Intersectin-1s deficiency in pulmonary pathogenesis

Protective effects of calcyclin-binding protein against pulmonary vascular remodeling in flow-associated pulmonary arterial hypertension

Background

Pulmonary arterial hypertension associated with congenital heart disease (CHD-PAH) is recognized as a cancer-like disease with a proliferative and pro-migratory phenotype in pulmonary artery smooth muscle cells (PASMCs). Calcyclin-binding protein/Siah-1-interacting protein (CacyBP/SIP) has been implicated in the progression of various cancers; however, it has not been previously studied in the context of CHD-PAH. Here, we aimed to examine the function of CacyBP/SIP in CHD-PAH and explore its potential as a novel regulatory target for the disease.

Methods

The expression of CacyBP/SIP in PASMCs was evaluated both in the pulmonary arterioles of patients with CHD-PAH and in high-flow-induced PAH rats. The effects of CacyBP/SIP on pulmonary vascular remodeling and PASMC phenotypic switch, proliferation, and migration were investigated. LY294002 (MedChemExpress, NJ, USA) was used to block the phosphoinositide 3-kinase/protein kinase B (PI3K/AKT) pathway to explore changes in PASMC dysfunction induced by low CacyBP/SIP levels. Hemodynamics and pulmonary arterial remodeling were further explored in rats after short-interfering RNA-mediated decrease of CacyBP/SIP expression.

Results

CacyBP/SIP expression was markedly reduced both in the remodeled pulmonary arterioles of patients with CHD-PAH and in high-flow-induced PAH rats. Low CacyBP/SIP expression promoted hPASMC phenotypic switch, proliferation, and migration via PI3K/AKT pathway activation. Our results indicated that CacyBP/SIP protected against pulmonary vascular remodeling through amelioration of hPASMC dysfunction in CHD-PAH. Moreover, after inhibition of CacyBP/SIP expression in vivo, we observed increased right ventricular hypertrophy index, poor hemodynamics, and severe vascular remodeling.

Conclusions

CacyBP/SIP regulates hPASMC dysfunction, and its increased expression may ameliorate progression of CHD-PAH.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-022-02137-z.

SPARC, a Novel Regulator of Vascular Cell Function in Pulmonary Hypertension

BACKGROUND

Pulmonary hypertension (PH) is a life-threatening disease, characterized by excessive pulmonary vascular remodeling, leading to elevated pulmonary arterial pressure and right heart hypertrophy. PH can be caused by chronic hypoxia, leading to hyper-proliferation of pulmonary arterial smooth muscle cells (PASMCs) and apoptosis-resistant pulmonary microvascular endothelial cells (PMVECs). On reexposure to normoxia, chronic hypoxia-induced PH in mice is reversible. In this study, the authors aim to identify novel candidate genes involved in pulmonary vascular remodeling specifically in the pulmonary vasculature.

METHODS

After microarray analysis, the authors assessed the role of SPARC (secreted protein acidic and rich in cysteine) in PH using lung tissue from idiopathic pulmonary arterial hypertension (IPAH) patients, as well as from chronically hypoxic mice. In vitro studies were conducted in primary human PASMCs and PMVECs. In vivo function of SPARC was proven in chronic hypoxia-induced PH in mice by using an adeno-associated virus-mediated Sparc knockdown approach.

RESULTS

C57BL/6J mice were exposed to normoxia, chronic hypoxia, or chronic hypoxia with subsequent reexposure to normoxia for different time points. Microarray analysis of the pulmonary vascular compartment after laser microdissection identified Sparc as one of the genes downregulated at all reoxygenation time points investigated. Intriguingly, SPARC was vice versa upregulated in lungs during development of hypoxia-induced PH in mice as well as in IPAH, although SPARC plasma levels were not elevated in PH. TGF-β1 (transforming growth factor β1) or HIF2A (hypoxia-inducible factor 2A) signaling pathways induced SPARC expression in human PASMCs. In loss of function studies, SPARC silencing enhanced apoptosis and reduced proliferation. In gain of function studies, elevated SPARC levels induced PASMCs, but not PMVECs, proliferation. Coculture and conditioned medium experiments revealed that PMVECs-secreted SPARC acts as a paracrine factor triggering PASMCs proliferation. Contrary to the authors' expectations, in vivo congenital Sparc knockout mice were not protected from hypoxia-induced PH, most probably because of counter-regulatory proproliferative signaling. However, adeno-associated virus-mediated Sparc knockdown in adult mice significantly improved hemodynamic and cardiac function in PH mice.

