Association of inflammatory mediators with pain perception

Nattokinase crude extract enhances oral mucositis healing

Background

Nattokinase (NK) is a promising alternative in the prevention and treatment of cardiovascular diseases due to its potent fibrinolytic activity. In this study, we investigated the effect of crude nattokinase extract on the healing of acetic acid-induced oral mucositis in mice.

Methods

Bacillus subtilis culture media (BSCM) was isolated into the supernatant, named nattokinase crude extract (NCE), and the pellet was named Bacillus subtilis mass (BSM). An oral mucositis model was established in mice by applying 50% glacial acetic acid to the buccal mucosa. According to the treatment conditions, the mice were divided into BSCM, NCE, BSM and phosphate buffered saline (PBS) groups. The weight of the mice, oral mucositis healing score and histopathological examination were used to evaluate the treatment.

Results

Fibrinolytic activities of BSCM, NCE and BSM were approximately 8069, 10,800 and 80 U/ml, respectively. The weight gain of mice in the NCE group was significantly different from the PBS group after three days’ treatment (p < 0.05). The oral mucositis score of NCE group was significantly higher than other groups (p < 0.05). The differences in histopathology scores between the NCE and other groups were statistically significant (p < 0.01).

Conclusions

NCE could possess remarkable potential to reduce pain and promote oral mucositis healing with minimal safety concerns. In this study, we first report that NCE from the supernatant of Bacillus subtilis can promote the healing of oral mucositis, which extends the application scope of NK.

Chitosan-poloxamer-based thermosensitive hydrogels containing zinc gluconate/recombinant human epidermal growth factor benefit for antibacterial and wound healing

Chitosan/poloxamer-based thermosensitive hydrogels containing zinc gluconate/recombinant human epidermal growth factor (ZnG/rhEGF@Chit/Polo) were developed as a convenient, safe and effective dressing for skin wound treatment. Their fabrication procedure and characterization were reported, and their morphology was examined by a scanning electron microscope. Antibacterial and biofilms activities were evaluated by in vitro tests to reveal the inhibitory effects and scavenging activity on the biofilms of Staphylococcus aureus and Pseudomonas aeruginosa. ZnG/rhEGF@Chit/Polo was also investigated as a potential therapeutic agent for wound healing therapy. In vivo wound healing studies on rats for 21 days proves that ZnG/rhEGF@Chit/Polo supplements the requisite Zn²⁺ and rhEGF for wound healing to promote the vascular remodeling and collagen deposition, facilitate fibrogenesis, and reduce the level of interleukin 6 for wound basement repair, and thus is a good wound therapy.

Macrophage-derived extracellular vesicles regulates USP5-mediated HDAC2/NRF2 axis to ameliorate inflammatory pain

Emerging research has highlighted the capacity of microRNA-23a-3p (miR-23a-3p) to alleviate inflammatory pain. However, the molecular mechanism by which miR-23a-3p attenuates inflammatory pain is yet to be fully understood. Hence, the current study aimed to elucidate the mechanism by which miR-23a-3p influences inflammatory pain. Bioinformatics was initially performed to predict the inflammatory pain related downstream targets of miR-23a-3p in macrophage-derived extracellular vesicles (EVs). An animal inflammatory pain model was established using Complete Freund's Adjuvant (CFA). The miR-23a-3p expression was downregulated in the microglia of CFA-induced mice, after which the inflammatory factors were determined by ELISA. FISH and immunofluorescence were performed to analyze the co-localization of miR-23a-3p and microglia. Interestingly, miR-23a-3p was transported to the microglia via M2 macrophage-EVs, which elevated the mechanical allodynia and the thermal hyperalgesia thresholds in mice model. The miR-23a-3p downstream target, USP5, was found to stabilize HDAC2 via deubiquitination to promote its expression while inhibiting the expression of NRF2. Taken together, the key findings of the current study demonstrate that macrophage-derived EVs containing miR-23a-3p regulates the HDAC2/NRF2 axis by decreasing USP5 expression to alleviate inflammatory pain, which may provide novel therapeutic targets for the treatment of inflammatory pain.

