Role of Calcitonin Gene-Related Peptide in Bone Repair after Cyclic Fatigue Loading

Calcitonin gene related peptide (CGRP) is a neuropeptide that is abundant in the sensory neurons which innervate bone. The effects of CGRP on isolated bone cells have been widely studied, and CGRP is currently considered to be an osteoanabolic peptide that has effects on both osteoclasts and osteoblasts. However, relatively little is known about the physiological role of CGRP in-vivo in the skeletal responses to bone loading, particularly fatigue loading.We used the rat ulna end-loading model to induce fatigue damage in the ulna unilaterally during cyclic loading. We postulated that CGRP would influence skeletal responses to cyclic fatigue loading. Rats were fatigue loaded and groups of rats were infused systemically with 0.9% saline, CGRP, or the receptor antagonist, CGRP(8-37), for a 10 day study period. Ten days after fatigue loading, bone and serum CGRP concentrations, serum tartrate-resistant acid phosphatase 5b (TRAP5b) concentrations, and fatigue-induced skeletal responses were quantified. We found that cyclic fatigue loading led to increased CGRP concentrations in both loaded and contralateral ulnae. Administration of CGRP(8-37) was associated with increased targeted remodeling in the fatigue-loaded ulna. Administration of CGRP or CGRP(8-37) both increased reparative bone formation over the study period. Plasma concentration of TRAP5b was not significantly influenced by either CGRP or CGRP(8-37) administration.CGRP signaling modulates targeted remodeling of microdamage and reparative new bone formation after bone fatigue, and may be part of a neuronal signaling pathway which has regulatory effects on load-induced repair responses within the skeleton

Dental management in patients with hypertension: challenges and solutions

Janet H Southerland,1 Danielle G Gill,1 Pandu R Gangula,2–4 Leslie R Halpern,1 Cesar Y Cardona,5 Charles P Mouton6 1Department of Oral and Maxillofacial Surgery, 2Department of Oral Biology and Research, 3Department of Physiology, 4Center for Women's Health Research, 5Department of Internal Medicine, 6Department of Family and Community Medicine, Meharry Medical College, Nashville, TN, USA Abstract: Hypertension is a chronic illness affecting more than a billion people worldwide. The high prevalence of the disease among the American population is concerning and must be considered when treating dental patients. Its lack of symptoms until more serious problems occur makes the disease deadly. Dental practitioners can often be on the frontlines of prevention of hypertension by evaluating preoperative blood pressure readings, performing risk assessments, and knowing when to consider medical consultation of a hypertensive patient in a dental setting. In addition, routine follow-up appointments and patients seen on an emergent basis, who may otherwise not be seen routinely, allow the oral health provider an opportunity to diagnose and refer for any unknown disease. It is imperative to understand the risk factors that may predispose patients to hypertension and to be able to educate them about their condition. Most importantly, the oral health care provider is in a pivotal position to play an active role in the management of patients presenting with a history of hypertension because many antihypertensive agents interact with pharmacologic agents used in the dental practice. The purpose of this review is to provide strategies for managing and preventing complications when treating the patient with hypertension who presents to the dental office. Keywords: high blood pressure, dental, guidelines, inflammation, metabolic disease, blood pressure medicine

A novel function of calcitonin gene-related peptide in body fluid Cl −

Vertebrates need to maintain extracellular chloride (Cl(−)) concentrations to ensure the normal operation of physiological processes; the transition from aquatic to terrestrial environments necessitated the development of sophisticated mechanisms to ensure Cl(−) homeostasis in the face of fluctuating Cl(−) levels. Zebrafish calcitonin gene-related peptide (CGRP), unlike its splice variant calcitonin, does not respond to environmental Ca(2+) levels. This study aimed to test the hypothesis that CGRP is involved in the control of body fluid Cl(−) homeostasis. Acclimation to high-Cl(−) artificial water stimulated the mRNA expression of cgrp and the receptor (crlr1) when compared with low-Cl(−). CGRP knockdown induced upregulation of the Na(+)-Cl(−) co-transporter (ncc2b), while overexpression of CGRP resulted in the downregulation of ncc2b mRNA synthesis and a simultaneous decrease in Cl(−) uptake in embryos. Consistent with these findings, knockdown of either cgrp or crlr1 was found to increase the density of NCC2b-expressing cells in embryos. This is the first demonstration that CGRP acts as a hypochloremic hormone through suppressing NCC2b expression and the differentiation of NCC-expressing ionocytes. Elucidation of this novel function of CGRP in fish body fluid Cl(−) homeostasis promises to enhance our understanding of the related physiology in vertebrates

Impairment of nitrergic system and delayed gastric emptying in low density lipoprotein receptor deficient female mice.

