Methylation of CALCA and CALCB in Pancreatic Ductal Adenocarcinoma.

Calcitonin gene-related peptide (CGRP) plays a diverse and intricate role in chronic low-grade inflammation and is closely related to specific cancers. It includes two subtypes, CALCA (αCGRP) and CALCB (ßCGRP), of which αCGRP expression accounts for more than 90%. Here, we show that methylation of CALCA and CALCB in pancreatic ductal adenocarcinoma was significantly higher than that in paracancer. Western blot and immunohistochemistry showed that CGRP, p-AKT, and p-CREB in the tumor tissues were lower than those in the paracarcinoma tissues. In vivo, the expressions of p-AKT and p-CREB in the pancreatic tissues of CALCA-KO rats were also lower than those of wild type. Methylation of CALCA and CALCB is increased in pancreatic adenocarcinoma, and under that condition, p-AKT and p-CREB levels were decreased.

The PLGA nanoparticles for sustainable release of CGRP to ameliorate the inflammatory and vascular disorders in the lung of CGRP-deficient rats.

The calcitonin gene-related peptide (CGRP) has been demonstrated relating to vascular and inflammatory regulations not only the nerve systems. As the anti-inflammation factor and the most potent vasodilator, the CGRP holds therapeutic potentials for the treatment of cardiovascular diseases which was, however, limited by its peptide nature and short half-life. With advantages in improving the stability, circulation time and protection from degradation, the nanoparticles were promising as delivery carriers for the peptide. Nevertheless, few nanoparticulate systems were developed to deliver the CGRP peptide for the modulation of vascular or inflammatory functions instead of neural regulation. In this study, the CGRP was encapsulated into the poly (lactic-co-glycolic acid) (PLGA) nanoparticle for sustained release of CGRP in vivo. The nanoparticles recovered the systemic level of CGRP and the vascular inflammatory factors in the CGRP+/- rats comparing to the administration of (Dulbecco's Phosphate Buffered Saline) DPBS or peptide only. With the decrease of vascular wall thickness and the attenuation of the T cell infiltration in the lung, the polymer based CGRP delivery system showed potentials to facilitate the therapeutic effects of the CGRP which may help for the development of CGRP-based therapy in vascular and inflammatory disorder related diseases.

Calcitonin Gene-Related Peptide-Induced Phosphorylation of STAT3 in Arcuate Neurons Is a Link in the Metabolic Benefits of Portal Glucose.

INTRODUCTION: Intestinal gluconeogenesis (IGN) exerts metabolic benefits in energy homeostasis via the neural sensing of portal glucose. OBJECTIVE: The aim of this work was to determine central mechanisms involved in the effects of IGN on the control of energy homeostasis. METHODS: We investigated the effects of glucose infusion into the portal vein, at a rate that mimics IGN, in conscious wild-type, leptin-deficient Ob/Ob and calcitonin gene-related peptide (CGRP)-deficient mice. RESULTS: We report that portal glucose infusion decreases food intake and plasma glucose and induces in the hypothalamic arcuate nucleus (ARC) the phosphorylation of STAT3, the classic intracellular messenger of leptin signaling. This notably takes place in POMC-expressing neurons. STAT3 phosphorylation does not require leptin, since portal glucose effects are observed in leptin-deficient Ob/Ob mice. We hypothesized that the portal glucose effects could require CGRP, a neuromediator previously suggested to suppress hunger. In line with this hypothesis, neither the metabolic benefits nor the phosphorylation of STAT3 in the ARC take place upon portal glucose infusion in CGRP-deficient mice. Moreover, intracerebroventricular injection of CGRP activates hypothalamic phosphorylation of STAT3 in mice, and CGRP does the same in hypothalamic cells. Finally, no metabolic benefit of dietary fibers (known to depend on the induction of IGN), takes place in CGRP-deficient mice. CONCLUSIONS: CGRP-induced phosphorylation of STAT3 in the ARC is part of the neural chain determining the hunger-modulating and glucose-lowering effects of IGN/portal glucose.

CGRP-Mediated Prolactin Upregulation: a Possible Pathomechanism in IgG4-Related Disease.

