A nano-phytochemical ophthalmic solution for marked improvement of corneal wound healing in healthy or diabetic mice

Aim: To formulate a novel nano-phytochemical ophthalmic solution to promote corneal wound healing. Methods: Dipotassium glycyrrhizinate (DG) and palmatine (PAL) were used to formulate this formulation marked as DG-PAL, and its efficacy and mechanisms for promoting corneal wound healing were evaluated in mice. Results: DG-PAL was easily fabricated with excellent physical profiles. In in vivo efficiency evaluations, DG-PAL demonstrated an excellent promoting effect on corneal epithelial/nerve wound healing in both healthy and diabetic mice. These effects were involved in the DG-PAL-induced decreased expression levels of HMGB1 and its signaling-related factors in the corneas and trigeminal neurons of the healthy or diabetic mice. Conclusion: DG-PAL possibly represents a promising ophthalmic solution for promoting corneal wound healing.

TRPV1-lineage somatosensory fibers communicate with taste neurons in the mouse parabrachial nucleus

Trigeminal neurons supply somatosensation to craniofacial tissues. In mouse brain, ascending projections from medullary trigeminal neurons arrive at taste neurons in the autonomic parabrachial nucleus, suggesting taste neurons participate in somatosensory processing. However, the genetic cell types that support this convergence were undefined. Using Cre-directed optogenetics and in vivo neurophysiology in anesthetized mice of both sexes, here we studied whether TRPV1-lineage nociceptive and thermosensory fibers are primary neurons that drive trigeminal circuits reaching parabrachial taste cells. We monitored spiking activity in individual parabrachial neurons during photoexcitation of the terminals of TRPV1-lineage fibers that arrived at the dorsal spinal trigeminal nucleus pars caudalis, which relays orofacial somatosensory messages to the parabrachial area. Parabrachial neural responses to oral delivery of taste, chemesthetic, and thermal stimuli were also recorded. We found that optical excitation of TRPV1-lineage fibers frequently stimulated traditionally defined taste neurons in lateral parabrachial nuclei. The tuning of neurons across diverse tastes associated with their sensitivity to excitation of TRPV1-lineage fibers, which only sparingly engaged neurons oriented to preferred tastes like sucrose. Moreover, neurons that responded to photostimulation of TRPV1-lineage afferents showed strong responses to temperature including noxious heat, which predominantly excited parabrachial bitter taste cells. Multivariate analyses revealed the parabrachial confluence of TRPV1-lineage signals with taste captured sensory valence information shared across aversive gustatory, nociceptive, and thermal stimuli. Our results reveal that trigeminal fibers with defined roles in thermosensation and pain communicate with parabrachial taste neurons. This multisensory convergence supports dependencies between gustatory and somatosensory hedonic representations in the brain.

HMGB1, NLRP3, IL-6 and ACE2 levels are elevated in COVID-19 with headache: a window to the infection-related headache mechanism

Background and aim Pathogenesis of COVID-19 -related headache is unknown, though the induction of the trigeminal neurons through inflammation is proposed. We aimed to investigate key systemic circulating inflammatory molecules and their clinical relations in COVID-19 patients with headache. Methods This cross-sectional study enrolled 88 COVID-19 patients, hospitalized on a regular ward during the second wave of the pandemic. Clinical characteristics of COVID-19 patients were recorded, and laboratory tests were studied. Results The mean ages of 48 COVID-19 patients with headache (47.71 ± 10.8) and 40 COVID-19 patients without headache (45.70 ± 12.72) were comparable. COVID-19 patients suffered from headache had significantly higher serum levels of HMGB1, NLRP3, ACE2, and IL-6 than COVID-19 patients without headache, whereas CGRP and IL-10 levels were similar in the groups. Angiotensin II level was significantly decreased in the headache group. COVID-19 patients with headache showed an increased frequency of pulmonary involvement and increased D- dimer levels. Furthermore, COVID-19 was more frequently associated with weight loss, nausea, and diarrhea in patients with headache. Serum NLRP3 levels were correlated with headache duration and hospital stay, while headache response to paracetamol was negatively correlated with HMGB1 and positively associated with IL-10 levels. Conclusion Stronger inflammatory response is associated with headache in hospitalized COVID-19 patients with moderate disease severity. Increased levels of the circulating inflammatory and/or nociceptive molecules like HMGB1, NLRP3, and IL-6 may play a role in the potential induction of the trigeminal system and manifestation of headache secondary to SARS-CoV-2 infection.

Erenumab-aooe: A promising monoclonal antibody for prophylactic pharmacotherapy in migraine.