Role of Neuroimmune Crosstalk in Mediating the Anti-inflammatory and Analgesic Effects of Acupuncture on Inflammatory Pain

Inflammatory pain is caused by peripheral tissue injury and inflammation. Inflammation leads to peripheral sensitization, which may further cause central sensitization, resulting in chronic pain and progressive functional disability. Neuroimmune crosstalk plays an essential role in the development and maintenance of inflammatory pain. Studies in recent years have shown that acupuncture can exert anti-inflammatory and analgesic effects by regulating peripheral (i.e., involving local acupoints and inflamed regions) and central neuroimmune interactions. At the local acupoints, acupuncture can activate the TRPV1 and TRPV2 channels of mast cells, thereby promoting degranulation and the release of histamine, adenosine, and other immune mediators, which interact with receptors on nerve endings and initiate neuroimmune regulation. At sites of inflammation, acupuncture enables the recruitment of immune cells, causing the release of opioid peptides, while also exerting direct analgesic effects via nerve endings. Furthermore, acupuncture promotes the balance of immune cells and regulates the release of inflammatory factors, thereby reducing the stimulation of nociceptive receptors in peripheral organs. Acupuncture also alleviates peripheral neurogenic inflammation by inhibiting the release of substance P (SP) and calcitonin gene-related peptide from the dorsal root ganglia. At the central nervous system level, acupuncture inhibits the crosstalk between glial cells and neurons by inhibiting the p38 MAPK, ERK, and JNK signaling pathways and regulating the release of inflammatory mediators. It also reduces the excitability of the pain pathway by reducing the release of excitatory neurotransmitters and promoting the release of inhibitory neurotransmitters from neurons and glial cells. In conclusion, the regulation of neuroimmune crosstalk at the peripheral and central levels mediates the anti-inflammatory and analgesic effects of acupuncture on inflammatory pain in an integrated manner. These findings provide novel insights enabling the clinical application of acupuncture in the treatment of inflammatory diseases.

Photobiomodulation inhibits inflammation in the temporomandibular joint of rats

Photobiomodulation (PBM) has been applied as a non-invasive technique for treating temporomandibular joint symptoms, especially on painful condition's relief, however the anti-inflammatory mechanism underlying the effect of PBM remains uncertain. This study aims to evaluate the mechanisms of action of PBM (808 nm) in a carrageenan-induced inflammation on temporomandibular joint (TMJ) of rats. In this study male Wistar rats were pre-treated with irradiation of a low-power diode laser for 15 s on TMJ (infra-red 808 nm, 100 mW, 50 J/cm² and 1.5 J) 15 min prior an injection in the temporomandibular joint of carrageenan (100 μg/TMJ). 1 h after the TMJ treatments, the rats were terminally anesthetized for joint cavity wash and periarticular tissues collect. Samples analysis demonstrated that PBM inhibit leukocytes chemotaxis in the TMJ and significantly reduces amounts of TNF-α, IL-1β and CINC-1. In addition, Western blotting analysis demonstrated that PBM significantly decreased the protein levels of P2X3 and P2X7 receptors in the periarticular tissues. On the other hand, PBM was able to increase protein level of IL-10 (anti-inflammatory cytokine). In summary, it is possible to suggest that PBM inhibit inflammatory chemotaxis, modulation the balance of the pro- and anti-inflammatory characteristics of inflammatory cells.

Comparative prospective randomized study of minimally invasive transpiriformis approach versus conventional posterolateral approach in total hip arthroplasty as measured by biology markers

Background

Minimally invasive surgery is becoming increasingly common, but evidence of the advantages of the minimally invasive transpiriformis approach in total hip arthroplasty is limited. Therefore, our single-centre randomized controlled trial evaluated the benefits of this approach versus the posterolateral approach.

Methods

Forty-nine patients undergoing the minimally invasive transpiriformis approach and 57 patients undergoing the posterolateral approach total hip arthroplasty were analyzed. The operative time, length of hospital stay, incision length, and peri-operative data related to the surgery were recorded. In both groups, serum CRP, IL-6, HGb, Hct, MB, CK-MB, and CK levels, Harris hip scores, and VAS scores were recorded.

Results

Patients who underwent the minimally invasive transpiriformis approach had a smaller surgical incision (9.10 ± 0.94 vs. 15.56 ± 1.20 cm, P = 0.00) and shorter hospital stay (6.20 ± 1.54 vs. 12.26 ± 2.97 days, P = 0.00) than those who underwent the posterolateral approach. Serum levels of CRP, IL-6, MB, CK-MB, and CK were also lower. According to the Harris hip score, the minimally invasive transpiriformis group showed significant improvement at one week and one month after surgery.

