NGF-Induced Upregulation of CGRP in Orofacial Pain Induced by Tooth Movement Is Dependent on Atp6v0a1 and Vesicle Release.

The nerve growth factor (NGF) and calcitonin gene-related peptide (CGRP) play a crucial role in the regulation of orofacial pain. It has been demonstrated that CGRP increases orofacial pain induced by NGF. V-type proton ATPase subunit an isoform 1 (Atp6v0a1) is involved in the exocytosis pathway, especially in vesicular transport in neurons. The objective was to examine the role of Atp6v0a1 in NGF-induced upregulation of CGRP in orofacial pain induced by experimental tooth movement. Orofacial pain was elicited by ligating closed-coil springs between incisors and molars in Sprague-Dawley rats. Gene and protein expression levels were determined through real-time polymerase chain reaction, immunostaining, and fluorescence in situ hybridization. Lentivirus vectors carrying Atp6v0a1 shRNA were used to knockdown the expression of Atp6v0a1 in TG and SH-SY5Y neurons. The release of vesicles in SH-SY5Y neurons was observed by using fluorescence dye FM1-43, and the release of CGRP was detected by Enzyme-Linked Immunosorbent Assy. Orofacial pain was evaluated through the rat grimace scale. Our results revealed that intraganglionic administration of NGF and Atp6v0a1 shRNA upregulated and downregulated CGRP in trigeminal ganglia (TG) and trigeminal subnucleus caudalis (Vc), respectively, and the orofacial pain was also exacerbated and alleviated, respectively, following administration of NGF and Atp6v0a1 shRNA. Besides, intraganglionic administration of NGF simultaneously caused the downregulation of Atp6v0a1 in TG. Moreover, the release of vesicles and CGRP in SH-SY5Y neurons was interfered by NGF and Atp6v0a1 shRNA. In conclusion, in the orofacial pain induced by experimental tooth movement, NGF induced the upregulation of CGRP in TG and Vc, and this process is dependent on Atp6v0a1 and vesicle release, suggesting that they are involved in the transmission of nociceptive information in orofacial pain.

Chemokine CXCL13 mediates orofacial neuropathic pain via CXCR5/ERK pathway in the trigeminal ganglion of mice.

BACKGROUND: Trigeminal nerve damage-induced neuropathic pain is a severely debilitating chronic orofacial pain syndrome. Spinal chemokine CXCL13 and its receptor CXCR5 were recently demonstrated to play a pivotal role in the pathogenesis of spinal nerve ligation-induced neuropathic pain. Whether and how CXCL13/CXCR5 in the trigeminal ganglion (TG) mediates orofacial pain are unknown. METHODS: The partial infraorbital nerve ligation (pIONL) was used to induce trigeminal neuropathic pain in mice. The expression of ATF3, CXCL13, CXCR5, and phosphorylated extracellular signal-regulated kinase (pERK) in the TG was detected by immunofluorescence staining and western blot. The effect of shRNA targeting on CXCL13 or CXCR5 on pain hypersensitivity was checked by behavioral testing. RESULTS: pIONL induced persistent mechanical allodynia and increased the expression of ATF3, CXCL13, and CXCR5 in the TG. Inhibition of CXCL13 or CXCR5 by shRNA lentivirus attenuated pIONL-induced mechanical allodynia. Additionally, pIONL-induced neuropathic pain and the activation of ERK in the TG were reduced in Cxcr5 (-/-) mice. Furthermore, MEK inhibitor (PD98059) attenuated mechanical allodynia and reduced TNF-α and IL-1ß upregulation induced by pIONL. TNF-α inhibitor (Etanercept) and IL-1ß inhibitor (Diacerein) attenuated pIONL-induced orofacial pain. Finally, intra-TG injection of CXCL13 induced mechanical allodynia, increased the activation of ERK and the production of TNF-α and IL-1ß in the TG of WT mice, but not in Cxcr5 (-/-) mice. Pretreatment with PD98059, Etanercept, or Diacerein partially blocked CXCL13-induced mechanical allodynia, and PD98059 also reduced CXCL13-induced TNF-α and IL-1ß upregulation. CONCLUSIONS: CXCL13 and CXCR5 contribute to orofacial pain via ERK-mediated proinflammatory cytokines production. Targeting CXCL13/CXCR5/ERK/TNF-α and IL-1ß pathway in the trigeminal ganglion may offer effective treatment for orofacial neuropathic pain.

