Role of VPAC2 receptor in monocrotaline-induced pulmonary hypertension in rats

Role of protein kinase D1 in vasoconstriction and haemodynamics in rats

AIMS

Protein kinase D (PKD), once considered an effector of protein kinase C (PKC), now plays many pathophysiological roles in various tissues. However, little is known about role of PKD in vascular function. We investigated the role of PKD in contraction of rat aorta and human aortic smooth muscle cells (HASMCs) and in haemodynamics in rats.

METHODS AND RESULTS

Isometric tension of rat aortic was measured to examine norepinephrine-induced contraction in the presence of PKD, PKC and Rho-kinase inhibitors. Phosphorylation of PKD1, myosin targeting subunit-1 (MYPT1), myosin light chain (MLC), CPI-17 and heat-shock protein 27 (HSP27), and actin polymerization were measured in the aorta. Phosphorylation of MYPT1 and MLC was also measured in HASMCs knocked down with specific siRNAs of PKD 1, 2 and 3. Intracellular calcium concentrations and cell shortening were measured in HASMCs. Norepinephrine-induced aortic contraction was accompanied by increased phosphorylation of PKD1, MYPT1 and MLC and actin polymerization, all of which were attenuated with PKD inhibitor CRT0066101. PKD1 phosphorylation was not inhibited by PKC inhibitor, chelerythrine or Rho kinase inhibitor, fasudil. In HASMCs, the phosphorylation of MYPT1 and MLC was attenuated by PKD1, but not PKD2, 3 knockdown. In HASMCs, CRT0066101 inhibited norepinephrine-induced cell shortening without affecting calcium concentration. Administration of CRT0066101 decreased systemic vascular resistance and blood pressure without affecting cardiac output in rats.

CONCLUSIONS

PKD1 may play roles in aorta contraction and haemodynamics via phosphorylation of MYPT1 and actin polymerization in a calcium-independent manner.

The role of vasoactive intestinal peptide in pulmonary diseases

Vasoactive intestinal peptide (VIP) is an abundant neurotransmitter in the lungs and other organs. Its discovery dates back to 1970. And VIP gains attention again due to the potential application in COVID-19 after a research wave in the 1980s and 1990s. The diverse biological impacts of VIP extend beyond its usage in COVID-19 treatment, encompassing its involvement in various pulmonary and systemic disorders. This review centers on the function of VIP in various lung diseases, such as pulmonary arterial hypertension, chronic obstructive pulmonary disease, asthma, cystic fibrosis, acute lung injury/acute respiratory distress syndrome, pulmonary fibrosis, and lung tumors. This review also outlines two main limitations of VIP as a potential medication and gathers information on extended-release formulations and VIP analogues.

Right ventricular overloading is attenuated in monocrotaline-induced pulmonary hypertension model rats with a disrupted Gpr143 gene, the gene that encodes the 3,4-l-dihydroxyphenyalanine (l-DOPA) receptor

Pulmonary hypertension (PH) is a severe and progressive disease that causes elevated right ventricular systolic pressure, right ventricular hypertrophy and ultimately right heart failure. However, the underlying pathophysiologic mechanisms are poorly understood. We previously showed that 3,4-l-dihydroxylphenyalanine (DOPA) sensitizes vasomotor response to sympathetic tone via coupling between the adrenergic receptor alpha1 (ADRA1) and a G protein-coupled receptor 143 (GPR143), a DOPA receptor. We investigated whether DOPA similarly enhances ADRA1-mediated contraction in pulmonary arteries isolated from rats, and whether GPR143 is involved in the PH pathogenesis. Pretreating the isolated pulmonary arteries with DOPA 1 μM enhanced vasoconstriction in response to phenylephrine, an ADRA1 agonist, but not to U-46619, a thromboxane A2 agonist or endothelin-1. We generated Gpr143 gene-deficient (Gpr143-/y) rats, and confirmed that DOPA did not augment phenylephrine-induced contractile response in Gpr143-/y rat pulmonary arteries. We utilized a rat model of monocrotaline (MCT)-induced PH. In the MCT model, the right ventricular systolic pressure was attenuated in the Gpr143-/y rats than in WT rats. Phenylephrine-induced cell migration and proliferation were also suppressed in Gpr143-/y pulmonary artery smooth muscle cells than in WT cells. Our result suggests that GPR143 is involved in the PH pathogenesis in the rat models of PH.

