Suppression of TLR4-MyD88 signaling pathway attenuated chronic mechanical pain in a rat model of endometriosis

Pathology of pain and its implications for therapeutic interventions

Pain is estimated to affect more than 20% of the global population, imposing incalculable health and economic burdens. Effective pain management is crucial for individuals suffering from pain. However, the current methods for pain assessment and treatment fall short of clinical needs. Benefiting from advances in neuroscience and biotechnology, the neuronal circuits and molecular mechanisms critically involved in pain modulation have been elucidated. These research achievements have incited progress in identifying new diagnostic and therapeutic targets. In this review, we first introduce fundamental knowledge about pain, setting the stage for the subsequent contents. The review next delves into the molecular mechanisms underlying pain disorders, including gene mutation, epigenetic modification, posttranslational modification, inflammasome, signaling pathways and microbiota. To better present a comprehensive view of pain research, two prominent issues, sexual dimorphism and pain comorbidities, are discussed in detail based on current findings. The status quo of pain evaluation and manipulation is summarized. A series of improved and innovative pain management strategies, such as gene therapy, monoclonal antibody, brain-computer interface and microbial intervention, are making strides towards clinical application. We highlight existing limitations and future directions for enhancing the quality of preclinical and clinical research. Efforts to decipher the complexities of pain pathology will be instrumental in translating scientific discoveries into clinical practice, thereby improving pain management from bench to bedside.

Research progress in rodent models of endometriosis

Endometriosis is a common and frequent disease in gynecology; its etiology and pathogenesis are partially understood and still not clear. The construction of suitable animal models is beneficial for basic research related to the disease. Currently, rodents have the advantages of low cost, fast reproduction, easy rearing, and a similar endometrial structure to humans. Depending on the purpose of the experiment, different molding methods have their advantages. In this paper, we describe the traditional methods of constructing endometriosis rodent models, compare their advantages and disadvantages, and introduce newly developed rodent models, such as cell line injection models, pain models, genetically engineered mouse models, fluorescent tracer models, iron overload models, chemical induction models, and methods of constructing rodent models of different subtypes of endometriosis. Fertility and treatment of endometriosis rodent models are also described. This study provides a reference for researchers in the selection of animal models for pathogenesis and drug treatment studies.

Autophagy regulation and redox perturbation by transcrocetin suppress the growth of endometriosis

Until non-hormonal therapeutic targets for endometriosis are suggested, we focused on mitochondrial function and autophagy regulation in the disease. Transcrocetin is a carotenoid and retinoic acid with high antioxidant potency and antiproliferative effects in several diseases. In this study, we demonstrated the therapeutic mechanisms of transcrocetin in endometriosis using the End1/E6E7 and VK2/E6E7 cell lines. Transcrocetin suppressed the viability and proliferation of these cell lines and did not affect the proliferation of normal uterine stromal cells. p21 Waf1/Cip1 as a cell cycle regulator and target of p53, were increased by transcrocetin and caused the G1 arrest via inhibition of cyclin-dependent kinase activity, which might further cause cell death. Furthermore, we confirmed endoplasmic reticulum stress and calcium ion dysregulation in the cytosol and mitochondrial matrix, disrupting the mitochondrial membrane potential. Mitochondrial bioenergetics were suppressed by transcrocetin, and oxidative phosphorylation-related gene expression was downregulated. Moreover, the proliferation of End1/E6E7 and VK2/E6E7 cells was regulated by transcrocetin-induced oxidative stress. Finally, we verified the impairment of autophagic flux following pre-treatment with chloroquine. Therefore, transcrocetin may be a potent therapeutic alternative for endometriosis.

Advances in molecular agents targeting toll-like receptor 4 signaling pathways for potential treatment of sepsis

Sepsis is a systemic inflammatory response syndrome caused by an infection. Toll-like receptor 4 (TLR4) is activated by endogenous molecules released by injured or necrotic tissues. Additionally, TLR4 is remarkably sensitive to infection of various bacteria and can rapidly stimulate host defense responses. The TLR4 signaling pathway plays an important role in sepsis by activating the inflammatory response. Accordingly, as part of efforts to improve the inflammatory response and survival rate of patients with sepsis, several drugs have been developed to regulate the inflammatory signaling pathways mediated by TLR4. Inhibition of TLR4 signal transduction can be directed toward either TLR4 directly or other proteins in the TLR4 signaling pathway. Here, we review the advances in the development of small-molecule agents and peptides targeting regulation of the TLR4 signaling pathway, which are characterized according to their structural characteristics as polyphenols, terpenoids, steroids, antibiotics, anthraquinones, inorganic compounds, and others. Therefore, regulating the expression of the TLR4 signaling pathway and modulating its effects has broad prospects as a target for the treatment of lung, liver, kidneys, and other important organs injury in sepsis.

