Deficiency in Aim2 affects viability and calcification of vascular smooth muscle cells from murine aortas and angiotensin-II induced aortic aneurysms

Adrenomedullin Improves Hypertension and Vascular Remodeling partly through the Receptor-Mediated AMPK Pathway in Rats with Obesity-Related Hypertension

Adrenomedullin (ADM) is a novel cardiovascular peptide with anti-inflammatory and antioxidant properties. Chronic inflammation, oxidative stress and calcification play pivotal roles in the pathogenesis of vascular dysfunction in obesity-related hypertension (OH). Our study aimed to explore the effects of ADM on the vascular inflammation, oxidative stress and calcification in rats with OH. Eight-week-old Sprague Dawley male rats were fed with either a Control diet or a high fat diet (HFD) for 28 weeks. Next, the OH rats were randomly subdivided into two groups as follows: (1) HFD control group, and (2) HFD with ADM. A 4-week treatment with ADM (7.2 μg/kg/day, ip) not only improved hypertension and vascular remodeling, but also inhibited vascular inflammation, oxidative stress and calcification in aorta of rats with OH. In vitro experiments, ADM (10 nM) in A7r5 cells (rat thoracic aorta smooth muscle cells) attenuated palmitic acid (PA, 200 μM) or angiotensin II (Ang II, 10 nM) alone or their combination treatment-induced inflammation, oxidative stress and calcification, which were effectively inhibited by the ADM receptor antagonist ADM22-52 and AMP-activated protein kinase (AMPK) inhibitor Compound C, respectively. Moreover, ADM treatment significantly inhibited Ang II type 1 receptor (AT1R) protein expression in aorta of rats with OH or in PA-treated A7r5 cells. ADM improved hypertension, vascular remodeling and arterial stiffness, and attenuated inflammation, oxidative stress and calcification in OH state partially via receptor-mediated AMPK pathway. The results also raise the possibility that ADM will be considered for improving hypertension and vascular damage in patients with OH.

The AIM2 inflammasome: A novel biomarker and target in cardiovascular disease

Absent in melanoma 2 (AIM2) is a cytoplasmic sensor that recognises the double-strand DNA. AIM2 inflammasome is a protein platform in the cell that initiates innate immune responses by cleaving pro-caspase-1 and converting IL-1β and IL-18 to their mature forms. Additionally, AIM2 inflammasome promotes pyroptosis by converting Gasdermin-D (GSDMD) to GSDMD-N fragments. An increasing number of studies have indicated the important and decisive roles of the AIM2 inflammasome, IL-1β, and pyroptosis in cardiovascular diseases, such as coronary atherosclerosis, myocardial infarction, ischaemia/reperfusion injury, heart failure, aortic aneurysm and ischaemic stroke. Here, we review the molecular mechanism of the activation and effect of the AIM2 inflammasome in cardiovascular disease, revealing new insights into pathogenic factors that may be targeted to treat cardiovascular disease and related dysfunctions.

Possible effects of fibroblast growth factor 21 on vascular calcification via suppressing activating transcription factor 4 mediated apoptosis and osteogenic transformation in rats

Vascular calcification (VC), a significant risk factor of many cardio-cerebral vascular diseases, is a perplexing issue with no effective treatment in clinical work up to now. Endoplasmic reticulum stress (ERS) mediated apoptosis has been proved to be a significant mechanism for initiating VC process. Activating transcription factor 4 (ATF4), a key transcription factor of ERS, is most closely associated with VC. Fibroblast growth factor 21 (FGF21), an atypical member of the FGFs family, has a protective biological function in various metabolic diseases by ERS pathways. However, the possible effects of FGF21 on VC by regulating ERS, especially through the ATF4 pathway, is still unclear. Our research provides the first evidence that exogenous FGF21 treatment can alleviate the vitam​​​​in D₃ plus nicotine-induced VC at least in part via suppressing ATF4 mediated apoptosis and osteogenic transformation in rats.

AIM2 Inflammasome Activation Contributes to Aortic Dissection in a Sporadic Aortic Disease Mouse Model

BACKGROUND

The absent in melanoma 2 (AIM2) inflammasome induces pyroptosis, tissue inflammation, and extracellular matrix destruction. We tested the hypothesis that the AIM2 inflammasome contributes to aortic aneurysm and dissection (AAD) development by promoting pyroptosis in smooth muscle cells (SMCs).