Similar to other immune-mediated diseases, IgG4-related disease (IgG4-RD) is the disease that develops in genetically susceptible individuals exposed to external or endogenous antigens. In the present study, it was confirmed that MAG (myelin-associated glycoprotein) antibodies (IgG, IgG4, and IgM) were detected by immunofluorescence (IFA) in serum of the patients with IgG4-RD. In vivo, the levels of prolactin and Th2 cytokines in CGRP+/- rats were higher than those in wild-type. Our findings indicate that the presence of CGRP-deficiency-mediated MAG antibodies is a probable molecular basis for the initial events which were triggered in IgG4-RD immune responses via prolactin upregulation.

Optogenetic stimulation of the motor cortex alleviates neuropathic pain in rats of infraorbital nerve injury with/without CGRP knock-down.

BACKGROUND: Previous studies have reported that electrical stimulation of the motor cortex is effective in reducing trigeminal neuropathic pain; however, the effects of optical motor cortex stimulation remain unclear. OBJECTIVE: The present study aimed to investigate whether optical stimulation of the primary motor cortex can modulate chronic neuropathic pain in rats with infraorbital nerve constriction injury. METHODS: Animals were randomly divided into a trigeminal neuralgia group, a sham group, and a control group. Trigeminal neuropathic pain was generated via constriction of the infraorbital nerve and animals were treated via selective inhibition of calcitonin gene-related peptide in the trigeminal ganglion. We assessed alterations in behavioral responses in the pre-stimulation, stimulation, and post-stimulation conditions. In vivo extracellular recordings were obtained from the ventral posteromedial nucleus of the thalamus, and viral and α-CGRP expression were investigated in the primary motor cortex and trigeminal ganglion, respectively. RESULTS: We found that optogenetic stimulation significantly improved pain behaviors in the trigeminal neuralgia animals and it provided more significant improvement with inhibited α-CGRP state than active α-CGRP state. Electrophysiological recordings revealed decreases in abnormal thalamic firing during the stimulation-on condition. CONCLUSION: Our findings suggest that optical motor cortex stimulation can alleviate pain behaviors in a rat model of trigeminal neuropathic pain. Transmission of trigeminal pain signals can be modulated via knock-down of α-CGRP and optical motor cortex stimulation.

Absence of α-calcitonin gene-related peptide modulates bone remodeling properties of murine osteoblasts and osteoclasts in an age-dependent way.

Mice with an overall deletion of the sensory neuropeptide α-calcitonin gene-related peptide (α-CGRP) develop an age-dependent osteopenic bone phenotype. Underlying molecular mechanisms of how αCGRP affects bone cell metabolism are not well understood. This study aims to characterize differences in metabolic parameters of osteoblast-like cells (OB) and differentiated bone marrow-derived macrophages (BMM)/osteoclast (OC) cultures isolated from 3 month (3 m) and 9 month old (9 m) α-CGRP-deficient mice (-/-) and age-matched WT controls. All WT bone cell cultures endogenously produced and secreted α-CGRP. We found higher BMM but reduced OB numbers and reduced OB vitality after isolation from 9 m compared to 3 m mice, independent of genotype. Absence of α-CGRP reduced cell spreading, increased apoptosis rate throughout osteogenic differentiation, and reduced ALP activity during late osteogenic differentiation in 9 m OB-/- cultures, whereas minor effects were found in 3 m OB-/- cultures. Cathepsin K activity was reduced in 3 m OC-/- cultures. On the contrary, 9 m OC-/- cells demonstrated increased proliferation and caspase3/7 activity. The absence of α-CGRP influenced bone formation and resorption rate differently in bone cells from 3 and 9 m old mice. In summary we suggest, that an increase of dysfunctional mature osteoblasts might occur during aging and contribute to the development of the osteopenic bone phenotype in mature adult (9 m) α-CGRP-deficient mice.

Deficiency of α Calcitonin-gene-related peptide impairs peri-implant angiogenesis and osseointegration via suppressive vasodilative activity.

