Potential role of the neuropeptide CGRP in the induction of differentiation of rat hepatic portal vein wall

CGRP Regulates the Age-Related Switch Between Osteoblast and Adipocyte Differentiation

Osteoporosis is a chronic age-related disease. During aging, bone marrow-derived mesenchymal stem cells (BMSCs) display increased adipogenic, along with decreased osteogenic, differentiation capacity. The aim of the present study was to investigate the effect of calcitonin gene-related peptide (CGRP) on the osteogenic and adipogenic differentiation potential of BMSC-derived osteoblasts. Here, we found that the level of CGRP was markedly lower in bone marrow supernatant from aged mice compared with that in young mice. In vitro experiments indicated that CGRP promoted the osteogenic differentiation of BMSCs while inhibiting their adipogenic differentiation. Compared with vehicle-treated controls, aged mice treated with CGRP showed a substantial promotion of bone formation and a reduction in fat accumulation in the bone marrow. Similarly, we found that CGRP could significantly enhance bone formation in ovariectomized (OVX) mice in vivo. Together, our results suggested that CGRP may be a key regulator of the age-related switch between osteogenesis and adipogenesis in BMSCs and may represent a potential therapeutic strategy for the treatment of age-related bone loss.

Calcitonin Gene-Related Peptide Downregulates Expression of Inducible Nitride Oxide Synthase and Caspase-3 after Intestinal Ischemia-Reperfusion Injury in Rats

BACKGROUND

Various investigations have demonstrated that calcitonin gene-related peptide (CGRP) plays an important role in mediating ischemic preconditioning. CGRP has been shown to mimic the protective effects of ischemic preconditioning and mitigate ischemia-reperfusion (I/R) injury in the heart, brain, gastrointestinal system, and other tissues. This study aimed to examine whether CGRP, a proven intestinal cytoprotective molecule, exerted its protective effects through modulation of inducible nitride oxide synthase (iNOS) and apoptosis after intestinal I/R injury.

METHODS

This animal study randomly divided 30 rats into the following five groups: (1) the normal control group, (2) the ischemia group with normal saline, (3) the I/R group with normal saline, (4) the ischemia group with CGRP (300 μg/kg), and (5) the I/R group with CGRP (300 μg/kg). Levels of iNOS messenger RNA (mRNA) and protein, and caspase-3 protein were determined by real-time quantitative polymerase chain reaction and Western blotting analyses, respectively. Statistical analysis was performed using analysis of variance with Dunn test.

RESULTS

The mRNA levels of iNOS increased after the intestinal ischemia or intestinal reperfusion phase (p < 0.01), and CGRP pretreatment significantly decreased iNOS mRNAs and protein levels (p < 0.01). The expression protein levels of caspase-3 increased after the intestinal ischemia or intestinal reperfusion phase. CGRP pretreatment significantly decreased the levels of caspase-3 proteins. CGRP intestinal cytoprotection is mediated, in part, by downregulation of expression of iNOS and caspase-3 after intestinal I/R injury.

CONCLUSION

The study indicates that the cytoprotective role of CGRP (i.e., antiapoptotic effect) after I/R injury could be via downregulation of iNOS, which may relieve I/R tissue damage by blocking iNOS activity.

Endogenous CGRP protects against neointimal hyperplasia following wire-induced vascular injury

Neointimal hyperplasia is the primary lesion underlying atherosclerosis and restenosis after percutaneous coronary intervention. Calcitonin gene-related peptide (CGRP) is produced by alternative splicing of the primary transcript of the calcitonin/CGRP gene. Originally identified as a strongly vasodilatory neuropeptide, CGRP is now known to be a pleiotropic peptide widely distributed in various organs and tissues. Our aim was to investigate the possibility that CGRP acts as an endogenous vasoprotective molecule. We compared the effect of CGRP deficiency on neointimal formation after wire-induced vascular injury in wild-type and CGRP knockout (CGRP-/-) mice. We found that neointimal formation after vascular injury was markedly enhanced in CGRP-/- mice, which also showed a higher degree of oxidative stress, as indicated by reduced expression of nitric oxide synthase, increased expression of p47phox, and elevated levels of 4HNE, as well as greater infiltration of macrophages. In addition, CGRP-deficiency led to increased vascular smooth muscle cell (VSMC) proliferation within the neointima. By contrast, bone marrow-derived cells had little or no effect on neointimal formation in CGRP-/-mice. In vitro analysis showed that CGRP-treatment suppressed VSMC proliferation, migration, and ERK1/2 activity. These results clearly demonstrate that endogenous CGRP suppresses the oxidative stress and VSMC proliferation induced by vascular injury. As a vasoprotective molecule, CGRP could be an important therapeutic target in cardiovascular disease.

Endogenous αCGRP protects against concanavalin A-induced hepatitis in mice

To evaluate hepatoprotective effect of alpha-calcitonin gene-related peptide (alphaCGRP), we compared the susceptibilities of alphaCGRP-/- and wild-type mice to concanavalin A (Con A)-induced hepatitis. Twelve hours after Con A administration, serum transaminases were markedly higher in alphaCGRP-/- than wild-type mice, and much more extensive TUNEL-positive lesions and DNA fragmentation were detected in the livers of alphaCGRP-/- mice. Notably, expression of IL-6 was selectively diminished in alphaCGRP-/- mice, suggesting that induction of IL-6 during acute inflammatory responses is blunted in alphaCGRP-/- mice. In addition, primary cultured alphaCGRP-/- hepatocytes were more susceptible to IFN-gamma-induced cell death than hepatocytes from wild-type mice. Administration of exogenous alphaCGRP reduced the incidence of apoptosis among hepatocytes and endothelial cells. It thus appears that alphaCGRP exerts a hepatoprotective effect by modulating cytokine expression and preventing apoptosis.