PI3K/AKT signaling pathway associates with pyroptosis and inflammation in patients with endometriosis

Endometriosis (EMS) is known to be closely associated with inflammation. We evaluate the possible mechanism linking the PI3K/AKT signaling pathway with pyroptosis and inflammation in EMS. We collected 30 patients undergoing laparoscopic for endometriosis as the EMS group and those undergoing surgery for uterine fibroids as the control group, from whom we collected serum, normal endometrium, eutopic endometrium and ectopic endometrium. Transmission electron microscopy (TEM) was used to observe the internal structure of endometrial cells. Western Blot was used to detect the protein expression of PI3K, P-PI3K, AKT, P-AKT, NLRP3, Caspase-1, GSDMD, and GSDMD-N. Immunohistochemistry (IHC) staining was used to detect the expression of PI3K, AKT, NLRP3, Caspase-1, GSDMD, and GSDMD-N proteins. Immunofluorescence (IF) staining was used to observe the expression of GSDMD-N. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to analyze the mRNA levels of PI3K, AKT, NLRP3, Caspase-1, GSDMD, and GSDMD-N. ELISA was used to detect serum levels of IL-1β, IL-18, TLR4, and NF-κB. We found that activation of PI3K/AKT signaling pathway in endometriosis significantly increased the level of cellular pyroptosis and inflammatory factors. Our results suggest that there is a positive correlation between the PI3K/AKT signaling pathway and pyroptosisas well as inflammation in EMS patients.

IL-6 from cerebrospinal fluid causes widespread pain via STAT3-mediated astrocytosis in chronic constriction injury of the infraorbital nerve

BACKGROUND

The spinal inflammatory signal often spreads to distant segments, accompanied by widespread pain symptom under neuropathological conditions. Multiple cytokines are released into the cerebrospinal fluid (CSF), potentially inducing the activation of an inflammatory cascade at remote segments through CSF flow. However, the detailed alteration of CSF in neuropathic pain and its specific role in widespread pain remain obscure.

METHODS

A chronic constriction injury of the infraorbital nerve (CCI-ION) model was constructed, and pain-related behavior was observed on the 7th, 14th, 21st, and 28th days post surgery, in both vibrissa pads and hind paws. CSF from CCI-ION rats was transplanted to naïve rats through intracisternal injection, and thermal and mechanical allodynia were measured in hind paws. The alteration of inflammatory cytokines in CCI-ION's CSF was detected using an antibody array and bioinformatic analysis. Pharmacological intervention targeting the changed cytokine in the CSF and downstream signaling was performed to evaluate its role in widespread pain.

RESULTS

CCI-ION induced local pain in vibrissa pads together with widespread pain in hind paws. CCI-ION's CSF transplantation, compared with sham CSF, contributed to vibrissa pad pain and hind paw pain in recipient rats. Among the measured cytokines, interleukin-6 (IL-6) and leptin were increased in CCI-ION's CSF, while interleukin-13 (IL-13) was significantly reduced. Furthermore, the concentration of CSF IL-6 was correlated with nerve injury extent, which gated the occurrence of widespread pain. Both astrocytes and microglia were increased in remote segments of the CCI-ION model, while the inhibition of astrocytes in remote segments, but not microglia, significantly alleviated widespread pain. Mechanically, astroglial signal transducer and activator of transcription 3 (STAT3) in remote segments were activated by CSF IL-6, the inhibition of which significantly mitigated widespread pain in CCI-ION.

CONCLUSION

IL-6 was induced in the CSF of the CCI-ION model, triggering widespread pain via activating astrocyte STAT3 signal in remote segments. Therapies targeting IL-6/STAT3 signaling might serve as a promising strategy for the widespread pain symptom under neuropathological conditions.