Conclusion

Compared to the posterolateral approach, the minimally invasive transpiriformis approach for total hip arthroplasty provided rapid functional recovery, elicited a significantly reduced post-operative inflammatory response, and caused less muscle damage.

TNF-α, CXCL-1 and IL-1 β as activators of the opioid system involved in peripheral analgesic control in mice

Tissue injury results in the release of inflammatory mediators, including a cascade of nociceptive substances, which contribute to development of hyperalgesia. In addition, during this process endogenous analgesic substances are also peripherally released with the aim of controlling the hyperalgesia. Thus, the present study aimed to investigate whether inflammatory mediators TNF-α, IL-1β, CXCL1, norepinephrine (NE) and prostaglandin E2 (PGE2) may be involved in the deflagration of peripheral endogenous modulation of inflammatory pain by activation of the opioid system. Thus, male Swiss mice and the paw withdrawal test were used. All substances were injected by the intraplantar route. Carrageenan, TNF-α, CXCL-1, IL1-β, NE and PGE2 induced hyperalgesia. Selectives μ (clocinamox), δ (naltrindole) and κ (norbinaltorphimine, nor-BNI) and non-selective (naloxone) opioid receptor antagonists potentiated the hyperalgesia induced by carrageenan, TNF-α, CXCL-1 and IL1-β. In contrast, when the enzyme N-aminopeptidase involved in the degradation of endogenous opioid peptides was inhibited by bestatin, the hyperalgesia was significantly reduced. In addition, the western blotting assay indicated that the expression of the opioid δ receptor was increased after intraplantar injection of carrageenan. The data obtained in this work corroborate the hypothesis that TNF-α, CXCL-1 and IL-β cause, in addition to hyperalgesia, the release of endogenous substances such as opioid peptides, which in turn exert endogenous control over peripheral inflammatory pain.

Epineural optogenetic activation of nociceptors initiates and amplifies inflammation

Activation of nociceptor sensory neurons by noxious stimuli both triggers pain and increases capillary permeability and blood flow to produce neurogenic inflammation1,2, but whether nociceptors also interact with the immune system remains poorly understood. Here we report a neurotechnology for selective epineural optogenetic neuromodulation of nociceptors and demonstrate that nociceptor activation drives both protective pain behavior and inflammation. The wireless optoelectronic system consists of sub-millimeter-scale light-emitting diodes embedded in a soft, circumneural sciatic nerve implant, powered and driven by a miniaturized head-mounted control unit. Photostimulation of axons in freely moving mice that express channelrhodopsin only in nociceptors resulted in behaviors characteristic of pain, reflecting orthodromic input to the spinal cord. It also led to immune reactions in the skin in the absence of inflammation and potentiation of established inflammation, a consequence of the antidromic activation of nociceptor peripheral terminals. These results reveal a link between nociceptors and immune cells, which might have implications for the treatment of inflammation.

Frequent exposure to varied home cage sizes alters pain sensitivity and some key inflammation-related biomarkers

BACKGROUND

Nature and size of rodent cages vary from one laboratory or country to another. Little is however known about the physiological implications of exposure to diverse cage sizes in animal-based experiments.

METHOD

Here, two groups of male Swiss mice (Control group - Cage stationed, and Test group - Cage migrated) were used for this study. The cage-migrated mice were exposed daily to various cage sizes used across laboratories in Nigeria while the cage-stationed mice exposed daily to different but the same cage size and shape. At the end of the 30 days exposure, top-rated paradigms were used to profile changes in physiological behaviours, and this was followed by evaluation of histological and biochemical metrics.

RESULTS

The study showed a significant (p < 0.05) decrease in blood glucose levels (at 60 and 120 min of oral glucose tolerance test) in the cage-migrated mice compared to cage-stationed mice. Strikingly, peripheral oxidative stress (plasma malondialdehyde) and pain sensitivity (formalin test, hot-and-cold plate test, and von Frey test) decreased significantly in cage-migrated mice compared to cage-stationed animals. Also, the pro-inflammation mediators (IL-6 and NF-κB) increased significantly in cage-migrated mice compared to cage-stationed mice. However, emotion-linked behaviours, neurotransmitters (serotonin, noradrenaline and GABA), brain and plasma electrolytes were not significantly difference in cage-migrated animals compared to cage-stationed mice.

