Females have lower salivary flow than males, before and after radiation therapy for head/neck cancer.

OBJECTIVE: To compare salivary flow rates between females and males, before and after radiation therapy (RT) for head and neck cancer (HNC). METHODS: Prospective observational multicenter cohort study (OraRad). Stimulated whole salivary flow was measured before RT and at 6 and 18 months after RT. RESULTS: Mean (95% confidence interval) salivary flow in g/min before RT was 0.81 (0.71, 0.90) in females (n = 107) and 1.20 (1.15, 1.25) in males (n = 391) (p < 0.001); at 6 months was 0.34 (0.24, 0.44) in females and 0.50 (0.44, 0.55) in males (p = 0.01); at 18 months was 0.49 (0.38, 0.59) in females and 0.70 (0.64, 0.75) in males (p < 0.001). Median nadir salivary flow after RT was 0.22 in females and 0.35 in males (p < 0.001). A lower nadir salivary flow in females, but not males, was associated with an increased risk for tooth failure (p = 0.02). CONCLUSIONS: Females with HNC have lower stimulated whole salivary flow than males, before and after RT. Low salivary flow after RT may be a risk factor for tooth failure among females. The lower pre-RT salivary flow rates in females, combined with prior literature in other populations, indicates that, in general, females have lower stimulated salivary flow than males.

Protease-Induced Excitation of Dorsal Root Ganglion Neurons in Response to Acute Perturbation of the Gut Microbiota Is Associated With Visceral and Somatic Hypersensitivity.

BACKGROUND & AIMS: Abdominal pain is a major symptom of diseases that are associated with microbial dysbiosis, including irritable bowel syndrome and inflammatory bowel disease. Germ-free mice are more prone to abdominal pain than conventionally housed mice, and reconstitution of the microbiota in germ-free mice reduces abdominal pain sensitivity. However, the mechanisms underlying microbial modulation of pain remain elusive. We hypothesized that disruption of the intestinal microbiota modulates the excitability of peripheral nociceptive neurons. METHODS: In vivo and in vitro assays of visceral sensation were performed on mice treated with the nonabsorbable antibiotic vancomycin (50 µg/mL in drinking water) for 7 days and water-treated control mice. Bacterial dysbiosis was verified by 16s rRNA analysis of stool microbial composition. RESULTS: Treatment of mice with vancomycin led to an increased sensitivity to colonic distension in vivo and in vitro and hyperexcitability of dorsal root ganglion (DRG) neurons in vitro, compared with controls. Interestingly, hyperexcitability of DRG neurons was not restricted to those that innervated the gut, suggesting a widespread effect of gut dysbiosis on peripheral pain circuits. Consistent with this, mice treated with vancomycin were more sensitive than control mice to thermal stimuli applied to hind paws. Incubation of DRG neurons from naive mice in serum from vancomycin-treated mice increased DRG neuron excitability, suggesting that microbial dysbiosis alters circulating mediators that influence nociception. The cysteine protease inhibitor E64 (30 nmol/L) and the protease-activated receptor 2 (PAR-2) antagonist GB-83 (10 µmol/L) each blocked the increase in DRG neuron excitability in response to serum from vancomycin-treated mice, as did the knockout of PAR-2 in NaV1.8-expressing neurons. Stool supernatant, but not colonic supernatant, from mice treated with vancomycin increased DRG neuron excitability via cysteine protease activation of PAR-2. CONCLUSIONS: Together, these data suggest that gut microbial dysbiosis alters pain sensitivity and identify cysteine proteases as a potential mediator of this effect.

Factors associated with oral hygiene compliance in patients treated with radiation therapy for head and neck cancer.

