Calcitonin gene-related peptide down-regulates bleomycin-induced pulmonary fibrosis

CGRP attenuates pulmonary vascular remodeling by inhibiting the cGAS-STING-NFκB pathway in pulmonary arterial hypertension

BACKGROUND

Hyperproliferation, inflammation, and mitochondrial abnormalities in pulmonary artery smooth muscle cells (PASMCs) underlie the pathological mechanisms of vascular remodeling in pulmonary arterial hypertension (PAH). Cytoplasmic mtDNA activates the cGAS-STING-NFκB pathway and secretes pro-inflammatory cytokines that may be involved in the pathogenesis of PAH. Calcitonin gene-related peptide (CGRP) acts as a vasodilator to regulate patterns of cellular energy metabolism and has vasodilatory and anti-inflammatory effects.

METHODS

The role of the cGAS-STING-NFκB signaling pathway in PAH vascular remodeling and the regulation of CGRP in the cGAS-STING-NFκB signaling pathway were investigated by echocardiography, morphology, histology, enzyme immunoassay, and fluorometry.

RESULTS

Monocrotaline (MCT) could promote right heart hypertrophy, pulmonary artery intima thickening, and inflammatory cell infiltration in rats. Cinnamaldehyde (CA)-induced CGRP release alleviates MCT-induced vascular remodeling in PAH. CGRP reduces PDGF-BB-induced proliferation, and migration, and downregulates smooth muscle cell phenotypic proteins. In vivo and in vitro experiments confirm that the mitochondria of PASMCs were damaged during PAH, and the superoxide and mtDNA produced by injured mitochondria activate the cGAS-STING-NFκB pathway to promote PAH process, while CGRP could play an anti-PAH role by protecting the mitochondria and inhibiting the cGAS-STING-NFκB pathway through PKA.

CONCLUSION

This study identifies that CGRP attenuates cGAS-STING-NFκB axis-mediated vascular remodeling in PAH through PKA.

Topical application of calcitonin gene-related peptide as a regenerative, antifibrotic, and immunomodulatory therapy for corneal injury

Calcitonin gene-related peptide (CGRP) is a multifunctional neuropeptide abundantly expressed by corneal nerves. Using a murine model of corneal mechanical injury, we found CGRP levels in the cornea significantly reduced after injury. Topical application of CGRP as an eye drop accelerates corneal epithelial wound closure, reduces corneal opacification, and prevents corneal edema after injury in vivo. CGRP promotes corneal epithelial cell migration, proliferation, and the secretion of laminin. It reduces TGF-β1 signaling and prevents TGF-β1-mediated stromal fibroblast activation and tissue fibrosis. CGRP preserves corneal endothelial cell density, morphology, and pump function, thus reducing corneal edema. Lastly, CGRP reduces neutrophil infiltration, macrophage maturation, and the production of inflammatory cytokines in the cornea. Taken together, our results show that corneal nerve-derived CGRP plays a cytoprotective, pro-regenerative, anti-fibrotic, and anti-inflammatory role in corneal wound healing. In addition, our results highlight the critical role of sensory nerves in ocular surface homeostasis and injury repair.

CGRP is essential for protection against alveolar epithelial cell necroptosis by activating the AMPK/L-OPA1 signaling pathway during acute lung injury

Alveolar epithelial cell (AEC) necroptosis is critical to disrupt the alveolar barrier and provoke acute lung injury (ALI). Here, we define calcitonin gene-related peptide (CGRP), the most abundant endogenous neuropeptide in the lung, as a novel modulator of AEC necroptosis in lipopolysaccharide (LPS)-induced ALI. Upon LPS-induced ALI, overexpression of Cgrp significantly mitigates the inflammatory response, alleviates lung tissue damage, and decreases AEC necroptosis. Similarly, CGRP alleviated AEC necroptosis under the LPS challenge in vitro. Previously, we identified that long optic atrophy 1 (L-OPA1) deficiency mediates mitochondrial fragmentation, leading to AEC necroptosis. In this study, we discovered that CGRP positively regulated mitochondrial fusion through stabilizing L-OPA1. Mechanistically, we elucidate that CGRP activates AMP-activated protein kinase (AMPK). Furthermore, the blockade of AMPK compromised the protective effect of CGRP against AEC necroptosis following the LPS challenge. Our study suggests that CRGP-mediated activation of the AMPK/L-OPA1 axis may have potent therapeutic benefits for patients with ALI or other diseases with necroptosis.