METHODS

We examined AIM2 expression in aortic tissues from patients with ascending thoracic aortic aneurysm (ATAA) and aortic dissection (ATAD) and from organ donor controls. AIM2's role in AAD development was evaluated in AIM2-deficient mice in a sporadic AAD model induced by challenging mice with a high-fat diet and angiotensin II infusion. The direct effects of dsDNA on SMC death in vitro were studied.

RESULTS

Western blot analyses showed that AIM2 was increased in ATAD compared to ATAA and control tissue. Immunofluorescence demonstrated increased AIM2 in SMCs and macrophages in the aortic media and adventitia of dissected tissue. Increased AIM2 abundance was associated with increased cleavage of caspase-1 and cleavage of gasdermin-D, indicating activation of pyroptosis. In a mouse model of sporadic AAD induced by high-fat diet and angiotensin II infusion, AIM2-deficient mice showed significant reduction in aortic dissection, but not aneurysm formation in all aortic segments, versus wild-type mice. Finally, treating cultured human aortic SMCs with double-stranded DNA induced AIM2 expression, caspase-1 cleavage, and gasdermin-D cleavage; these effects were reduced by silencing AIM2 and caspase-1 genes, suggesting involvement of the AIM2 inflammasome in cytosolic DNA-induced activation of SMC pyroptosis.

CONCLUSIONS

Activation of the AIM2 inflammasome cascade contributes to aortic degeneration and dissection, in part, by activating pyroptosis.

Contribution of the innate and adaptive immune systems to aortic dilation in murine mucopolysaccharidosis type I

BACKGROUND

Adult immunocompetent male C57Bl/6 mucopolysaccharidosis, type I (MPSI) mice develop aortic insufficiency (AI), dilated ascending aortas and decreased cardiac function, findings not observed in immune incompetent adult male NSG MPSI mice. We sought to determine why.

METHODS

Cardiac ultrasound measurements of ascending aorta and left ventricular dimensions and Doppler interrogation for AI were performed in 6-month-old male B6 MPSI (N = 12), WT (N = 6), NSG MPSI (N = 8), NSG (N = 6) mice. Urinary glycosaminoglycans, RNA sequencing with quantitative PCR were performed and aortic pathology assessed by routine and immunohistochemical staining on subsets of murine aortas.

RESULTS

Ascending aortic diameters were significantly greater, left ventricular function significantly decreased, and AI significantly more frequent in B6 MPSI mice compared to NSG MPSI mice (p < 0.0001, p = 0.008 and p = 0.02, respectively); NSG and B6 WT mice showed no changes. Urinary glycosaminoglycans were significantly greater in B6 and NSG MPSI mice and both were significantly elevated compared to WT controls (p = 0.003 and p < 0.0001, respectively). By RNA sequencing, all 11 components of the inflammasome pathway were upregulated in B6 MUT, but only Aim2 and Ctsb in NSG MUT mice and none in WT controls. Both B6 and NSG MUT mice demonstrated variably-severe intramural inflammation, vacuolated cells, elastin fragmentation and disarray, and intense glycosaminoglycans on histological staining. B6 MPSI mice demonstrated numerous medial MAC2+ macrophages and adventitial CD3+ T-cells while MAC2+ macrophages were sparse and CD3+ T-cells absent in NSG MPSI mice.

CONCLUSIONS

Aortic dilation, AI and decreased cardiac function occur in immunocompetent B6 MPSI male mice but not in immune incompetent NSG MPSI mice, unrelated to GAG excretion, upregulation of Ctsb, or routine histologic appearance. Upregulation of all components of the inflammasome pathway in B6 MUT, but not NSG MUT mice, and abundant medial MAC2 and adventitial CD3 infiltrates in B6, but not NSG, MPSI aortas differentiated the two strains. These results suggest that the innate and adaptive immune systems play a role in these cardiac findings which may be relevant to human MPSI.

Inflammasome Targeted Therapy as Novel Treatment Option for Aortic Aneurysms and Dissections: A Systematic Review of the Preclinical Evidence