Grape seed-derived procyanidins decreases neuropathic pain and nerve regeneration by suppression of toll-like receptor 4-myeloid differentiation factor-88 signaling

Background: Recent studies have shown that peripheral nerve regeneration process is closely related to neuropathic pain. Toll-like receptor 4 (TLR4) signaling was involved in different types of pain and nerve regeneration. TLR4 induced the recruitment of myeloid differentiation factor-88 adaptor protein (MyD88) and NF-κB-depended transcriptional process in sensory neurons and glial cells, which produced multiple cytokines and promoted the induction and persistence of pain. Our study aimed to investigate procyanidins's effect on pain and nerve regeneration via TLR4-Myd88 signaling. Methods: Spinal nerve ligation (SNL) model was established to measure the analgesic effect of procyanidins. Anatomical measurement of peripheral nerve regeneration was measured by microscopy and growth associated protein 43 (GAP43) staining. Western blotting and/or immunofluorescent staining were utilized to detect TLR4, myeloid differentiation factor-88 adaptor protein (MyD88), ionized calcium-binding adapter molecule 1 (IBA1) and nuclear factor kappa-B-p65 (NF-κB-p65) expression, as well as the activation of astrocyte and microglia. The antagonist of TLR4 (LPS-RS-Ultra, LRU) were intrathecally administrated to assess the behavioral effects of blocking TLR4 signaling on pain and nerve regeneration. Result: Procyanidins reduced mechanical allodynia, thermal hyperalgesia and significantly suppressed the number of nerve fibers regenerated and the degree of myelination in SNL model. Compared with sham group, TLR4, MyD88, IBA1 and phosphorylation of NF-κB-p65 were upregulated in SNL rats which were reversed by procyanidins administration. Additionally, procyanidins also suppressed activation of spinal astrocytes and glial cells. Conclusion: Suppression of TLR4-MyD88 signaling contributes to the alleviation of neuropathic pain and reduction of nerve regeneration by procyanidins.

Recent advances in the treatment of pain in endometriosis: A bibliometric analysis of experimental models

Background and Aim

Treatment of endometriosis involves pain relief which is achieved through the administration of analgesics and non-steroidal anti-inflammatory drugs, with or without the addition of hormone therapy. At present, studies investigating endometriosis pain management using experimental rat models and the use of medications are scarce. Therefore, this study aimed to systematically evaluate research trends and critical points in the field of endometriosis pain management using experimental models.

Materials and Methods

A total of 30 publications related to this topic that were published from 2012 to 2022 were retrieved from various databases, including Web of Science, Scopus, PubMed, Embase, and CINAHL, using appropriate English keywords. The quality of the publications was evaluated using impact metrics, productivity, term density mapping, and author network.

Results

The average publication rate was three articles per year, reaching its peak in 2021 at five articles per year. The United States and China were found to be the most productive countries, with 12 and 10 publications per year, respectively. The field of medicine (37.0%) was the most abundant, although the H-index was relatively low (13:13). Term density mapping involved the search of 542 keywords, of which 35 were selected, with only 8 exhibiting significant density.

Conclusion

In the past decade, there has been a shortage of publications that have addressed pain in endometriosis in experimental models and, within this context the majority of the production and publication in this field has been performed by the United States and China. After performing this bibliometric review, it can be inferred that more research is required in this field, to develop new approaches and treatments for endometriotic pain.

Toll-like receptor 4: A potential therapeutic target for multiple human diseases

The immune response plays a pivotal role in the pathogenesis of diseases. Toll-like receptor 4 (TLR4), as an intrinsic immune receptor, exhibits widespread in vivo expression and its dysregulation significantly contributes to the onset of various diseases, encompassing cardiovascular disorders, neoplastic conditions, and inflammatory ailments. This comprehensive review centers on elucidating the architectural and distributive characteristics of TLR4, its conventional signaling pathways, and its mode of action in diverse disease contexts. Ultimately, this review aims to propose novel avenues and therapeutic targets for clinical intervention.

PAG neuronal NMDARs activation mediated morphine-induced hyperalgesia by HMGB1-TLR4 dependent microglial inflammation

