Pain Transmission Research Articles

TRPM8 Channels: Advances in Structural Studies and Pharmacological Modulation.

The transient receptor potential melastatin subtype 8 (TRPM8) is a cold sensor in humans, activated by low temperatures (>10, <28 °C), but also a polymodal ion channel, stimulated by voltage, pressure, cooling compounds (menthol, icilin), and hyperosmolarity. An increased number of experimental results indicate the implication of TRPM8 channels in cold thermal transduction and pain detection, transmission, and maintenance in different tissues and organs. These channels also have a repercussion on different kinds of life-threatening tumors and other pathologies, which include urinary and respiratory tract dysfunctions, dry eye disease, and obesity. This compendium firstly covers newly described papers on the expression of TRPM8 channels and their correlation with pathological states. An overview on the structural knowledge, after cryo-electron microscopy success in solving different TRPM8 structures, as well as some insights obtained from mutagenesis studies, will follow. Most recently described families of TRPM8 modulators are also covered, along with a section of molecules that have reached clinical trials. To finalize, authors provide an outline of the potential prospects in the TRPM8 field.

In Vivo Dissection of Two Intracellular Pathways Involved in the Spinal Oxytocin-Induced Antinociception in the Rat

Behavioral and electrophysiological data show that at the spinal level, oxytocin inhibits pain transmission by activation of oxytocin receptors (OTRs). Canonically, OTRs are coupled to Gq proteins, which induce a rise of intracellular Ca2+ by activating the phospholipase C (PLC). However, in vitro data showed that OTRs cause a plethora of intracellular events, some related to the activation of Gi proteins. Using a behavioral approach, we analyzed the main in vivo intracellular pathway elicited by spinal oxytocin during a peripheral inflammatory/persistent nociceptive stimulus. Intrathecal oxytocin reduces early (number of flinches) and late (mechanical allodynia) formalin-induced nociception, an effect abolished by the OTR antagonist (L-368,899). Furthermore, the antinociception observed during the early phase (acute inflammatory) was also reverted by U-73122 (PLC inhibitor) but not by pertussis toxin (Gαi/o protein inhibitor) or gallein (Gβγ subunit inhibitor). In contrast, the late oxytocin-induced behavioral analgesia was blocked by pertussis and gallein but not by U-73122. Since oxytocin's effects during the early phase were also antagonized by Nω-nitro-l-arginine methyl ester, ODQ, or glibenclamide (inhibitors of nitric oxide synthase [NOS], soluble guanylyl cyclase [GC], and K+ATP channels, respectively), the role of two differential pathways elicited by oxytocin is supported. Hence, we showed in in vivo experiments that oxytocin recruits two differential spinal intracellular pathways mediated by Gq (PLC/NOS/GC/K+ATP) or Gi proteins during a peripheral nociceptive stimulus.

Diurnal Variation in Trigeminal Pain Sensitivity in Mice.

Management of time and circadian disruption is an extremely important factor in basic research on pain and analgesia. Although pain is known to vary throughout the day, the mechanism underlying this circadian variation remains largely unknown. In this study, we hypothesized that the process of pain transmission to the central nervous system (after receiving nociceptive stimuli from outside the body) would show day-night differences. Ten-week-old male mice were kept under a strict 12/12-h light/dark cycle for at least 10 days. Formalin was then injected into the second branch region of the trigeminal nerve and the duration of pain-related behaviors (PRBs) was assessed. Immunohistochemical staining was then performed, and the c-Fos-immunopositive cells in the trigeminal spinal tract subnucleus caudalis (Sp5C) were counted. The results showed that the duration of PRBs was longer and the number of c-Fos immunopositive cells in the Sp5C was higher at nighttime than during the day. In addition, the trigeminal ganglia (TG) were extracted from the mice and examined by quantitative real-time PCR to evaluate the daytime and nighttime expression of nociceptive receptors. The results showed that the mRNA expression of transient receptor potential ankyrin 1 in the TG was significantly higher at night than during the day. These results suggest that pain in the trigeminal nerve region is more intense at nighttime, when rodents are active, than during the daytime, partly due to differences in nociceptor expression.

Effects of remifentanil on human C20 microglial pro-inflammatory activation.

