Down-regulation Of Calcitonin Gene-related Peptide Research Articles

Changes of Subjective Symptoms and Tear Film Biomarkers Following Lenticule Extraction.

To investigate the influence of lenticule extraction on subjective symptoms and objective biomarkers of dry eye and to clarify relationships between markers and find indicators for subjective symptoms after lenticule extraction. Right eyes of myopic patients undergoing lenticule extraction surgery (n = 35) were examined preoperatively and 5 and 90 days postoperatively using established clinical dry eye examination methods (tear film break-up time [BUT], Schirmer test, lissamine green and fluorescein staining, and Ocular Surface Disease Index (OSDI) questionnaire). A patient subset was also examined after 1 year (n = 14). Tear samples were eluted from Schirmer strips and then measured with enzyme-linked immunosorbent assays (calcitonin gene-related peptide (CGRP), interleukin-1β, IL-6, IL-8, matrix metallopeptidase 9 [MMP-9], nerve growth factor, and tumor necrosis factor-α). Postoperatively, unpreserved ofloxacin and dexamethasone eye drops were given (four times a day for 10 days). BUT decreased at days 5 (P = .023) and 90 (P = .025). Lissamine green staining increased at day 90 (P = .036). OSDI values increased at day 5 (total values, vision-related function, ocular symptoms, all P < .001, but not environmental triggers) and at day 90 (vision-related function, P = .017). A downregulation of CGRP (P = .006) and MMP-9 levels (P = .042) was observed on day 5 compared to day 90. Due to incongruity of patient symptoms, clinical signs, and tear protein changes, no predictive indicator was found, but some patients reported increased discomfort. Changes after lenticule extraction are not exclusively due to dry eye. [J Refract Surg. 2023;39(9):597-604.].

Dietary capsaicin normalizes CGRP peptidergic DRG neurons in experimental diabetic peripheral neuropathy

Diabetic sensory neuropathy leads to impairment of peripheral sensory nerves and downregulation of calcitonin gene-related peptide (CGRP) in a functionally specific subset of peripheral sensory neurons mediating pain. Whether CGRP plays a neuroprotective role in peripheral sensory nerve is unclear. We evaluated alterations in noxious thermal sensation and downregulation of CGRP in the 8 weeks after induction of diabetes in rats. We supplemented capsaicin in the diet of the animals to upregulate CGRP and reversed the downregulation of the neuropeptide in the dorsal root ganglion (DRG) neurons dissociated from the diabetic animals, via gene transfection and exogenous CGRP, to test disease-preventing and disease-limiting effects of CGRP. Significant preservation of the nociceptive sensation, CGRP in spinal cord and DRG neurons, and number of CGRP-expressing neurons was found in the diabetic animals given capsaicin. Improvement in the survival of the neurons and the outgrowth of neurites was achieved in the neurons transfected by LV-CGRP or by exogenous CGRP, paralleling the correction of abnormalities of intracellular reactive oxygen species and mitochondrial transmembrane potentials. The results suggest that downregulation of CGRP impairs viability, regeneration and function of peripheral sensory neurons while capsaicin normalizes the CGRP peptidergic DRG neurons and function of the sensory nerves.

Activation orexin 1 receptors in the ventrolateral periaqueductal gray matter attenuate nitroglycerin-induced migraine attacks and calcitonin gene related peptide up-regulation in trigeminal nucleus caudalis of rats

This study aims to explore whether orexin 1 receptors (Orx1R) in the ventrolateral periaqueductal gray matter (vlPAG) play a role in the modulation of migraine headaches in adult male Wistar rats. To model chronic migraine-associated pain, nitroglycerin (NTG) (5 mg/kg/IP) was administered to test subjects every second day for 9 days. After the last NTG injection, rats were randomly separated into the following groups (n = 6): orexin-A (OrxA) groups that received intra-vlPAG OrxA (25, 50, and 100 pM), an Orx1R antagonist group, a SB-334867 (20 μM) group; and a SB-334867 (20 μM) + OrxA (100 pM) group. After 10 min, migraine-associated behavioral symptoms were recorded in all animals for up to 90 min. Light-dark chamber and hot plate tests were used for assessing light aversion and thermal hyperalgesia, respectively. Calcitonin gene-related peptide (CGRP)-positive cells were detected in the trigeminal nucleus caudalis (Vc) by immunofluorescence microscopy. NTG caused significant freezing behavior, which was prevented by all OrxA doses. Moreover, OrxA (100 pM) could obstruct NTG-induced increases in facial rubbing and decreases in climbing and body grooming. Furthermore, NTG-induced light aversion and thermal hyperalgesia were attenuated by OrxA at doses of 50 and 100 pM. The effects of OrxA were significantly blocked by SB-334867 (20 μM). Besides, OrxA (100 pM) decreased NTG-induced CGRP upregulation. The data revealed that the activation of Orx1Rs in the vlPAG is effective in relieving NTG-induced migraine symptoms mainly by the downregulation of CGRP in the Vc of rats.

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

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. 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. 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.