Morphine is one of the most effective and widely used analgesic drugs. However, chronic morphine use caused opioid-induced hyperalgesia (OIH). The development of OIH limits the use of morphine. The mechanisms of OIH are not fully understood. Toll-like receptor4 (TLR4) and glutamate receptors in the periaqueductal gray (PAG) are critical in OIH, however, the association between TLR4 and N-methyl-D-aspartate Receptors (NMDARs) activation in PAG remains unclear. Microglia activation, increased TLR4/p65 nuclear factor-kappa B (p65 NF-κB) and proinflammatory cytokines in microglia, and phosphorylation of NMDAR1 subunit (NR1) and NMDAR2B subunit (NR2B) in neurons were observed in PAG of OIH mice. Up-regulations of TLR4/p65 NF-κB and proinflammatory cytokines (IL-1β, IL-6, TNF-α) in BV2 cells were prevented by inhibiting and knocking down TLR4. By inhibiting myeloid differentiation factor 2 (MD2) and knocking down the High-mobility group box 1 (HMGB1), we found that morphine activated TLR4 by HMGB1 but not MD2. We co-cultured Neuro-2a (N2A) with BV2 microglial cell line and found that instead of directly phosphorylating NMDAR subunits, morphine increased the phosphorylation of NR1 and NR2B by inducing TLR4-mediated microglia inflammation. Knocking TLR4 out of PAG by Lentivirus-GFP-TLR4 shRNA reversed these changes and relieved OIH. Our findings suggested that the secretion of HMGB1 induced by morphine-activated TLR4 in microglia, and the proinflammatory factors released by activated microglia phosphorylated NR1 and NR2B of adjacent neurons, induced increased neuronal excitability. In conclusion, TLR4/NMDARs in PAG were involved in the development and maintenance of OIH and supported novel strategies for OIH treatment.

Neuraxial drug delivery in pain management: An overview of past, present, and future

Activation of neuraxial nociceptive linkages leads to a high level of encoding of the message that is transmitted to the brain and that can initiate a pain state with its attendant emotive covariates. As we review here, the encoding of this message is subject to a profound regulation by pharmacological targeting of dorsal root ganglion and dorsal horn systems. Though first shown with the robust and selective modulation by spinal opiates, subsequent work has revealed the pharmacological and biological complexity of these neuraxial systems and points to several regulatory targets. Novel therapeutic delivery platforms, such as viral transfection, antisense and targeted neurotoxins, point to disease-modifying approaches that can selectively address the acute and chronic pain phenotype. Further developments are called for in delivery devices to enhance local distribution and to minimize concentration gradients, as frequently occurs with the poorly mixed intrathecal space. The field has advanced remarkably since the mid-1970s, but these advances must always address the issues of safety and tolerability of neuraxial therapy.

Fucoxanthin alleviated atherosclerosis by regulating PI3K/AKT and TLR4/NFκB mediated pyroptosis in endothelial cells

Fucoxanthin, a type of natural xanthophyll carotenoid, is mainly present in seaweeds and various microalgae. This compound has been proved to possess multiple functions including antioxidation, anti-inflammation and anti-tumor. Atherosclerosis is widely deemed as a chronic inflammation disease, and as the basis of vascular obstructive disease. However, there is rare research about fucoxanthin's effects on atherosclerosis. In this study, we demonstrated that the plaque area of mice treated with fucoxanthin was significantly reduced compared to the group that did not receive fucoxanthin. In addition, Bioinformatics analysis showed that PI3K/AKT signaling might be involved in the protective effect of fucoxanthin, and this hypothesis was then verified in vitro endothelial cell experiments. Besides, our further results showed that endothelial cell mortality measured by TUNEL and flow cytometry was significantly increased in the oxidized low-density lipoprotein (ox-LDL) treatment group while significantly decreased in the fucoxanthin treatment group. In addition, the pyroptosis protein expression level in the fucoxanthin group was significantly lower than that in the ox-LDL group, which indicated that fucoxanthin improved the pyroptosis level of endothelial cells. Furthermore, it was revealed that TLR4/NFκB signaling were also participated in the protection of fucoxanthin on endothelial pyroptosis. Moreover, the protection of fucoxanthin on endothelial cell pyroptosis was abrogated when PI3K/AKT was inhibited or TLR4 was overexpressed, which further suggested the anti-pyroptosis effect of fucoxanthin was mediated through regulations of PI3K/AKT and TLR4/NFκB signaling.

SARS-CoV-2 envelope protein triggers depression-like behaviors and dysosmia via TLR2-mediated neuroinflammation in mice

BACKGROUND

Depression and dysosmia have been regarded as primary neurological symptoms in COVID-19 patients, the mechanism of which remains unclear. Current studies have demonstrated that the SARS-CoV-2 envelope (E) protein is a pro-inflammatory factor sensed by Toll-like receptor 2 (TLR2), suggesting the pathological feature of E protein is independent of viral infection. In this study, we aim to ascertain the role of E protein in depression, dysosmia and associated neuroinflammation in the central nervous system (CNS).

