Calcitonin gene-related peptide (CGRP) and its effects on protein release in vitro in the developing submandibular gland of the rat

Neuropeptide Profiles of Mammalian Male Genital Tract: Distribution and Functional Relevance in Reproduction

Neuropeptides are secretory peptides characterized by small chains of amino acids linked by peptide bonds. They are majorly found in some mammalian neurons and glial cells, where they modulate a variety of physiological homeostasis. In the male genital tract, they are mostly found in the neuronal fibers supplying the vasculature, smooth muscle layer, interstitium, and lamina propria of the tunica mucosa of the various reproductive organs. Functionally, neuropeptides are strongly implicated in vascular temperature regulations, spermatozoa extrusion, epididymal content transportation, and movement of accessory gland secretions. This review provides an overview of neuropeptides with respect to their synthesis, release, and mechanism of actions, with emphasis on the locally acting neuropeptides, such as substance P (SP), neuropeptide Y (NPY), vasoactive intestinal peptides (VIP), calcitonin gene-related peptide (CGRP), galanin (GAL), cholecystokinin (CCK), C-terminal flanking peptide of NPY (CPON), peptide histidine isoleucine (PHI), and met- and leu-enkephalins (M-ENK and L-ENK) along the male genital tract (i.e., the spermatic cord, testis, epididymis, ductus deferens, and accessory sex organs) of 14 species of mammals and their marked influence on reproduction. This review also revealed from documented reports that the vast majority of neuropeptides present in the autonomic nerve supply to the male genital tract probably coexist with other peptides or with various neurotransmitters (tyrosine hydroxylase, dopamine beta hydroxylase, and 5-hydroxytryptamine). In addition, documented evidence of variation in age, season, and intraspecies differences were identified as notable factors of influence in peptidergic nerve fiber distribution.

Expression of aquaporin 5 during murine palatine glands development: a light and electron microscopic immunocytochemical study

Although aquaporin 5 (AQP5) seems to play a role in cytodifferentiation and cell proliferation during the development of salivary glands, its distribution during minor salivary glands development has been scarcely reported. This study examined the temporal-spatial distribution of AQP5 in the developing rat palatine glands using light and electron microscopy. At embryonic (E) age E18, AQP5 labeling was observed on the cell membranes of some terminal bulb cells. After lumenization at E20, AQP5 labeled the apical membrane in acini where a lumen existed, in addition to displaying positive diffuse cytoplasmic and cell membrane staining. At the electron microscopic level, AQP5 labeled the supranuclear cytoplasm and the luminal microvilli along the apical membrane. At birth, AQP5 was also localized to the lateral membranes associated ultrastructurally with the microvilli of intercellular canaliculi. After postnatal (PN) day PN7, mucous acini and serous demilunes showed reactivity. AQP5 reached peak reactivity around PN13 with a similar staining pattern in all acini, but had reduced dramatically by PN21. Thereafter, AQP5 reactivity was mainly associated with serous cells in adults. In conclusion, the transitory expression of AQP5 during palatine glands development may reflect changing physiological functions of the secretory cells and/or AQP5 throughout the maturation of the glands.

Distribution of nerve fibers during the development of palatine glands in rats

BACKGROUND

Salivary gland maturation and function are modulated by the nervous system. Nevertheless, little is known about salivary gland innervation during development, particularly minor salivary glands. This study investigated the development of the innervation of the palatine glands of rat.

MATERIALS AND METHODS

Frozen sections of rat palatine glands at different stages were immunohistochemically labeled for detection of the general nerve markers protein gene product 9.5 (PGP 9.5) and growth associated protein 43 (GAP-43), and the autonomic nerve markers calcitonin gene-related peptide (CGRP) and neuropeptide Y (NPY).