Both aortic aneurysm and dissection are life threatening pathologies. In the lack of a conservative medical treatment, the only therapy consists of modifying cardiovascular risk factors and either surgical or endovascular treatment. Like many other cardiovascular diseases, in particular atherosclerosis, aortic aneurysm and dissection have a strong inflammatory phenotype. Inflammasomes are part of the innate immune system. Upon stimulation they form multi protein complexes resulting mainly in activation of interleukin-1β and other cytokines. Considering the gathering evidence, that inflammasomes are decisively involved in the emergence and progression of aortic diseases, inflammasome targeted therapy provides a promising new treatment approach. A systematic review following the PRISMA guidelines on the current preclinical data regarding the potential role of inflammasome targeted drug therapy as novel treatment option for aortic aneurysms and dissections was performed. Included were all rodent models of aortic disease (aortic aneurysm and dissection) evaluating a drug therapy with direct or indirect inhibition of inflammasomes and a suitable control group with the use of the same aortic model without the inflammasome targeted therapy. Primary and secondary outcomes were incidence of aortic disease, aortic rupture, aortic related death, and the maximum aortic diameter. The literature search of MEDLINE (via PubMed), the Web of Science, EMBASE and the Cochrane Central Registry of Registered Trials (CENTRAL) resulted in 8,137 hits. Of these, four studies met the inclusion criteria and were therefore eligible for data analysis. In all of them, targeting of the NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome effectively reduced the incidence of aortic disease and aortic rupture, and additionally reduced destruction of the aortic wall. Treatment strategies aiming at other inflammasomes could not be identified. In conclusion, inflammasome targeted therapies, more precisely targeting the NLRP3 inflammasome, have shown promising results in rodent models and deserve further investigation in preclinical research to potentially translate them into clinical research for the treatment of human patients with aortic disease. Regarding other inflammasomes, more preclinical research is needed to investigate their role in the pathophysiology of aortic disease.

Protocol Registration: PROSPERO 2021 CRD42021279893, https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021279893

Targeting regulated cell death in aortic aneurysm and dissection therapy

Regulated cell death (RCD) is a basic biological phenomenon associated with cell and tissue homeostasis. Recent studies have enriched our understanding of RCD, and many novel cell death types, such as ferroptosis and pyroptosis, have been discovered and defined. Aortic aneurysm and dissection (AAD) is a life-threatening condition, but the pathogenesis remains largely unclear. A series of studies have indicated that the death of smooth muscle cells, endothelial cells and inflammatory cells participates in the development of AAD and that corresponding interventions could alleviate disease progression. Many treatments against cell death have been used to impede the process of AAD in vitro and in vivo, which provides strategies to protect against this condition. In this review, we focus on various types of regulated cell death and provide a framework of their roles in AAD, and the information contributes to further exploration of the molecular mechanisms of AAD.

Inflammasomes in the Pathophysiology of Aortic Disease

Aortic diseases comprise aneurysms, dissections, and several other pathologies. In general, aging is associated with a slow but progressive dilation of the aorta, along with increased stiffness and pulse pressure. The progression of aortic disease is characterized by subclinical development or acute presentation. Recent evidence suggests that inflammation participates causally in different clinical manifestations of aortic diseases. As of yet, diagnostic imaging and surveillance is mainly based on ultrasonography, computed tomography (CT), and magnetic resonance imaging (MRI). Little medical therapy is available so far to prevent or treat the majority of aortic diseases. Endovascular therapy by the introduction of covered stentgrafts provides the main treatment option, although open surgery and implantation of synthetic grafts remain necessary in many situations. Because of the risks associated with surgery, there is a need for identification of pharmaceutical targets interfering with the pathophysiology of aortic remodeling. The participation of innate immunity and inflammasome activation in different cell types is common in aortic diseases. This review will thus focus on inflammasome activities in vascular cells of different chronic and acute aortic diseases and discuss their role in development and progression. We will also identify research gaps and suggest promising therapeutic targets, which may be used for future medical interventions.

κ-opioid receptor stimulation alleviates rat vascular smooth muscle cell calcification via PFKFB3-lactate signaling

In the present study, the effects and mechanism of action of U50,488H (a selective κ-opioid receptor agonist) on calcification of rat vascular smooth muscle cells (VSMCs) induced by β-glycerophosphate (β-GP) were investigated. VSMCs were isolated and cultured in traditional FBS-based media. A calcification model was established in VSMCs under hyperphosphatemia and intracellular calcium contents. Alkaline phosphatase (ALP), lactate dehydrogenase (LDH), and lactate were detected in cell culture supernatants before and after treatment. Alizarin red staining was used to detect the degree of calcification of VSMCs. Expression levels of key molecules of osteogenic markers, fructose-2,6-biphosphatase 3 (PFKFB3), and proline hydroxylase 2 (PHD2), were determined using western blotting. Further, vascular calcification was induced by vitamin D3 plus nicotine in rats and isolated thoracic aortas, calcium concentration was assessed in rat aortic rings in vitro. We demonstrated that U50,488H inhibited VSMC calcification in a concentration-dependent manner. Moreover, U50,488H significantly inhibited osteogenic differentiation and ALP activity in VSMCs pretreated with β-GP. Further studies confirmed that PFKFB3 expression, LDH level, and lactate content significantly increased during calcification of VSMCs; U50,488H reversed these changes. PHD2 expression showed the opposite trend compared to PFKFB3 expression. nor-BNI or 3-PO abolished U50,488H protective effects. Besides, U50,488H inhibited VSMC calcification in rat aortic rings ex vivo. Collectively, our experiments show that κ-opioid receptor activation inhibits VSMC calcification by reducing PFKFB3 expression and lactate content, providing a potential drug target and strategy for the clinical treatment of vascular calcification.