Remifentanil (RF) is a potent short-acting μ-opioid receptor agonist. Although preferred for its unique pharmacokinetics, the clinical use may be limited by hyperalgesia. Preclinical studies have shown a potential role of microglia on the development of hyperalgesia, with limited and conflicting evidence on RF. Considering the role of microglia in the initiation and maintenance of brain inflammation and their different responses among species, we aimed at characterizing RF effects on human adult microglia in vitro. RF was tested at clinically relevant concentrations on the human microglial C20 cell line. Expression and release of interleukin-6 (IL-6) and brain derived neurotrophic factor (BDNF) were assessed under basal and inflammatory conditions. The expression and secretion of IL-6 significantly increased in C20 cells in response to pro-inflammatory cytokines. RF did not modify this response neither under basal nor under inflammatory conditions. No toxicity due to RF was detected. The drug displayed a modest stimulatory effect on the production of BDNF. Although RF does not exert direct pro-inflammatory actions on human adult microglia, its effects on BDNF, a crucial mediator of pain transmission, suggest a possible role on neuroinflammation and pain perception.

Milnacipran for the Treatment of Fibromyalgia.

This is a comprehensive review of the literature regarding the use of milnacipran in treating fibromyalgia. A chronic pain disorder with other system disturbances, fibromyalgia is often resistant to many therapeutic approaches. This review presents the background, evidence, and indications for using milnacipran as a treatment option for this condition. The definition of fibromyalgia has evolved over many years as it is a relatively tricky syndrome to measure objectively. Today, it is characterized by chronic, widespread pain accompanied by alterations in sleep, mood, and other behavioral aspects. A variety of therapeutic regimens currently used to treat the syndrome as a singular approach are rarely effective.Milnacipran is one of three drugs currently approved by the FDA for the treatment of fibromyalgia. It acts as a serotonin and norepinephrine reuptake inhibitor, which results in decreased pain transmission. Milnacipran remains an effective treatment option for fibromyalgia in adults and needs to be further evaluated with existing therapeutic approaches. Fibromyalgia is a broad-spectrum disorder primarily characterized by chronic pain coupled with disturbances in cognitive functioning and sleep. The progression of this syndrome is often debilitating and significantly affects the quality of life. Milnacipran is one of three FDA-approved drugs used to alleviate the symptom burden and is comparatively more therapeutic in specific domains of fibromyalgia. A more holistic approach is needed to treat fibromyalgia effectively and further research, including direct comparison studies, should be conducted to fully evaluate the usefulness of this drug.

The role of G‐protein‐coupled receptor kinase 2 in diabetic mechanical hyperalgesia in rats

Previous studies have indicated a negative correlation between GRK2 expression and pain development and transmission. Here, we investigated whether G-protein-coupled receptor kinase 2 (GRK2) was involved in regulating diabetic mechanical hyperalgesia (DMH). The adeno-associated viral vectors containing the GRK2 gene (AAV-GRK2) were used to up-regulate GRK2 protein expression. The expression of GRK2 and exchange protein directly activated by cyclic adenosine monophosphate 1 (Epac1) in the dorsal root ganglion (DRG) of lumbar 4-6 was detected via immunoblotting and immunohistochemistry, and the transfection of the GRK2 gene was detected by immunofluorescence. Low levels of GRK2 were able to sustain STZ-induced pain in DMH rats. Intrathecal injection of AAV-GRK2 vector up-regulated GRK2 expression, providing pain rain to rats with DMH. With an increase in DMH duration, there was a decrease in paw withdrawal threshold (PWT) value, aggravating the pain, resulting in a decreasing pattern in GRK2 protein expression over time, whereas Epac1 protein expression showed an opposite trend. GRK2 expression regulated DMH progression and is expected to play a role in the development of targeted therapy for DMH. GRK2 and Epac1 expressions play a vital role in maintaining pain in DMH rats.

