in the RVLM during SIH are largely unknown. METHODS: The morphology and phenotype of microglia and the neuronal mitochondrial injury in vivo were analyzed by immunofluorescence, Western blot, RT-qPCR, transmission electron microscopy, and kit detection. The underlying mechanisms of microglia-derived tumor necrosis factor-α (TNF-α) on neuronal mitochondrial function were investigated through in vitro and in vivo experiments such as immunofluorescence and Western blot. The effect of TNF-α on blood pressure (BP) regulation was determined in vivo via intra-RVLM microinjection of TNF-α receptor antagonist R7050. RESULTS: The results demonstrated that BP, heart rate (HR), renal sympathetic nerve activity (RSNA), plasma norepinephrine (NE), and electroencephalogram (EEG) power increased in SIH rats. Furthermore, the branching complexity of microglia in the RVLM of SIH rats decreased and polarized into M1 phenotype, accompanied by upregulation of TNF-α. Increased neuronal mitochondria injury was observed in the RVLM of SIH rats. Mechanistically, Sirtuin 3 (Sirt3) and p-AMPK expression were markedly downregulated in both SIH rats and TNF-α-treated N2a cells. AMPK activator A769662 upregulated AMPK-Sirt3 signaling pathway and consequently reversed TNF-α-induced mitochondrial dysfunction. Microinjection of TNF-α receptor antagonist R7050 into the RVLM of SIH rats significantly inhibited the biological activities of TNF-α, increased p-AMPK and Sirt3 levels, and alleviated neuronal mitochondrial injury, thereby reducing c-FOS expression, RSNA, plasma NE, and BP. CONCLUSIONS: This study revealed that microglia-derived TNF-α in the RVLM impairs neuronal mitochondrial function in SIH possibly through inhibiting the AMPK-Sirt3 pathway. Therefore, microglia-derived TNF-α in the RVLM may be a possible therapeutic target for the intervention of SIH.

CircRNA Galntl6 sponges miR-335 to ameliorate stress-induced hypertension through upregulating Lig3 in rostral ventrolateral medulla.

Rostral ventrolateral medulla (RVLM) is thought to serve as a major vasomotor center that participates in controlling the progression of stress-induced hypertension (SIH). Circular RNAs (circRNAs) perform important functions in the regulation of diverse physiological and pathological processes. However, information concerning the functions of RVLM circRNAs on SIH remains limited. RNA sequencing was performed to profile circRNA expression in RVLMs from SIH rats, which were induced by electric foot shocks and noises. The functions of circRNA Galntl6 in reducing blood pressure (BP) and its potential molecular mechanisms on SIH were investigated via various experiments, such as Western blot and intra-RVLM microinjection. A total of 12,242 circRNA transcripts were identified, among which circRNA Galntl6 was dramatically downregulated in SIH rats. The upregulation of circRNA Galntl6 in RVLM effectively decreased the BP, sympathetic outflow, and neuronal excitability in SIH rats. Mechanistically, circRNA Galntl6 directly sponged microRNA-335 (miR-335) and restrained it to reduce oxidative stress. Reintroduction of miR-335 observably reversed the circRNA Galntl6-induced attenuation of oxidative stress. Furthermore, Lig3 can be a direct target of miR-335. MiR-335 inhibition substantially increased the expression of Lig3 and suppressed oxidative stress, and these favorable effects were blocked by Lig3 knockdown. CircRNA Galntl6 is a novel factor that impedes SIH development, and the circRNA Galntl6/miR-335/Lig3 axis represents one of the possible mechanisms. These findings demonstrated circRNA Galntl6 as a possibly useful target for the prevention of SIH.

PDZD8-mediated endoplasmic reticulum-mitochondria associations regulate sympathetic drive and blood pressure through the intervention of neuronal mitochondrial homeostasis in stress-induced hypertension.

Neuronal hyperexcitation in the rostral ventrolateral medulla (RVLM) drives heightened sympathetic nerve activity and contributes to the etiology of stress-induced hypertension (SIH). Maintenance of mitochondrial functions is central to neuronal homeostasis. PDZD8, an endoplasmic reticulum (ER) transmembrane protein, tethers ER to mitochondria. However, the mechanisms of PDZD8-mediated ER-mitochondria associations regulating neuronal mitochondrial functions and thereby mediating blood pressure (BP) in the RVLM of SIH were largely unknown. SIH rats were subjected to intermittent electric foot shocks plus noise for 2 h twice daily for 15 consecutive days. The underlying mechanisms of PDZD8 were investigated through in vitro experiments by using small interfering RNA and through in vivo experiments, such as intra-RVLM microinjection and Western blot analysis. The function of PDZD8 on BP regulation in the RVLM was determined in vivo via the intra-RVLM microinjection of adeno-associated virus (AAV)2-r-Pdzd8. We found that the c-Fos-positive RVLM tyrosine hydroxylase (TH) neurons, renal sympathetic nerve activity (RSNA), plasma norepinephrine (NE) level, BP, and heart rate (HR) were elevated in SIH rats. ER-mitochondria associations in RVLM neurons were significantly reduced in SIH rats. PDZD8 was mainly expressed in RVLM neurons, and mRNA and protein levels were markedly decreased in SIH rats. In N2a cells, PDZD8 knockdown disrupted ER-mitochondria associations and mitochondrial structure, decreased mitochondrial membrane potential (MMP) and respiratory metabolism, enhanced ROS levels, and reduced catalase (CAT) activity. These effects suggested that PDZD8 dysregulation induced mitochondrial malfunction. By contrast, PDZD8 upregulation in the RVLM of SIH rats could rescue neuronal mitochondrial function, thereby suppressing c-Fos expression in TH neurons and decreasing RSNA, plasma NE, BP, and HR. Our results indicated that the dysregulation of PDZD8-mediated ER-mitochondria associations led to the loss of the activity homeostasis of RVLM neurons by disrupting mitochondrial functions, thereby participating in the regulation of SIH pathology.