CONCLUSION

Taken together, these results suggest that varied size cage-to-cage exposure of experimental mice could affect targeted behavioural and biomolecular parameters of pain and inflammation, thus diminishing research reproducibility, precipitating false negative/positive results and leading to poor translational outcomes.

Preoperative quantitative sensory testing and robot-assisted laparoscopic hysterectomy for endometrial cancer: can chronic postoperative pain be predicted?

Objectives Chronic postoperative pain is prevalent after robot-assisted laparoscopic hysterectomy for endometrial cancer. Preoperative Quantitative Sensory Testing (QST) has been utilized to identify patients at risk of developing chronic postoperative pain after a range of surgical procedures. The aim of this prospective, observational study was to (1) determine the prevalence of chronic postoperative pain, (2) assess selected preoperative risk factors for chronic postoperative pain, and (3) evaluate if preoperative QST profiling could predict the development of chronic postoperative pain following robot-assisted laparoscopic hysterectomy for endometrial cancer. Methods One-hundred and sixty consecutive patients were included and handheld pressure algometry, cuff pressure algometry, temporal summation of pain, conditioned pain modulation, and heat pain thresholds were assessed prior to surgery. Patients were asked to fill out a questionnaire concerning pain in the pre- and post-operative time period six months after surgery. Chronic postoperative pain was defined as persistent, moderate to severe pain (mean visual analogue scale (VAS)≥3) on a daily basis six months after surgery. Results The prevalence of chronic postoperative pain after robot-assisted laparoscopic hysterectomy for endometrial cancer was of 13.6% (95% CI 8.4-20.4%). Patients that would develop chronic postoperative pain had a lower BMI (p=0.032), a higher prevalence of preoperative pelvic pain (p<0.001), preoperative heat pain hyperalgesia (p=0.043) and a higher level of acute postoperative pain (p<0.001) when compared to patients that would not develop chronic postoperative pain. A logistic regression model demonstrated that the presence of preoperative pelvic pain was a significant, independent predictive risk factor for development of chronic postoperative pain (OR=6.62, 95% CI 2.26-19.44), whereas none of the QST parameters could predict postoperative pain. Conclusions Preoperative QST assessment could not predict the development of chronic postoperative pain despite preoperative heat pain hyperalgesia in patients that would develop chronic postoperative pain.

Baicalin attenuates inflammatory pain associated depressive symptoms via Akt-mediated adult hippocampal neurogenesis

Depression is one of main symptoms accompanying thermal hyperalgesia and mechanical allodynia induced by inflammatory pain. On physiological level, depressive symptoms could be attenuated by sufficient level of hippocampal neural plasticity. Adult hippocampal neurogenesis (AHN) plays critical roles in clearing panic memory, increasing psychiatric adaptability and preventing depressive emotion. Thus, targeting AHN is the applicable strategy to improve neural functions impaired and attenuate inflammatory pain. Previous reports indicate natural compound baicalin (BA) is one of the effective agents to promote AHN. In present study, we tested the effects of BA in mouse model of inflammatory pain as well as its biological underpinning. Behavioral tests indicate that BA treatment attenuated thermal hyperalgesia, mechanical allodynia and depressive symptoms. Meanwhile, treatment of BA promoted growth and differentiation of neural stem cells in hippocampus. AHN blocker temozolomide (TMZ) resulted in significant suppressed effects of BA to promote AHN, suggesting the critical role of AHN in regulating behavioral effects of BA to inflammatory pain. Akt plays the critical roles in the effects of BA to attenuate inflammatory pain induced symptoms. Prohibiting of Akt with GSK960693 dramatically prevented the effects of BA in attenuating inflammatory pain induced behavioral symptoms. Taken together, BA is the potential pain killer to alleviating inflammatory pain via Akt-mediated adult hippocampal neurogenesis.

