Sneezing reflex is mediated by a peptidergic pathway from nose to brainstem.

Sneezing is a vital respiratory reflex frequently associated with allergic rhinitis and viral respiratory infections. However, its neural circuit remains largely unknown. A sneeze-evoking region was discovered in both cat and human brainstems, corresponding anatomically to the central recipient zone of nasal sensory neurons. Therefore, we hypothesized that a neuronal population postsynaptic to nasal sensory neurons mediates sneezing in this region. By screening major presynaptic neurotransmitters/neuropeptides released by nasal sensory neurons, we found that neuromedin B (NMB) peptide is essential for signaling sneezing. Ablation of NMB-sensitive postsynaptic neurons in the sneeze-evoking region or deficiency in NMB receptor abolished the sneezing reflex. Remarkably, NMB-sensitive neurons further project to the caudal ventral respiratory group (cVRG). Chemical activation of NMB-sensitive neurons elicits action potentials in cVRG neurons and leads to sneezing behavior. Our study delineates a peptidergic pathway mediating sneezing, providing molecular insights into the sneezing reflex arc.

A basophil-neuronal axis promotes itch.

Itch is an evolutionarily conserved sensation that facilitates expulsion of pathogens and noxious stimuli from the skin. However, in organ failure, cancer, and chronic inflammatory disorders such as atopic dermatitis (AD), itch becomes chronic, intractable, and debilitating. In addition to chronic itch, patients often experience intense acute itch exacerbations. Recent discoveries have unearthed the neuroimmune circuitry of itch, leading to the development of anti-itch treatments. However, mechanisms underlying acute itch exacerbations remain overlooked. Herein, we identify that a large proportion of patients with AD harbor allergen-specific immunoglobulin E (IgE) and exhibit a propensity for acute itch flares. In mice, while allergen-provoked acute itch is mediated by the mast cell-histamine axis in steady state, AD-associated inflammation renders this pathway dispensable. Instead, a previously unrecognized basophil-leukotriene (LT) axis emerges as critical for acute itch flares. By probing fundamental itch mechanisms, our study highlights a basophil-neuronal circuit that may underlie a variety of neuroimmune processes.

mMrgprA3/mMrgprC11/hMrgprX1: Potential therapeutic targets for allergic contact dermatitis-induced pruritus in mice and humans.

BACKGROUND: Although the Mas-related G-protein-coupled receptors (Mrgprs) play essential roles in itch detection, their contribution to allergic contact dermatitis (ACD)-associated itch remains unclear. OBJECTIVES: To investigate whether Mrgprs are involved in ACD and whether Mrgprs can be identified as potential therapeutic targets. METHODS: Mrgpr-clusterΔ-/- mice and human MrgprX1 (hMrgprX1) transgenic mice were used to evaluate the function of Mrgprs in oxazolone-induced ACD. RESULTS: Utilizing an ACD model, we found that Mrgpr-clusterΔ-/- mice display significantly reduced pruritus. Among 12 Mrgprs deleted in Mrgpr-clusterΔ-/- mice, the expression of MrgprC11 and MrgprA3 was significantly increased in the ACD model, which also innervated the skin and spinal cord at higher-than-normal densities. The proportions of dorsal root ganglia neurons responding to bovine adrenal medulla peptide 8-22 and chloroquine were also remarkably increased in the ACD model, resulting in enhanced itch behaviour. To study the function of human Mrgprs in ACD-induced itch, we used hMrgprX1 transgenic mice, which rescued the severe itch defect of Mrgpr-clusterΔ-/- mice in the ACD model. Remarkably, pharmacological blockade of hMrgprX1 significantly attenuates ACD itch in hMrgprX1 transgenic mouse. CONCLUSIONS: Our study provides the first evidence that Mrgprs are involved in ACD-induced chronic itch, which provides new avenues for itch management in ACD.

TRPV1 in Pain and Itch.