αCGRP deficiency aggravates pulmonary fibrosis by activating the PPARγ signaling pathway

In order to explore whether αCGRP (Calca) deficiency aggravates pulmonary fibrosis (PF). Clinical data from patients with PF (n = 52) were retrospectively analyzed. Lung tissue from a bleomycin (BLM)-induced rat model was compared with that of Calca-knockout (KO) and wild type (WT) using immunohistochemistry, RNA-seq, and UPLC-MS/MS metabolomic analyses. The results showed that decreased αCGRP expression and activation of the type 2 immune response were detected in patients with PF. In BLM-induced and Calca-KO rats, αCGRP deficiency potentiated apoptosis of AECs and induced M2 macrophages. RNA-seq identified enrichment of pathways involved in nuclear translocation and immune system disorders in Calca-KO rats compared to WT. Mass spectrometry of lung tissue from Calca-KO rats showed abnormal lipid metabolism, including increased levels of LTB4, PDX, 1-HETE. PPAR pathway signaling was significantly induced in both transcriptomic and metabolomic datasets in Calca-KO rats, and immunofluorescence analysis confirmed that the nuclear translocation of PPARγ in BLM-treated and Calca-KO rats was synchronized with STAT6 localization in the cytoplasmic and nuclear fractions. In conclusion, αCGRP is protective against PF, and αCGRP deficiency promotes M2 polarization of macrophages, probably by activating the PPARγ pathway, which leads to activation of the type 2 immune response and accelerates PF development.

CGRP induces myofibroblast differentiation and the production of extracellular matrix in MRC5s via autocrine and paracrine signalings

There are contradictory views on which calcitonin gene-related peptide (CGRP) causes pulmonary fibrosis. Fibrotic potency of CGRP was tested and compared to that of transforming growth factor-β (TGF-β). Myofibroblast differentiation, cell proliferation, and activations of TGF-β and Wnt pathways were examined for 24, 48, and 72 h in A549 and MRC5 cell lines stimulated with CGRP and TGF-β. CGRP-induced cell proliferation in MRC5s early on while cell proliferation in A549 occurred progressively. CGRP promoted fibroblast-myofibroblast differentiation by inducing the transcription of ACTA2, COL1A1, SMAD2/3, and SMAD4 genes, the production of collagen, fibronectin, α-smooth muscle actin, and activation of TGF-β signaling starting from 24 h. Additionally, TGF-β signaling induced by CGRP decreased the DKK1 level and activated the Wnt signaling in MRC5s. After CGRP stimulation, Wnt7a levels were increased from 24 to 72 h, while Wnt5a levels were elevated at 72 h in MRC5s. CGRP did not induce epithelial-mesenchymal transition in A549s, unlike TGF-β. A comparison of fibrotic potency of CGRP and TGF-β showed that TGF-β is a powerful profibrotic molecule and induces earlier myofibroblast differentiation. Even so, CGRP promotes myofibroblast differentiation and extracellular matrix production by inducing Smad-dependent-TGF-β and Wnt signalings via autocrine and paracrine signalings in MRC5s.

CGRP derived from cardiac fibroblasts is an endogenous suppressor of cardiac fibrosis

AIMS

Aberrant activation of cardiac fibroblasts leads to cardiac fibrosis, and evolving evidences suggest that endogenous bioactive substances derived from cardiac fibroblasts regulate cardiac fibroblasts activation in an autocrine/paracrine manner. Here we first presented evidence that cardiac fibroblasts can synthesize and secrete calcitonin gene-related peptide (CGRP), therefore, this study aimed to investigate the role of cardiac fibroblasts-derived CGRP in cardiac fibroblasts activation and its regulative mechanism.