Comparative Study of Postoperative Pain Relief Using Preincisional Versus Postincisional Infiltration With 0.25% Bupivacaine in Abdominal Hysterectomy Under General Anesthesia

Background and Aims:Hysterectomy, probably the most common non-pregnancy related surgery performed in gynaecology, is associated with moderate to severe post-operative pain. Wound infiltration with local anaesthetic agent reduces the transmission of pain from the wound, in addition, local inflammatory response to the injury is also suppressed. The infiltration of local anaesthesia can be done either pre- or post-operatively. The present study was designed to determine the efficacy of pre-incisional infiltration versus post-incisional infiltration with 0.25% Bupivacaine in providing post-operative pain relief in patients undergoing abdominal hysterectomy.Methods:In Prospective Interventional Randomised study, 90 female patients posted for elective abdominal hysterectomy under general anaesthesia were randomly allocated into three equal groups of 30 patients each.Group I:Patients receiving subcutaneous infiltration with 40 mL of 0.25% Bupivacaine 5 mins before skin incision.Group II:Patients receiving subcutaneous infiltration of surgical area with 40 mL of 0.25% Bupivacaine at end of surgery (after peritoneal closure).Group III (Control Group):Patients receiving no local anaesthetic infiltration. Observations were made for the duration of effective analgesia from end of the surgery until the first use of rescue analgesic along with the frequency and cumulative amount of rescue analgesics in 24 hours.Results:We found that at baseline, pain score of patients in Group III (3.87±1.17) was maximum followed by that in Group I (2.57±0.90) and minimum in Group II (2.20±0.61). Requirement of first analgesia was earliest in Group III (79.50±23.90 minutes) followed by Group I (136.83±13.16 minutes) and last in Group II (146.17±12.78 minutes), in addition, cumulative dose of analgesia was required by patients in Group III (152.50±36.76 mg) followed by that in Group I (132.50±37.80 mg) and minimum by that in Group II (115.00±38.06 mg).Conclusion:Subcutaneous infiltration of Bupivacaine either pre-incisional or post-incisional, helped to reduce the immediate post-operative pain intensity, delayed the first rescue analgesic requirement, reduced the post-operative dose and frequency of rescue analgesia. However, post-incisional intervention had an edge over pre-incisional intervention.

Nerve Growth Factor-Targeted Molecular Theranostics Based on Molybdenum Disulfide Nanosheet-Coated Gold Nanorods (MoS2-AuNR) for Osteoarthritis Pain.

Osteoarthritis (OA) is a leading cause of chronic pain in the elderly worldwide. Yet current diagnosis and therapy for OA pain are subjective and nonspecific with significant adverse effects. Here, we introduced a theranostic nanoprobe based on molybdenum disulfide nanosheet-coated gold nanorods (MoS2-AuNR) targeting never growth factor (NGF), a key player in pain sensation, for photoacoustic pain imaging and near-infrared (NIR) imaging-guided photothermal analgesic therapy. MoS2 coating significantly improved the photoacoustic and photothermal performance of AuNR. Functionalization of MoS2-AuNR nanoprobes by conjugating with NGF antibody enabled active targeting on painful OA knees in a surgical OA murine model. We observed that our functional nanoprobes accumulated in the OA knee rather than the contralateral intact one, and the amount was correlated with the severity of mechanical allodynia in our mouse model. Under imaging guidance, NIR-excited photothermal therapy could mitigate mechanical allodynia and walking imbalance behavior for both subacute and chronic stages of OA in a preclinical setting. This molecular theranostic approach enabled us to specifically localize the source of OA pain and efficiently block peripheral pain transmission.

Antinociceptive Effect of BPC-157 in the Formalin-induced Pain Model

Objectives Body protective compound-157 (BPC-157) is a stable gastric pentadecapeptide that has been effective in trials aiming to increase wound healing capabilities and decrease inflammatory cell influx, including studies on the healing of muscles and tendons. There are no studies about the effect of BPC-157 on pain transmission via nociception. This study examined the antinociceptive effects of BPC-157 using formalin tests and immunohistochemistry. Methods Rats were randomly divided into the control, morphine and BPC-157 groups. Pain behavior was quantified periodically at 5- and 35- min intervals (representative values of phases 1 and 2) by counting the number of flinches exhibited by the injected paw after injection. The dorsal root ganglia (DRG) and spinal cords (SC) were collected, and then, the number of cytokine-positive cells was determined via immunostaining. Results BPC-157 dose-dependently decreased the number of flinches during phase 1 but did not decrease the number of flinches during phase 2. During phase 1, interleukin-1β (IL-1β) in the DRG tissue was significantly different in the morphine, 10 μg/kg BPC-157, and 20 μg/kg BPC-157 groups. During phase 2, statistical significance was achieved in the DRG tissue in the morphine, 20 μg/kg BPC-157, and 40 μg/kg BPC-157 groups. During phase 1, interleukin-6 was significantly different in the DRG tissue in the morphine group and the SC tissue in the 10 μg/kg BPC-157 group. During phase 2, statistical significance was achieved in the morphine group and the BPC-157 20 μg/kg group in both the DRG and SC tissues. There were no significant differences in tumor necrosis factor-α between the DRG and SC tissues. Conclusions BPC-157 was effective during phase 1 but not during phase 2, as determined by the formalin test. BPC-157 decreased the expression of IL-1β in the DRG tissue in phases 1 and 2.