Transient receptor potential vanilloid type 1 (TRPV1) is a nonselective cation channel that is intensively expressed in the peripheral nerve system and involved in a variety of physiological and pathophysiological processes in mammals. Its activity is of great significance in transmitting pain or itch signals from peripheral sensory neurons to the central nervous system. The alteration or hypersensitivity of TRPV1 channel is well evidenced under various pathological conditions. Moreover, accumulative studies have revealed that TRPV1-expressing (TRPV1+) sensory neurons mediate the neuroimmune crosstalk by releasing neuropeptides to innervated tissues as well as immune cells. In the central projection, TRPV1+ terminals synapse with the secondary neurons for the transmission of pain and itch signalling. The intense involvement of TRPV1 and TRPV1+ neurons in pain and itch makes it a potential pharmaceutical target. Over decades, the basis of TRPV1 channel structure, the nature of its activity, and its modulation in pathological processes have been broadly studied and well documented. Herein, we highlight the role of TRPV1 and its associated neurons in sensing pain and itch. The fundamental understandings of TRPV1-involved nociception, pruriception, neurogenic inflammation, and cell-specific modulation will help bring out more effective strategies of TRPV1 modulation in treating pain- and itch-related diseases.

Response of Chinese Anesthesiologists to the COVID-19 Outbreak.

The coronavirus disease 2019, named COVID-19 officially by the World Health Organization (Geneva, Switzerland) on February 12, 2020, has spread at unprecedented speed. After the first outbreak in Wuhan, China, Chinese anesthesiologists encountered increasing numbers of infected patients since December 2019. Because the main route of transmission is via respiratory droplets and close contact, anesthesia providers are at a high risk when responding to the devastating mass emergency. So far, actions have been taken including but not limited to nationwide actions and online education regarding special procedures of airway management, oxygen therapy, ventilation support, hemodynamic management, sedation, and analgesia. As the epidemic situation has lasted for months (thus far), special platforms have also been set up to provide free mental health care to all anesthesia providers participating in acute and critical caring for COVID-19 patients. The current article documents the actions taken, lesson learned, and future work needed.

NLRP3 inflammasome as a potential treatment in ischemic stroke concomitant with diabetes.

The NLRP3 (nucleotide-binding oligomerization domain-like receptor [NLR] family pyrin domain-containing 3) inflammasome is a member of the NLR family of innate immune cell sensors. These are crucial regulators of cytokine secretions, which promote ischemic cell death and insulin resistance. This review summarizes recent progress regarding the NLRP3 inflammasome as a potential treatment for ischemic stroke in patients with diabetes, two complicated diseases that often occur together. Stroke worsens glucose metabolism abnormalities, and the outcomes after stroke are more serious for diabetic patients compared with those without diabetes. Inflammation contributes to organ injury after ischemic stroke and diabetes. Recent research has focused on inhibiting the activation of inflammasomes and thus reducing the maturation of proinflammatory cytokines such as interleukin (IL)-1ß and IL-18. Studies suggest that inhibition of NLRP3 prevents or alleviates both ischemic stroke and diabetes. Targeting against the assembly and activity of the NLRP3 inflammasome is a potential and novel therapy for inflammasome-associated diseases, including ischemic stroke concomitant with diabetes.

Inhibition of NLRP3 Inflammasome Ameliorates Cerebral Ischemia-Reperfusion Injury in Diabetic Mice.

Sustained activation of NLRP3 inflammasome is closely related to diabetes and stroke. However, it is unknown whether NLRP3 inflammasome plays an essential role in stroke in diabetes. We aim to investigate the effect and the potential mechanism of NLRP3 inflammasome in diabetic mice with cerebral ischemia-reperfusion injury. A type 2 diabetic mouse model was induced by a high-fat diet and streptozotocin (STZ). Diabetic mice received MCC950 (the specific molecule NLRP3 inhibitor) or vehicle 60 minutes before the middle cerebral artery occlusion (MCAO) and reperfusion. MCC950 reduced the neurological deficit score of 24 h after cerebral ischemia reperfusion and improved the 28-day survival rate of cerebral ischemia-reperfusion injury in diabetic mice. Furthermore, we found that the mRNA transcription levels of NLRP3, IL-1ß, and caspase-1 in the core ischemic area were remarkably amplified in diabetic mice with cerebral ischemia-reperfusion injury, whereas this phenomenon was obviously attenuated by MCC950 pretreatment. In conclusion, the NLRP3 inflammasome was involved in the complex diseases of diabetic stroke. MCC950, the NLRP3 specific inhibitor, ameliorated diabetic mice with cerebral ischemia-reperfusion injury and improved the 28-day survival rate during the recovery stage of ischemic stroke.