METHODS

Depression-like behaviors and olfactory function were observed in both female and male mice receiving intracisternal injection of E protein. Immunohistochemistry was applied in conjunction with RT-PCR to evaluate glial activation, blood-brain barrier status and mediators synthesis in the cortex, hippocampus and olfactory bulb. TLR2 was pharmacologically blocked to determine its role in E protein-related depression-like behaviors and dysosmia in mice.

RESULTS

Intracisternal injection of E protein evoked depression-like behaviors and dysosmia in both female and male mice. Immunohistochemistry suggested that the E protein upregulated IBA1 and GFAP in the cortex, hippocampus and olfactory bulb, while ZO-1 was downregulated. Moreover, IL-1β, TNF-α, IL-6, CCL2, MMP2 and CSF1 were upregulated in both cortex and hippocampus, whereas IL-1β, IL-6 and CCL2 were upregulated in the olfactory bulb. Furtherly, inhibiting microglia, rather than astrocytes, alleviated depression-like behaviors and dysosmia induced by E protein. Finally, RT-PCR and immunohistochemistry suggested that TLR2 was upregulated in the cortex, hippocampus and olfactory bulb, the blocking of which mitigated depression-like behaviors and dysosmia induced by E protein.

CONCLUSIONS

Our study demonstrates that envelope protein could directly induce depression-like behaviors, dysosmia, and obvious neuroinflammation in CNS. TLR2 mediated depression-like behaviors and dysosmia induced by envelope protein, which could serve as a promising therapeutic target for neurological manifestation in COVID-19 patients.

The Unmet Needs for Studying Chronic Pelvic/Visceral Pain Using Animal Models

The different definitions of chronic pelvic/visceral pain used by international societies have changed over the years. These differences have a great impact on the way researchers study chronic pelvic/visceral pain. Recently, the role of systemic changes, including the role of the central nervous system, in the perpetuation and chronification of pelvic/visceral pain has gained weight. Consequently, researchers are using animal models that resemble those systemic changes rather than using models that are organ- or tissue-specific. In this review, we discuss the advantages and disadvantages of using bladder-centric and systemic models, enumerating some of the central nervous system changes and pain-related behaviors occurring in each model. We also present some drawbacks when using animal models and pain-related behavior tests and raise questions about possible, yet to be demonstrated, investigator-related bias. We also suggest new approaches to study chronic pelvic/visceral pain by refining existing animal models or using new ones.

Toll-like receptor 4 signaling pathway in sensory neurons mediates remifentanil-induced postoperative hyperalgesia via transient receptor potential ankyrin 1

Background: Remifentanil-induced postoperative hyperalgesia (RIH) refers to a state of hyperalgesia or aggravated pre-existing pain after remifentanil exposure. There has been considerable interest in understanding and preventing RIH. However, the mechanisms responsible for RIH are still not completely understood. Toll-like receptor 4 (TLR4), a classic innate immune receptor, has been detected in sensory neurons and participates in various nociceptive conditions, whereas its role in RIH remains unclear. Transient receptor potential ankyrin 1 (TRPA1) always serves as a nociceptive channel, whereas its role in RIH has not yet been investigated. This study aimed to determine whether the TLR4 signaling pathway in sensory neurons engaged in the development of RIH and the possible involvement of TRPA1 during this process. Methods: A rat model of remifentanil-induced postoperative hyperalgesia (RIH) was established, which presented decreased paw withdrawal mechanical threshold (PWMT) and paw withdrawal thermal latency (PWTL). The mRNA and protein expression levels of TLR4, phosphorylated NF-κB, and TRPA1 in the dorsal root ganglion (DRG) from RIH model were analyzed by real-time PCR, western blot, and immunofluorescence. The TLR4 antagonist TAK-242 and the TRPA1 antagonist HC-030031 were applied to determine the role of sensory neuron TLR4 signaling and TRPA1 in RIH. Results: Compared with control, PWMT and PWTL were significantly decreased in RIH model. Moreover, the mRNA and protein expression of TLR4 and TRPA1 in DRG were upregulated after remifentanil exposure together with increased NF-κB phosphorylation. TLR4 antagonist TAK-242 mitigated mechanical pain in RIH together with downregulated expression of TLR4, phosphorylated NF-κB, and TRPA1 in DRG neurons. In addition, TRPA1 antagonist HC-030031 also alleviated mechanical pain and decreased TRPA1 expression in RIH without affecting TLR4 signaling in DRG. Conclusions: Taken together, these results suggested that activation of TLR4 signaling pathway engaged in the development of RIH by regulating TRPA1 in DRG neurons. Blocking TLR4 and TRPA1 might serve as a promising therapeutic strategy for RIH.