The role of dentate gyrus dopaminergic receptors in the lateral hypothalamic-induced antinociception during persistent inflammatory pain in male rats

The lateral hypothalamus (LH) is one of the key brain areas involved in pain modulation. Also, the dentate gyrus (DG) of the hippocampus expresses various receptors, including dopaminergic receptors. Dopaminergic receptors play a key role in pain transmission and modulation within the brain. The present study aimed to investigate the involvement of DG dopaminergic receptors in the LH-induced antinociception during the presence of inflammatory pain. Male Wistar rats were used in this study. Cannulae were unilaterally implanted in their skull for microinjections into the LH and DG. The LH was chemically stimulated by carbachol injection (250 nM/0.5 μl saline). In separate groups, different doses (0.25, 1, and 4 μg/0.5 μl vehicle) of the D1- and D2-like dopamine receptor antagonists (SCH23390 and Sulpiride, respectively) were microinjected into the DG, 5 min prior to intra-LH injection of carbachol. Five min after the second injection, formalin test as a persistent inflammatory pain model in animals was done in all rats. The results revealed that carbachol could induce antinociception following formalin injection into rat’s hind paw. The 4 μg dose of both antagonists significantly reduced the LH stimulation-induced antinociception in both phases of formalin pain responses. Although the 1 μg dose of sulpiride significantly reduced antinociception during both phases, 1 μg SCH23390 could only reduce this antinociception during the late phase. These findings demonstrate the involvement of DG dopaminergic receptors in the LH-induced antinociception. The results also suggest that the effectiveness of DG dopaminergic receptors is more pronounced during the late phase of formalin-induced pain responses.

3D magnetic resonance spectroscopic imaging reveals links between brain metabolites and multidimensional pain features in fibromyalgia.

Fibromyalgia is a centralized multidimensional chronic pain syndrome, but its pathophysiology is not fully understood. We applied 3D magnetic resonance spectroscopic imaging (MRSI), covering multiple cortical and subcortical brain regions, to investigate the association between neuro-metabolite (e.g. combined glutamate and glutamine, Glx; myo-inositol, mIno; and combined (total) N-acetylaspartate and N-acetylaspartylglutamate, tNAA) levels and multidimensional clinical/behavioural variables (e.g. pain catastrophizing, clinical pain severity and evoked pain sensitivity) in women with fibromyalgia (N=87). Pain catastrophizing scores were positively correlated with Glx and tNAA levels in insular cortex, and negatively correlated with mIno levels in posterior cingulate cortex (PCC). Clinical pain severity was positively correlated with Glx levels in insula and PCC, and with tNAA levels in anterior midcingulate cortex (aMCC), but negatively correlated with mIno levels in aMCC and thalamus. Evoked pain sensitivity was negatively correlated with levels of tNAA in insular cortex, MCC, PCC and thalamus. These findings support single voxel placement targeting nociceptive processing areas in prior 1 H-MRS studies, but also highlight other areas not as commonly targeted, such as PCC, as important for chronic pain pathophysiology. Identifying target brain regions linked to multidimensional symptoms of fibromyalgia (e.g. negative cognitive/affective response to pain, clinical pain, evoked pain sensitivity) may aid the development of neuromodulatory and individualized therapies. Furthermore, efficient multi-region sampling with 3D MRSI could reduce the burden of lengthy scan time for clinical research applications of molecular brain-based mechanisms supporting multidimensional aspects of fibromyalgia. This large N study linked brain metabolites and pain features in fibromyalgia patients, with a better spatial resolution and brain coverage, to understand a molecular mechanism underlying pain catastrophizing and other aspects of pain transmission. Metabolite levels in self-referential cognitive processing area as well as pain-processing regions were associated with pain outcomes. These results could help the understanding of its pathophysiology and treatment strategies for clinicians.