RESULTS

PGP 9.5 and GAP-43-immunoreactive fibers (IRF) were present in the mesenchyme and in association with developing acini, ducts and blood vessels. GAP-43-IRF were more abundant and diffuse than PGP 9.5-IRF at early stages, but showed similar distribution with growth, ramifying out from thick bundles in connective tissues until encircling the secretory units observed around postnatal day 21 (PN21). CGRP-IRF were detected in the mesenchyme at embryonic day 20 (E20) and PN0. CGRP-IRF became numerous around PN7 and PN10. They then decreased to the adult level at PN21, mainly located around ducts and infrequently blood vessels. NPY-IRF were sparsely detected in the mesenchyme at E20, then detected in close proximity to acini in addition to blood vessels at PN3. NPY-IRF increased till reaching the adult stage, and were mainly associated with blood vessels and around mucous cells and some serous demilunes.

CONCLUSION

The findings indicated a developmental modification of the sensory and autonomic innervation which may play a role in the functional maturation of the palatine salivary glands.

Salivary levels of CGRP and VIP in rhinosinusitis and migraine patients

BACKGROUND

Secretion of calcitonin gene-related peptide (CGRP) from trigeminal nerves and vasoactive intestinal peptide (VIP) from parasympathetic nerves is involved in the pathophysiology of migraine and rhinosinusitis. Analysis of these neuropeptides in human saliva samples can be used as markers of trigeminal and parasympathetic nerve activity in patients between and during attacks as well as in response to specific treatments.

OBJECTIVE

To compare the amount of trigeminal sensory and parasympathetic nerve activation by measuring CGRP and VIP levels in the saliva of subjects experiencing noninfectious allergic rhinosinusitis, migraine with sinus symptoms, and no symptoms.

METHODS

Subjects were enrolled in three groups. Group A: subjects without a history of migraine, "sinus" headache, or allergic rhinosinusitis within the previous 6 months. Group B: subjects with chronic recurrent noninfectious rhinosinusitis and no history of migraine or "sinus" headache. Group C: subjects with self-described "sinus" headaches whose symptoms met International Headache Society diagnostic criteria (1.1 or 1.2) for migraine. The total amount of CGRP and VIP present in saliva collected under normal, pathological, and therapeutic conditions was determined by radioimmunoassay. Neuropeptide levels were normalized to total volume and amount of protein, and levels were correlated to onset and change in clinical symptoms.

RESULTS

Total volume, total protein, and CGRP and VIP levels did not significantly change in saliva collected on consecutive days in the clinic and at the subject's home, respectively. No appreciable change in baseline salivary levels of CGRP and VIP was detected in control subjects. However, baseline salivary levels of CGRP and VIP were significantly elevated between attacks in allergic rhinosinusitis and migraine subjects compared to control values. For rhinosinusitis subjects, the amount of CGRP and VIP during attacks returned to baseline values following treatment with pseudoephedrine and relief of symptoms. Similarly, CGRP and VIP levels during a migraine headache were significantly reduced within 2 hours after sumatriptan treatment and reported symptom relief.

CONCLUSION

Correlation of CGRP and VIP saliva levels observed in our study supports physiologically coordinated regulation of trigeminal and parasympathetic nerve activation in allergic rhinosinusitis and migraine patients between and during attacks as well as following treatment. Furthermore, our findings demonstrate that analysis of human saliva neuropeptides may provide a semiquantitative index of pathological and therapeutic states and, therefore, function as a clinical model for studying neuronal mechanisms involved in migraine and rhinosinusitis.

Role of nerve growth factor in the regulation of parotid cell differentiation induced by rat serum

The present study was undertaken to examine the factors that regulate rat serum (RS)- and nerve growth factor (NGF)-induced differentiation in a rat parotid acinar cell line. RS elicited extracellular signal-regulated kinase (ERK1/ERK2) activation within 5min, while cyclic AMP (cAMP) levels transiently rose after 6hr. RS also elicited a rise in amylase mRNA levels within 30min, which preceded the rise in amylase protein levels. A possible role for NGF was suggested by the findings that parotid cells express both TrkA and p75 receptors. The immunoreactivity of these NGF receptors was reduced during exposure to RS. Following prolonged incubation in RS when ERK activity subsided to near basal levels, NGF restored ERK1/ERK2 activity to the elevated level initially observed in RS. NGF was ineffective when cells were incubated in fetal bovine serum. NGF, when incubated in combination with the cAMP-generating neuropeptides, calcitonin gene-related peptide and vasoactive intestinal peptide, markedly enhanced the cellular amylase content produced by RS. We conclude that parotid cell differentiation arises from an activation of cell surface receptors by humoral factors in combination with NGF and cAMP-generating neuropeptides.

