miR-193b-3p and miR-346 Exert Antihypertensive Effects in the Rostral Ventrolateral Medulla

BACKGROUND

Rostral ventrolateral medulla (RVLM) neuron hyperactivity raises sympathetic outflow, causing hypertension. MicroRNAs (miRNAs) contribute to diverse biological processes, but their influence on RVLM neuronal excitability and blood pressure (BP) remains widely unexplored.

METHODS AND RESULTS

The RVLM miRNA profiles in spontaneously hypertensive rats were unveiled using RNA sequencing. Potential effects of these miRNAs in reducing neuronal excitability and BP and underlying mechanisms were investigated through various experiments. Six hundred thirty-seven miRNAs were identified, and reduced levels of miR-193b-3p and miR-346 were observed in the RVLM of spontaneously hypertensive rats. Increased miR-193b-3p and miR-346 expression in RVLM lowered neuronal excitability, sympathetic outflow, and BP in spontaneously hypertensive rats. In contrast, suppressing miR-193b-3p and miR-346 expression in RVLM increased neuronal excitability, sympathetic outflow, and BP in Wistar Kyoto and Sprague-Dawley rats. Cdc42 guanine nucleotide exchange factor (Arhgef9) was recognized as a target of miR-193b-3p. Overexpressing miR-193b-3p caused an evident decrease in Arhgef9 expression, resulting in the inhibition of neuronal apoptosis. By contrast, its downregulation produced the opposite effects. Importantly, the decrease in neuronal excitability, sympathetic outflow, and BP observed in spontaneously hypertensive rats due to miR-193b-3p overexpression was greatly counteracted by Arhgef9 upregulation.

CONCLUSIONS

miR-193b-3p and miR-346 are newly identified factors in RVLM that hinder hypertension progression, and the miR-193b-3p/Arhgef9/apoptosis pathway presents a potential mechanism, highlighting the potential of targeting miRNAs for hypertension prevention.

A Multi-Omics Approach to Defining Target Organ Injury in Youth with Primary Hypertension

BACKGROUND

Primary hypertension in childhood tracks into adulthood and may be associated with increased cardiovascular risk. Studies conducted in children and adolescents provide an opportunity to explore the early cardiovascular target organ injury (CV-TOI) in a population free from many of the co-morbid cardiovascular disease risk factors that confound studies in adults.

METHODS

Youths (n=132, mean age 15.8 years) were stratified by blood pressure (BP) as low, elevated, and high-BP and by left ventricular mass index (LVMI) as low- and high-LVMI. Systemic circulating RNA, miRNA, and methylation profiles in peripheral blood mononuclear cells and deep proteome profiles in serum were determined using high-throughput sequencing techniques.

RESULTS

VASH1 gene expression was elevated in youths with high-BP with and without high-LVMI. VASH1 expression levels positively correlated with systolic BP (r=0.3143, p=0.0034). The expression of hsa-miR-335-5p, one of the VASH1- predicted miRNAs, was downregulated in high-BP with high-LVMI youths and was inversely correlated with systolic BP (r=-0.1891, p=0.0489). GSE1 hypermethylation, circulating PROZ upregulation (log 2 FC=0.61, p=0.0049 and log 2 FC=0.62, p=0.0064), and SOD3 downregulation (log 2 FC=-0.70, p=0.0042 and log 2 FC=-0.64, p=0.010) were observed in youths with elevated BP and high-BP with high-LVMI. Comparing the transcriptomic and proteomic profiles revealed elevated HYAL1 levels in youths displaying high-BP and high-LVMI.

CONCLUSIONS

The findings are compatible with a novel blood pressure-associated mechanism that may occur through impaired angiogenesis and extracellular matrix degradation through dysregulation of Vasohibin-1 and Hyaluronidase1 was identified as a possible mediator of CV-TOI in youth with high-BP and suggests strategies for ameliorating TOI in adult-onset primary hypertension.

Evaluating the pro-survival potential of apoptotic bodies derived from 2D- and 3D- cultured adipose stem cells in ischaemic flaps

In the realm of large-area trauma flap transplantation, averting ischaemic necrosis emerges as a pivotal concern. Several key mechanisms, including the promotion of angiogenesis, the inhibition of oxidative stress, the suppression of cell death, and the mitigation of inflammation, are crucial for enhancing skin flap survival. Apoptotic bodies (ABs), arising from cell apoptosis, have recently emerged as significant contributors to these functions. This study engineered three-dimensional (3D)-ABs using tissue-like mouse adipose-derived stem cells (mADSCs) cultured in a 3D environment to compare their superior biological effects against 2D-ABs in bolstering skin flap survival. The findings reveal that 3D-ABs (85.74 ± 4.51) % outperform 2D-ABs (76.48 ± 5.04) % in enhancing the survival rate of ischaemic skin flaps (60.45 ± 8.95) % (all p < 0.05). Mechanistically, they stimulated angiogenesis, mitigated oxidative stress, suppressed apoptosis, and facilitated the transition of macrophages from M1 to M2 polarization (all p < 0.05). A comparative analysis of microRNA (miRNA) profiles in 3D- and 2D-ABs identified several specific miRNAs (miR-423-5p-up, miR30b-5p-down, etc.) with pertinent roles. In summary, ABs derived from mADSCs cultured in a 3D spheroid-like arrangement exhibit heightened biological activity compared to those from 2D-cultured mADSCs and are more effective in promoting ischaemic skin flap survival. These effects are attributed to their influence on specific miRNAs.

Pharmacological and molecular mechanisms of miRNA-based therapies for targeting cardiovascular dysfunction

Advances in understanding gene expression regulation through epigenetic mechanisms have contributed to elucidating the regulatory mechanisms of noncoding RNAs as pharmacological targets in several diseases. MicroRNAs (miRs) are a class of evolutionarily conserved, short, noncoding RNAs regulating in a concerted manner gene expression at the post-transcriptional level by targeting specific sequences of the 3'-untranslated region of mRNA. Conversely, mechanisms of cardiovascular disease (CVD) remain largely elusive due to their life-course origins, multifactorial pathophysiology, and co-morbidities. In this regard, CVD treatment with conventional medications results in therapeutic failure due to progressive resistance to monotherapy, which overlooks the multiple factors involved, and reduced adherence to poly-pharmacology approaches. Consequently, considering its role in regulating complete gene pathways, miR-based drugs have appreciably progressed into preclinical and clinical testing. This review summarizes the current knowledge about the mechanisms of miRs in cardiovascular disease, focusing specifically on describing how clinical chemistry and physics have improved the stability of the miR molecule. In addition, a comprehensive review of the main miRs involved in cardiovascular disease and the clinical trials in which these molecules are used as active pharmacological molecules is provided.

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.

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.

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.