Calcitonin gene-related peptide regulates mitogen-activated protein kinase pathway to decrease transforming growth factor β1-induced hepatic plasminogen activator inhibitor-1 mRNA expression in HepG2 cells

Neuromodulation of bone: Role of different peptides and their interactions (Review)

Our understanding of the skeletal system has been expanded upon the recognition of several neural pathways that serve important roles in bone metabolism and skeletal homeostasis, as bone tissue is richly innervated. Considerable evidence provided by in vitro, animal and human studies have further elucidated the importance of a host of hormones and local factors, including neurotransmitters, in modulating bone metabolism and osteo-chondrogenic differentiation, both peripherally and centrally. Various cells of the musculoskeletal system not only express receptors for these neurotransmitters, but also influence their endogenous levels in the skeleton. As with a number of physiological systems in nature, a neuronal pathway regulating bone turnover will be neutralized by another pathway exerting an opposite effect. These neuropeptides are also critically involved in articular cartilage homeostasis and pathogenesis of degenerative joint disorders, such as osteoarthritis. In the present Review, data on the role of several neuronal populations in nerve-dependent skeletal metabolism is examined, and the molecular events involved are explored, which may reveal broader relationships between two apparently unrelated organs.

Maladjustment of β-CGRP/α-CGRP Regulation of AQP5 Promotes Transition of Alveolar Epithelial Cell Apoptosis to Pulmonary Fibrosis

This study explored the triggering mechanism of interstitial lung disease (ILD). We established the effects of immunogenic and neurogenic calcitonin gene-related peptide (CGRP) imbalance on the regulation of aquaporin 5 (AQP5) expression and the repair responses that promote the transition from alveolar epithelial cell (AEC) apoptosis to pulmonary fibrosis. Newly diagnosed ILD patients (n = 60) were enrolled, whose serological levels of β-CGRP, α-CGRP, AQP5, receptor activity modifying protein 1, and receptor component protein were detected by ELISA. Th1 and Th2 cytokines and CD4⁺ and CD8⁺ cells were measured by flow cytometry method. In vivo, bleomycin (BLM) was set for modeling pulmonary fibrosis. A CALCA-HET model was set as a chronic pulmonary fibrosis model. Hematoxylin-eosin, immunohistochemistry, and Masson's trichrome staining were performed to assess the role of apoptosis in the injured lung. The concentrations of cytokines were determined by cytokine antibody arrays. Abnormal activation of serological CD4⁺ T lymphocytes and predominant Th2 response was established in the patients with ILD. Moreover, the ratio of β-CGRP/α-CGRP positively correlated with the increased level of AQP5 in patients with ILD. In vivo, a significant increase of AQP5 and β-CGRP at the chronic stage of pulmonary fibrosis was induced by BLM in the mice model, whereas the expression of AQP5 protein was generally lower in the acute alveolitis phase. Moreover, the levels of AQP5 and α-CGRP in the CALCA-HET rats were lower than those of the normal saline group. The high ratio β-CGRP/α-CGRP enhanced the expression of AQP5, inhibited transforming growth factor-β1 (TGFβ1)/P-Smad1/Smad4 pathway, and upregulated the NRF2 signal, whereas the apoptosis of AECs was significantly reduced in late-stage pulmonary fibrosis. The imbalance of β-CGRP/α-CGRP may be associated with the predominance of Th2 response and participate in the process of AEC apoptosis in lung fibrosis. The high ratio of β-CGRP/α-CGRP may elevate the level of AQP5 through inactivation of the TGF-β1/smad1 signaling pathway and upregulation of the Nrf2 signaling in the chronic stage of pulmonary fibrosis.

Crosstalk between neuropeptides SP and CGRP in regulation of BMP2-induced bone differentiation

AIM OF THE STUDY

The peripheral nervous system is involved in regulation of bone metabolism via sensory and sympathetic innervation. Substance P (SP) and calcitonin gene-related peptide (CGRP) are two sensory neuropeptides that have been associated with regulation of osteogenic differentiation. However, the interaction between SP and CGRP both with each other and the bone morphogenetic protein 2 (BMP2) in regulation of osteogenic differentiation has not been studied. Therefore, the aim of this study was to investigate the interaction between SP and CGRP on BMP2-induced bone differentiation using model progenitor cells.

MATERIALS AND METHODS

C2C12 myoblasts and MC3T3 pre-osteoblasts were treated with SP and CGRP, both individually and in combination, in the presence of BMP2. The effects of the neuropeptides on BMP2-induced osteogenic differentiation were assessed by measuring alkaline phosphatase (ALP) activity, mineralization, and expression of osteogenic markers.

RESULTS

Both SP and CGRP enhanced BMP2 signaling, Runx2 mRNA expression, as well as mineralization in vitro. Co-stimulation with SP and CGRP resulted in down-regulation of BMP2-induced bone differentiation, suggesting potential crosstalk between the two neuropeptides in regulation of BMP2 signaling.

CONCLUSIONS

Based on the results shown here, CGRP can mitigate augmenting effects of SP on BMP2 signaling and the three pathways potentially converge on Runx2 to regulate BMP2-induced bone differentiation.

A Novel α-Calcitonin Gene-Related Peptide Analogue Protects Against End-Organ Damage in Experimental Hypertension, Cardiac Hypertrophy, and Heart Failure

Supplemental Digital Content is available in the text.

Research into the therapeutic potential of α-calcitonin gene–related peptide (α-CGRP) has been limited because of its peptide nature and short half-life. Here, we evaluate whether a novel potent and long-lasting (t_½ ≥7 hours) acylated α-CGRP analogue (αAnalogue) could alleviate and reverse cardiovascular disease in 2 distinct murine models of hypertension and heart failure in vivo.

Inhibition of the TGFβ signalling pathway by cGMP and cGMP-dependent kinase I in renal fibrosis

Agents that enhance production of nitric oxide (NO) and cyclic guanosine monophosphate (cGMP) ameliorate the progression of renal fibrosis. However, the molecular mechanism of this process is not fully understood. We hypothesize that the antifibrotic effects of cGMP and cGMP‐dependent kinase I (cGKI) are mediated via regulation of the TGFβ signalling pathway, both via ERK and the Smad‐dependent route. Kidney fibrosis was induced by unilateral ureter obstruction (UUO) in wild‐type and cGKI‐deficient (cGKI‐KO) mice. The cGMP/cGKI signalling pathway was activated by application of the soluble guanylate cyclase (sGC) stimulator BAY 41‐8543 (BAY), beginning 1 day after UUO. After 7 days, the antifibrotic effects of BAY were analysed by measuring mRNA and protein expression of characteristic fibrotic biomarkers. The effects of cGMP/TGFβ on cultured fibroblasts were also analysed in vitro. BAY application influenced the activity of the extracellular matrix (ECM)‐degrading matrix metalloproteases (MMP2 and MMP9) and their inhibitor tissue inhibitors of metalloproteinase‐1, the secretion of cytokines (e.g. IL‐6) and the expression pattern of ECM proteins (e.g. collagen, fibronectin) and profibrotic mediators (e.g. connective tissue growth factors and plasminogen‐activator inhibitor‐1). Activation of the cGMP/cGKI signalling pathway showed protective effects against fibrosis which were mediated by inhibition of P‐Erk1/2 and translocation of P‐smad3. The elucidation of these signalling mechanisms might support the development of new therapeutic options regarding cGMP/cGKI‐mediated antifibrotic actions.