Migraine is one form of disorder affecting the quality of life of patient. The term chronic migraine refers to a clinical condition summarized by migraines headache on fifteen days usually per monthly episode. Most commonly patients on pharmacotherapy of migraine include Ergot derivatives, Opioids, and Analgesics for a period range of ten days per month. The CGRP is involved in pathology and physiology of origin of neurovascular headaches via migraine at both peripheral and central levels. The CGRP is highly expressed in trigeminal neurons (small myelinated Ad and unmyelinated C fibers) co-localized with other neuropeptides (e.g., substance P). The CGRP levels are increased into external jugular venous blood ipsilateral to pain during headache phase of migraine attack. Also the saliva and serum CGRP levels are increased during migraine and interracially in patients with CM. Scope: Erenumab-aooe, CGRPr antagonist, being the latest approved drug administered via subcutaneous route as 70 mg per month for prophylactic regime of migraine in adult patients, the results documented as per clinical trials data are very promising and thus Erenumab-aooe is an emerging hope to improve quality of life. Conclusion: CM is not fully treated as the pharmacotherapy response is at the poor level and also limited pharmacotherapy is available, however the emergence of Erenumab- aooe, CGRPr antagonist as the one of the latest drug approval for the prophylaxis of migraine in adults.

HMGB1, NLRP3, IL-6 and ACE2 Levels Are Elevated in COVID-19 with Headache: A Window to the Infection-Related Headache Mechanism

BACKGROUND AND AIM: Pathogenesis of COVID-19 -related headache is unknown, though the induction ofthe trigeminal neurons throughinflammation is proposed. Weaimed to investigatekey systemic circulating inflammatory moleculesand their clinical relations in COVID-19 patients with headache. METHODS: Thiscross-sectional study enrolled 88COVID-19 patients,hospitalized on a regular ward during the second wave of the pandemic.Clinical characteristics of COVID-19 patients were recorded,and laboratory testswere studied.RESULTS: The mean agesof 48 COVID-19 patients with headache (47.71±10.8) and 40 COVID-19 patients without headache (45.70±12.72) were comparable. COVID-19 patients suffered from headache had significantly higher serum levels of HMGB1, NLRP3, ACE2, and IL-6 than COVID-19 patients without headache, whereasCGRP and IL-10 levels were similar in the groups. Angiotensin II level was significantly decreased in the headache group.COVID-19 patients with headache showedan increased frequency of pulmonary involvement and increased D- dimer levels. Furthermore, COVID-19 was more frequently associated with weight loss, nausea, and diarrhea in patients with headache. The frequency of anosmia and ageusia did not reach significant levelsbetween the two groups. Serum NLRP3 levels were correlated with headache duration and hospital stay, while headache response to paracetamol was negatively correlated with HMGB1 and positively associated with IL-10 levels. CONCLUSION: Stronger inflammatory response is associated with headache in hospitalized COVID-19 patients with moderate disease severity.Increased levels of the circulating inflammatory and/or nociceptive molecules like HMGB1, NLRP3, and IL-6 may play a role in the potential induction of the trigeminalsystem and manifestation of headache secondary to SARS-CoV-2 infection.

Loss of Elp1 disrupts trigeminal ganglion neurodevelopment in a model of Familial Dysautonomia

Familial Dysautonomia (FD) is a sensory and autonomic neuropathy caused by a mutation in Elongator complex protein 1 (ELP1). FD patients have small trigeminal nerves and impaired perception of facial pain and temperature. These signals are relayed by nociceptive neurons in the trigeminal ganglion, a structure comprised of both neural crest- and placode-derived cells. Mice lacking Elp1 in neural crest derivatives (Elp1 CKO) are born with smaller trigeminal ganglia, suggesting Elp1 is important for trigeminal ganglion development, yet the function of Elp1 in this context is unknown. We demonstrate Elp1 expression in both neural crest- and placode-derived trigeminal neurons, which our data suggest give rise to primarily TrkA- and TrkB/C-expressing neurons, respectively. While Elp1 is not required for initial trigeminal ganglion formation, Elp1 CKO trigeminal neurons exhibit abnormal axon outgrowth and decreased target innervation. Developing nociceptors that express the receptor TrkA are especially vulnerable to Elp1 loss. TrkA expression is decreased in Elp1 CKO trigeminal nerve endings, coinciding with increased cell death. Subsequently, fewer TrkA neurons are present in the Elp1 CKO trigeminal ganglion, indicating Elp1 supports the target innervation and survival of trigeminal nociceptors. These findings explain the loss of facial pain and temperature sensation in FD.