Dysfunction of VIPR2 leads to myopia in humans and mice

Background

Myopia is the leading cause of refractive errors. As its pathogenesis is poorly understood, we determined if the retinal VIP-VIPR2 signalling pathway axis has a role in controlling signalling output that affects myopia development in mice.

Methods

Association analysis meta-study, single-cell transcriptome, bulk RNA sequencing, pharmacological manipulation and VIPR2 gene knockout studies were used to clarify if changes in the VIP-VIPR2 signalling pathway affect refractive development in mice.

Results

The SNP rs6979985 of the VIPR2 gene was associated with high myopia in a Chinese Han cohort (randomceffect model: p=0.013). After either 1 or 2 days’ form deprivation (FD) retinal VIP mRNA expression was downregulated. Retinal single-cell transcriptome sequencing showed that VIPR2 was expressed mainly by bipolar cells. Furthermore, the cAMP signalling pathway axis was inhibited in some VIPR2+ clusters after 2 days of FD. The selective VIPR2 antagonist PG99-465 induced relative myopia, whereas the selective VIPR2 agonist Ro25-1553 inhibited this response. In Vipr2 knockout (Vipr2-KO) mice, refraction was significantly shifted towards myopia (p<0.05). The amplitudes of the bipolar cell derived b-waves in 7-week-old Vipr2-KO mice were significantly larger than those in their WT littermates (p<0.05).

Conclusions

Loss of VIPR2 function likely compromises bipolar cell function based on presumed changes in signal transduction due to altered signature electrical wave activity output in these mice. As these effects correspond with increases in form deprivation myopia (FDM), the VIP-VIPR2 signalling pathway axis is a viable novel target to control the development of this condition.

The role of regulatory neuropeptides and neurotrophic factors in asthma pathophysiology

In the last decade, the attention of scientists in the field of biomedicine is focused on studying the relationship between the immunological and neurogenic components of the inflammatory response and their contribution to the pathophysiology of allergic inflammation in asthma. The review is devoted to detailing the mechanism of neurogenic inflammation involving regulatory neuropeptides (substance P, vasoactive intestinal peptide, calcitonin gene-related peptide) in the pathogenesis of bronchial hyperreactivity in asthma. The role of neurotrophic growth factors (nerve growth factor, brain-derived neurotrophic factor) in the regulation of remodeling of bronchi in asthma has been analyzed. The study of neuroimmune mechanisms in the pathophysiology of asthma will it possible to find new therapeutic targets in this research area.

A Synthetic Agonist to Vasoactive Intestinal Peptide Receptor-2 Induces Regulatory T Cell Neuroprotective Activities in Models of Parkinson's Disease

A paradigm shift has emerged in Parkinson’s disease (PD) highlighting the prominent role of CD4⁺ Tregs in pathogenesis and treatment. Bench to bedside research, conducted by others and our own laboratories, advanced a neuroprotective role for Tregs making pharmacologic transformation of immediate need. Herein, a vasoactive intestinal peptide receptor-2 (VIPR2) peptide agonist, LBT-3627, was developed as a neuroprotectant for PD-associated dopaminergic neurodegeneration. Employing both 6-hydroxydopamine (6-OHDA) and α-synuclein (α-Syn) overexpression models in rats, the sequential administration of LBT-3627 increased Treg activity without altering cell numbers both in naïve animals and during progressive nigrostriatal degeneration. LBT-3627 administration was linked to reductions of inflammatory microglia, increased survival of dopaminergic neurons, and improved striatal densities. While α-Syn overexpression resulted in reduced Treg activity, LBT-3627 rescued these functional deficits. This occurred in a dose-dependent manner closely mimicking neuroprotection. Taken together, these data provide the basis for the use of VIPR2 agonists as potent therapeutic immune modulating agents to restore Treg activity, attenuate neuroinflammation, and interdict dopaminergic neurodegeneration in PD. The data underscore an important role of immunity in PD pathogenesis.

Effects of vasopressin during a pulmonary hypertensive crisis induced by acute hypoxia in a rat model of pulmonary hypertension

BACKGROUND

A pulmonary hypertensive crisis (PHC) can be a life-threatening condition. We established a PHC model by exposing rats with monocrotaline (MCT)-induced pulmonary hypertension to acute hypoxia, and investigated the effects of vasopressin, phenylephrine, and norepinephrine on the PHC.