BACKGROUND: Patients who are oral hygiene noncompliant (OHNC) are more likely to lose teeth after radiation therapy (RT) for head and neck cancer (HNC), which increases the risk of developing osteoradionecrosis. A previous study revealed that patients who were OHNC at baseline (BL) who became oral hygiene compliant during follow-up had the best tooth-failure outcomes. The purpose of this study was to identify factors associated with oral hygiene compliance (OHC), overall, and among those who were BL OHNC. METHODS: This was an observational, prospective, cohort study of 518 patients with HNC assessed before RT and at post-RT follow-up visits every 6 months for 2 years. Patient and treatment-related information was collected at BL and during follow-up, including self-reported OHC. OHC was defined as toothbrushing at least twice daily and flossing at least once daily. RESULTS: Of the 296 patients who self-reported being BL OHNC, 44 (14.9%) became oral hygiene compliant at all follow-up visits. Among this group, those who had dental insurance (P = .026), surgery before RT (P = .008), limited mouth opening before RT (P = .001), compliant fluoride use (P = .023), primary RT site of oral cavity (P = .004), and primary surgical site of larynx and hypopharynx (P = .042) were more likely to become oral hygiene compliant post-RT. CONCLUSIONS: The reasons for the cohort of patients with HNC in this study being OHNC are multifaceted and relate to socioeconomic factors and cancer characteristics. PRACTICAL IMPLICATIONS: Finding ways to increase OHC and fluoride use among patients with HNC who are at greatest risk of being OHNC should be explored.

Measurement of the Association of Pain with Clinical Characteristics in Oral Cancer Patients at Diagnosis and Prior to Cancer Treatment.

Aim: Oral cancer patients suffer pain at the site of the cancer, which degrades quality of life (QoL). The University of California San Francisco Oral Cancer Pain Questionnaire (UCSFOCPQ), the only validated instrument specifically designed for measuring oral cancer pain, measures the intensity and nature of pain and the level of functional restriction due to pain. Purpose: The aim of this study was to compare pain reported by untreated oral cancer patients on the UCSFOCPQ with pain they reported on the Brief Pain Inventory (BPI), an instrument widely used to evaluate cancer and non-cancer pain. Patients and Methods: The correlation between pain measured by the two instruments and clinical characteristics were analyzed. Thirty newly diagnosed oral cancer patients completed the UCSFOCPQ and the BPI. Results: Pain severity measurements made by the UCSFOCPQ and BPI were concordant; however, the widely used BPI average pain over 24 hours score appeared less sensitive to detect association of oral cancer pain with clinical characteristics of patients prior to treatment (nodal status, depth of invasion, DOI). A BPI average score that includes responses to questions that measure both pain severity and interference with function performs similarly to the UCSFOCPQ in detection of associations with nodal status, pathologic T stage (pT stage), stage and depth of invasion (DOI). Conclusion: Pain assessment instruments that measure sensory and interference dimensions of oral cancer pain correlate with biologic features and clinical behavior.

Reduced mouth opening in patients with head and neck cancer treated with radiation therapy: an analysis of the Clinical Registry of Dental Outcomes in Head and Neck Cancer Patients (OraRad).

OBJECTIVE: Trismus/reduced mouth opening (RMO) is a common side effect of radiotherapy (RT) for head and neck cancer (HNC). The objective was to measure RMO, identify risk factors for RMO, and determine its impact on quality of life (QOL). STUDY DESIGN: OraRad is an observational, prospective, multicenter cohort study of patients receiving curative intent RT for HNC. Interincisal mouth opening measurements (n = 565) and patient-reported outcomes were recorded before RT and every 6 months for 2 years. Linear mixed-effects models were used to evaluate change in mouth opening and assess the relationship between trismus history and change in QOL measures. RESULTS: Interincisal distance decreased from a mean (SE) of 45.1 (0.42) mm at baseline to 42.2 (0.44) at 6 months, with slight recovery at 18 months (43.3, 0.46 mm) but no additional improvement by 24 months. The odds of trismus (opening <35 mm) were significantly higher at 6 months (odds ratio [OR] = 2.21, 95% CI: 1.30 to 3.76) and 12 months (OR = 1.87, 95% CI: 1.08 to 3.25) compared with baseline. Females were more likely to experience trismus at baseline and during follow-up (P < .01). Patients with oral cavity cancer had the highest risk for trismus at baseline and post-RT (P < .01). RMO was associated with higher RT dose to the primary site and receiving concomitant chemotherapy (P < .01). Trismus was associated with self-reported difficulty opening the mouth and dry mouth (P < .01). CONCLUSIONS: A decrease in mouth opening is a common treatment-related toxicity after RT, with some recovery by 18 months. Trismus has a significant impact on survivor QOL.