Waste anesthetic gas exposure and strategies for solution.

As inhaled anesthetics are widely used, medical staff have inevitably suffered from exposure to anesthetic waste gases (WAGs). Whether chronic exposure to WAGs has an impact on the health of medical staff has long been a common concern, but conclusions are not consistent. Many measures and equipment have been proposed to reduce the concentration of WAGs as far as possible. This review aims to dissect the current exposure to WAGs and its influence on medical staff in the workplace and the environment, and summarize strategies to reduce WAGs.

A novel TRPM8 agonist relieves dry eye discomfort.

BACKGROUND: Physical cooling of the eye surface relieves ocular discomfort, but translating this event to drug treatment of dry eye discomfort not been studied. Here, we synthesized a water-soluble TRPM8 receptor agonist called cryosim-3 (C3, 1-diisopropylphosphorylnonane) which selectively activates TRPM8 (linked to cooling) but not TRPV1 or TRPA1 (linked to nociception) and tested C3 in subjects with mild forms of dry eye disease. METHODS: A set of 1-dialkylphosphoryalkanes were tested for activation of TRPM8, TRPV1 and TRPA1 receptors in transfected cells. The bioactivity profiles were compared by perioral, topical, and intravenous delivery to anesthetized rats. The selected lead candidate C3 or vehicle (water) was applied with a cotton gauze pad to upper eyelids of patients with dry eye disease (n = 30). Cooling sensation, tear film break-up time (TBUT), basal tear secretion, and corneal staining were evaluated. C3 was then applied four times daily for 2 weeks to patients using a pre-loaded single unit applicator containing 2 mg/mL of C3 in water (n = 20) or water only. TBUT, basal tear secretion, and corneal staining, and three questionnaires surveys of ocular discomfort (VAS scale, OSDI, and CVS symptoms) were analyzed before and at 1 and 2 weeks thereafter. RESULTS: C3 was a selective and potent TRPM8 agonist without TRPV1 or TRPA1 activity. In test animals, the absence of shaking behavior after C3 perioral administration made it the first choice for further study. C3 increased tear secretion in an animal model of dry eye disease and did not irritate when wiped on eyes of volunteers. C3 singly applied (2 mg/ml) produced significant cooling in <5 min, an effecting lasting 46 min with an increase in tear secretion for 60 min. C3 applied for 2 weeks also significantly increased basal tear secretion with questionnaire surveys of ocular discomfort indices clearly showing improvement of symptoms at 1 and 2 weeks. No complaints of irritation or pain were reported by any subject. CONCLUSIONS: C3 is a promising candidate for study of TRPM8 function on the eye surface and for relief of dry eye discomfort. TRIAL REGISTRATION: ISRCTN24802609 and ISRCTN13359367 . Registered 23 March 2015 and 2 September 2015.

A Combined Water Extract of Frankincense and Myrrh Alleviates Neuropathic Pain in Mice via Modulation of TRPV1.

Frankincense and myrrh are widely used in clinics as a pair of herbs to obtain a synergistic effect for relieving pain. To illuminate the analgesia mechanism of frankincense and myrrh, we assessed its effect in a neuropathic pain mouse model. Transient receptor potential vanilloid 1 (TRPV1) plays a crucial role in neuropathic pain and influences the plasticity of neuronal connectivity. We hypothesized that the water extraction of frankincense and myrrh (WFM) exerted its analgesia effect by modulating the neuronal function of TRPV1. In our study, WFM was verified by UHPLC-TQ/MS assay. In vivo study showed that nociceptive response in mouse by heat and capsaicin induced were relieved by WFM treatment. Furthermore, thermal hypersensitivity and mechanical allodynia were also alleviated by WFM treatment in a chronic constriction injury (CCI) mouse model. CCI resulted in increased TRPV1 expression at both the mRNA and protein levels in predominantly small-to-medium neurons. However, after WFM treatment, TRPV1 expression was reverted in real-time PCR, Western blot, and immunofluorescence experiments. Calcium response to capsaicin was also decreased in cultured DRG neurons from CCI model mouse after WFM treatment. In conclusion, WFM alleviated CCI-induced mechanical allodynia and thermal hypersensitivity via modulating TRPV1.