METHODS

Four weeks after MCT 60 mg kg^-1 administration i.v., right ventricular systolic pressure (RVSP), systolic BP (SBP), mean BP (MBP), cardiac index (CI), and pulmonary vascular resistance index (PVRI) were measured. PHC defined as an RVSP exceeding or equal to SBP was induced by changing the fraction of inspiratory oxygen to 0.1. Rats were subsequently treated by vasopressin, phenylephrine, or norepinephrine, followed by assessment of systemic haemodynamics, isometric tension of femoral and pulmonary arteries, cardiac function, blood gas composition, and survival.

RESULTS

PHC was associated with increased RV dilatation and paradoxical septal motion. Vasopressin increased MBP [mean (standard error)] from 52.6 (3.8) to 125.0 (8.9) mm Hg and CI from 25.4 (2.3) to 40.6 (1.8) ml min^-1 100 g^-1 while decreasing PVRI. Vasopressin also improved RV dilatation, oxygenation, and survival in PHC. In contrast, phenylephrine increased MBP from 54.8 (2.3) to 96.8 (3.2) mm Hg without improving cardiac pump function. Norepinephrine did not alter MBP. Vasopressin contracted femoral but not pulmonary arteries, whereas phenylephrine contracted both arterial beds. Hence, improvements with vasopressin in PHC might be associated with decreased PVRI and selective systemic vasoconstriction.

CONCLUSIONS

In this rat model of a PHC, vasopressin, but not phenylephrine or norepinephrine, resulted in better haemodynamic and vascular recovery.

GPCRs in pulmonary arterial hypertension: tipping the balance

Pulmonary arterial hypertension (PAH) is a progressive, fatal disease characterised by increased pulmonary vascular resistance and excessive proliferation of pulmonary artery smooth muscle cells (PASMC). GPCRs, which are attractive pharmacological targets, are important regulators of pulmonary vascular tone and PASMC phenotype. PAH is associated with the altered expression and function of a number of GPCRs in the pulmonary circulation, which leads to the vasoconstriction and proliferation of PASMC and thereby contributes to the imbalance of pulmonary vascular tone associated with PAH; drugs targeting GPCRs are currently used clinically to treat PAH and extensive preclinical work supports the utility of a number of additional GPCRs. Here we review how GPCR expression and function changes with PAH and discuss why GPCRs continue to be relevant drug targets for the disease.

NFATc3 and VIP in Idiopathic Pulmonary Fibrosis and Chronic Obstructive Pulmonary Disease

Idiopathic pulmonary fibrosis (IPF) and chronic obstructive pulmonary disease (COPD) are both debilitating lung diseases which can lead to hypoxemia and pulmonary hypertension (PH). Nuclear Factor of Activated T-cells (NFAT) is a transcription factor implicated in the etiology of vascular remodeling in hypoxic PH. We have previously shown that mice lacking the ability to generate Vasoactive Intestinal Peptide (VIP) develop spontaneous PH, pulmonary arterial remodeling and lung inflammation. Inhibition of NFAT attenuated PH in these mice suggesting a connection between NFAT and VIP. To test the hypotheses that: 1) VIP inhibits NFAT isoform c3 (NFATc3) activity in pulmonary vascular smooth muscle cells; 2) lung NFATc3 activation is associated with disease severity in IPF and COPD patients, and 3) VIP and NFATc3 expression correlate in lung tissue from IPF and COPD patients. NFAT activity was determined in isolated pulmonary arteries from NFAT-luciferase reporter mice. The % of nuclei with NFAT nuclear accumulation was determined in primary human pulmonary artery smooth muscle cell (PASMC) cultures; in lung airway epithelia and smooth muscle and pulmonary endothelia and smooth muscle from IPF and COPD patients; and in PASMC from mouse lung sections by fluorescence microscopy. Both NFAT and VIP mRNA levels were measured in lungs from IPF and COPD patients. Empirical strategies applied to test hypotheses regarding VIP, NFATc3 expression and activity, and disease type and severity. This study shows a significant negative correlation between NFAT isoform c3 protein expression levels in PASMC, activity of NFATc3 in pulmonary endothelial cells, expression and activity of NFATc3 in bronchial epithelial cells and lung function in IPF patients, supporting the concept that NFATc3 is activated in the early stages of IPF. We further show that there is a significant positive correlation between NFATc3 mRNA expression and VIP RNA expression only in lungs from IPF patients. In addition, we found that VIP inhibits NFAT nuclear translocation in primary human pulmonary artery smooth muscle cells (PASMC). Early activation of NFATc3 in IPF patients may contribute to disease progression and the increase in VIP expression could be a protective compensatory mechanism.