Neuropilin-1 is a co-receptor for NGF and TrkA-evoked pain.

Nerve growth factor (NGF) monoclonal antibodies (mAb) are one of the few patient-validated non-opioid treatments for chronic pain, despite failing to gain FDA approval due to worsened joint damage in some osteoarthritis patients. Herein, we demonstrate that neuropilin-1 (NRP1) is a nociceptor-enriched co-receptor for NGF that is necessary for tropomyosin-related kinase A (TrkA) signaling of pain. NGF binds NRP1 with nanomolar affinity. NRP1 and G Alpha Interacting Protein C-terminus 1 (GIPC1), a NRP1/TrkA adaptor, are coexpressed with TrkA in human and mouse nociceptors. NRP1 small molecule inhibitors and blocking mAb prevent NGF-stimulated action potential firing and activation of Na+ and Ca2+ channels in human and mouse nociceptors and abrogate NGF-evoked and inflammatory nociception in mice. NRP1 knockdown blunts NGF-stimulated TrkA phosphorylation, kinase signaling and transcription, whereas NRP1 overexpression enhances NGF and TrkA signaling. As well as interacting with NGF, NRP1 forms a heteromeric complex with TrkA. NRP1 thereby chaperones TrkA from the biosynthetic pathway to the plasma membrane and then to signaling endosomes, which enhances NGF-induced TrkA dimerization, endocytosis and signaling. Knockdown of GIPC1, a PDZ-binding protein that scaffolds NRP1 and TrkA to myosin VI, abrogates NGF-evoked excitation of nociceptors and pain-like behavior in mice. We identify NRP1 as a previously unrecognized co-receptor necessary for NGF/TrkA pain signaling by direct NGF binding and by chaperoning TrkA to the plasma membrane and signaling endosomes via the adaptor protein GIPC1. Antagonism of NRP1 and GIPC1 in nociceptors offers a long-awaited alternative to systemic sequestration of NGF with mAbs for the treatment of pain.

Calcitonin Related Polypeptide Alpha Mediates Oral Cancer Pain.

Oral cancer patients suffer pain at the site of the cancer. Calcitonin gene related polypeptide (CGRP), a neuropeptide expressed by a subset of primary afferent neurons, promotes oral cancer growth. CGRP also mediates trigeminal pain (migraine) and neurogenic inflammation. The contribution of CGRP to oral cancer pain is investigated in the present study. The findings demonstrate that CGRP-immunoreactive (-ir) neurons and neurites innervate orthotopic oral cancer xenograft tumors in mice. Cancer increases anterograde transport of CGRP in axons innervating the tumor, supporting neurogenic secretion as the source of CGRP in the oral cancer microenvironment. CGRP antagonism reverses oral cancer nociception in preclinical oral cancer pain models. Single-cell RNA-sequencing is used to identify cell types in the cancer microenvironment expressing the CGRP receptor components, receptor activity modifying protein 1 Ramp1 and calcitonin receptor like receptor (CLR, encoded by Calcrl). Ramp1 and Calcrl transcripts are detected in cells expressing marker genes for Schwann cells, endothelial cells, fibroblasts and immune cells. Ramp1 and Calcrl transcripts are more frequently detected in cells expressing fibroblast and immune cell markers. This work identifies CGRP as mediator of oral cancer pain and suggests the antagonism of CGRP to alleviate oral cancer pain.

Tooth-level predictors of tooth loss and exposed bone after radiation therapy for head and neck cancer.