Blood supply is essential for the bone healing process to obtain successful osseointegration. α Calcitonin gene-related peptide (αCGRP) is osteoanabolic and is the most potent microvascular vasodilator currently known with validated angiogenic effect in vitro. We previously demonstrated that lentiviral αCGRP overexpression vector system could express the gene effectively to enhance titanium implant osseointegration. In this study, we investigated the effect of αCGRP on peri-implant angiogenesis during healing process in vivo. Based on investigation of blood vessel alteration in the peri-implant region of wild-type mice, we found a reduced angiogenesis alongside a decline in bone-implant contact percentage and bone mass in αCGRP -/- mice. Overexpression of αCGRP could partly rescue the impairment. Alterations were also detected in three-dimensional vascular structural parameters and expression of bone and vessel related genes. The results showed αCGRP increased vascular volume fraction and mean vessel size, as well as spatially relocated vessels approximate to the region of bone formation. And angiogenic and osteogenic genes were significantly upregulated in the transfection and αCGRP+/+ group. These results suggested that αCGRP played a synergic role in angiogenesis and osseointegration, partly as a consequence of its vasodilative activity.

Inhibition of osteogenesis surrounding the titanium implant by CGRP deficiency.

Previous studies have suggested one of the neurotransmitters, calcitonin gene-related peptide (CGRP), modulates local regulation of bone metabolism; however, the regulating signaling pathway is still being explored. The objective of this study was to determine whether CGRP deficiency affects the osteogenesis surrounding titanium implants in vivo. Titanium screws were implanted in 72 adult rats, which were divided into three groups randomly: Sham, inferior alveolar neurectomy (IAN), and IAN+CGRP. Saline solution containing CGRP (concentration: 100 nmol/L) was injected into the area surrounding the implants in the IAN+CGRP group every day post operation. According to histological observations and Micro-CT, osteogenesis surrounding the implant was suppressed in the IAN group compared to that in the Sham and IAN+CGRP groups; the highest degree of osteogenesis was observed in the Sham group. This effect was also proved via the gene expressions of osteocalcin and runt-related transcription factor 2 surrounding the implant by real-time (RT) PCR analysis. In addition, through immunofluorescence staining and RT-PCR analysis, levels of CGRP and ß-catenin were also reduced in the IAN group, while the highest expression was observed in the Sham group (p < 0.05). Our results collectively suggest that the titanium implant bone model established by IAN exhibited CGRP deficiency and reduced osteogenesis surrounding the implant. Additionally, the expression analyses suggest that the canonical Wnt signaling pathway could be involved in this process of bone metabolism in vivo.

CGRPα within the Trpv1-Cre population contributes to visceral nociception.

The role of calcitonin gene-related peptide (CGRP) in visceral and somatic nociception is incompletely understood. CGRPα is highly expressed in sensory neurons of dorsal root ganglia and particularly in neurons that also express the transient receptor potential cation channel subfamily V member 1 (Trpv1). Therefore, we investigated changes in visceral and somatic nociception following deletion of CGRPα from the Trpv1-Cre population using the Cre/lox system. In control mice, acetic acid injection (0.6%, ip) caused significant immobility (time stationary), an established indicator of visceral pain. In CGRPα-mCherrylx/lx;Trpv1-Cre mice, the duration of immobility was significantly less than controls, and the distance CGRPα-mCherrylx/lx;Trpv1-Cre mice traveled over 20 min following acetic acid was significantly greater than controls. However, following acetic acid injection, there was no difference between genotypes in the writhing reflex, number of abdominal licks, or forepaw wipes of the cheek. CGRPα-mCherrylx/lx;Trpv1-Cre mice developed more pronounced inflammation-induced heat hypersensitivity above baseline values compared with controls. However, analyses of noxious acute heat or cold transmission revealed no difference between genotypes. Also, odor avoidance test, odor preference test, and buried food test for olfaction revealed no differences between genotypes. Our findings suggest that CGRPα-mediated transmission within the Trpv1-Cre population plays a significant role in visceral nociceptive pathways underlying voluntary movement. Monitoring changes in movement over time is a sensitive parameter to identify differences in visceral nociception, compared with writhing reflexes, abdominal licks, or forepaw wipes of the cheek that were unaffected by deletion of CGRPα- from Trpv1-Cre population and likely utilize different mechanisms. NEW & NOTEWORTHY The neuropeptide calcitonin gene-related peptide (CGRP) is highly colocalized with transient receptor potential cation channel subfamily V member 1 (TRPV1)-expressing primary afferent neurons, but the functional role of CGRPα specifically in these neurons is unknown in pain processing from visceral and somatic afferents. We used cre-lox recombination to conditionally delete CGRPα from TRPV1-expressing neurons in mice. We show that CGRPα from within TRPV1-cre population plays an important role in visceral nociception but less so in somatic nociception.