New insights on the arylpiperazinylalkyl pyridazinone ET1 as potent antinociceptive and anti-inflammatory agent

Pyridazine derivatives, such as arylpiperazinylalkyl pyridazinones, display antinociceptive effects to thermal and chemical stimuli. Here, we extended our previous knowledge on the pharmacological profile of 4-amino-6-methyl-2-(3-(4-(4-methylcyclohexa-1,3-dien-1-yl)piperazin-1-yl)propyl)-5-vinylpyridazin-3(2H)-one, here referred as ET1, paving the way for the comprehension of its complete mechanism of action. To this aim, we have evaluated the mouse behavioural responses in several animal models of pain, the effect of ET1 in the murine model of zymosan-induced paw oedema and air-pouch, assessing the cytokines and the cellular phenotype and finally, an in vitro radioligand binding study was performed on a panel of 30 different receptors. In the formalin test, ET1 reduced both neurogenic and inflammatory phase of nociception induced by the aldehyde. Similarly, ET1 strongly reduced paw licking response in the capsaicin test, the abdominal stretching in the writhing test and the carrageenan-induced thermal hyperalgesia. ET1 also evoked a long-lasting reduction of thermal hyperalgesia. Furthermore, ET1 produced a long-lasting anti-inflammatory effect in the zymosan-induced mouse paw oedema and air-pouch through the selective inhibition of inflammatory monocytes recruitment and the modulation of IL-1β, IL-6, TNF-α and MCP-1. Binding experiments confirmed an inhibitory effect on adrenergic α_1A, α_1B and α_2A receptors subtypes and, for the first time, a moderate affinity was observed for the following receptors: histamine H₁, imidazoline I₂, sigma non-opioid intracellular receptor 1 and σ2. These results prompt ET1 as a potent analgesic and anti-inflammatory agent, and support the possibility that it may be suitable for clinical applications in a wide-range of inflammatory-based diseases.

The role of P2X4 receptors in chronic pain: A potential pharmacological target

Chronic pain is a common symptom of most clinical diseases, which seriously affects the psychosomatic health of patients and brings some pain to patients. Due to its pathological mechanism is very complicated and the treatment of chronic pain has always been a difficult problem in clinical. Normally, drugs are usually used to relieve pain, but the analgesic effect is not good, especially for cancer pain patients, the analgesic effect is poor. Therefore, exploring the pathogenesis and treatment of chronic pain has aroused the interest of many researchers. A large number of studies have shown that the role of ATP and P2X4 receptor (P2X4R) play an important role in the pathogenesis of chronic pain. P2X4R is dependent on ATP ligand-gated ion channel receptor, which can be activated by ATP and plays an important role in the information transmission of nerve system and the formation of pain. Therefore, in this paper, we comprehensively described the structure and biological functions of P2X4R, and outlined behavioral evaluation methods of chronic pain models. Moreover, we also explored the inherent relationship between P2X4R and chronic pain, and described the therapeutic effect of P2X4R antagonist on chronic pain, and provided some valuable help for the treatment of chronic pain.

Antinociceptive Effects of Emodin on CFA-Induced Inflammatory Pain in Rats

The effect of emodin on complete Freund’s adjuvant (CFA)-induced inflammatory pain in rats and its potential molecular mechanism was investigated. For this, a rat model of inflammatory pain induced by CFA was established and rats were treated with emodin by intraperitoneal injection. The pain threshold was evaluated by the von Frey, thermo hyperalgesia, and cold plate tests. The mRNA expression of transient receptor potential channel ankyrin type-1 ( Trpa1) and transient receptor potential vanilloid 1 ( Trpv1) was detected by quantitative reverse transcription polymerase chain reaction, and the level of inflammatory cytokines was determined by enzyme-linked immunosorbent assay. The mechanical and thermal pain thresholds of CFA-treated rats were significantly lower than those of the control rats, while the paw withdrawal responses in response to cold stimulation were higher than that of the control group. Emodin treatment significantly improved CFA-induced hyperalgesia. Further results showed that emodin inhibits the upregulation of Trpa1 and Trpv1 mRNA expression in the dorsal root ganglion (DRG) of rats with inflammatory pain compared with the control group. Emodin also significantly reduced the levels of tumor necrosis factor alpha (TNF-α), interleukin 1 beta (IL-1β), and interleukin 6 (IL-6) in the serum of rats with inflammatory pain. Thus, emodin may inhibit hyperalgesia induced by inflammatory stimulation by downregulating the mRNA expression of Trpa1 and Trpv1 in DRG neurons and reducing the levels of TNF-α, IL-1β, and IL-6.