BACKGROUND: The objective of this study was to identify tooth-level risk factors for use during preradiation dental care management to predict risk of tooth failure (tooth lost or declared hopeless) and exposed bone after radiation therapy (RT) for head and neck cancer (HNC). METHODS: The authors conducted a prospective observational multicenter cohort study of 572 patients receiving RT for HNC. Participants were examined by calibrated examiners before RT and then every 6 months until 2 years after RT. Analyses considered time to tooth failure and chance of exposed bone at a tooth location. RESULTS: The following pre-RT characteristics predicted tooth failure within 2 years after RT: hopeless teeth not extracted pre-RT (hazard ratio [HR], 17.1; P < .0001), untreated caries (HR, 5.0; P < .0001), periodontal pocket 6 mm or greater (HR, 3.4; P = .001) or equaling 5 mm (HR, 2.2; P = .006), recession over 2 mm (HR, 2.8; P = .002), furcation score of 2 (HR, 3.3; P = .003), and any mobility (HR, 2.2; P = .008). The following pre-RT characteristics predicted occurrence of exposed bone at a tooth location: hopeless teeth not extracted before RT (risk ratio [RR], 18.7; P = .0002) and pocket depth 6 mm or greater (RR, 5.4; P = .003) or equaling 5 mm (RR, 4.7; P = .016). Participants with exposed bone at the site of a pre-RT dental extraction averaged 19.6 days between extraction and start of RT compared with 26.2 days for participants without exposed bone (P = .21). CONCLUSIONS: Individual teeth with the risk factors identified in this study should be considered for extraction before RT for HNC, with adequate healing time before start of RT. PRACTICAL IMPLICATIONS: The findings of this trial will facilitate evidence-based dental management of the care of patients receiving RT for HNC. This clinical trial was registered at Clinicaltrials.gov. The registration number is NCT02057510.

Therapeutic antagonism of the neurokinin 1 receptor in endosomes provides sustained pain relief.

The hypothesis that sustained G protein-coupled receptor (GPCR) signaling from endosomes mediates pain is based on studies with endocytosis inhibitors and lipid-conjugated or nanoparticle-encapsulated antagonists targeted to endosomes. GPCR antagonists that reverse sustained endosomal signaling and nociception are needed. However, the criteria for rational design of such compounds are ill-defined. Moreover, the role of natural GPCR variants, which exhibit aberrant signaling and endosomal trafficking, in maintaining pain is unknown. Herein, substance P (SP) was found to evoke clathrin-mediated assembly of endosomal signaling complexes comprising neurokinin 1 receptor (NK1R), Gαq/i, and ßarrestin-2. Whereas the FDA-approved NK1R antagonist aprepitant induced a transient disruption of endosomal signals, analogs of netupitant designed to penetrate membranes and persist in acidic endosomes through altered lipophilicity and pKa caused sustained inhibition of endosomal signals. When injected intrathecally to target spinal NK1R+ve neurons in knockin mice expressing human NK1R, aprepitant transiently inhibited nociceptive responses to intraplantar injection of capsaicin. Conversely, netupitant analogs had more potent, efficacious, and sustained antinociceptive effects. Mice expressing C-terminally truncated human NK1R, corresponding to a natural variant with aberrant signaling and trafficking, displayed attenuated SP-evoked excitation of spinal neurons and blunted nociceptive responses to SP. Thus, sustained antagonism of the NK1R in endosomes correlates with long-lasting antinociception, and domains within the C-terminus of the NK1R are necessary for the full pronociceptive actions of SP. The results support the hypothesis that endosomal signaling of GPCRs mediates nociception and provides insight into strategies for antagonizing GPCRs in intracellular locations for the treatment of diverse diseases.

Oral health-related quality of life after radiation therapy for head and neck cancer: the OraRad study.