Effect of lentiviral vector overexpression α-calcitonin gene-related peptide on titanium implant osseointegration in α-CGRP-deficient mice.

α-Calcitonin gene-related peptide (α-CGRP) plays a significant pathophysiological role in bone development, metabolism and remodeling around dental implants. However, the half-life of α-CGRP in plasma is only 10min, which affects its long-time application and an alternative approach should be developed to deliver α-CGRP over long periods of time. The aim of this study is to investigate whether a lentiviral α-CGRP overexpression vector system can express this target-gene longer at peri-implant sites, thus enhancing osseointegration. Animals were divided to the following groups: α-CGRP-/-, α-CGRP-/- with lentivirus transfection and α-CGRP+/+ mice. IVIS Spectrum imaging observations identified the successful transfection of α-CGRP around experimental implants inserted in the femurs at 5days after injection. Histomorphometrical analysis indicated an increase of bone-implant contact (BIC) at 1-month healing in the transfection group. Moreover, real-time RT-PCR and western blot results of bone-related markers Runx2, Osterix, and BSP levels elevated in lentivirus-transfected mice at 21days, compared to the untreated α-CGRP-/- mice. There was no significant difference between the transfection group and α-CGRP+/+ group. Further α-CGRP protein detection confirmed the persistent expression of this transgene at 21days post-operatively. These results suggest that this lentiviral vector system expresses α-CGRP in an effective, appropriate and sustained manner, which might have a potential application in enhancing titanium implant osseointegration.

Maturation of suprathreshold auditory nerve activity involves cochlear CGRP-receptor complex formation.

In adult animals, the neuropeptide calcitonin gene-related peptide (CGRP) is contained in cochlear efferent fibers projecting out to the cochlea, and contributes to increased suprathreshold sound-evoked activity in the adult auditory nerve. Similarly, CGRP applied to the lateral-line organ (hair cell organ) increases afferent nerve activity in adult frogs (post-metamorphic day 30), yet this increase is developmentally delayed from post-metamorphic day 4-30. In this study, we discovered that there was also a developmental delay in increased suprathreshold sound-evoked activity auditory nerve between juvenile and adult mice similar to what had been observed previously in frog. Moreover, juvenile mice with a targeted deletion of the αCGRP gene [CGRP null (-/-)] did not show a similar developmental increase in nerve activity, suggesting CGRP signaling is involved. This developmental delay is not due to a delay in CGRP expression, but instead is due to a delay in receptor formation. We observed that the increase in sound-evoked nerve activity is correlated with increased formation of cochlear CGRP receptors, which require three complexed proteins (CLR, RAMP1, RCP) to be functional. CGRP receptor formation in the cochlea was incomplete at 1 month of age (juvenile), but complete by 3 months (adult), which corresponded to the onset of suprathreshold enhancement of sound-evoked activity in wild-type animals. Taken together, these data support a model for cochlear function that is enhanced by maturation of CGRP receptor complexes.

Facilitated spinal neuropeptide signaling and upregulated inflammatory mediator expression contribute to postfracture nociceptive sensitization.