Enhanced itch elicited by capsaicin in a chronic itch model.

Chronic itch (pruritus) is an important clinical problem. However, the underlying molecular basis has yet to be understood. The Transient Receptor Potential Vanilloid 1 channel is a heat-sensitive cation channel expressed in primary sensory neurons and involved in both thermosensation and pain, but its role in chronic itch remains elusive. Here, we for the first time revealed an increased innervation density of Transient Receptor Potential Vanilloid 1-expressing sensory fibers in the skin afflicted with chronic itch. Further analysis indicated that this phenomenon is due to an expansion of Transient Receptor Potential Vanilloid 1-expressing sensory neurons under chronic itch conditions. As a functional correlates of this neuronal expansion, we observed an enhanced neuronal responsiveness to capsaicin under the dry skin conditions. Importantly, the neuronal hypersensitivity to capsaicin results in itch, rather than pain sensation, suggesting that the up-regulated Transient Receptor Potential Vanilloid 1 underlies the pain-to-itch switch under chronic itchy conditions. The study shows that there are different mechanisms of chronic pain and itching, and Transient Receptor Potential Vanilloid 1 plays an important role in chronic itch.

Emulsified Isoflurane Protects Against Transient Focal Cerebral Ischemia Injury in Rats via the PI3K/Akt Signaling Pathway.

BACKGROUND: Phosphoinositide-3-kinase (PI3K)/protein kinase B (Akt) pathway activation may promote neuronal survival via neuroprotection during inflammation after cerebral ischemia. In this study, we investigated whether IV pretreatment with emulsified isoflurane (EI) could decrease ischemic brain injury related to the PI3K/Akt pathway. METHODS: Male Sprague-Dawley rats received different doses of IV EI (1, 2, 4, or 8 mL/kg/h) or Intralipid (8 mL/kg/h) for 30 minutes (n = 6-12 per group), followed by middle cerebral artery occlusion (MCAO) for 100 minutes to induce transient focal ischemia. The neurologic score and infarct volume were measured 48 hours after MCAO. Immunostaining, Western blot analysis, and an enzyme-linked immunosorbent assay were used to assess EI effects on the cell inflammatory response, high-mobility group box-1 release, and phosphorylated Akt (expression. LY294002, a PI3K inhibitor, was also infused into the ventricular space before EI to determine the effect of EI. RESULTS: Four milliliters per kilogram per hour of EI reduced the infarct size (21.08 ± 11.24 vs 37.09 ± 10.46, P = 0.006), improved neurologic scores after MCAO (1.13 ± 0.48 vs 1.95 ± 0.65, P = 0.015), significantly reinforced neuronal survival (982.7 ± 364.4 vs 439.8 ± 278.4, P = 0.036), and inhibited CD68 macrophage/macroglial infiltration in the ischemic core (188.2 ± 49.1 vs 282 ± 49.4, P = 0.018) compared with the vehicle group. In the EI pretreatment group, the serum high-mobility group box-1 concentration (3.62 ± 0.72 vs 5.73 ± 0.65, P < 0.001) was decreased, and the cerebral phosphorylated Akt level (50.33 ± 4.73 vs 37.5 ± 3.11, P = 0.007) was increased at 48 hours, which was inhibited by LY294002 compared with the vehicle group (5.31 ± 0.72 vs 5.73 ± 0.65, P = 0.216; 43.00 ± 4.84 vs 37.5 ± 3.11, P = 0.091). CONCLUSIONS: These findings suggest that EI pretreatment protects against ischemic brain injury via the inhibition of cerebral inflammation and is associated with the PI3K-Akt pathway in rats with MCAO. This drug may be a novel therapeutic agent for patients after stroke.