BACKGROUND: In the current study, we have investigated whether low density lipoprotein receptor knockout mice (LDLR-KO), moderate oxidative stress model and cholesteremia burden display gastroparesis and if so whether nitrergic system is involved in this setting. In addition, we have investigated if sepiapterin (SEP) supplementation attenuated impaired nitrergic system and delayed gastric emptying. METHODS: Gastric emptying and nitrergic relaxation were measured in overnight fasting mice. nNOSα dimerization, anti-oxidant markers such as Nrf2, GCLM, GCLC, HO-1, catalase (CAT), and superoxide dismutase (SOD1) were measured using standard methods. Biopterin levels and intestinal transit time were measured using HPLC and dye migration assay, respectively. Wild type (WT) and LDLR-KO were supplemented with SEP. KEY RESULTS: In LDLR null stomachs: (i) significant reduction in rate of gastric emptying, gastric pyloric and fundus nitrergic relaxation and nNOSα dimerization, (ii) elevated oxidized biopterins and reduced ratio of BH(4) /BH(2)  + B, (iii) reduced Nrf2 and GCLC protein expression and no change in GCLM, HO-1, CAT, SOD1, and (iv) accelerated small intestinal motility were noticed. Supplementation of SEP restored delayed gastric emptying, impaired pyloric and fundus nitrergic relaxation with restoration of nNOS dimerization and nNOS expression. CONCLUSIONS and INFERENCES: This novel data suggests that hyperlipidemia and/or suppression of selective antioxidants may be a potential cause of developing gastroparesis in diabetic patients

Loss of NRF2 impairs gastric nitrergic stimulation and function

Emerging research suggests that antioxidant gene expression has the potential to suppress the development of gastroparesis. However, direct genetic evidence that definitively supports this concept is lacking. We used mice carrying a targeted disruption of Nfe2l2, the gene that encodes the transcription factor NRF2 and directs antioxidant Phase II gene expression, as well as mice with a targeted disruption of Gclm, the modifier subunit for glutamate-cysteine ligase, to test the hypothesis that defective antioxidant gene expression contributes to development of gastroparesis. Although expression of heme oxygenase-1 remained unchanged, expression of GCLC, GCLM, SOD1, and CAT was down-regulated in gastric tissue from Nrf2 mice compared to wild-type animals. Tetrahydrobiopterin oxidation was significantly elevated and nitrergic relaxation was impaired in Nrf2 mouse gastric tissue. In vitro studies showed a significant decrease in NO release in Nrf2 mouse gastric tissue. Nrf2 mice displayed delayed gastric emptying. The use of Gclm mice demonstrated that the loss of glutamate-cysteine ligase function enhanced tetrahydrobiopterin oxidation while impairing nitrergic relaxation. These results provide genetic evidence that loss of antioxidant gene expression can contribute to the development of gastroparesis and suggest that NRF2 represents a potential therapeutic target. © 2011 Elsevier Inc. All rights reserved

Impairment of Nrf2- and nitrergic-mediated gastrointestinal motility in an MPTP mouse model of Parkinson's disease.

BACKGROUND:Gastrointestinal (GI) motility dysfunction is the most common non-motor symptom of Parkinson's disease (PD). Studies have indicated that GI motility functions are impaired before the onset of PD. AIMS:To investigate the underlying mechanism of PD-induced GI dysmotility in MPTP (1-methyl 4-phenyl 1,2,3,6-tetrahydropyridine)-induced animal model. METHODS:C57BL/6 mice were administered with or without a selective dopamine neurotoxin, MPTP, to induce parkinsonian symptoms. In addition to in vivo studies, in vitro experiments were also conducted in colon specimens using l-methyl-4-phenylpyridinium (MPP+), a metabolic product of MPTP. Gastric emptying, colon motility, nitrergic relaxation, and western blot experiments were performed as reported. RESULTS:MPTP-induced PD mice showed decreased expression of nuclear factor erythroid 2-related factor (Nrf2) and its target phase II genes in gastric and colon neuromuscular tissues. Decreased levels of tetrahydrobiopterin (BH4, a critical cofactor for nNOS dimerization) associated with uncoupling of nNOS in gastric and colon tissues exposed to MPTP. Impaired enteric nitrergic system led to delayed gastric emptying and slower colonic motility compared to the control mice. In vitro results in colon specimens confirm that activation of Nrf2 restored MPP+-induced suppression of alpha-synuclein, tyrosine hydroxylase (TH), Nrf2, and heme oxygenase-1. In vitro exposure to L-NAME [N(w)-nitro-L-arginine methyl ester], a NOS synthase inhibitor, reduced protein expression of TH in colon tissue homogenates. CONCLUSIONS:Loss of Nrf2/BH4/nNOS expression in PD impairs antioxidant gene expression, which deregulates NO synthesis, thereby contributing to the development of GI dysmotility and constipation. Nitric oxide appears to be important to maintain dopamine synthesis in the colon.</p