CONCLUSIONS

This study provides evidence for the involvement of SPARC in the pathogenesis of human PH and chronic hypoxia-induced PH in mice, most likely by affecting vascular cell function.

Sex differences in the proliferation of pulmonary artery endothelial cells: implications for plexiform arteriopathy

The sex-biased disease pulmonary arterial hypertension (PAH) is characterized by the proliferation and overgrowth of dysfunctional pulmonary artery endothelial cells (PAECs). During inflammation associated with PAH, granzyme B cleaves intersectin-1 to produce N-terminal (EH_ITSN) and C-terminal (SH3A-E_ITSN) protein fragments. In a murine model of PAH, EH_ITSN triggers plexiform arteriopathy via p38-ELK1-c-Fos signaling. The SH3A-E_ITSN fragment also influences signaling, having dominant-negative effects on ERK1 and ERK2 (also known as MAPK3 and MAPK1, respectively). Using PAECs engineered to express tagged versions of EH_ITSN and SH3A-E_ITSN, we demonstrate that the two ITSN fragments increase both p38-ELK1 activation and the ratio of p38 to ERK1 and ERK2 activity, leading to PAEC proliferation, with female cells being more responsive than male cells. Furthermore, expression of EH_ITSN substantially upregulates the expression and activity of the long non-coding RNA Xist in female PAECs, which in turn upregulates the X-linked gene ELK1 and represses expression of krüppel-like factor 2 (KLF2). These events are recapitulated by the PAECs of female idiopathic PAH patients, and may account for their proliferative phenotype. Thus, upregulation of Xist could be an important factor in explaining sexual dimorphism in the proliferative response of PAECs and the imbalanced sex ratio of PAH.

Intersectin-Cdc42 interaction is required for orderly meiosis in porcine oocytes

Intersectins (ITSNs) have been shown to act as adaptor proteins that govern multiple cellular events via regulating Cdc42 activity. However, it remains to be determined whether the ITSN-Cdc42 pathway is functional in porcine oocytes. To address this question, we used a small molecule, ZCL278, to selectively disrupt the ITSN2-Cdc42 interaction. In the present study, we find that porcine oocytes exposed to ZCL278 are unable to completely progress through meiosis. Meanwhile, the spindle defects and chromosomal congression failure are frequently detected in these oocytes. In support of this, we observed the accumulated distribution of vesicle-like ITSN2 signals around the chromosome/spindle region during porcine oocyte maturation. In addition, our results also showed that inhibition of the ITSN-Cdc42 interaction impairs the actin polymerization in porcine oocytes. In summary, the findings support a model where ITSNs, through the interaction with Cdc42, modulates the assembly of meiotic apparatus and actin polymerization, consequently ensuring the orderly meiotic progression during porcine oocyte maturation.

Insights on the epigenetic mechanisms underlying pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH), characterized by localized increased arterial blood pressure in the lungs, is a slow developing long-term disease that can be fatal. PAH is characterized by inflammation, vascular tone imbalance, pathological pulmonary vascular remodeling, and right-sided heart failure. Current treatments for PAH are palliative and development of new therapies is necessary. Recent and relevant studies have demonstrated that epigenetic processes may exert key influences on the pathogenesis of PAH and may be promising therapeutic targets in the prevention and/or cure of this condition. The aim of the present mini-review is to summarize the occurrence of epigenetic-based mechanisms in the context of PAH physiopathology, focusing on the roles of DNA methylation, histone post-translational modifications and non-coding RNAs. We also discuss the potential of epigenetic-based therapies for PAH.