[Flavanoids Extracted from Onion Inhibited Activation of Microglia and Release of Proinflammatory Factors around the Hematoma in ICH Model Rats].

OBJECTIVE: To study flavanoids extracted from onion (FEO) on the number of activated microglia and the release of proinflammatory factors in intracerebral hemorrhage (ICH) model rat at different time points, and to explore its possible mechanism for treating ICH. METHODS: Totally 100 Wistar rats were used for preparing ICH model, and ICH model was successfully established in 90 of them. The 90 rats were randomly divided into the sham-operation group (n =10) , the ICH group (n =40) , the FEO group (n =40). Totally 100 [L autoblood was injected from fixed position to rats in the ICH group and the FEO group during modeling. Meanwhile, FEO at 0. 2 mL/10 g was given to rats in the FEO group, twice daily. No drug intervention was given to rats in the ICH group and the sham-operation group. Each group was further sub-divided into 5 sub-groups according to different time points such as 6, 24, 48, 72 h, and 7 days. There were 8 rats in each sub-group of the ICH group and the FEO group, 10 groups in total. There were 2 rats in each subgroup of the sham-operation group, 5 groups in total. Neurological functions at different time points were observed by Garcia JH. The injury degree of brain tissue was observed at dif- ferent time points using HE staining. Activated microglia around hematoma were observed at different time points after ICH by using immunohistochemical staining. Expressions of TNF-α and IL-1 ß at different time points after ICH was detected using ELISA. RESULTS: In the ICH group, degenerated and necrotic zone occurred around hematoma after injecting autoblood, cells were untidily arranged with irregular nucleus, partial nucleus were shrunken with lamellar interstitial edema of the medulla. As time went by, degenerated and necrotic zone was dilated; vacant zone occurred around cells; cells were unevenly distributed with reduced neuron numbers. Meanwhile, infiltration of lymphocytes and neutrophils occurred. In the FEO group after FEO intervention, necrotic cells were lesser, cell arrangement and nucleus morphology were obviously alleviated, and infiltration of inflammatory cells was reduced at corresponding time points. Compared with the sham-operation group, behavioral scores at 5 time points all decreased, the number of activated microglia was added, and expressions of TNF-α and IL-1 ß in hematoma tissue increased in the ICH group (P <0. 01). Compared with the ICH group, behavioral scores at 48 and 72 h, as well as day 7 all increased, the number of activated microglia was reduced, and expressions of TNF-α and IL-1ß in hematoma tissue decreased in the FEO group (P <0. 01). CONCLUSION: FEO using the ethanol reflux method could improve symptoms of ICH model rats possibly by inhibiting activation of microolia and the release of proinflammatory factors around the hematoma.

Transient receptor potential A1 activation prolongs isoflurane induction latency and impairs respiratory function in mice.

BACKGROUND: Isoflurane is a potent volatile anesthetic; however, it evokes airway irritation and neurogenic constriction through transient receptor potential (TRP) A1 channels and sensitizes TRPV1 channels, which colocalizes with TRPA1 in most of the vagal C-fibers innervating the airway. However, little is known about the precise effects of these two channels on the respiratory function during isoflurane anesthesia. METHODS: By using a rodent behavioral model and whole-body plethysmograph, the authors examined the response of Trpa1 and Trpv1 mice to isoflurane anesthesia and monitored their respiratory functions during anesthesia. RESULTS: This study showed that Trpa1 mice (n = 9), but not Trpv1 mice (n = 11), displayed a shortened induction latency compared with wild-type mice (n = 10) during isoflurane anesthesia (33 ± 2.0 s in wild-type and 33 ± 3.8 s in Trpv1 vs. 17 ± 1.8 in Trpa1 at 2.2 minimum alveolar concentrations). By contrast, their response to the nonpungent volatile anesthetic sevoflurane is indistinguishable from wild-type mice (24 ± 3.6 s in wild-type vs. 26 ± 1.0 s in Trpa1 at 2.4 minimum alveolar concentrations). The authors discovered that Trpa1 mice inhaled more anesthetic but maintained better respiratory function. Further respiration pattern analysis revealed that isoflurane triggered nociceptive reflexes and led to prolonged resting time between breaths during isoflurane induction as well as decreased dynamic pulmonary compliance, an indicator of airway constriction, throughout isoflurane anesthesia in wild-type and Trpv1 mice, but not in Trpa1 mice. CONCLUSION: Activation of TRPA1 by isoflurane negatively affects anesthetic induction latency by altering respiratory patterns and impairing pulmonary compliance.