Upregulation of vasoactive intestinal polypeptide (VIP) and calcitonin gene-related peptide (CGRP) expression in stellate ganglia of children with congenital cardiovascular lesions

The distribution patterns of vasoactive intestinal polypeptide (VIP) and calcitonin gene-related peptide (CGRP) immunoreactivities (IR) in stellate ganglia of human neonates and infants with congenital heart and vascular lesions were investigated by the method of indirect immunohistochemistry. The results demonstrated upregulation of VIP and CGRP expression in principal ganglionic neurons independently of the type of lesion. It is suggested that the activation of neuropeptide synthesis in stellate ganglia is a compensatory reaction of ganglionic neurons in response to congenital cardiovascular lesions, in regulation of heart contractility, and as a trophic influence on the ischemic myocardium. Hypoxia is the main inducing factor for the upregulation of VIP and CGRP expression in sympathetic neurons.

Interaction of calcitonin gene-related peptide (CGRP), substance P (SP) and conventional autonomic agonists in rat submandibular salivary peroxidase release in vitro

Our previous immunohistochemical studies reveal that several neuropeptides, such as substance P and calcitonin gene-related peptide, innervate the major salivary glands of the mouse, rat and human. The aim of the study was to clarify their interactions by measuring their effects alone or with conventional autonomic agonists (carbachol, phenylephrine and isoproterenol) on peroxidase secretion of incubated submandibular gland slices. Calcitonin gene-related peptide evoked significant increase in peroxidase activity of the secretion only when used at 10(-5) M concentration, while substance P evoked significant, dose-dependent increase at much lower concentrations (10(-10) M). Adrenergic and cholinergic agonists enhanced peroxidase activity. Interestingly, substance P inhibited both phenylephrine and isoproterenol induced increase in peroxidase activity. Calcitonin gene-related peptide did not affect the inhibition caused by substance P. Our results demonstrate that in the salivary gland tissue substance P alone or in conjunction with adrenergic agonists result in opposing secretory responses with the doses used in vitro. Conversely, the response mediated by adrenergic receptors may be critically affected by simultaneous occupation of substance P receptors.

Tachykinins in the gut. Part II. Roles in neural excitation, secretion and inflammation

The preprotachykinin-A gene-derived peptides substance (substance P; SP) and neurokinin (NK) A are expressed in intrinsic enteric neurons, which supply all layers of the gut, and extrinsic primary afferent nerve fibers, which innervate primarily the arterial vascular system. The actions of tachykinins on the digestive effector systems are mediated by three different types of tachykinin receptor, termed NK1, NK2 and NK3 receptors. Within the enteric nervous system, SP and NKA are likely to mediate, or comediate, slow synaptic transmission and to modulate neuronal excitability via stimulation of NK3 and NK1 receptors. In the intestinal mucosa, tachykinins cause net secretion of fluid and electrolytes, and it appears as if SP and NKA play a messenger role in intramural secretory reflex pathways. Secretory processes in the salivary glands and pancreas are likewise influenced by tachykinins. The gastrointestinal arterial system may be dilated or constricted by tachykinins, whereas constriction and an increase in the vascular permeability are the only effects seen in the venous system. Various gastrointestinal disorders are associated with distinct changes in the tachykinin system, and there is increasing evidence that tachykinins participate in the hypersecretory, vascular and immunological disturbances associated with infection and inflammatory bowel disease. In a therapeutic perspective, it would seem conceivable that tachykinin antagonists could be exploited as antidiarrheal, antiinflammatory and antinociceptive drugs.