LncRNA INPP5F ameliorates stress-induced hypertension via the miR-335/Cttn axis in rostral ventrolateral medulla.

AIMS: The rostral ventrolateral medulla (RVLM) is an essential vasomotor center responsible for regulating the development of stress-induced hypertension (SIH). Long non-coding RNAs (lncRNAs) play critical roles in various physiopathology processes, but existing research on the functions of RVLM lncRNAs on SIH has been lacking. In this study, we investigated the roles of RVLM lncRNAs in SIH. METHODS: Genome-wide lncRNA profiles in RVLM were determined by RNA sequencing in a SIH rat model established using electric foot shocks plus noises. The hypotensive effect of lncRNA INPP5F and the underlying mechanisms of lncRNA INPP5F on SIH were explored through in vivo and in vitro experiments, such as intra-RVLM microinjection and immunofluorescence. RESULTS: We discovered 10,179 lncRNA transcripts, among which the lncRNA INPP5F expression level was significantly decreased in SIH rats. Overexpression of lncRNA INPP5F in RVLM dramatically reduced the blood pressure, sympathetic nerve activity, and neuronal excitability of SIH rats. LncRNA INPP5F overexpression markedly increased Cttn expression and reduced neural apoptosis by activating the PI3K-AKT pathway, and its inhibition had opposite effects. Mechanistically, lncRNA INPP5F acted as a sponge of miR-335, which further regulated the Cttn expression. CONCLUSION: LncRNA INPP5F was a key factor that inhibited SIH progression, and the identified lncRNA INPP5F/miR-335/Cttn/PI3K-AKT/apoptosis axis represented one of the possible mechanisms. LncRNA INPP5F could serve as a therapeutic target for SIH.

ASC Regulates Subcutaneous Adipose Tissue Lipogenesis and Lipolysis via p53/AMPKα Axis.

Obesity has become an extensive threat to human health due to associated chronic inflammation and metabolic diseases. Apoptosis-associated speck-like protein (ASC) is a critical link between inflammasome and apoptosis-inducing proteins. In this study, we aimed to clarify the role of ASC in lipid metabolism. With high-fat diet (HFD) and knockout leptin gene mice (ob/ob), we found that ASC expression in subcutaneous adipose tissue (SAT) correlated with obesity. It could also positively regulate the reprogramming of cellular energy metabolism. Stromal vascular fractions (SVF) cells derived from the SAT of Asc-/- mice or SVF from wild-type (WT) mice transfected with ASC siRNA were used to further investigate the underlying molecular mechanisms. We found ASC deficiency could lead to lipogenesis and inhibit lipolysis in SAT, aggravating lipid accumulation and impairing metabolic balance. In addition, our results showed that p53 and AMPKα expression were inhibited in SAT when ASC level was low. p53 and AMP-activated protein kinase α (AMPKα) were then assessed to elucidate whether they were downstream of ASC in regulating lipid metabolism. Our results revealed that ASC deficiency could promote lipid accumulation by increasing lipogenesis and decreasing lipolysis through p53/AMPKα axis. Regulation of ASC on lipid metabolism might be a novel therapeutic target for obesity.

Up-regulation of miR-335 and miR-674-3p in the rostral ventrolateral medulla contributes to stress-induced hypertension.

The rostral ventrolateral medulla (RVLM) is known as the vasomotor center that plays a crucial role in mediating the development of stress-induced hypertension (SIH). MicroRNAs (miRNAs) are involved in many different biological processes and diseases. However, studies that evaluated the roles of miRNAs in the RVLM during SIH do not exist. Here, we performed RNA sequencing to explore the genome-wide miRNA profiles in RVLM in an SIH rat model established by administering electric foot-shocks and noises. The function of miRNAs in blood pressure regulation was determined in vivo via the intra-RVLM microinjection of the agomir or antagomir. Furthermore, the underlying mechanisms of miRNAs on SIH were investigated through in vitro and in vivo experiments, like gain-of-function. We discovered 786 miRNA transcripts among which 4 were differentially expressed. The over-expression of miR-335 and miR-674-3p in RVLM dramatically increased the heart rate (HR), arterial blood pressure (ABP), systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP) levels of normotensive rats, whereas the knockdown of miR-335 and miR-674-3p in RVLM markedly reduced the HR, ABP, SBP, DBP, and MAP levels of SIH rats. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) annotation revealed that miR-335 and miR-674-3p participated in regulating the development of SIH from different aspects, like apoptosis-multiple species pathway. Sphk1, whose expression was markedly decreased in SIH, was identified as a novel target of miR-335. MiR-335 over-expression substantially reduced the expression of Sphk1 and promoted neural apoptosis, and its inhibition had opposite effects. Re-introduction of Sphk1 dramatically abrogated the apoptosis induced by miR-335. This study provides the first systematic dissection of the RVLM miRNA landscape in SIH. MiR-335 and miR-674-3p act as SIH promoters, and the identified miR-335/Sphk1/apoptosis axis represents one of the possible mechanisms. These miRNAs can be exploited as potential targets for the molecular-based therapy of SIH.