Peptidomimetics of Arg-Phe-NH2 as small molecule agonists of Mas-related gene C (MrgC) receptors.

A series of Arg-Phe-NH2 peptidomimetics containing an Arg mimetic were synthesized and tested as agonists of human MrgX1, rat MrgC, and mouse MrgC11 receptors. As predicted from the previously established species specificity, these peptidomimetics were found to be devoid of MrgX1 agonist activity. In contrast, these compounds acted as agonists of MrgC and/or MrgC11 with varying degrees of potency. These new peptidomimetics should complement the existing small molecule human MrgX1 agonists and enhance our ability to assess the therapeutic utility of targeting Mrg receptors in rodent models.

Corrigendum: Involvement of endoplasmic reticulum stress in trigeminal ganglion corneal neuron injury in dry eye disease.

[This corrects the article DOI: 10.3389/fnmol.2023.1083850.].

Decreased connexin 40 expression of the sinoatrial node mediates ischemic stroke-induced arrhythmia in mice.

BACKGROUND: Arrhythmia is the most common cardiac complication after ischemic stroke. Connexin 40 is the staple component of gap junctions, which influences the propagation of cardiac electrical signals in the sinoatrial node. However, the role of connexin 40 in post-stroke arrhythmia remains unclear. METHODS: In this study, a permanent middle cerebral artery occlusion model was used to simulate the occurrence of an ischemic stroke. Subsequently, an electrocardiogram was utilized to record and assess variations in electrocardiogram measures. In addition, optical tissue clearing and whole-mount immunofluorescence staining were used to confirm the anatomical localization of the sinoatrial node, and the sinoatrial node tissue was collected for RNA sequencing to screen for potential pathological mechanisms. Lastly, the rAAV9-Gja5 virus was injected with ultrasound guidance into the heart to increase Cx40 expression in the sinoatrial node. RESULTS: We demonstrated that the mice suffering from a permanent middle cerebral artery occlusion displayed significant arrhythmia, including atrial fibrillation, premature ventricular contractions, atrioventricular block, and abnormal electrocardiogram parameters. Of note, we observed a decrease in connexin 40 expression within the sinoatrial node after the ischemic stroke via RNA sequencing and western blot. Furthermore, rAAV9-Gja5 treatment ameliorated the occurrence of arrhythmia following stroke. CONCLUSIONS: In conclusion, decreased connexin 40 expression in the sinoatrial node contributed to the ischemic stroke-induced cardiac arrhythmia. Therefore, enhancing connexin 40 expression holds promise as a potential therapeutic approach for ischemic stroke-induced arrhythmia.

Monocyte-Derived Macrophages Aggravate Cardiac Dysfunction After Ischemic Stroke in Mice.