Migraine and neuroinflammation: the inflammasome perspective

Background Neuroinflammation has an important role in the pathophysiology of migraine, which is a complex neuro-glio-vascular disorder. The main aim of this review is to highlight findings of cortical spreading depolarization (CSD)-induced neuroinflammatory signaling in brain parenchyma from the inflammasome perspective. In addition, we discuss the limited data of the contribution of inflammasomes to other aspects of migraine pathophysiology, foremost the activation of the trigeminovascular system and thereby the generation of migraine pain. Main body Inflammasomes are signaling multiprotein complexes and key components of the innate immune system. Their activation causes the production of inflammatory cytokines that can stimulate trigeminal neurons and are thus relevant to the generation of migraine pain. The contribution of inflammasome activation to pain signaling has attracted considerable attention in recent years. Nucleotide-binding domain (NOD)-like receptor family pyrin domain containing 3 (NLRP3) is the best characterized inflammasome and there is emerging evidence of its role in a variety of inflammatory pain conditions, including migraine. In this review, we discuss, from an inflammasome point of view, cortical spreading depolarization (CSD)-induced neuroinflammatory signaling in brain parenchyma, the connection with genetic factors that make the brain vulnerable to CSD, and the relation of the inflammasome with diseases that are co-morbid with migraine, including stroke, epilepsy, and the possible links with COVID-19 infection. Conclusion Neuroinflammatory pathways, specifically those involving inflammasome proteins, seem promising candidates as treatment targets, and perhaps even biomarkers, in migraine.

Glutamate Signaling, Associated With Satellite Glial Cells That Envelop Small Trigeminal Ganglion Neurons Is Highly Involved in the Neuropathic Pain

Recent studies implicate glutamate release from satellite glial cells (SGCs) surrounding the primary sensory neurons in the mechanisms of pathologic pain. However, little is known about the population of SGCs in the trigeminal ganglion that is involved in glutamate signaling associated with craniofacial neuropathic pain. To address this issue, we used quantitative analysis of electron microscopic immunogold labeling to investigate the changes in glutamate levels in trigeminal neurons and their enveloping SGCs in a rat model of craniofacial neuropathic pain, chronic constriction injury of inferior alveolar nerve (CCI-ION). The density of immunogold, a measure for glutamate concentration, in the neuronal cell bodies of all sizes, and in the SGCs surrounding them, was significantly higher in rats with CCI-ION than in sham-operated rats. This effect was more pronounced for the small neurons (2.2 times higher) and their SGCs (1.8 times higher) than for the medium and the large neurons and their SGCs, respectively. These findings suggest that each populations of SGCs and their surrounding trigeminal neurons of different type are involved in the glutamate signaling associated with neuropathic pain at a different level.

Effects of CGRP-Primed Dental Pulp Stem Cells on Trigeminal Sensory Neurons

Dental pulp stem cells (DPSCs) are important in tooth physiology, contributing to development, repair, regeneration, and immunomodulatory processes. However, their role in inflammatory mechanisms underlying pulpitis is not well understood. We evaluated the influence of DPSCs stimulated with calcitonin gene-related peptide (CGRP), a proinflammatory neuropeptide, on the expression of mediators released from DPSCs and the effect of these mediators on sensory neuron activity. Human DPSCs were treated with either control media or media containing CGRP (10−8 M) for 7 d, and the conditioned media (CM) containing DPSC-released mediators was collected. The expression of cytokines and chemokines from DPSCs was evaluated by reverse transcription quantitative polymerase chain reaction. The effects of the CM from CGRP-primed DPSCs (primed DPSC-CM) were evaluated on sensory afferents by using primary cultures of mouse trigeminal neurons and an organotypic model of cultured human pulp slices. Mouse trigeminal neurons and human pulp explants were pretreated for 24 h with control or primed DPSC-CM and then stimulated with capsaicin. Afferent activity was measured by quantifying the response to capsaicin via live cell calcium imaging in mouse neurons and CGRP released from pulp explants. Gene expression analysis showed that primed DPSCs overexpressed some proinflammatory cytokines and chemokines, including chemokines CXCL1 and CXCL8, which are both agonists of the receptor CXCR2 expressed in sensory neurons. Primed DPSC-CM increased human pulp sensory afferent activity as compared with control DPSC-CM. Similarly, primed DPSC-CM increased the intensity of calcium responses in cultured mouse trigeminal neurons. Furthermore, the CXCR2 antagonist SB225002 prevented trigeminal neuron sensitization to capsaicin induced by primed DPSC-CM. In conclusion, mediators released by DPSCs, primed with the proinflammatory mediator CGRP, induce neuronal sensitization through CXCR2 receptor. These data suggest that DPSCs might contribute to pain symptoms that develop in pulpitis.