Susan Diana Brain

BACKGROUND: Thoracic aortic dissection (TAD) is a life-threatening aortic disease without effective medical treatment. Disruption of vascular smooth muscle cell (VSMC) homeostasis plays a vital role in triggering TAD. ELA (ELABELA) is a novel endogenous ligand for APJ (angiotensin receptor AT1–related receptor protein). However, the effects of ELA on TAD formation and development remain elusive. METHODS: Four-week-old C57BL/6J male mice were treated with β-aminopropionitrile monofumarate or β-aminopropionitrile monofumarate combined with Ang II (angiotensin II) to induce TAD models, and the aortic rupture occurred mainly in the descending thoracic region. ELA or saline was infused via osmotic minipumps into mice for 4 weeks. Transcriptomic studies and VSMC-derived conditioned medium were used to investigate the downstream molecular mechanisms of ELA. RESULTS: ELA infusion mitigated TAD development and prevented aortic media degradation in mice, which was reversed by APJ antagonist ML221. Exogenous ELA prevented the disruption of VSMC homeostasis under PDGF (platelet-derived growth factor) stimulation in VSMCs. Based on transcriptomic studies, we showed that ELA significantly inhibits NLRP3 (NLR family pyrin domain-containing 3)/IL (interleukin)-1β pathway activation and modulates NET (neutrophil extracellular trap) formation in vivo and in vitro. In human neutrophils, ELA significantly inhibited NETs’ formation, which is prevented by reactive oxidative species supplementation. Using VSMC-derived conditioned medium, we showed that NLRP3/IL-1β–related NETs’ formation connects cellular signaling from VSMCs to neutrophils, leading to disruption of VSMC homeostasis. Notably, ELA was downregulated in both plasma and aortic tissues of human TAD, and lower plasma ELA levels were associated with an increased risk of TAD. CONCLUSIONS: We provide evidence that ELA prevents TAD progression and aortic medial degeneration, primarily by maintaining VSMC homeostasis, which may be linked to the inhibition of NETosis in neutrophils and NLRP3/IL-1β–related cellular signaling between VSMCs and neutrophils. ELA shows promise as a target for pharmacological therapy and diagnostic TAD management.

Background and Purpose: Endothelial cells play central roles in increasing vascular permeability and leukocyte recruitment. Therapeutic approaches for treating endothelial cell barrier dysfunction to reduce unwanted fluid accumulation in tissues are limited. Phosphatidylinositol‐4,5‐bisphosphate 3‐kinase (PI3K) enzymes are implicated in signalling inflammatory endothelial permeability and leukocyte recruitment. We investigated the ability of PI3K inhibitors to influence cutaneous oedema formation and neutrophil accumulation. Experimental Approach: We used cultured endothelial cells to determine the effects of inflammatory mediators on permeability and vascular leakage, and a murine model of vascular inflammation in mouse skin in vivo . The effects of inflammatory mediators that induce vascular leakage and neutrophil accumulation (TNFα, IL‐1β and C5a) were examined, with the neuropeptides substance P and α‐CGRP used as controls. The ability of PI3K inhibitors to modulate inflammatory responses was studied. Key Results: A broad spectrum PI3K inhibitor (PI‐103) and a selective inhibitor of the class 1A p110α catalytic subunit (BYL‐719/alpelisib) inhibited endothelial morphological changes and permeability induced by TNFα and IL‐1β in vitro . In vivo , oedema and neutrophil accumulation induced by TNFα and IL‐1β, but not by the complement fragment C5a, is inhibited by BYL‐719, whereas PI‐103 blocks effects of all three mediators. Neither influences the acute oedema formation induced by neuropeptides. Conclusions and Implications: Selective p110α inhibition of vascular inflammation may provide a novel therapeutic pathway for limiting adverse tissue swelling. Moreover, the limited effect of BYL‐719 on C5a‐mediated responses implies that this innate component of the immune response will continue to provide essential defence activity during p110α blockade.

Chikungunya virus (CHIKV), the causative agent of the chikungunya fever, is an alphavirus widely transmitted by the bite of the female mosquito of the genus Aedes sp., especially in tropical and subtropical regions. Brazil is the country most affected by the microorganism. CHIKV classically induces articular pain, which can become long lasting for even years in a great number of the infected individuals, reducing their quality of life. The mechanisms of CHIKV-induced pain are poorly understood, but recent evidence indicated a role for the transient receptor potential vanilloid 1 (TRPV1) in this pathology. Herein, we assessed the ability of intra-articularly injected inactivated CHIKV or its RNA to trigger nociception in mice. Both stimuli induced bilateral secondary hyperalgesia to mechanical and heat stimuli. These responses were attenuated by TRPV1 ablation or antagonism. Joint structural alterations and increased cartilage TRPV1 protein expression were detected in the ipsilateral knee joints injected with either CHIKV or viral RNA. However, the lack of this receptor did not influence the histological changes triggered by CHIKV or RNA. The results further support the role of TRPV1 in CHIKV-induced pain and highlight its importance in the chronic phase of the disease.