PURPOSE: Head and neck cancer (HNC) treatment results in morbidity impacting quality of life (QOL) in survivorship. This analysis evaluated changes in oral health-related QOL (OH-QOL) up to 2 years after curative intent radiation therapy (RT) for HNC patients and factors associated with these changes. METHODS: 572 HNC patients participated in a multicenter, prospective observational study (OraRad). Data collected included sociodemographic, tumor, and treatment variables. Ten single-item questions and 2 composite scales of swallowing problems and senses problems (taste and smell) from a standard QOL instrument were assessed before RT and at 6-month intervals after RT. RESULTS: The most persistently impacted OH-QOL variables at 24 months included: dry mouth; sticky saliva, and senses problems. These measures were most elevated at the 6-month visit. Aspects of swallowing were most impacted by oropharyngeal tumor site, chemotherapy, and non-Hispanic ethnicity. Problems with senses and dry mouth were worse with older age. Dry mouth and sticky saliva increased more among men and those with oropharyngeal cancer, nodal involvement, and use of chemotherapy. Problems with mouth opening were increased by chemotherapy and were more common among non-White and Hispanic individuals. A 1000 cGy increase in RT dose was associated with a clinically meaningful change in difficulty swallowing solid food, dry mouth, sticky saliva, sense of taste, and senses problems. CONCLUSIONS: Demographic, tumor, and treatment variables impacted OH-QOL for HNC patients up to 2 years after RT. Dry mouth is the most intense and sustained toxicity of RT that negatively impacts OH-QOL of HNC survivors. GOV IDENTIFIER: NCT02057510; first posted February 7, 2014.

Sympathetic modulation of tumor necrosis factor alpha-induced nociception in the presence of oral squamous cell carcinoma.

ABSTRACT: Head and neck squamous cell carcinoma (HNSCC) causes more severe pain and psychological stress than other types of cancer. Despite clinical evidence linking pain, stress, and cancer progression, the underlying relationship between pain and sympathetic neurotransmission in oral cancer is unknown. We found that human HNSCC tumors and mouse tumor tissue are innervated by peripheral sympathetic and sensory nerves. Moreover, ß-adrenergic 1 and 2 receptors (ß-ARs) are overexpressed in human oral cancer cell lines, and norepinephrine treatment increased ß-AR2 protein expression as well as cancer cell proliferation in vitro. We have recently demonstrated that inhibition of tumor necrosis factor alpha (TNFα) signaling reduces oral cancer-induced nociceptive behavior. Norepinephrine-treated cancer cell lines secrete more TNFα which, when applied to tongue-innervating trigeminal neurons, evoked a larger Ca 2+ transient; TNF-TNFR inhibitor blocked the increase in the evoked Ca 2+ transient. Using an orthotopic xenograft oral cancer model, we found that mice demonstrated significantly less orofacial cancer-induced nociceptive behavior during systemic ß-adrenergic inhibitory treatment with propranolol. Furthermore, chemical sympathectomy using guanethidine led to a significant reduction in tumor size and nociceptive behavior. We infer from these results that sympathetic signaling modulates oral cancer pain through TNFα secretion and tumorigenesis. Further investigation of the role of neurocancer communication in cancer progression and pain is warranted.

The contribution of endocytosis to sensitization of nociceptors and synaptic transmission in nociceptive circuits.

ABSTRACT: Chronic pain involves sensitization of nociceptors and synaptic transmission of painful signals in nociceptive circuits in the dorsal horn of the spinal cord. We investigated the contribution of clathrin-dependent endocytosis to sensitization of nociceptors by G protein-coupled receptors (GPCRs) and to synaptic transmission in spinal nociceptive circuits. We determined whether therapeutic targeting of endocytosis could ameliorate pain. mRNA encoding dynamin (Dnm) 1 to 3 and adaptor-associated protein kinase 1 (AAK1), which mediate clathrin-dependent endocytosis, were localized to primary sensory neurons of dorsal root ganglia of mouse and human and to spinal neurons in the dorsal horn of the mouse spinal cord by RNAScope. When injected intrathecally to mice, Dnm and AAK1 siRNA or shRNA knocked down Dnm and AAK1 mRNA in dorsal root ganglia neurons, reversed mechanical and thermal allodynia and hyperalgesia, and normalized nonevoked behavior in preclinical models of inflammatory and neuropathic pain. Intrathecally administered inhibitors of clathrin, Dnm, and AAK1 also reversed allodynia and hyperalgesia. Disruption of clathrin, Dnm, and AAK1 did not affect normal motor functions of behaviors. Patch clamp recordings of dorsal horn neurons revealed that Dnm1 and AAK1 disruption inhibited synaptic transmission between primary sensory neurons and neurons in lamina I/II of the spinal cord dorsal horn by suppressing release of synaptic vesicles from presynaptic primary afferent neurons. Patch clamp recordings from dorsal root ganglion nociceptors indicated that Dnm siRNA prevented sustained GPCR-mediated sensitization of nociceptors. By disrupting synaptic transmission in the spinal cord and blunting sensitization of nociceptors, endocytosis inhibitors offer a therapeutic approach for pain treatment.