Tibia fracture induces exaggerated substance P (SP) and calcitonin gene-related peptide (CGRP) signaling and neuropeptide-dependent nociceptive and inflammatory changes in the hind limbs of rats similar to those seen in complex regional pain syndrome. Inflammatory changes in the spinal cord contribute to nociceptive sensitization in a variety of animal pain models. This study tested the hypothesis that fracture-induced exaggerated neuropeptide signaling upregulates spinal inflammatory mediator expression, leading to postfracture hind limb nociceptive sensitization. At 4 weeks after performing tibia fracture and casting in rats, we measured hind limb allodynia, unweighting, warmth, edema, and spinal cord neuropeptide and inflammatory mediator content. The antinociceptive effects of intrathecally injected neuropeptide and inflammatory mediator receptor antagonists were evaluated in fracture rats. Transgenic fracture mice lacking SP or the CGRP RAMP1 receptor were used to determine the effects of neuropeptide signaling on postfracture pain behavior and spinal inflammatory mediator expression. Hind limb allodynia, unweighting, warmth, edema, increased spinal SP and CGRP, and increased spinal inflammatory mediator expression (TNF, IL-1, IL-6, CCL2, and nerve growth factor) were observed at 4 weeks after fracture in rats. Fracture-induced increases in spinal inflammatory mediators were not observed in fracture mice lacking SP or the CGRP receptor, and these mice had attenuated postfracture nociceptive sensitization. Intrathecal injection of selective receptor antagonists for SP, CGRP, TNF, IL-1, IL-6, CCL2, or nerve growth factor each reduced pain behaviors in the fracture rats. Collectively, these data support the hypothesis that facilitated spinal neuropeptide signaling upregulates the expression of spinal inflammatory mediators contributing to nociceptive sensitization in a rodent fracture model of complex regional pain syndrome.

TRPM8 on mucosal sensory nerves regulates colitogenic responses by innate immune cells via CGRP.

TRPM8 is the molecular sensor for cold; however, the physiological role of TRPM8+ neurons at mucosal surfaces is unclear. Here we evaluated the distribution and peptidergic properties of TRPM8+ fibers in naive and inflamed colons, as well as their role in mucosal inflammation. We found that Trpm8(-/-) mice were hypersusceptible to dextran sodium sulfate (DSS)-induced colitis, and that Trpm8(-/-) CD11c+ DCs (dendritic cells) showed hyperinflammatory responses to toll-like receptor (TLR) stimulation. This was phenocopied in calcitonin gene-related peptide (CGRP) receptor-deficient mice, but not in substance P receptor-deficient mice, suggesting a functional link between TRPM8 and CGRP. The DSS phenotype of CGRP receptor-deficient mice could be adoptively transferred to wild-type (WT) mice, suggesting that CGRP suppresses the colitogenic activity of bone marrow-derived cells. TRPM8+ mucosal fibers expressed CGRP in human and mouse colon. Furthermore, neuronal CGRP contents were increased in colons from naive and DSS-treated Trpm8(-/-) mice, suggesting deficient CGRP release in the absence of TRPM8 triggering. Finally, treatment of Trpm8(-/-) mice with CGRP reversed their hyperinflammatory phenotype. These results suggest that TRPM8 signaling in mucosal sensory neurons is indispensable for the regulation of innate inflammatory responses via the neuropeptide CGRP.

Enhanced behavioral responses to cold stimuli following CGRPα sensory neuron ablation are dependent on TRPM8.

BACKGROUND: Calcitonin gene-related peptide-α (CGRPα) is a classic marker of peptidergic nociceptive neurons and is expressed in myelinated and unmyelinated dorsal root ganglia (DRG) neurons. Recently, we found that ablation of Cgrpα-expressing sensory neurons reduced noxious heat sensitivity and enhanced sensitivity to cold stimuli in mice. These studies suggested that the enhanced cold responses were due to disinhibition of spinal neurons that receive inputs from cold-sensing/TRPM8 primary afferents; although a direct role for TRPM8 was not examined at the time. RESULTS: Here, we ablated Cgrpα-expressing sensory neurons in mice lacking functional TRPM8 and evaluated sensory responses to noxious heat, cold temperatures, and cold mimetics (acetone evaporative cooling and icilin). We also evaluated thermoregulation in these mice following an evaporative cold challenge. We found that ablation of Cgrpα-expressing sensory neurons in a Trpm8-/- background reduced sensitivity to noxious heat but did not enhance sensitivity to cold stimuli. Thermoregulation following the evaporative cold challenge was not affected by deletion of Trpm8 in control or Cgrpα-expressing sensory neuron-ablated mice. CONCLUSIONS: Our data indicate that the enhanced behavioral responses to cold stimuli in CGRPα sensory neuron-ablated mice are dependent on functional TRPM8, whereas the other sensory and thermoregulatory phenotypes caused by CGRPα sensory neuron ablation are independent of TRPM8.

Loss of α-calcitonin gene-related peptide (αCGRP) reduces the efficacy of the Vestibulo-ocular Reflex (VOR).

