Calcitonin gene-related peptide increases the production of glycosaminoglycans but not of collagen type I and III in cultures of rat fat-storing cells

Influence of sensory neuropeptides on human cutaneous wound healing process

BACKGROUND

Close interactions exist between primary sensory neurons of the peripheral nervous system (PNS) and skin cells. The PNS may be implicated in the modulation of different skin functions as wound healing.

OBJECTIVE

Study the influence of sensory neurons in human cutaneous wound healing.

METHODS

We incubated injured human skin explants either with rat primary sensory neurons from dorsal root ganglia (DRG) or different neuropeptides (vasoactive intestinal peptide or VIP, calcitonin gene-related peptide or CGRP, substance P or SP) at various concentrations. Then we evaluated their effects on the proliferative and extracellular matrix (ECM) remodeling phases, dermal fibroblasts adhesion and differentiation into myofibroblasts.

RESULTS

Thus, DRG and all studied neuromediators increased fibroblasts and keratinocytes proliferation and act on the expression ratio between collagen type I and type III in favor of collagen I, particularly between the 3rd and 7th day of culture. Furthermore, the enzymatic activities of matrix metalloprotesases (MMP-2 and MMP-9) were increased in the first days of wound healing process. Finally, the adhesion of human dermal fibroblasts and their differentiation into myofibroblasts were promoted after incubation with neuromediators. Interestingly, the most potent concentrations for each tested molecules, were the lowest concentrations, corresponding to physiological concentrations.

CONCLUSION

Sensory neurons and their derived-neuropeptides are able to promote skin wound healing.

Immunocytochemical study on the liver innervation in patients with cirrhosis

In the liver, the autonomic nervous system plays an important role in degenerative and inflammatory changes. The aim of the present study was to investigate the distribution of neuronal fibres containing neuropeptides in livers of 5 patients with cirrhosis by immunocytochemical localization at the light and electron microscopical level of substance P (SP), neuropeptide Y (NPY), somatostatin (SOM), and calcitonin gene-related peptide (CGRP). In patients with alcoholic cirrhosis, a decreased number of neuronal fibres was found in the portal tract and fibrous septa as well as in the sinusoids of regenerative nodules. NPY- and SP-immunoreactive neuronal fibres were more numerous than CGRP-containing fibres. They were located mainly in portal tracts. These findings led to the conclusion that peptidergic innervation plays a role in inflammatory and fibrotic changes in cirrhotic liver.

Receptors mediating CGRP-induced relaxation in the rat isolated thoracic aorta and porcine isolated coronary artery differentiated by h(alpha) CGRP(8-37)

1 Receptors mediating CGRP-induced vasorelaxation were investigated in rat thoracic aorta and porcine left anterior descending (LAD) coronary artery and anterior interventricular artery (AIA), using CGRP agonists, homologues and the antagonist h(alpha) CGRP(8-37). 2 In the endothelium-intact rat aorta, h(alpha) CGRP, h(beta) CGRP, rat beta CGRP and human adrenomedullin caused relaxation with similar potencies. Compared with h(alpha) CGRP, rat amylin was about 25 fold less potent, while [Cys(ACM2,7)] h(alpha) CGRP and salmon calcitonin were at least 1000 fold weaker. 3 H(alpha) CGRP(8-37) (up to 10(-5) M) did not antagonize responses to h(alpha) CGRP, h(beta) CGRP or rat beta CGRP (apparent pKB <5). Peptidase inhibitors did not increase either the effect of h(alpha) CGRP or [Cys(ACM,2,7)] h(alpha) CGRP, while h(alpha) CGRP(8-37) remained inactive. Endothelium-dependent relaxation produced by h(alpha) CGRP was accompanied by increases in cyclic AMP and cyclic GMP, that were not inhibited by h(alpha) CGRP(8-37) (10(-5) M). 4 In porcine LAD and AIA, h(alpha) CGRP produced relaxation in an endothelium-independent manner. H(alpha) CGRP(8-37) competitively antagonized h(alpha) CGRP responses (pA2 6.3 and 6.7 (Schild slope 0.9+/-0.1, each), in LAD and AIA, respectively). In LAD artery, h(alpha) CGRP-induced relaxation was accompanied by increases in cyclic AMP that were inhibited by h(alpha) CGRP(8-37) (10(-7)-10(5 )). 5 In conclusion, the antagonist affinity for h(alpha) CGRP(8-37) in porcine coronary artery is consistent with a CGRP1 receptor, while the lack of h(alpha) CGRP(8-37) antagonism in rat aorta could suggest either a CGRP receptor different from CGRP1 and CGRP2 type, or a non-CGRP receptor.