Protease-activated receptors in health and disease.

Proteases are signaling molecules that specifically control cellular functions by cleaving protease-activated receptors (PARs). The four known PARs are members of the large family of G protein-coupled receptors. These transmembrane receptors control most physiological and pathological processes and are the target of a large proportion of therapeutic drugs. Signaling proteases include enzymes from the circulation; from immune, inflammatory epithelial, and cancer cells; as well as from commensal and pathogenic bacteria. Advances in our understanding of the structure and function of PARs provide insights into how diverse proteases activate these receptors to regulate physiological and pathological processes in most tissues and organ systems. The realization that proteases and PARs are key mediators of disease, coupled with advances in understanding the atomic level structure of PARs and their mechanisms of signaling in subcellular microdomains, has spurred the development of antagonists, some of which have advanced to the clinic. Herein we review the discovery, structure, and function of this receptor system, highlight the contribution of PARs to homeostatic control, and discuss the potential of PAR antagonists for the treatment of major diseases.

Oral cancer patients experience mechanical and chemical sensitivity at the site of the cancer.

INTRODUCTION: Oral cancer patients suffer severe chronic and mechanically-induced pain at the site of the cancer. Our clinical experience is that oral cancer patients report new sensitivity to spicy foods. We hypothesized that in cancer patients, mechanical and chemical sensitivity would be greater when measured at the cancer site compared to a contralateral matched normal site. METHODS: We determined mechanical pain thresholds (MPT) on the right and left sides of the tongue of 11 healthy subjects, and at the cancer and contralateral matched normal site in 11 oral cancer patients in response to von Frey filaments in the range of 0.008 to 300 g (normally not reported as painful). We evaluated chemical sensitivity in 13 healthy subjects and seven cancer patients, who rated spiciness/pain on a visual analog scale in response to exposure to six paper strips impregnated with capsaicin (0-10 mM). RESULTS: Mechanical detection thresholds (MDT) were recorded for healthy subjects, but not MPTs. By contrast, MPTs were measured at the site of the cancer in oral cancer patients (7/11 patients). No MPTs were measured at the cancer patients' contralateral matched normal sites. Measured MPTs were correlated with patients' responses to the University of California Oral Cancer Pain Questionnaire. Capsaicin sensitivity at the site of the cancer was evident in cancer patients by a leftward shift of the cancer site capsaicin dose-response curve compared to that of the patient's contralateral matched normal site. We detected no difference in capsaicin sensitivity on the right and left sides of tongues of healthy subjects. CONCLUSIONS: Mechanical and chemical sensitivity testing was well tolerated by the majority of oral cancer patients. Sensitivity is greater at the site of the cancer than at a contralateral matched normal site.

Oral Cancer Cells Release Vesicles that Cause Pain.