Association between genetic polymorphisms in Ca(v)2.3 (R-type) Ca2+ channels and fentanyl sensitivity in patients undergoing painful cosmetic surgery.

Individual differences in the sensitivity to fentanyl, a widely used opioid analgesic, lead to different proper doses of fentanyl, which can hamper effective pain treatment. Voltage-activated Ca(2+) channels (VACCs) play a crucial role in the nervous system by controlling membrane excitability and calcium signaling. Ca(v)2.3 (R-type) VACCs have been especially thought to play critical roles in pain pathways and the analgesic effects of opioids. However, unknown is whether single-nucleotide polymorphisms (SNPs) of the human CACNA1E (calcium channel, voltage-dependent, R type, alpha 1E subunit) gene that encodes Cav2.3 VACCs influence the analgesic effects of opioids. Thus, the present study examined associations between fentanyl sensitivity and SNPs in the human CACNA1E gene in 355 Japanese patients who underwent painful orofacial cosmetic surgery, including bone dissection. We first conducted linkage disequilibrium (LD) analyses of 223 SNPs in a region that contains the CACNA1E gene using genomic samples from 100 patients, and a total of 13 LD blocks with 42 Tag SNPs were observed within and around the CACNA1E gene region. In the preliminary study using the same 100 genomic samples, only the rs3845446 A/G SNP was significantly associated with perioperative fentanyl use among these 42 Tag SNPs. In a confirmatory study using the other 255 genomic samples, this SNP was also significantly associated with perioperative fentanyl use. Thus, we further analyzed associations between genotypes of this SNP and all of the clinical data using a total of 355 samples. The rs3845446 A/G SNP was associated with intraoperative fentanyl use, 24 h postoperative fentanyl requirements, and perioperative fentanyl use. Subjects who carried the minor G allele required significantly less fentanyl for pain control compared with subjects who did not carry this allele. Although further validation is needed, the present findings show the possibility of the involvement of CACNA1E gene polymorphisms in fentanyl sensitivity.

Re-expression of the methylated EDNRB gene in oral squamous cell carcinoma attenuates cancer-induced pain.

Endothelin-1 is a vasoactive peptide that activates both the endothelin A (ET(A)) and endothelin B (ET(B)) receptors, and is secreted in high concentrations in many different cancer environments. Although ET(A) receptor activation has an established nociceptive effect in cancer models, the role of ET(B) receptors on cancer pain is controversial. EDNRB, the gene encoding the ET(B) receptor, has been shown to be hypermethylated and transcriptionally silenced in many different cancers. In this study we demonstrate that EDNRB is heavily methylated in human oral squamous cell carcinoma lesions, which are painful, but not methylated in human oral dysplasia lesions, which are typically not painful. ET(B) mRNA expression is reduced in the human oral squamous cell carcinoma lesions as a consequence of EDNRB hypermethylation. Using a mouse cancer pain model, we show that ET(B) receptor re-expression attenuates cancer-induced pain. These findings identify EDNRB methylation as a novel regulatory mechanism in cancer-induced pain and suggest that demethylation therapy targeted at the cancer microenvironment has the potential to thwart pain-producing mechanisms at the source, thus freeing patients of systemic analgesic toxicity.

Genomics and the new perspectives for temporomandibular disorders.