Mdivi-1, a mitochondrial fission inhibitor, reduces angiotensin-II- induced hypertension by mediating VSMC phenotypic switch

Vascular smooth muscle cell (VSMC) phenotypic switch plays an essential role in the pathogenesis of hypertension. Mitochondrial dynamics, such as mitochondrial fission, can also contribute to VSMC phenotypic switch. Whether mitochondrial fission act as a novel target for anti-hypertensive drug development remains unknown. In the present study, we confirmed that angiotensin II (AngII) rapidly and continuously induced mitochondrial fission in VSMCs. We also detected the phosphorylation status of dynamin-related protein-1 (Drp1), a key protein involved in mitochondrial fission, at Ser616 site; and observed Drp1 mitochondrial translocation in VSMCs or arteries of AngII-induced hypertensive mice. The Drp1 inhibitor mitochondrial division inhibitor-1 (Mdivi-1) dramatically reversed AngII-induced Drp1 phosphorylation, mitochondrial fission, and reactive oxidative species generation. Treatment with Mdivi-1 (20 mg/kg/every other day) significantly attenuated AngII-induced hypertension (22 mmHg), arterial remodeling, and cardiac hypertrophy, in part by preventing VSMC phenotypic switch. In addition, Mdivi-1 treatment was not associated with liver or renal functional injury. Collectively, these results indicate that Mdivi-1 inhibited mitochondrial fission, recovered mitochondrial activity, and prevented AngII-induced VSMC phenotypic switch, resulting in reduced hypertension.

The Trinity of cGAS, TLR9, and ALRs Guardians of the Cellular Galaxy Against Host-Derived Self-DNA

The immune system has evolved to protect the host from the pathogens and allergens surrounding their environment. The immune system develops in such a way to recognize self and non-self and develops self-tolerance against self-proteins, nucleic acids, and other larger molecules. However, the broken immunological self-tolerance leads to the development of autoimmune or autoinflammatory diseases. Pattern-recognition receptors (PRRs) are expressed by immunological cells on their cell membrane and in the cytosol. Different Toll-like receptors (TLRs), Nod-like receptors (NLRs) and absent in melanoma-2 (AIM-2)-like receptors (ALRs) forming inflammasomes in the cytosol, RIG (retinoic acid-inducible gene)-1-like receptors (RLRs), and C-type lectin receptors (CLRs) are some of the PRRs. The DNA-sensing receptor cyclic GMP–AMP synthase (cGAS) is another PRR present in the cytosol and the nucleus. The present review describes the role of ALRs (AIM2), TLR9, and cGAS in recognizing the host cell DNA as a potent damage/danger-associated molecular pattern (DAMP), which moves out to the cytosol from its housing organelles (nucleus and mitochondria). The introduction opens with the concept that the immune system has evolved to recognize pathogens, the idea of horror autotoxicus, and its failure due to the emergence of autoimmune diseases (ADs), and the discovery of PRRs revolutionizing immunology. The second section describes the cGAS-STING signaling pathway mediated cytosolic self-DNA recognition, its evolution, characteristics of self-DNAs activating it, and its role in different inflammatory conditions. The third section describes the role of TLR9 in recognizing self-DNA in the endolysosomes during infections depending on the self-DNA characteristics and various inflammatory diseases. The fourth section discusses about AIM2 (an ALR), which also binds cytosolic self-DNA (with 80–300 base pairs or bp) that inhibits cGAS-STING-dependent type 1 IFN generation but induces inflammation and pyroptosis during different inflammatory conditions. Hence, this trinity of PRRs has evolved to recognize self-DNA as a potential DAMP and comes into action to guard the cellular galaxy. However, their dysregulation proves dangerous to the host and leads to several inflammatory conditions, including sterile-inflammatory conditions autoinflammatory and ADs.