The analgesic potential of glycosides derived from medicinal plants

Pain represents an unpleasant sensation linked to actual or potential tissue damage. In the early phase, the sensation of pain is caused due to direct stimulation of the sensory nerve fibers. On the other hand, the pain in the late phase is attributed to inflammatory mediators. Current medicines used to treat inflammation and pain are effective; however, they cause severe side effects, such as ulcer, anemia, osteoporosis, and endocrine disruption. Increased attention is recently being focused on the examination of the analgesic potential of phytoconstituents, such as glycosides of traditional medicinal plants, because they often have suitable biological activities with fewer side effects as compared to synthetic drugs. The purpose of this article is to review for the first time the current state of knowledge on the use of glycosides from medicinal plants to induce analgesia and anti-inflammatory effect. Various databases and search engines, including PubMed, ScienceDirect, Scopus, Web of Science and Google Scholar, were used to search and collect relevant studies on glycosides with antinociceptive activities. The results led to the identification of several glycosides that exhibited marked inhibition of various pain mediators based on different well-established assays. Additionally, these glycosides were found to induce most of the analgesic effects through cyclooxygenase and lipoxygenase pathways. These findings can be useful to identify new candidates which can be clinically developed as analgesics with better bioavailability and reduced side effects. Graphical abstract Analgesic mechanisms of plant glycosides.

Platelet-derived growth factor activates nociceptive neurons by inhibiting M-current and contributes to inflammatory pain

Supplemental Digital Content is Available in the Text.

Our work reveals that the platelet-derived growth factor-BB, by inhibiting nociceptive M-type potassium channels, acts as a pain-inducing proinflammatory factor that significantly contributes to inflammatory pain.

Endogenous inflammatory mediators contribute to the pathogenesis of pain by acting on nociceptors, specialized sensory neurons that detect noxious stimuli. Here, we describe a new factor mediating inflammatory pain. We show that platelet-derived growth factor (PDGF)-BB applied in vitro causes repetitive firing of dissociated nociceptor-like rat dorsal root ganglion neurons and decreased their threshold for action potential generation. Injection of PDGF-BB into the paw produced nocifensive behavior in rats and led to thermal and mechanical pain hypersensitivity. We further detailed the biophysical mechanisms of these PDGF-BB effects and show that PDGF receptor–induced inhibition of nociceptive M-current underlies PDGF-BB–mediated nociceptive hyperexcitability. Moreover, in vivo sequestration of PDGF or inhibition of the PDGF receptor attenuates acute formalin-induced inflammatory pain. Our discovery of a new pain-facilitating proinflammatory mediator, which by inhibiting M-current activates nociceptive neurons and thus contributes to inflammatory pain, improves our understanding of inflammatory pain pathophysiology and may have important clinical implications for pain treatment.

TRPV1 Responses in the Cerebellum Lobules V, VIa and VII Using Electroacupuncture Treatment for Inflammatory Hyperalgesia in Murine Model

Inflammatory pain sensation is an important symptom which protects the body against additional tissue damage and promotes healing. Discovering long-term and effective treatments for pain remains crucial in providing efficient healthcare. Electroacupuncture (EA) is a successful therapy used for pain relief. We aimed to investigate effects and mechanisms of Complete Freund’s Adjuvant (CFA)-inducing inflammatory pain in the cerebellum, and the inhibition of this inflammatory hyperalgesia using EA at Zusanli acupoint (ST36). The results display a significant increase in mechanical and thermal sensitivities in the CFA and CFA + SHAM groups, which was significantly reduced in the CFA+EA and CFA + KO groups. This evidence was substantiated in the protein levels observed using immunoblotting, and presented with significant escalations after CFA inducing inflammatory hyperalgesia in CFA and CFA + SHAM groups. Then, they were significantly attenuated by EA in the CFA + EA group. Furthermore, the CFA + transient receptor vanilloid member 1 (TRPV1)^−/− group indicated similar significant decreases of protein expression. Additionally, a concomitant overexpression in lobule VIa was also observed in immunofluorescence. These consequences suggest that CFA-induced inflammatory pain provokes modifications in cerebellum lobules V, VIa and VII, which can subsequently be regulated by EA treatment at the ST36 through its action on TRPV1 and related molecular pathways.