The field of temporomandibular disorders (TMD) is experiencing significant changes in terms of aetiology and treatment. Researchers and clinicians are becoming increasingly aware of the possibility that genetic variations may play a role in pain perception and onset of TMD. In this review, we purpose to briefly describe these allelic variants, how they may be involved in TMD pathophysiology and how they may affect TMD treatment. Studies have already pointed the association between TMD and genetic polymorphisms in the oestrogen receptor alpha, adrenergic receptor beta 2, serotonin receptor, serotonin transporter and catechol-O-methyltransferase genes, and other candidate genes continue to emerge. The main implication of these findings refers to the promising possibilities of "genome/omics-based personalised care", which consists of tailoring individual treatment based on personalised medication, depending on the individual genetic differences and early diagnosis and prognosis of the disorder, preventing acute pain conditions from becoming chronic. The following years of research shall focus on collecting and endorsing these findings if we are to provide patients in pain with efficient and successful TMD treatments.

Chronic facial pain in the female patient: treatment updates.

Over the past decade, gender-related differences in pain and analgesia have been examined in experimental settings with conflicting evidence on whether men and women differ in their response to pain. New advances in research have begun to investigate the influence of genetic factors in moderating sex differences in analgesic response. This article provides oral and maxillofacial surgeons with evidence-based data on the issues of chronic pain between the sexes to suggest alternative approaches to the management of pain in their male and female patients.

Association between estrogen receptor polymorphism and pain susceptibility in female temporomandibular joint osteoarthritis patients.

The purpose of this study was to investigate the possible association between estrogen receptor alpha (ERalpha) polymorphism and pain susceptibility in female symptomatic temporomandibular joint (TMJ) osteoarthritis (OA) patients. A patient group of 100 women, diagnosed as TMJ OA according to the research diagnostic criteria for temporomandibular disorders, were selected, and 74 women with no signs and symptoms of temporomandibular disorder were assigned to a control group. Pvu II and Xba I restriction fragment length polymorphisms were analyzed by direct haplotyping. The patient group was divided into three subgroups according to a visual analog scale (VAS): mild pain (0.05). TMJ OA patients carrying the PX haplotype were found to have a significantly higher risk of moderate or severe pain compared to those without the PX haplotype, suggesting that ERalpha polymorphism may be associated with pain susceptibility in female TMJ OA patients.

Why is depression comorbid with chronic myofascial face pain? A family study test of alternative hypotheses.

A number of explanations have been proposed to account for findings that rates of depression are elevated in persons with chronic, non-malignant pain disorders (CNPDs); for example, that CNPDs are variants of depression (e.g. 'masked depression'), that the stress of living with CNPDs contribute to the onset of depression ('diathesis-stress'), or that the correlation of CNPDs and depression is a methodological artifact of studying treatment-seeking samples. These alternative hypotheses are tested for one specific CNPD, chronic myofascial face pain, using a family study methodology. The procedure was to conduct direct psychiatric interviews with 106 patients with a history of carefully diagnosed myofascial face pain, 118 acquaintance controls without personal histories of myofascial face pain, and a random sample of adult first degree relatives of these case and control probands. The probands were further subdivided into four roughly equal samples consisting of cases with and without personal histories of major depressive disorder (MDD), and controls with and without personal histories of MDD. Dates of initial onsets of myofascial face pain and MDD in patient probands were obtained from interviews and records. The main results were that, compared to control probands without personal histories of MDD, MDD and depressive spectrum disorders (DSD) were elevated in the first degree relatives of control probands with personal histories of early onset MDD, but not in the first degree relatives of myofascial face pain probands with or without personal histories of early or late onset MDD. This outcome is consistent with the hypothesis that living with chronic myofascial face pain contributes to elevated rates of depression. It is inconsistent with the alternative hypotheses that this CNPD is a variant of depression or that the elevated MDD rates are simply an artifact of selection into treatment. The implications of these results and additional results consistent with them are discussed.