Dysregulation of endothelial barrier integrity can lead to vascular leak and potentially fatal oedema. TNF-α controls endothelial permeability during inflammation and requires the actin organizing Ezrin-Radixin-Moesin (ERM) proteins. We identified TRAF2 and NCK-interacting kinase (TNIK) as a kinase directly phosphorylating and activating ERM, specifically at the plasma membrane of primary human endothelial cells. TNIK mediates TNF-α–dependent cellular stiffness and paracellular gap formation in vitro and is essential in driving inflammatory oedema formation in vivo. Unlike its homologs, TNIK activity is negatively and reversibly regulated by H ₂ O ₂ -mediated oxidation of C202 within the kinase domain. TNIK oxidation results in intermolecular disulfide bond formation and loss of kinase activity. Pharmacologic inhibition of endogenous reactive oxygen species production in endothelial cells elevated TNIK-dependent ERM phosphorylation, endothelial cell contraction, and cell rounding. Together, we highlight an interplay between TNIK, ERM phosphorylation, and redox signalling in regulating TNF-induced endothelial cell permeability.

TRPC5 is a non-selective cation channel that is expressed in cardiomyocytes, but there is a lack of knowledge of its (patho)physiological role in vivo. Here, we examine the role of TRPC5 on cardiac function under basal conditions and during cardiac hypertrophy. Cardiovascular parameters were assessed in wild-type (WT) and global TRPC5 knockout (KO) mice. Despite no difference in blood pressure or activity, heart rate was significantly reduced in TRPC5 KO mice. Echocardiography imaging revealed an increase in stroke volume, but cardiac contractility was unaffected. The reduced heart rate persisted in isolated TRPC5 KO hearts, suggesting changes in basal cardiac pacing. Heart rate was further investigated by evaluating the reflex change following drug-induced pressure changes. The reflex bradycardic response following phenylephrine was greater in TRPC5 KO mice but the tachycardic response to SNP was unchanged, indicating an enhancement in the parasympathetic control of the heart rate. Moreover, the reduction in heart rate to carbachol was greater in isolated TRPC5 KO hearts. To evaluate the role of TRPC5 in cardiac pathology, mice were subjected to abdominal aortic banding (AAB). An exaggerated cardiac hypertrophy response to AAB was observed in TRPC5 KO mice, with an increased expression of hypertrophy markers, fibrosis, reactive oxygen species, and angiogenesis. This study provides novel evidence for a direct effect of TRPC5 on cardiac function. We propose that (1) TRPC5 is required for maintaining heart rate by regulating basal cardiac pacing and in response to pressure lowering, and (2) TRPC5 protects against pathological cardiac hypertrophy.

The combustion of fossil fuels contributes to air pollution (AP), which was linked to about 8.79 million global deaths in 2018, mainly due to respiratory and cardiovascular-related effects. Among these, particulate air pollution (PM2.5) stands out as a major risk factor for heart health, especially during vulnerable phases. Our prior study showed that premature exposure to 1,2-naphthoquinone (1,2-NQ), a chemical found in diesel exhaust particles (DEP), exacerbated asthma in adulthood. Moreover, increased concentration of 1,2-NQ contributed to airway inflammation triggered by PM2.5, employing neurogenic pathways related to the up-regulation of transient receptor potential vanilloid 1 (TRPV1). However, the potential impact of early-life exposure to 1,2-naphthoquinone (1,2-NQ) on atrial fibrillation (AF) has not yet been investigated. This study aims to investigate how inhaling 1,2-NQ in early life affects the autonomic adrenergic system and the role played by TRPV1 in these heart disturbances. C57Bl/6 neonate male mice were exposed to 1,2-NQ (100 nM) or its vehicle at 6, 8, and 10 days of life. Early exposure to 1,2-NQ impairs adrenergic responses in the right atria without markedly affecting cholinergic responses. ECG analysis revealed altered rhythmicity in young mice, suggesting increased sympathetic nervous system activity. Furthermore, 1,2-NQ affected β1-adrenergic receptor agonist-mediated positive chronotropism, which was prevented by metoprolol, a β1 receptor blocker. Capsazepine, a TRPV1 blocker but not a TRPC5 blocker, reversed 1,2-NQ-induced cardiac changes. In conclusion, neonate mice exposure to AP 1,2-NQ results in an elevated risk of developing cardiac adrenergic dysfunction, potentially leading to atrial arrhythmia at a young age.

Oedema formation and polymorphonuclear leukocyte (neutrophil) accumulation are involved in both acute and chronic inflammation. Calcitonin gene-related peptide (CGRP) is a sensory neuropeptide that is released from stimulated sensory nerves. CGRP is a potent vasodilator neuropeptide, especially when administered to the cutaneous microvasculature, with a long duration of action. Here, we have investigated the ability of vasodilator amounts of CGRP to modulate oedema formation and neutrophil accumulation induced in the cutaneous microvasculature of the mouse. To learn more about the mechanism of action of endogenous CGRP, we have investigated the response to the inflammatory stimulants tumour necrosis factor alpha (TNFα) and carrageenan in three different murine models: a model where sensory nerves were depleted by resiniferatoxin (RTX); a pharmacological method to investigate the effect of a selective CGRP receptor antagonist; and a genetic approach using wildtype (WT) and αCGRP knockout (KO) mice. Our results show that exogenous CGRP potentiates oedema formation induced by substance P (SP) and TNFα. This is further supported by our findings from sensory nerve-depleted mice (in the absence of all neuropeptides), which indicated that sensory nerves are involved in mediating the oedema formation and neutrophil accumulation induced by TNFα, and also carrageenan in cutaneous microvasculature. Furthermore, endogenous CGRP was shown to contribute to this inflammatory response as carrageenan-induced oedema formation is attenuated in WT mice treated with the CGRP receptor antagonist, and in αCGRPKO mice. It is therefore concluded that CGRP can contribute to inflammation by promoting oedema formation in skin, but this response is dependent on the pro-inflammatory stimulus and circumstance.

Editorial: Calcitonin Gene-Related Peptide: Novel Biology and Treatments