The neuroactive peptide calcitonin-gene related peptide (CGRP) is known to act at efferent synapses and their targets in hair cell organs, including the cochlea and lateral line. CGRP is also expressed in vestibular efferent neurons as well as a number of central vestibular neurons. Although CGRP-null (-/-) mice demonstrate a significant reduction in cochlear nerve sound-evoked activity compared with wild-type mice, it is unknown whether and how the loss of CGRP influence vestibular system function. Vestibular function was assessed by quantifying the vestibulo-ocular reflex (VOR) in alert mice. The loss of CGRP in (-/-) mice was associated with a reduction of the VOR gain of ≈50% without a concomitant change in phase. Using immunohistochemistry, we confirmed that, although CGRP staining was absent in the vestibular end-organs of null (-/-) mice, cholinergic staining appeared normal, suggesting that the overall gross development of vestibular efferent innervation was unaltered. We further confirmed that the observed deficit in vestibular function of null (-/-) mice was not the result of nontargeted effects at the level of the extraocular motor neurons and/or their innervation of extraocular muscles. Analysis of the relationship between vestibular quick phase amplitude and peak velocity revealed that extraocular motor function was unchanged, and immunohistochemistry revealed no abnormalities in motor endplates. Together, our findings show that the neurotransmitter CGRP plays a key role in ensuring VOR efficacy.

An ongoing role of α-calcitonin gene-related peptide as part of a protective network against hypertension, vascular hypertrophy, and oxidative stress.

α-Calcitonin gene-related peptide (αCGRP) is a vasodilator, but there is limited knowledge of its long-term cardiovascular protective influence. We hypothesized that αCGRP protects against the onset and development of angiotensin II-induced hypertension and have identified protective mechanisms at the vascular level. Wild-type and αCGRP knockout mice that have similar baseline blood pressure were investigated in the angiotensin II hypertension model for 14 and 28 days. αCGRP knockout mice exhibited enhanced hypertension and aortic hypertrophy. αCGRP gene expression was increased in dorsal root ganglia and at the conduit and resistance vessel level of wild-type mice at both time points. ßCGRP gene expression was also observed and shown to be linked to plasma levels of CGRP. Mesenteric artery contractile and relaxant responses in vitro and endothelial NO synthase expression were similar in all groups. The aorta exhibited vascular hypertrophy, increased collagen formation, and oxidant stress markers in response to angiotensin II, with highest effects observed in αCGRP knockout mice. Gene and protein expression of endothelial NO synthase was lacking in the aortae after angiotensin II treatment, especially in αCGRP knockout mice. These results demonstrate the ongoing upregulation of αCGRP at the levels of both conduit and resistance vessels in vascular tissue in a model of hypertension and the direct association of this with protection against aortic vascular hypertrophy and fibrosis. This upregulation is maintained at a time when expression of aortic endothelial NO synthase and antioxidant defense genes have subsided, in keeping with the concept that the protective influence of αCGRP in hypertension may have been previously underestimated.

Deficiency of alpha-calcitonin gene-related peptide induces inflammatory responses and lethality in sepsis.

In the present study, we examined the role of alpha-calcitonin gene-related peptide (αCGRP) on expression of neuropeptides in the brain, inflammatory responses, and survival rate in septic shock condition. We examined expression of neuropeptides such as αCGRP, proopiomelanocortin (POMC), corticotrophin releasing hormone (CRH), and proenkephalin (ProENK) in the hippocampus and hypothalamus in C57BL/6 (WT) or αCGRP-/- (KO) mice subjected to sepsis. Cecal ligation and puncture (CLP) or lipopolysaccharide/D-galactosamine (LPS/D-GalN) treatment showed significant increases of hippocampal and hypothalamic αCGRP, POMC, CRH, and ProENK mRNA levels in WT mice, but not ProENK mRNA in the hypothalamus at 6h after on-set of sepsis. However, enhanced mRNA levels of POMC, CRH, and ProENK genes were not increased in the hippocampus and hypothalamus of CLP-subjected KO mice at 6h following sepsis. KO mice treated with LPS/D-GalN displayed a significant enhancement of plasma corticosterone, aspartate aminotransferase, and alanine aminotransferase levels compared to LPS/D-GalN treated WT mice at 12h after induction of sepsis. In addition, plasma levels of pro-inflammatory cytokines, such as IL-1ß and TNF-α, were also further increased in KO mice compared to WT mice at 24h after CLP or LPS/D-GalN treatment. Interestingly, mRNA expressions of IL-6 and IL-10, anti-inflammatory cytokines, were synergistically enhanced in liver and lymph node of KO mice compared to WT mice at 6h after CLP. However, plasma level of IL-10 but not IL-6 was significantly decreased in KO mice compared to WT mice at 24h after CLP or LPS/D-GalN challenge. The survival rate of KO mice was significantly reduced compared to WT mice following mild (1 punch) and moderate (2 punch) CLP and LPS/D-GalN administration. Taken together, our findings suggest that the activation of αCGRP may induce other neuropeptides associated with immunomodulation at CNS level and modulate immune responses as enhancing anti-inflammatory cytokines and reducing pro-inflammatory cytokines during the sepsis.