METHODS AND RESULTS

The abundantly expression of CGRP in rat, mouse, and human myocardium allowed us to explore the cellular origin of CGRP, and found that the cardiac CGRP was mainly derived from cardiac fibroblasts. Activating TRPA1 with a specific agonist allyl isothiocyanate promoted the synthesis and secretion of CGRP, as well as intracellular Ca2+. These effects were reversed by TRPA1-specific antagonist HC030031 and Ca2+ chelator BAPTA-AM. TGF-β1 was applied to induce the activation of cardiac fibroblasts, and found that TGF-β1 can increase the mRNA expression and secretion levels of CGRP in cardiac fibroblasts. Either CGRP8-37 (CGRP receptor antagonist) or α-CGRP small interfering RNA (siRNA) aggravated TGF-β1-induced proliferation, differentiation, collagen production, and instigated inflammation in cardiac fibroblasts. Moreover, TGF-β1-induced NF-κB activation including IκBα phosphorylation and p65 nuclear translocation were also promoted by CGRP8-37 and α-CGRP siRNA. NF-κB inhibitor pyrrolidinedithiocarbamate ammonium (PDTC) reversed the effects of CGRP8-37 on NF-κB activation. The promotive effects of CGRP8-37 on TGF-β1-induced activation of cardiac fibroblasts were all reversed by PDTC. Monocrotaline (MCT) induces pulmonary arterial hypertension, progressively leading to right ventricular fibrosis. This model of cardiac fibrosis was developed here to test the potentially beneficial effects of TRPA1 activation in vivo. The non-toxic TRPA1 agonist Cinnamaldehyde (CA) inhibited MCT-induced elevation in right ventricle systolic pressure, RV/LV + S, and right ventricular collagen accumulation, as well as down-regulation of CGRP. CA increased the synthesis and secretion of CGRP, and inhibited TGF-β1-induced activation in cardiac fibroblasts.

CONCLUSION

Our data suggested an autocrine role for cardiac fibroblasts-derived CGRP in suppressing activation of cardiac fibroblasts through inhibiting NF-κB activation. Increasing autocrine CGRP by activating TRPA1 can ameliorate cardiac fibrosis. These findings support the notion that CGRP derived from cardiac fibroblasts is an endogenous suppressor of cardiac fibrosis.

Circulating Levels of Calcitonin Gene-Related Peptide Are Lower in COVID-19 Patients

Background

To better understand the biology of COVID-19, we have explored the behavior of calcitonin gene-related peptide (CGRP), an angiogenic, vasodilating, and immune modulating peptide, in severe acute respiratory syndrome coronavirus 2 positive patients.

Methods

Levels of CGRP in the serum of 57 COVID-19 patients (24 asymptomatic, 23 hospitalized in the general ward, and 10 admitted to the intensive care unit) and healthy donors (n = 24) were measured by enzyme-linked immunosorbent assay (ELISA). In addition, to better understand the physiological consequences of the observed variations, we investigated by immunofluorescence the distribution of receptor activity modifying protein 1 (RAMP1), one of the components of the CGRP receptor, in autopsy lung specimens.

Results

CGRP levels were greatly decreased in COVID-19 patients (P < 0.001) when compared to controls, and there were no significant differences due to disease severity, sex, age, or comorbidities. We found that COVID-19 patients treated with proton pump inhibitors had lower levels of CGRP than other patients not taking this treatment (P = 0.001). RAMP1 immunoreactivity was found in smooth muscle cells of large blood vessels and the bronchial tree and in the airways´ epithelium. In COVID-19 samples, RAMP1 was also found in proliferating type II pneumocytes, a common finding in these patients.

Conclusions

The lower levels of CGRP should negatively impact the respiratory physiology of COVID-19 patients due to vasoconstriction, improper angiogenesis, less epithelial repair, and faulty immune response. Therefore, restoring CGRP levels in these patients may represent a novel therapeutic approach for COVID-19.

Gastrin-releasing peptide induces fibrotic response in MRC5s and proliferation in A549s

Idiopathic pulmonary fibrosis (IPF) is a complex lung disease, whose build-up scar tissue is induced by several molecules. Gastrin-releasing peptide (GRP) is released from pulmonary neuroendocrine cells, alveolar macrophages, and some nerve endings in the lung. A possible role of GRP in IPF is unclear. We aimed to investigate the fibrotic response to GRP, at the cellular level in MRC5 and A549 cell lines. The proliferative and fibrotic effects of GRP on these cells were evaluated by using BrdU, immunoblotting, immunofluorescence and qRT-PCR for molecules associated with myofibroblast differentiation, TGF-β and Wnt signalling. All doses of GRP increased the amount of BrdU incorporation in A549 cells. In contrast, the amount of BrdU increased in MRC5 cells in the first 24 h, though progressively decreased by 72 h. GRP did not stimulate epithelial-mesenchymal transition in A549 cells, rather, it stimulated the differentiation of MRC5 cells into myofibroblasts. Furthermore, GRP induced gene and protein expressions of p-Smad2/3 and Smad4, and reduced the levels of Smad7 in MRC5 cells. In addition, GRP decreased Wnt5a protein levels and stimulated β-catenin activation by increasing Wnt4, Wnt7a and β-catenin protein levels. GRP caused myofibroblast differentiation by inducing TGF-βand Wnt pathways via paracrine and autocrine signalling in MRC5 cells. In conclusion, GRP may lead to pulmonary fibrosis due to its proliferative and fibrotic effects on lung fibroblasts. The abrogation of GRP-mediated signal activation might be considered as a treatment modality for fibrotic lung diseases. Video Abstract.