G-Protein-Coupled Receptors and Ischemic Stroke: a Focus on Molecular Function and Therapeutic Potential.

In ischemic stroke, there is only one approved drug, tissue plasminogen activator, to be used in clinical conditions for thrombolysis. New neuroprotective therapies for ischemic stroke are desperately needed. Several targets and pathways have been shown to confer neuroprotective effects in ischemic stroke. G-protein-coupled receptors (GPCRs) are one of the most frequently targeted receptors for developing novel therapeutics for central nervous system disorders. GPCRs are a large family of cell surface receptors that response to a wide variety of extracellular stimuli. GPCRs are involved in a wide range of physiological and pathological processes. More than 90% of the identified non-sensory GPCRs are expressed in the brain, where they play important roles in regulating mood, pain, vision, immune responses, cognition, and synaptic transmission. There is also good evidence that GPCRs are implicated in the pathogenesis of stroke. This review narrates the pathophysiological role and possible targeted therapy of GPCRs in ischemic stroke.

Overcoming Stress, Hunger, and Pain: Cocaine- and Amphetamine-Regulated Transcript Peptide's Promise.

Cocaine- and amphetamine-regulated transcript encodes an eponymous peptide, CARTp, which exerts diverse pharmacologic actions in the central and peripheral nervous systems, as well as in several endocrine organs, including pancreas. Here we review those diverse actions, the physiological relevance of which had remained unestablished until recently. With the identification of a CARTp receptor, GPR160, the physiologic importance and therapeutic potential of CARTp or analogs are being revealed. Not only is the CARTp-GPR160 interaction essential for the circadian regulation of appetite and thirst but also for the transmission of nerve injury-induced pain. Molecular approaches now are uncovering additional physiologically relevant actions and the development of acute tissue-specific gene compromise approaches may reveal even more physiologically relevant actions of this pluripotent ligand/receptor pair.

P061 Immune cell infiltrations of myenteric plexus in IBD – characterization and implications

Abstract Background IBD frequently causes chronic abdominal pain and visceral hypersensitivity. To understand development of pain in IBD in more detail, we analyzed the inflammatory infiltration of the enteric nervous system (ENS). A crucial signaling point for pain transmission is the myenteric plexus situated in the smooth muscle layer of the colon wall. We investigated (i) the immune cell infiltration within the myenteric plexus, (ii) neuronal cell survival and (iii) expression of neurotransmitters by immunostaining in surgical colonic samples from patients with Crohn′s disease (CD) or ulcerative colitis (UC). Methods FFPE material from surgeries (ileocecal resections and colectomies) was collected from 12 UC, nine CD and 11 patients that received surgeries for non-inflammatory reasons (controls). Immune cell composition, neurotransmitter expression and cell survival were analyzed by quantifying immune cell infiltration of the myenteric ganglia in immunohistochemistry sections. Immune cells within the myenteric plexus were defined as intraganglionar cells. The neurotransmitters CGRP and substance P as well as annexin V as a cell death marker were quantified based on their expression within the myenteric ganglia. Results CD3+CD4+ intraganglionar T-cells (216 ± 44 cells/mm²) were found to be increased for CD myenteric plexus compared to controls (79 ± 35 cells/mm²) (p=0.04) (see Fig. 1). For CD and UC, the cell counts of CD3+CD8+ lymphocytes infiltrating the myenteric plexus were significantly increased (controls: 39 ± 18 cells/mm², CD: 281 ± 105 cells/mm² (p=0.0004), UC: 177 ± 59 cells/mm² (p=0.04), Intraganglionar Foxp3+ T-cells were not significantly changed. Intraganglionar CD163+ and CD68+ monocytes were increased in CD (CD68+ monocytes: control: 377 ± 50 cells/mm², CD: 1278 ± 264 cells/mm², p=0.002 and CD163+ monocytes: control: 501 ± 97 cells/mm², CD: 963 ± 236 cells/mm², p=0.04). Expression levels of the neurotransmitter CGRP were found to be increased for UC myenteric plexus (control: 1.8 ± 0.2 units of intensity, UC: 2.8 ± 0.2 units of intensity, p=0.005). Substance P was found to be reduced in the myenteric plexus of CD patients if compared to controls (control: 2.1 ± 0.1 units of intensity, CD: 1.5 ± 0.2 units of intensity, p=0.007). UC myenteric plexus showed more annexin V-positive cells than control patients. Conclusion The intraganglionar immune cell composition of myenteric plexus in IBD comprises CD3+CD4+, CD3+CD8 T-cells in UC and CD3+CD4+, CD3+CD8+ and CD3+Foxp3+ T-cells as well as CD68+ and CD163+ monocytes in CD. In UC myenteric ganglia levels of the neurotransmitter CGRP are increased whereas substance P expression is reduced in CD. UC-affected myenteric plexus show increased levels of apoptosis in comparison to controls.