Mice lacking the neuropeptide alpha-calcitonin gene-related peptide are protected against diet-induced obesity.

Alpha-calcitonin gene-related peptide (alphaCGRP) is a neuropeptide that is expressed in motor and sensory neurons. It is a powerful vasodilator and has been implicated in diverse metabolic roles. However, its precise physiological function remains unclear. In this study, we investigated the role of alphaCGRP in lipid metabolism by chronically challenging alphaCGRP-specific knockout (alphaCGRP(-/-)) and control mice with high-fat diet regimens. At the start of the study, both animal groups displayed similar body weights, serum lipid markers, and insulin sensitivity. However, alphaCGRP(-/-) mice displayed higher core temperatures, increased energy expenditures, and a relative daytime (nonactive) depression in respiratory quotients, which indicated increased beta-oxidation. In response to fat feeding, alphaCGRP(-/-) mice were comparatively protected against diet-induced obesity with an attenuated body weight gain and an overall reduction in adiposity across all the three diets examined. AlphaCGRP(-/-) mice also displayed improved glucose handling and insulin sensitivity, lower im and hepatic lipid accumulation, and improved overall metabolic health. These findings define a new role for alphaCGRP as a mediator of energy metabolism and opens up therapeutic opportunities to target CGRP action in obesity.

Mechanisms underlying the hypertensive response induced by capsaicin.

Acute ingestion of large quantity of chili peppers (rich source of capsaicin) produced hypertensive crisis in a patient. The hypertensive response was explained on the basis of decreased vasodilator substance calcitonin gene-related peptide (CGRP) from sensory nerve terminals by capsaicin. Here we present our experimental observations in anaesthetized rats regarding the mechanisms underlying hypertensive response induced by capsaicin. Our results demonstrate non-involvement of adrenergic and angiotensinergic mechanisms and also the cardiac changes in producing the response. Thus, the direct action of capsaicin on vascular smooth muscle or the activation of endothelin is proposed.

Neuronal system-dependent facilitation of tumor angiogenesis and tumor growth by calcitonin gene-related peptide.

A neuropeptide, calcitonin gene-related peptide (CGRP), is widely distributed in neuronal systems and exhibits numerous biological activities. Using CGRP-knockout mice (CGRP(-/-)), we examined whether or not endogenous CGRP facilitates angiogenesis indispensable to tumor growth. CGRP increased tube formation by endothelial cells in vitro and enhanced sponge-induced angiogenesis in vivo. Tumor growth and tumor-associated angiogenesis in CGRP(-/-) implanted with Lewis lung carcinoma (LLC) cells were significantly reduced compared with those in wild-type (WT) mice. A CGRP antagonist, CGRP8-37 or denervation of sciatic nerves (L(1-5)) suppressed LLC growth in the sites of denervation compared with vehicle infusion or sham operation. CGRP precursor mRNA levels in the dorsal root ganglion in LLC-bearing WT were increased compared with those in non-LLC-bearing mice. This increase was abolished by denervation. The expression of VEGF in tumor stroma was down-regulated in CGRP(-/-). These results indicate that endogenous CGRP facilitates tumor-associated angiogenesis and tumor growth and suggest that relevant CGRP may be derived from neuronal systems including primary sensory neurons and may become a therapeutic target for cancers.