BACKGROUND: Cardiac damage induced by ischemic stroke, such as arrhythmia, cardiac dysfunction, and even cardiac arrest, is referred to as cerebral-cardiac syndrome (CCS). Cardiac macrophages are reported to be closely associated with stroke-induced cardiac damage. However, the role of macrophage subsets in CCS is still unclear due to their heterogeneity. Sympathetic nerves play a significant role in regulating macrophages in cardiovascular disease. However, the role of macrophage subsets and sympathetic nerves in CCS is still unclear. METHODS AND RESULTS: In this study, a middle cerebral artery occlusion mouse model was used to simulate ischemic stroke. ECG and echocardiography were used to assess cardiac function. We used Cx3cr1GFPCcr2RFP mice and NLRP3-deficient mice in combination with Smart-seq2 RNA sequencing to confirm the role of macrophage subsets in CCS. We demonstrated that ischemic stroke-induced cardiac damage is characterized by severe cardiac dysfunction and robust infiltration of monocyte-derived macrophages into the heart. Subsequently, we identified that cardiac monocyte-derived macrophages displayed a proinflammatory profile. We also observed that cardiac dysfunction was rescued in ischemic stroke mice by blocking macrophage infiltration using a CCR2 antagonist and NLRP3-deficient mice. In addition, a cardiac sympathetic nerve retrograde tracer and a sympathectomy method were used to explore the relationship between sympathetic nerves and cardiac macrophages. We found that cardiac sympathetic nerves are significantly activated after ischemic stroke, which contributes to the infiltration of monocyte-derived macrophages and subsequent cardiac dysfunction. CONCLUSIONS: Our findings suggest a potential pathogenesis of CCS involving the cardiac sympathetic nerve-monocyte-derived macrophage axis.

A neural-mast cell axis regulates skin microcirculation in diabetes.

Changes in microcirculation lead to the progression of organ pathology in diabetes. Although neuroimmune interactions contribute to a variety of conditions, it is still unclear whether abnormal neural activities affect microcirculation related to diabetes. Using laser speckle contrast imaging, we examined the skin of patients with type 2 diabetes and found that their microvascular perfusion was significantly compromised. This phenomenon was recapitulated in a high-fat-diet-driven murine model of type 2 diabetes-like disease. In this setting, although both macrophages and mast cells were enriched in the skin, only mast cells and associated degranulation were critically required for the microvascular impairment. Sensory neurons exhibited enhanced TRPV1 activities, which triggered mast cells to degranulate and compromise skin microcirculation. Chemical and genetic ablation of TRPV1+ nociceptors robustly improve skin microcirculation status. Substance P (SP) is a neuropeptide and was elevated in the skin and sensory neurons in the context of type 2 diabetes. Exogenous administration of SP resulted in impaired skin microcirculation, whereas neuronal knockdown of SP dramatically prevented mast cell degranulation and consequently improved skin microcirculation. Overall, our findings indicate a neural-mast cell axis underlying skin microcirculation disturbance in diabetes and shed light on neuroimmune therapeutics for diabetes-related complications.

Inhibition of PARP1 improves cardiac function after myocardial infarction via up-regulated NLRC5.

The incidence and mortality rate of myocardial infarction are increasing per year in China. The polarization of macrophages towards the classically activated macrophages (M1) phenotype is of utmost importance in the progression of inflammatory stress subsequent to myocardial infarction. Poly (ADP-ribose) polymerase 1(PARP1) is the ubiquitous and best characterized member of the PARP family, which has been reported to support macrophage polarization towards the pro-inflammatory phenotype. Yet, the role of PARP1 in myocardial ischemic injury remains to be elucidated. Here, we demonstrated that a myocardial infarction mouse model induced cardiac damage characterized by cardiac dysfunction and increased PARP1 expression in cardiac macrophages. Inhibition of PARP1 by the PJ34 inhibitors could effectively alleviate M1 macrophage polarization, reduce infarction size, decrease inflammation and rescue the cardiac function post-MI in mice. Mechanistically, the suppression of PARP1 increase NLRC5 gene expression, and thus inhibits the NF-κB pathway, thereby decreasing the production of inflammatory cytokines such as IL-1ß and TNF-α. Inhibition of NLRC5 promote infection by effectively abolishing the influence of this mechanism discussed above. Interestingly, inhibition of NLRC5 promotes cardiac macrophage polarization toward an M1 phenotype but without having major effects on M2 macrophages. Our results demonstrate that inhibition of PARP1 increased NLRC5 gene expression, thereby suppressing M1 polarization, improving cardiac function, decreasing infarct area and attenuating inflammatory injury. The aforementioned findings provide new insights into the proinflammatory mechanisms that drive macrophage polarization following myocardial infarction, thereby introducing novel potential targets for future therapeutic interventions in individuals affected by myocardial infarction.