Cervical spinal cord injury-induced neuropathic pain in male mice is associated with a persistent pro-inflammatory macrophage/microglial response in the superficial dorsal horn

A significant portion of individuals living with traumatic spinal cord injury (SCI) experiences some degree of debilitating neuropathic pain (NP). This pain remains largely intractable in a majority of cases, due in part to an incomplete understanding of its underlying mechanisms. Central sensitization, an increase in excitability of pain transmission neurons located in superficial dorsal horn (sDH), plays a key role in development and maintenance of SCI-induced NP. Resident microglia and peripheral monocyte-derived macrophages (referred to collectively as MMΦ) are involved in promoting SCI-induced DH neuron hyperexcitability. Importantly, these MMΦ consist of populations of cells that can exert pro-inflammatory or anti-inflammatory signaling within injured spinal cord. It is critical to spatiotemporally characterize this heterogeneity to understand MMΦ contribution to NP after SCI. Given that a majority of SCI cases are cervical in nature, we used a model of unilateral C5/C6 contusion that results in persistent at-level thermal hyperalgesia and mechanical allodynia, two forms of NP-related behavior, in the forepaw. The aim of this study was to characterize the sDH MMΦ response within intact cervical spinal cord segments caudal to the lesion (i.e. the location of primary afferent nociceptive input from the forepaw plantar surface). Cervical SCI promoted a persistent MMΦ response in sDH that coincided with the chronic NP phenotype. Using markers of pro- and anti-inflammatory MMΦ, we found that the MMΦ population within sDH exhibited significant heterogeneity that evolved over time post-injury, including a robust and persistent increase in pro-inflammatory MMΦ that was especially pronounced at later times. C5/C6 contusion SCI also induced below-level thermal hyperalgesia and mechanical allodynia in the hindpaw; however, we did not observe a pronounced MMΦ response in sDH of L4/L5 spinal cord, suggesting that different inflammatory cell mechanisms occurring in sDH may be involved in at-level versus below-level NP following SCI. In conclusion, our findings reveal significant MMΦ heterogeneity both within and across pain transmission locations after SCI. These data also show a prominent and persistent pro-inflammatory MMΦ response, suggesting a possible role in DH neuron hyperexcitability and NP.

Allopurinol for fibromyalgia pain in adults: A randomized controlled trial.

Allopurinol is a potent inhibitor of the enzyme xanthine oxidase used in the treatment of hyperuricemia and gout. Because it is well known that purines exert multiple affects on pain transmission, we hypothesized that the inhibition of xanthine oxidase by allopurinol could be a valid strategy to treat pain in humans. This study aimed to compare the analgesic efficacy of oral allopurinol versus placebo as an adjuvant therapy in patients displaying fibromyalgia. This randomized, double-blinded, placebo-controlled study included 60 women with the diagnosis of fibromyalgia. Patients were randomly assigned to receive either oral allopurinol 300mg (n=31) or placebo (n=29) twice daily during 30days. The patients were submitted to evaluation for pain sensitivity, anxiety, depression, and functional status before treatment, and 15 and 30days thereafter. Oral administration of allopurinol 300mg twice daily was ineffective in improving pain scores measured by several tools up to 30days of treatment (P>0.05). Additionally, no significant effects of allopurinol over anxiety, depressive symptoms, and functional status of fibromyalgia patients were observed in the present study. Although previous findings indicated that allopurinol could present intrinsic analgesic effects in both animals and humans, this study showed no benefit of the use of oral allopurinol as an adjuvant strategy during 30days in women displaying fibromyalgia. However, considering previous promising results, new prospective studies are still valid to further investigate allopurinol and more selective purine derivatives in the management of pain syndromes.