Aberrant expression of calcitonin gene-related peptide and its correlation with prognosis in severe childhood pneumonia

OBJECTIVES

The purpose of this study was to evaluate the relationship between the serum levels of calcitonin gene-related peptide (CGRP) and the prognosis of pediatric patients with severe pneumonia.

METHODS

Children diagnosed with severe pneumonia (n=76) were stratified into the survival (n=58) and non-survival groups (n=18) according to their 28-day survival status and into the non-risk (n=51), risk (n=17) and high-risk (n=8) categories based on the pediatric critical illness score (PCIS). Demographic data and laboratory results were collected. Serum CGRP levels were determined by enzyme-linked immunosorbent assay (ELISA). A receiver operating characteristic (ROC) curve was generated to determine the cutoff score for high CGRP levels.

RESULTS

Serum CGRP levels were significantly higher in the survival group than in the non-survival group and were significantly higher in the non-risk group than in the risk and high-risk groups. The ROC curve for the prognostic potential of CGRP yielded a significant area under the curve (AUC) value with considerable sensitivity and specificity.

CONCLUSION

Our findings show that CGRP downregulation might be a diagnostic marker that predicts the prognosis and survival of children with severe pneumonia.

Aloperine suppresses human pulmonary vascular smooth muscle cell proliferation via inhibiting inflammatory response

Abnormal pulmonary arterial vascular smooth muscle cells (PASMCs) proliferation is critical pathological feature of pulmonary vascular remodeling that acts as driving force in the initiation and development of pulmonary arterial hypertension (PAH), ultimately leading to pulmonary hypertension. Aloperine is a main active alkaloid extracted from the traditional Chinese herbal Sophora alopecuroides and possesses outstanding antioxidation and anti-inflammatory effects. Our group found Aloperine has protective effects on monocroline-induced pulmonary hypertension in rats by inhibiting oxidative stress in previous researches. However, the anti-inflammation effects of Aloperine on PAH remain unclear. Therefore, to further explore whether the beneficial role of Aloperine on PAH was connected with its anti-inflammatory effects, we performed experiments in vitro. Aloperine significantly inhibited the proliferation and DNA synthesis of human pulmonary artery smooth muscle cells (HPASMCs) induced by platelet-derived growth factor-BB, blocked progression through G₀/G₁to S phase of the cell cycle and promoted total ratio of apoptosis. In summary, these results suggested that Aloperine negatively regulated nuclear factor-κB signaling pathway activity to exert protective effects on PAH and suppressed HPASMCs proliferation therefore has a potential value in the treatment of pulmonary hypertension by negatively modulating pulmonary vascular remodeling.

Knockout of α-calcitonin gene-related peptide attenuates cholestatic liver injury by differentially regulating cellular senescence of hepatic stellate cells and cholangiocytes

α-Calcitonin gene-related peptide (α-CGRP) is a 37-amino acid neuropeptide involved in several pathophysiological processes. α-CGRP is involved in the regulation of cholangiocyte proliferation during cholestasis. In this study, we aimed to evaluate if α-CGRP regulates bile duct ligation (BDL)-induced liver fibrosis by using a α-CGRP knockout (α-CGRP^-/-) mouse model. α-CGRP^-/- and wild-type (WT) mice were subjected to sham surgery or BDL for 7 days. Then, liver fibrosis and cellular senescence as well as the expression of kinase such as p38 and C-Jun N-terminal protein kinase (JNK) in mitogen-activated protein kinases (MAPK) signaling pathway were evaluated in total liver, together with measurement of cellular senescence in cholangiocytes or hepatic stellate cells (HSCs). There was enhanced hepatic expression of Calca (coding α-CGRP) and the CGRP receptor components (CRLR, RAMP-1 and RCP) in BDL and in both WT α-CGRP^-/- and BDL α-CGRP^-/- mice, respectively. Moreover, there was increased CGRP serum levels and hepatic mRNA expression of CALCA and CGRP receptor components in late-stage PSC samples compared to healthy control samples. Depletion of α-CGRP reduced liver injury and fibrosis in BDL mice that was associated with enhanced cellular senescence of hepatic stellate cells and reduced senescence of cholangiocytes as well as decreased activation of p38 and JNK MAPK signaling pathway. Cholangiocyte supernatant from BDL α-CGRP^-/- mice inhibited the activation and increased cellular senescence of cultured human HSCs (HHSCs) compared to HHSCs stimulated with BDL cholangiocyte supernatant. Taken together, endogenous α-CGRP promoted BDL-induced cholestatic liver fibrosis through differential changes in senescence of HSCs and cholangiocytes and activation of p38 and JNK signaling. Modulation of α-CGRP/CGRP receptor signaling may be key for the management of biliary senescence and liver fibrosis in cholangiopathies.