Association of down-regulation of calcitonin gene-related peptide and substance P with increase of myocardial vulnerability in diabetic neuropathic rats

Diabetic patients present high co-morbidities of neuropathy and severer consequences of coronary heart disease. But the pathological mechanism is still unclear. Here we investigated a potential association of diabetic impairment of sensory nerves with increase of vulnerability of myocardium in acute myocardial ischemia/reperfusion. A rat model of diabetes mellitus was induced by high fat and sugar diet plus a small dose of streptozotocin. Impairment of sensory nerves was evaluated by measurement of changes in tail flick latency to noxious thermal stimulation and calcitonin gene-related peptide (CGRP) and substance P (SP) in the dorsal root ganglia (DRG) and the myocardium of the heart were examined. The myocardial injury was examined by infarct size, apoptosis ratio of cardiomyocytes and cardiac troponin I in the animals underwent acute myocardial ischemia (for 30min) and reperfusion (for 120min). The effects of CGRP and SP on cardiomyocyte injury induced by high glucose and hypoxia/reoxygenation were tested in cultured myocytes. The diabetic animals presented significant elevation of noxious thermal threshold with obvious reduction of the contents of CGRP and SP in the DRG and the myocardium. Importantly, the diabetic animals showed significant increases of infarct size, myocyte apoptosis and serum cardiac troponin I after acute myocardial ischemia/reperfusion, compared to the non-diabetic control. Furthermore, exogenously administered CGRP and SP attenuated the myocyte injury induced by the high concentration of glucose and hypoxia/reoxygenation. These findings suggested that impairment of sensory nerves with significant reduction of CGRP and SP in DRG, ventricular myocardium and serum may be associated with increase of myocardial vulnerability in acute myocardial ischemia/reperfusion in streptozotocin-induced diabetic rats.

Inhibitory effect of calcitonin gene-related peptide on hypoxia-induced rat pulmonary artery smooth muscle cells proliferation: Role of ERK1/2 and p27

Calcitonin gene-related peptide (CGRP) inhibits angiotensin II-induced proliferation of aortic smooth muscle cells via inactivation of extracellular signal-regulated protein kinase 1/2 (ERK1/2). ERK1/2 is necessary for the degradation or down-regulation of the cell cycle inhibitor p27, and is also crucial in mediating proliferation of pulmonary artery smooth muscle cells (PASMCs). Whether ERK1/2/p27 signal pathway is involved in CGRP-mediated pathogenesis of pulmonary hypertension and vascular remodeling remains unknown. Pulmonary hypertension was induced by hypoxia in rats, and capsaicin (50mg/kg, s.c.) was used to deplete endogenous CGRP. Proliferation of cultured PASMCs was determined by BrdU incorporation method and flow cytometry. The expression/level of CGRP, p27, ERK1/2, c-fos and c-myc was analyzed by radioimmunoassay, immunohistochemistry, real-time PCR or Western blot. Sensory CGRP depletion by capsaicin exacerbated hypoxia-induced pulmonary hypertension in rats, as shown by an increase in right ventricle systolic pressure, mean pulmonary artery pressure and vascular hypertrophy, accompanied with decreased p27 expression and increased expression of phosphorylated ERK1/2, c-fos and c-myc. Exogenous application of CGRP significantly inhibited hypoxia-induced proliferation of PASMCs concomitantly with increased p27 expression and decreased expression of phosphorylated ERK1/2, c-fos and c-myc. These effects of CGRP were abolished in the presence of CGRP8–37. Knockdown of p27 also reversed the inhibitory effect of CGRP on proliferation of PASMCs and expression of c-fos and c-myc, but not on ERK1/2 phosphorylation. These results suggest that CGRP inhibits hypoxia-induced proliferation of PASMCs via ERK1/2/p27/c-fos/c-myc pathway. Down-regulation of CGRP may contribute to remodeling of pulmonary arteries in hypoxia-induced pulmonary hypertension.

Calcitonin gene-related peptide gene expression in collagen-induced arthritis is differentially regulated in primary afferents and motoneurons: influence of glucocorticoids

Calcitonin gene-related peptide is involved in peripheral and spinal mechanisms of inflammatory pain. In this paper, we used collagen II-induced arthritis in the rat as a model to investigate the influence of chronic arthritic pain on calcitonin gene-related peptide gene expression in sensory and motor pathways. Additionally, we examined the effect of the glucocorticoid drug budesonide on arthritis-induced changes of calcitonin gene-related peptide expression and constitutive calcitonin gene-related peptide expression. Thirteen days after the immunization with native rat collagen type II rats developed a progressive and chronic polyarthritis which was scored with respect to the degree of swelling and/or redness of the paw and ankle joints. Budesonide significantly attenuated the extent of arthritis. Changes in calcitonin gene-related peptide expression were evaluated by semiquantitative in situ hybridization and immunocytochemistry on day 21 post-immunization. In sensory neurons of dorsal root ganglia of arthritic rats, a significant increase in calcitonin gene-related peptide messenger RNA and protein levels was seen. These increases were completely blocked by budesonide. Also in dorsal root ganglia of non-arthritic rats, budesonide had an effect, with reduced calcitonin gene-related peptide messenger RNA levels below constitutive concentrations. Image analysis of calcitonin gene-related peptide immunoreactivity revealed that changes in calcitonin gene-related peptide expression were due to alterations in calcitonin gene-related peptide expression levels rather than to de novo synthesis or changes in the numbers of calcitonin gene-related peptide expressing neurons. In spinal motoneurons of arthritic rats, marked decreases in calcitonin gene-related peptide messenger RNA and protein levels were measured. These reductions were attenuated by budesonide. The changes in calcitonin gene-related peptide expression in motoneurons correlated with the severity of arthritis in the ipsilateral hind paw. Budesonide had no effects on calcitonin gene-related peptide messenger RNA levels in motoneurons of non-arthritic rats. The opposite regulation of calcitonin gene-related peptide gene expression in primary sensory and spinal somatomotor pathways in collagen-induced arthritis suggests that calcitonin gene-related peptide plays a specific role in both chronic inflammatory pain and arthritis-induced motor dysfunction. The sensitivity of constitutive and inflammation-induced sensory calcitonin gene-related peptide expression to budesonide treatment may indicate that the beneficial effects of steroid treatment in inflammation is partly mediated by down-regulation of calcitonin gene-related peptide in sensory neurons involved in neurogenic inflammation.