Dietary supplementation of n-3 PUFAs ameliorates LL37-induced rosacea-like skin inflammation via inhibition of TLR2/MyD88/NF-κB pathway

Rosacea is a facial chronic inflammatory skin disease with dysfunction of immune and neurovascular system and treatments for rosacea are challenging. N-3 polyunsaturated fatty acids (PUFAs), one of essential fatty acids, are needed for health maintenance and exert anti-inflammation and immunomodulatory effects in a series of cutaneous diseases such as atopic dermatitis and photoaging through dietary supplementation. However, the role of n-3 PUFAs on rosacea remains to be elucidated. In this study, KEGG enrichment analysis and GO analysis indicated that the biological process and signaling pathways, including chemokine signaling pathway, regulated by n-3 PUFAs highly overlapped with those in the pathogenic biological process of rosacea, especially the erythema telangiectasia type. Next, mice were randomized to fed with a customized n-3 PUFAs diet. We showed that n-3 PUFAs ameliorated skin erythema, inhibited dermal inflammatory cell infiltration (mast cells, neutrophils, and CD4 +T cells) and suppressed elevated pro-inflammatory cytokines in LL37-induced rosacea-like mice. Besides, n-3 PUFAs were also verified to repress angiogenesis in LL37-induced mice skin. Further investigation revealed that n-3 PUFAs attenuated LL37-induced inflammation via TLR2/ MyD88/ NF-κB pathway both in mice and in keratinocytes. In conclusion, our findings underscore that dietary supplementation of n-3 PUFAs have the potential to become an efficient and safe clinical therapeutic candidate for rosacea.

CHIP induces ubiquitination and degradation of HMGB1 to regulate glycolysis in ovarian endometriosis

Ovarian endometriosis is a common gynecological condition that can cause infertility in women of childbearing age. However, the pathogenesis is still unknown. We demonstrate that the carboxyl terminus of Hsc70-interacting protein (CHIP) is a negative regulator in the development of endometriosis and reduces HMGB1 expression in endometriotic cells. Meanwhile, CHIP interacts with HMGB1 and promotes its ubiquitinated degradation, thereby inhibiting aerobic glycolysis and the progression of endometriosis. Furthermore, the CHIP agonist YL-109 effectively suppresses the growth of ectopic endometrium in endometriosis mouse model, which could be a potential therapeutic approach for endometriosis. In conclusion, our data suggest that CHIP may inhibit the development of endometriosis by suppressing the HMGB1-related glycolysis.

Bushen Wenyang Huayu Decoction Targets TLR4/NF-κB Mediated Autophagy to Treat Endometriosis Effectively

Endometriosis has been found to be closely related to autophagy. This study aimed to elucidate the possible mechanism of Bushen Wenyang Huayu Decoction (BWHD) in treating endometriosis (EMs) by targeting TLR4/NF-κB-mediated autophagy. Autologous grafting was used to generate the EMs model in rats. Once the model was developed, BWHD high-dose and low-dose groups received intragastric administration of BWHD, and the gestrinone group served as a positive control. Immunofluorescence labeling and Western blotting were used for the protein expression of toll-like receptor 4 (TLR4), nuclear transcription factor-κB (NF-κB), Beclin-1, and selective autophagy connector protein P62 (P62). Quantitative real-time polymerase chain reaction (qRT-PCR) was used to analyze mRNA levels of TLR4, NF-κB, Beclin-1, and P62. We found that BWHD significantly reduced the size of ectopic lesions in rats with EMs, regulated reproductive hormone levels, and alleviated the cell autophagy level. It suggested that BWHD could be an effective treatment of EMs by targeting TLR4/NF-κB signaling pathway.