TO COMPARE THE EFFICACY OF GENICULAR NERVE BLOCK AND INJECTION OF HYLAN G-F 20 VERSUS GENICULAR NERVE BLOCK ONLY FOR IMPROVING PAIN AND FUNCTION OF GRADE-II AND GRADE-III OSTEOARTHRITIS KNEE

Introduction: Osteoarthritis (OA) of knee joint is a degenerative joint disease; heterogeneous and progressive in nature. Clinically presented with stiffness, swelling and pain which leads to a decrease in the quality of life. The presence of chronic knee pain has been found to be a strong predictor of future disability and dependency in older adults. Usually managed conservatively but if conservative treatment fails, Total Knee Replacement (TKR) is traditionally considered. This is associated with multiple perioperative morbidities. On the contrary, many patients are not suitable for surgical procedure and some do not want to go for surgical intervention. As many patients are not surgical candidates due to co-morbidities or unwillingness; other treatment options available are being sought for. The genicular nerve block (GNB) reduces pain and improves patient functions by blocking pain transmission of the sensory nerves. Combining this genicular nerve block with viscosupplementation (Injection Hylan G-F 20) appears to play a role and can be tried in patients suffering in grade II and grade III (radiological grading) osteo arthritis. There is paucity of information so as to compare the efcacy of genicular nerve block and injection of Hylan G-F 20 versus genicular nerve block only. Material And Methods: This Parallel group open label randomized controlled trial was done between July, 2018 to December, 2019 (Eighteen months). Patients with knee pain in grade II and III, OA knee attending the PMR OPD in IPGME&amp;R, Kolkata in the specied tenure was considered for the study. The selected patients were allotted by random table. All the procedures were performed by single person. A total number of 60 patients with knee osteoarthritis of grade II and III, who did not respond with conservative management were included. Combined therapy of intra-articular injection of Hylan G-F 20 and genicular nerve block in Group 1 (Genicular Nerve Block and Injection Hylan G-F 20) and Genicular Nerve Block only in Group 2, performed to 30 patients in each arm. The three branches of the genicular nerve [superior lateral (SL), superior medial (SM), and inferior medial (IM) genicular nerves] were selected. Patients were evaluated initially (0 week) and at the 4th and 12th week followed up after intervention using VAS and WOMAC scale. Ultrasound guided genicular nerve block conducted under strict asepsis after proper dressing and draping with the visualization of genicular nerves (upper medial, upper lateral and lower medial quadrant) by musculoskeletal probe of Ultrasound machine (SAMSUNG/ Model PT60A/Musculoskeletal probe 12MHz). Injection Hylan G-F 20 (6 ml) intra-articular injection was given under strict asepsis. Results: 47% patients in group 1 and 67% patients in group 2 were in between 60-69 years. There is female preponderance in both the groups. WOMAC-pain score for dual intervention at 4th week was statistically signicantly lower compared to WOMAC-pain score obtained at any time of observation and any type of intervention. WOMAC- stiffness score for dual intervention at 4th week was statistically signicantly lower compared to WOMAC- stiffness score obtained at any time of observation. WOMAC SCORE: The changes in each intervention group at 0-week, 4th week and 12th week were statistically signicant. Statistically signicant difference of two groups were lost during 4th and 12th weeks observation. VAS: During 4th and 12th weeks observation, statistically signicantly different VAS score was observed among the two interventions; Genicular nerve block with injection consistently had a lower VAS score. This nding imply that Genicular nerve block alone did reduce the pain; however, reduction was greater in case of Genicular nerve block with Injection Hylan G-F 20 in both 4th and 12th week of observation. Conclusion: Genicular Nerve Block with injection HYLAN GF 20 (Combined Therapy Group) and Genicular Nerve Block alone are effective method of pain reduction in osteoarthritis knee. Combined Therapy doesn't have an added advantage as per WOMAC Score. But Combined therapy has a denite advantage over Genicular Nerve Block alone as per VAS Score.

Angiotensin (1-7) Attenuates the Nociceptive Behavior Induced by Substance P and NMDA via Spinal MAS1.