Oral cancer pain is attributed to the release from cancers of mediators that sensitize and activate sensory neurons. Intraplantar injection of conditioned media (CM) from human tongue cancer cell line HSC-3 or OSC-20 evokes nociceptive behavior. By contrast, CM from noncancer cell lines, DOK, and HaCaT are non-nociceptive. Pain mediators are carried by extracellular vesicles (EVs) released from cancer cells. Depletion of EVs from cancer cell line CM reverses mechanical allodynia and thermal hyperalgesia. CM from non-nociceptive cell lines become nociceptive when reconstituted with HSC-3 EVs. Two miRNAs (hsa-miR-21-5p and hsa-miR-221-3p) are identified that are present in increased abundance in EVs from HSC-3 and OSC-20 CM compared to HaCaT CM. The miRNA target genes suggest potential involvement in oral cancer pain of the toll like receptor 7 (TLR7) and 8 (TLR8) pathways, as well as signaling through interleukin 6 cytokine family signal transducer receptor (gp130, encoded by IL6ST) and colony stimulating factor receptor (G-CSFR, encoded by CSF3R), Janus kinase and signal transducer and activator of transcription 3 (JAK/STAT3). These studies confirm the recent discovery of the role of cancer EVs in pain and add to the repertoire of algesic and analgesic cancer pain mediators and pathways that contribute to oral cancer pain.

Sustained endosomal release of a neurokinin-1 receptor antagonist from nanostars provides long-lasting relief of chronic pain.

Soft polymer nanoparticles designed to disassemble and release an antagonist of the neurokinin 1 receptor (NK1R) in endosomes provide efficacious yet transient relief from chronic pain. These micellar nanoparticles are unstable and rapidly release cargo, which may limit the duration of analgesia. We examined the efficacy of stable star polymer nanostars containing the NK1R antagonist aprepitant-amine for the treatment of chronic pain in mice. Nanostars continually released cargo for 24 h, trafficked through the endosomal system, and disrupted NK1R endosomal signaling. After intrathecal injection, nanostars accumulated in endosomes of spinal neurons. Nanostar-aprepitant reversed mechanical, thermal and cold allodynia and normalized nociceptive behavior more efficaciously than free aprepitant in preclinical models of neuropathic and inflammatory pain. Analgesia was maintained for >10 h. The sustained endosomal delivery of antagonists from slow-release nanostars provides effective and long-lasting reversal of chronic pain.

Radiation therapy for head and neck cancer leads to gingival recession associated with dental caries.

OBJECTIVE: The aim of this study was to examine effects of radiation therapy (RT) for head and neck cancer (HNC) on periodontal disease and relationships to caries. STUDY DESIGN: A multicenter prospective observational cohort study (OraRad) was conducted in patients undergoing RT for HNC. Assessments were conducted by calibrated examiners at the pre-RT (baseline) visit (n = 533), the 12-month visit (n = 414), and the 24-month visit (n = 365). RESULTS: The average whole mouth mean (standard error (SE)) distance from the cementoenamel junction to the gingival margin (CEJ-GM) decreased significantly from 0.43 (0.04) mm at baseline to 0.24 (0.04) mm at 12 months and 0.11 (0.04) mm at 24 months (P ≤ .001). Whole mouth mean (SE) percentage of sites with CEJ-GM distance of <0 mm increased significantly from 23.3% (1.0%) at baseline to 28.5% (1.0%) at 12 months and 30.5% (1.1%) at 24 months (P ≤ .02). Higher mean radiation dose to the mandible was associated with a greater increase in the percentage of mandibular sites with CEJ-GM distance of <0 mm (P = .003). Both mean CEJ-GM distance and the percentage of sites with a CEJ-GM distance <0 mm were strongly associated with whole mouth mean proportion of decayed, missing, and filled surfaces, as well as proportion of decayed or filled facial/buccal surfaces specifically, (P < .001), with greater gingival recession associated with increased caries. CONCLUSIONS: RT for HNC leads to mandibular gingival recession in a dose-dependent manner. This gingival recession may contribute to increased risk for cervical caries seen in these patients.

Oral cancer induced TRPV1 sensitization is mediated by PAR2 signaling in primary afferent neurons innervating the cancer microenvironment.