Reduction of Silent Information Regulator 1 Activates Interleukin-33/ST2 Signaling and Contributes to Neuropathic Pain Induced by Spared Nerve Injury in Rats

Emerging studies have demonstrated that interleukin (IL)-33 and its receptor ST2 act as key factors in inflammatory diseases. Moreover, accumulating evidence has suggested that cytokines, including tumor necrosis factor (TNF)-α and IL-1β, trigger an inflammatory cascade. SIRT1 has been shown to suppress the expression of inflammatory cytokines. However, the effects of SIRT1 on IL-33/ST2 signaling and initiation of the inflammatory cascade via modulation of TNF-α and IL-1β by IL-33 remain unclear. In the present study, we found that the dorsal root ganglion (DRG) IL-33 and ST2 were upregulated in a rat model of spared nerve injury (SNI) and intrathecal injection of either IL-33 or ST2 antibodies alleviated mechanical allodynia and downregulated TNF-α and IL-1β induced by SNI. In addition, activation of SIRT1 decreased enhanced DRG IL-33/ST2 signaling in SNI rats. Artificial inactivation of SIRT1 via intrathecal injection of an SIRT1 antagonist could induce mechanical allodynia and upregulate IL-33 and ST2. These results demonstrated that reduction in SIRT1 could induce upregulation of DRG IL-33 and ST2 and contribute to mechanical allodynia induced by SNI in rats.

Therapeutic Potential of Flavonoids in Pain and Inflammation: Mechanisms of Action, Pre-Clinical and Clinical Data, and Pharmaceutical Development

Pathological pain can be initiated after inflammation and/or peripheral nerve injury. It is a consequence of the pathological functioning of the nervous system rather than only a symptom. In fact, pain is a significant social, health, and economic burden worldwide. Flavonoids are plant derivative compounds easily found in several fruits and vegetables and consumed in the daily food intake. Flavonoids vary in terms of classes, and while structurally unique, they share a basic structure formed by three rings, known as the flavan nucleus. Structural differences can be found in the pattern of substitution in one of these rings. The hydroxyl group (-OH) position in one of the rings determines the mechanisms of action of the flavonoids and reveals a complex multifunctional activity. Flavonoids have been widely used for their antioxidant, analgesic, and anti-inflammatory effects along with safe preclinical and clinical profiles. In this review, we discuss the preclinical and clinical evidence on the analgesic and anti-inflammatory proprieties of flavonoids. We also focus on how the development of formulations containing flavonoids, along with the understanding of their structure-activity relationship, can be harnessed to identify novel flavonoid-based therapies to treat pathological pain and inflammation.

Antibacterial, anti-inflammatory and peroxidase-mediated cyclooxygenase-1 inhibitory properties of Fusarium solani extract

Context: Nigerian soil fungi population is unexplored. It is hypothesized that they harbour new bioactive chemicals. This hypothesis is based on the large percentage of currently approved medicines that originated from soil-inhabiting micro-organisms Objectives: To investigate the antimicrobial and anti-inflammatory properties of Fusarium solani ethyl acetate (EtOAc) extract selected based on its broad spectrum of antimicrobial potential in an overlay experiment with seven other soil fungi strains. Materials and methods: Fungus number 6 (F6), identified by molecular characterization as Fusarium solani (Mart.) Sacc (Nectriaceae) was selected for studies from eight purified soil fungi due to its superior broad-spectrum antibiotics producing potential following agar overlay experiment. F6 was fermented for 21 d and the minimum inhibitory concentration (MIC) of its EtOAc fermentation extract (dose range: 12.5-100 µg/mL) was determined using agar dilution method for Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, Escherichia coli, Salmonella typhi and anti-inflammatory properties determined using rat-paw (250-500 mg/kg) and xylene induced oedema (250-500 µg/kg) (in Swiss albino rats and mice) models, respectively. The ability of the extract to inhibit cyclooxygenase (COX) enzyme was also determined in vitro using Cayman test kit-760111. Result: The MIC of the EtOAc extract was <12.5 µg/mL for S. aureus, P. aeruginosa and Escherichia coli. It inhibited xylene induced oedema by 65% compared with 61% observed for diclofenac and was significantly (p < 0.05) better than diclofenac in rat-paw-oedema model within the first phase of inflammation. The extract inhibited COX-1 peroxidase-mediated activities with an IC₅₀ below 5 µg/mL. Conclusions: The extract exhibited strong antibacterial and anti-inflammatory properties, warranting further investigations into therapeutic potential of this fungus. This study design can be adapted in soil fungi metabolomic investigations. We report for the first time the potent anti-inflammatory property of the ethyl acetate extract of soil strain of F. solani with a possible mechanism of action that involves the inhibition of COX enzyme.