Betaine Attenuates Monocrotaline-Induced Pulmonary Arterial Hypertension in Rats via Inhibiting Inflammatory Response

Background: Pulmonary arterial hypertension (PAH) is characterized by increased pulmonary vascular resistance, leading to right ventricular failure and death. Recent studies have suggested that chronic inflammatory processes are involved in the pathogenesis of PAH. Several studies have demonstrated that betaine possesses outstanding anti-inflammatory effects. However, whether betaine exerts protective effects on PAH by inhibiting inflammatory responses in the lungs needs to be explored. To test our hypothesis, we aimed to investigate the effects of betaine on monocrotaline-induced PAH in rats and attempted to further clarify the possible mechanisms. Methods: PAH was induced by monocrotaline (50 mg/kg) and oral administration of betaine (100, 200, and 400 mg/kg/day). The mean pulmonary arterial pressure, right ventricular systolic pressure, and right ventricle hypertrophy index were used to evaluate the development of PAH. Hematoxylin and eosin staining and Masson staining were performed to measure the extents of vascular remodeling and proliferation in fibrous tissue. Monocyte chemoattractant protein-1 (MCP-1) and endothelin-1 (ET-1) were also detected by immunohistochemical staining. Nuclear factor-κB (NF-κB), tumor necrosis factor alpha (TNF-α), and interleukin-1β (IL-1β) were assessed by Western blot. Results: This study showed that betaine improved the abnormalities in right ventricular systolic pressure, mean pulmonary arterial pressure, right ventricle hypertrophy index, and pulmonary arterial remodeling induced by monocrotaline compared with the PAH group. The levels of MCP-1 and ET-1 also decreased. Western blot indicated that the protein expression levels of NF-κB, TNF-α, and IL-1β significantly decreased (p < 0.01). Conclusion: Our study demonstrated that betaine attenuated PAH through its anti-inflammatory effects. Hence, the present data may offer novel targets and promising pharmacological perspectives for treating monocrotaline-induced PAH.

CGRP 8-37 enhances lipopolysaccharide-induced acute lung injury and regulating aquaporin 1 and 5 expressions in rats

Calcitonin gene-related peptide (CGRP) has been shown to play important roles in biological functions. However, there is very little evidence on the value of CGRP in lipopolysaccharide (LPS)-induced acute lung injury/acute respiratory distress syndrome (ALI/ARDS). Therefore, this study aimed to investigate the role of CGRP in LPS-induced ALI in rats. In the experiment, Sprague-Dawley (SD) rats were randomized into control, an antagonist of α-calcitonin gene-related peptide receptor (CGRP8-37), LPS groups, and CGRP8-37 + LPS groups. ALI model was prepared through retrograde injection of LPS (10 mg/kg). At 6 and 12 h, bronchoalveolar lavage was performed and used to assess total cell count and levels of tumor necrosis factor-α, interleukin-1β, -6, and -10 by enzyme-linked immunosorbent assay (ELISA). Lung tissue was collected for assessing wet-to-dry (W/D) ratio, hematoxylin and eosin staining. Aquaporin (AQP)-1 and -5 expressions in lung tissues were detected by quantitative PCR and Western blot. The results showed that histological injury, total cell count, and W/D ratio significantly reduced in LPS group after 6 h. The levels of inflammatory cytokines in CGRP8-37 + LPS-treated rats were higher than that in LPS-treated rats (all, P < 0.001). Real-time RT-PCR analysis showed that levels of AQP-1 in rats from CGRP8-37 + LPS group was lower than that in LPS-treated rats (P = 0.005 and P < 0.001). Western blotting analysis showed that AQP-1 protein levels at 6 h significantly decreased in CGRP8-37 + LPS rats. Together, our data suggest that CGRP antagonists, CGRP8-37 could enhance ALI induced by LPS in the rat model, and regulate the expression levels of AQP-1 and AQP-5 by affecting inflammatory cytokines. Thereby, regulating endogenous CGRP may be a potential treatment for ALI/ARDS.