Oral cancer patients report sensitivity to spicy foods and liquids. The mechanism responsible for chemosensitivity induced by oral cancer is not known. We simulate oral cancer-induced chemosensitivity in a xenograft oral cancer mouse model using two-bottle choice drinking and conditioned place aversion assays. An anatomic basis of chemosensitivity is shown in increased expression of TRPV1 in anatomically relevant trigeminal ganglion (TG) neurons in both the xenograft and a carcinogen (4-nitroquinoline 1-oxide)-induced oral cancer mouse models. The percent of retrograde labeled TG neurons that respond to TRPV1 agonist, capsaicin, is increased along with the magnitude of response as measured by calcium influx, in neurons from the cancer models. To address the possible mechanism of TRPV1 sensitivity in tongue afferents, we study the role of PAR2, which can sensitize the TRPV1 channel. We show co-expression of TRPV1 and PAR2 on tongue afferents and using a conditioned place aversion assay, demonstrate that PAR2 mediates oral cancer-induced, TRPV1-evoked sensitivity in an oral cancer mouse model. The findings provide insight into oral cancer-mediated chemosensitivity.

The impact of head and neck radiotherapy on salivary flow and quality of life: Results of the ORARAD study.

OBJECTIVES: Salivary hypofunction and xerostomia, are common side effects of radiotherapy, negatively impacting quality of life. The OraRad study presents results on the longitudinal impact of radiotherapy on salivary flow and patient-reported outcomes. PATIENTS AND METHODS: Prospective, multicenter cohort study of 572 patients receiving curative-intent head and neck radiotherapy (RT). Stimulated salivary flow (SSF) rate and patient-reported outcomes were measured prior to RT and at 6- and 18-months post-RT. Linear mixed effects models examined the relationship between RT dose and change in salivary flow, and change in patient-reported outcomes. RESULTS: 544 patients had baseline salivary flow measurement, with median (IQR) stimulated flow rate of 0.975 (0.648, 1.417) g/min. Average RT dose to parotid glands was associated with change in salivary flow post-RT (p < 0.001). Diminished flow to 37% of pre-RT level was observed at 6 months (median: 0.358, IQR: 0.188 to 0.640 g/min, n = 481) with partial recovery to 59% of pre-RT at 18 months (median: 0.575, IQR: 0.338 to 0.884 g/min, n = 422). Significant improvement in patient-reported swallowing, senses (taste and smell), mouth opening, dry mouth, and sticky saliva (p-values < 0.03) were observed between 6 and 18 months post-RT. Changes in swallowing, mouth opening, dry mouth, and sticky saliva were significantly associated with changes in salivary flow from baseline (p-values < 0.04). CONCLUSION: Salivary flow and patient-reported outcomes decreased as a result of RT, but demonstrated partial recovery during follow-up. Continued efforts are needed to improve post-RT salivary function to support quality of life.

Schwann cell endosome CGRP signals elicit periorbital mechanical allodynia in mice.

Efficacy of monoclonal antibodies against calcitonin gene-related peptide (CGRP) or its receptor (calcitonin receptor-like receptor/receptor activity modifying protein-1, CLR/RAMP1) implicates peripherally-released CGRP in migraine pain. However, the site and mechanism of CGRP-evoked peripheral pain remain unclear. By cell-selective RAMP1 gene deletion, we reveal that CGRP released from mouse cutaneous trigeminal fibers targets CLR/RAMP1 on surrounding Schwann cells to evoke periorbital mechanical allodynia. CLR/RAMP1 activation in human and mouse Schwann cells generates long-lasting signals from endosomes that evoke cAMP-dependent formation of NO. NO, by gating Schwann cell transient receptor potential ankyrin 1 (TRPA1), releases ROS, which in a feed-forward manner sustain allodynia via nociceptor TRPA1. When encapsulated into nanoparticles that release cargo in acidified endosomes, a CLR/RAMP1 antagonist provides superior inhibition of CGRP signaling and allodynia in mice. Our data suggest that the CGRP-mediated neuronal/Schwann cell pathway mediates allodynia associated with neurogenic inflammation, contributing to the algesic action of CGRP in mice.