Pain reduction and improved vascular health associated with daily consumption of an anti-inflammatory dietary supplement blend

Purpose: The objective for this clinical pilot study was to evaluate changes to chronic pain, vascular health, and inflammatory markers when consuming a dietary supplement blend (DSB, CytoQuel^®), containing curcumin, resveratrol, tocotrienols, N-Acetylcysteine, and epigallocatechin gallate.

Materials and methods: An open-label study design was used where 21 study participants were evaluated at baseline and at 2 and 8 weeks after consuming DSB. Participants were randomized to consume 3 capsules once daily versus 2 capsules twice daily. Pain and activities of daily living questionnaires were used to gather subjective data on pain levels and interference with daily living. Blood pressure was measured in both arms and ankles, and the ankle-brachial index (ABI) calculated. Blood samples were used to evaluate markers associated with inflammation and cardiovascular health.

Results: Highly significant reduction of chronic pain was seen after 8 weeks (p<0.01), both at rest and when physically active. Faster improvement was seen when consuming 3 capsules once daily, compared to 2 capsules twice daily. The pain reduction resulted in improved sleep quality (p<0.1), and improved social functioning (p<0.01), and less need for support from others (p<0.05), Normalization of mildly elevated ABI at study start was seen after 2 weeks. Plasma fibrinogen and von Willebrand Factor and serum matrix metalloproteinase-9 (MMP-9) showed reduction after 2 weeks (not significant), whereas a reduction in serum interleukin-1 receptor antagonist-a (IL-1ra) was statistically significant after 2 weeks (p<0.05). Correlation between pain reduction and changes to MMP-9 after 8 weeks was highly significant (P<0.01), whereas correlation between pain reduction and changes to IL-1ra reached significance at 2 weeks for the group consuming 3 caps once daily (p<0.04).

Conclusion: Consuming DSB helped manage pain, increased comfort during daily activities, and improved vascular function. This was associated with selective effects on specific blood biomarkers associated with inflammation and vascular health.

Technological development of microemulsions with perspectives for pain treatment: a patent review

INTRODUCTION

Microemulsions are thermodynamically stable translucent systems widely used for systemic delivery of drugs. The present study is the first to analyze the biotechnological potential of microemulsion systems for therapeutic purposes, through transdermal route, for pain treatment.

AREAS COVERED

Patents were searched in the World Intellectual Property Organization (WIPO), European Patent Office (Espacenet), United States Patent and Trademark Office (USPTO) and National Institute of Intellectual Property (INPI). The inclusion criteria were published patents containing the keywords; 'microemulsion' and 'transdermal' in their title or abstract. 208 patents were found. However, only those patents which mentioned in their abstract or in their description the use of microemulsion system (object of invention) for pain treatment were selected. Were excluded duplicate patents and those that did not report pharmacological use of MEs specifically for pain treatment. Thus, sixteen patents were selected and described in the present study.

EXPERT OPINION

Patents were found that focused specifically on the development process of microemulsion systems, the inclusion of essential oils in microemulsions, which place microemulsions as delivery systems for NSAIDs and other substances, as well as microemulsions for transdermal administration. These studies reinforce the therapeutic applicability of MEs in the treatment of acute and chronic pain.

Defining the role of glucocorticoids in inflammation

An established body of knowledge and clinical practice has argued in favor of the use of glucocorticoids in various chronic inflammatory and autoimmune diseases. However, the very well-known adverse effects associated with their treatment hampers continuation of therapy with glucocorticoids. Analyses of the molecular mechanisms underlying the actions of glucocorticoids have led to the discovery of several mediators that add complexity and diversity to the puzzling world of these hormones and anti-inflammatory drugs. Such mediators hold great promise as alternative pharmacologic tools to be used as anti-inflammatory drugs with the same properties as glucocorticoids, but avoiding their metabolic side effects. This review summarizes findings about the molecular targets and mediators of glucocorticoid function.