Sensory nerves affect the recruitment and differentiation of rat periovarian brown adipocytes during cold acclimation

Rat periovarian adipose tissue contains a low number of uncoupling protein-expressing brown adipocytes scattered into lobules of white fat. Their increase following cold acclimation is matched by a major increase in noradrenergic and neuropeptide Y-, substance P- and calcitonin gene-related peptide-containing nerves. To ascertain whether periovarian fat is provided with sensory nerves, and whether any relationship exists between such nerves (in particular the calcitonin gene-related peptide-containing fibers found in cold-acclimated rats in close association with brown adipocytes) and brown fat recruitment, the effects of capsaicin desensitization on neuropeptide-containing nerves and brown adipocyte density were studied in the periovarian tissue of rats kept at 20 degrees C and on a group acclimated to 4 degrees C for 14 days. In both groups, systemic capsaicin administration considerably reduced the expression of substance P and calcitonin gene-related peptide in vascular-nerve bundles and parenchyma. In cold-acclimated rats, the increase in brown adipocyte density was significantly checked by capsaicin administration (21.11 versus 7.96 brown adipocytes/mm2, P&lt;0.05). Finally, ultrastructural investigation showed the occurrence of brown adipocyte precursors filled with aggregates of glycogen and poorly differentiated multilocular adipocytes in capsaicin-treated cold-acclimated rats. These data suggest that periovarian adipose tissue is indeed provided with sensory neuropeptide-containing nerves and that they play a role in the recruitment and differentiation of brown adipocytes.

Influence of capsaicin-sensitive afferent fibers on acetic acid-induced chronic gastric ulcers in rats

Accumulating evidence indicates that capsaicin-sensitive afferent fibers play a pivotal role in acute gastroprotection. However, whether they also influence healing of chronic gastric ulcers is still unknown. The effects of ablation of sensory neurons on acetic acid-induced chronic gastric ulcers in rats were investigated at morphologic and biochemical levels by computerized imaging analysis of the ulcerated area, histologic examination, and neuropeptide determination. Afferent nerve ablation, as a result of treating rats with a neurotoxic dose of capsaicin (50 + 50 mg/kg subcutaneously over 2 days), produced a significant increase in the ulcer area at 1 and 2 weeks after acetic acid injection. The delay in ulcer healing was associated with a marked and persistent decrease in tissue calcitonin gene-related peptide-like immunoreactivity, whereas gastric vasoactive intestinal polypeptide was unaffected by capsaicin pretreatment. Histologically, as compared with control rats, capsaicin-desensitized animals only differed in a slight increase in the inflammatory infiltrate during the early phase of ulcer formation. These findings suggest that capsaicin-sensitive afferent fibers may play a role in the healing of chronic experimental gastric ulcers in rats, but the underlying mechanisms remain to be elucidated and deserve further investigation.

Therapeutic potential of capsaicin-like molecules: studies in animals and humans

Capsaicin-sensitive primary afferent neurons in the peripheral nervous system are widely distributed to both the somatic and visceral territories: their inactivation following capsaicin "desensitization" is expected to produce analgesia and to be useful for a number of human diseases such as asthma, urinary incontinence, inflammatory diseases of the gut, arthritis and psoriasis. The present communication reviews the therapeutic potential of capsaicin-like drugs in the pathophysiology of the mammalian urinary bladder.

Calcitonin gene-related peptide: multiple actions, multiple receptors

Calcitonin gene-related peptide (CGRP) shows diversity both in its effects and its receptors. It is likely to have roles as a neurotransmitter, neuromodulator, local hormone and trophic factor. Its effects include rapid changes in neuronal activity, relaxation of many types of smooth muscle, actions on metabolism and changes in gene expression. Receptor heterogeneity has been revealed from experiments comparing agonist potency ratios and antagonist affinities. The evidence from these approaches is reviewed in this article and a speculative receptor classification scheme is proposed. Some of the likely future directions for CGRP research are discussed.