A microsatellite DNA-derived oligodeoxynucleotide attenuates lipopolysaccharide-induced acute lung injury in mice by inhibiting the HMGB1-TLR4-NF-κB signaling pathway

Acute lung injury (ALI) with uncontrolled inflammatory response has high morbidity and mortality rates in critically ill patients. Pathogen-associated molecular patterns (PAMPs) are involved in the development of uncontrolled inflammatory response injury and associated lethality. In this study, we investigated the inhibit effect of MS19, a microsatellite DNA-derived oligodeoxynucleotide (ODN) with AAAG repeats, on the inflammatory response induced by various PAMPs in vitro and in vivo. In parallel, a microsatellite DNA with AAAC repeats, named as MS19-C, was used as controls. We found that MS19 extensively inhibited the expression of inflammatory cytokines interleukin (IL)-6 and tumor necrosis factor (TNF)-α induced by various PAMPs stimulation, including DNA viruses, RNA viruses, bacterial components lipopolysaccharide (LPS), and curdlan, as well as the dsDNA and dsRNA mimics, in primed bone marrow-derived macrophage (BMDM). Other than various PAMPs, MS19 also demonstrated obvious effects on blocking the high mobility group box1 (HMGB1), a representative damage-associated-molecular pattern (DAMP), nuclear translocation and secretion. With the base substitution from G to C, MS19-C has been proved that it has lost the inhibitory effect. The inhibition is associated with nuclear factor kappa B (NF-κB) signaling but not the mitogen-activated protein kinase (MAPK) transduction. Moreover, MS19 capable of inhibiting the IL-6 and TNF-α production and blocking the HMGB1 nuclear translocation and secretion in LPS-stimulated cells was used to treat mice ALI induced by LPS in vivo. In the ALI mice model, MS19 significantly inhibited the weight loss and displayed the dramatic effect on lessening the ALI by reducing consolidation, hemorrhage, intra-alveolar edema in lungs of the mice. Meanwhile, MS19 could increase the survival rate of ALI by downregulating the inflammation cytokines HMGB1, TNF-a, and IL-6 production in the bronchoalveolar lavage fluid (BALF). The data suggest that MS19 might display its therapeutic role on ALI by inhibiting the HMGB1-TLR4-NF-κB signaling pathway.

An Update on the Multifaceted Role of NF-kappaB in Endometriosis

Endometriosis remains a common but challenging gynecological disease among reproductive-aged women with an unclear pathogenesis and limited therapeutic options. Numerous pieces of evidence suggest that NF-κB signaling, a major regulator of inflammatory responses, is overactive in endometriotic lesions and contributes to the onset, progression, and recurrence of endometriosis. Several factors, such as estrogen, progesterone, oxidative stress, and noncoding RNAs, can regulate NF-κB signaling in endometriosis. In the present review, we discuss the mechanisms by which these factors regulate NF-κB during endometriosis progression and provide an update on the role of NF-κB in affecting endometriotic cells, peritoneal macrophages (PMs) as well as endometriosis-related symptoms, such as pain and infertility. Furthermore, the preclinical drugs for blocking NF-κB signaling in endometriosis are summarized, including plant-derived medicines, NF-κB inhibitors, other known drugs, and the potential anti-NF-κB drugs predicted through the Drug-Gene Interaction Database. The present review discusses most of the studies concerning the multifaceted role of NF-κB signaling in endometriosis and provides a summary of NF-κB-targeted treatment in detail.

Astrocyte-microglia interaction through C3/C3aR pathway modulates neuropathic pain in rats model of chronic constriction injury

Neuropathic pain (NP) is the cardinal symptom of neural injury, and its underlying molecular mechanism needs further investigation. Complements, especially complement 3 (C3), are involved in the pathophysiology of many neurological disorders, while the specific role of C3 in NP is still obscure. In this study, we found that both C3 and its receptor C3aR were upregulated in the spinal dorsal horn in a rat chronic constriction injury (CCI) model. In addition, C3 was mainly detected in astrocytes, while C3aR was expressed in microglia and neuron. Intrathecal injection of C3 antibody and C3aR antagonist alleviated NP in CCI model together with reduced M1 polarization of microglia. Our finding suggested that blockade of the C3/C3aR pathway might be a novel strategy for NP.

Sex Differences in TLR4 Expression in SHR Do Not Contribute to Sex Differences in Blood Pressure or the Renal T cell Profile