The intrathecal (i.t.) injection of substance P (SP) and N-methyl-D-aspartate (NMDA) induce transient nociceptive response by activating neurokinin (NK) 1 and NMDA receptors, respectively. We have recently reported that angiotensin (Ang) (1-7), an N-terminal fragment of Ang II, could alleviate several types of pain including neuropathic and inflammatory pain by activating spinal MAS1. Here, we investigated whether Ang (1-7) can inhibit the SP- and NMDA-induced nociceptive response. The nociceptive response induced by an i.t. injection of SP or NMDA was assessed by measuring the duration of hindlimb scratching directed toward the flank, biting and/or licking of the hindpaw or the tail for 5 min. Localization of MAS1 and either NK1 or NMDA receptors in the lumbar superficial dorsal horn was determined by immunohistochemical observation. The nociceptive response induced by SP and NMDA was attenuated by the i.t. co-administration of Ang (1-7) (0.03-3 pmol) in a dose-dependent manner. The inhibitory effects of Ang (1-7) (3 pmol) were attenuated by A779 (100 pmol), a MAS1 antagonist. Moreover, immunohistochemical analysis showed that spinal MAS1 co-localized with NK1 receptors and NMDA receptors on cells in the dorsal horn. Taken together, the i.t. injection of Ang (1-7) attenuated the nociceptive response induced by SP and NMDA via spinal MAS1, which co-localized with NK1 and NMDA receptors. Thus, the spinal Ang (1-7)/MAS1 pathway could represent a therapeutic target to effectively attenuate spinal pain transmission caused by the activation of NK1 or NMDA receptors.

The Multifaceted Mas-Related G Protein-Coupled Receptor Member X2 in Allergic Diseases and Beyond.

Recent research on mast cell biology has turned its focus on MRGPRX2, a new member of the Mas-related G protein-coupled subfamily of receptors (Mrgprs), originally described in nociceptive neurons of the dorsal root ganglia. MRGPRX2, a member of this group, is present not only in neurons but also in mast cells (MCs), specifically, and potentially in other cells of the immune system, such as basophils and eosinophils. As emerging new functions for this receptor are studied, a variety of both natural and pharmacologic ligands are being uncovered, linked to the ability to induce receptor-mediated MC activation and degranulation. The diversity of these ligands, characterized in their human, mice, or rat homologues, seems to match that of the receptor’s interactions. Natural ligands include host defense peptides, basic molecules, and key neuropeptides such as substance P and vasointestinal peptide (known for their role in the transmission of pain and itch) as well as eosinophil granule-derived proteins. Exogenous ligands include MC secretagogues such as compound 48/80 and mastoparan, a component of bee wasp venom, and several peptidergic drugs, among which are members of the quinolone family, neuromuscular blocking agents, morphine, and vancomycin. These discoveries shed light on its capacity as a multifaceted participant in naturally occurring responses within immunity and neural stimulus perception, as in responses at the center of immune pathology. In host defense, the mice Mrgprb2 has been proven to aid mast cells in the detection of peptidic molecules from bacteria and in the release of peptides with antimicrobial activities and other immune mediators. There are several potential actions described for it in tissue homeostasis and repair. In the realm of pathologic response, there is evidence to suggest that this receptor is also involved in chronic inflammation. Furthermore, MRGPRX2 has been linked to the pathophysiology of non-IgE-mediated immediate hypersensitivity drug reactions. Different studies have shown its possible role in other allergic diseases as well, such as asthma, atopic dermatitis, contact dermatitis, and chronic spontaneous urticaria. In this review, we sought to cover its function in physiologic processes and responses, as well as in allergic and nonallergic immune disease.

NIPSNAP protein family emerges as a sensor of mitochondrial health.

Since their discovery over two decades ago, the molecular and cellular functions of the NIPSNAP family of proteins (NIPSNAPs) have remained elusive until recently. NIPSNAPs interact with a variety of mitochondrial and cytoplasmic proteins. They have been implicated in multiple cellular processes and associated with different physiologic and pathologic conditions, including pain transmission, Parkinson's disease, and cancer. Recent evidence demonstrated a direct role for NIPSNAP1 and NIPSNAP2 proteins in regulation of mitophagy, a process that is critical for cellular health and maintenance. Importantly, NIPSNAPs contain a 110 amino acid domain that is evolutionary conserved from mammals to bacteria. However, the molecular function of the conserved NIPSNAP domain and its potential role in mitophagy have not been explored. It stands to reason that the highly conserved NIPSNAP domain interacts with a substrate that is ubiquitously present across all species and can perhaps act as a sensor for mitochondrial health.