Hypertension is a primary risk factor for the development of cardiovascular disease. Mechanisms controlling blood pressure (BP) in men and women are still being investigated, however, there is increasing evidence supporting a role for the innate immune system. Specifically, Toll-like receptors (TLR), and TLR4 in particular, have been implicated in the development of hypertension in male spontaneously hypertensive rats (SHR). Despite established sex differences in BP control and inflammatory markers in hypertensive males and females, little is known regarding the role of TLR4 in hypertension in females. Our hypotheses were that male SHR have greater TLR4 expression compared to females, and that sex differences in TLR4 contribute to sex differences in BP and the T cell profile. To test these hypotheses, initial studies measured renal TLR4 protein expression in 13-week old male and female SHR. Additional SHR were implanted with telemetry devices and randomized to treatment with either IgG or TLR4 neutralizing antibodies. Untreated control male SHR have greater TLR4 protein expression in the kidney compared to females. However, treatment with TLR4 neutralizing antibody for 2 weeks did not significantly alter BP in either male or female SHR. Interestingly, neutralization of TLR4 increased renal CD3⁺ T cells in female SHR, with no alteration in CD4⁺ T cells or CD8⁺ T cells in either sex. Taken together, our data indicates that although male SHR have greater renal TLR4 expression than females, TLR4 does not contribute to the higher BP and more pro-inflammatory renal T cell prolife in males vs. females.

Component-target network and mechanism of Qufeng Zhitong capsule in the treatment of neuropathic pain

ETHNOPHARMACOLOGICAL RELEVANCE

Qufeng Zhitong capsule (QFZTC) is a traditional Chinese medicine (TCM) clinically used for treating pain. However, the active ingredients of QFZTC and its pharmacological mechanism in the treatment of neuropathic pain (NP) remain unclear.

AIM OF THE STUDY

We aimed to identify the active ingredients of QFZTC and reveal its target genes and underlying mechanism of action in NP.

MATERIALS AND METHODS

High-performance liquid chromatography (HPLC) was used to identify the active ingredients of QFZTC. Network pharmacology analysis was conducted to determine the core targets and pathway enrichment of QFZTC. An NP mice model was established through chronic compression injury (CCI) surgery of the sciatic nerve, while von Frey instrumentation and a thermal stimulator were employed to measure the sensitivity of mice to mechanical and thermal stimuli. Immunofluorescence was used to observe the expression of TLR4 and p-P65 in microglia. Western blotting was used to detect the levels of protein expression of Iba-1, TLR4, MyD88, P65, p-P65, and c-Fos, while ELISA kits were used to detect the release of TNF-α, IL-6, and IL-1β.

RESULTS

Seven active ingredients were identified in QFZTC: gallic acid, loganylic acid, syringin, corilagin, loganin, ellagic acid, and osthole. Network analysis identified TLR4, TNF, IL6, IL1β, and c-Fos as core targets, and Toll-like receptors and NF-κB as core signaling pathways. Treatment with QFZTC significantly relieved mechanical allodynia and thermal hyperalgesia in CCI mice models. CCI induced an increase in the expression of TLR4 and p-P65 in microglia, whereas QFZTC dose-dependently reduced the expression of Iba-1, TLR4, MyD88, and p-P65 in the spinal cord. QFZTC inhibited the expression of the c-Fos pain marker and reduced the expression of the TNF-α, IL-6, and IL-1β inflammatory factors.

CONCLUSION

We combined the active ingredients of QFZTC with network pharmacology research to clarify its biological mechanism in the treatment of NP. We demonstrated that QFZTC reduced NP in mice probably through regulating the spinal microglia via the TLR4/MyD88/NF-κB signaling pathway. Hence, QFZTC could be regarded as a potential drug for relieving NP.

Post-Translational Modification of HMGB1 Disulfide Bonds in Stimulating and Inhibiting Inflammation

High mobility group box 1 protein (HMGB1), a highly conserved nuclear DNA-binding protein, is a “damage-associated molecular pattern” molecule (DAMP) implicated in both stimulating and inhibiting innate immunity. As reviewed here, HMGB1 is an oxidation-reduction sensitive DAMP bearing three cysteines, and the post-translational modification of these residues establishes its proinflammatory and anti-inflammatory activities by binding to different extracellular cell surface receptors. The redox-sensitive signaling mechanisms of HMGB1 also occupy an important niche in innate immunity because HMGB1 may carry other DAMPs and pathogen-associated molecular pattern molecules (PAMPs). HMGB1 with DAMP/PAMP cofactors bind to the receptor for advanced glycation end products (RAGE) which internalizes the HMGB1 complexes by endocytosis for incorporation in lysosomal compartments. Intra-lysosomal HMGB1 disrupts lysosomal membranes thereby releasing the HMGB1-transported molecules to stimulate cytosolic sensors that mediate inflammation. This HMGB1-DAMP/PAMP cofactor pathway slowed the development of HMGB1-binding antagonists for diagnostic or therapeutic use. However, recent discoveries that HMGB1 released from neurons mediates inflammation via the TLR4 receptor system, and that cancer cells express fully oxidized HMGB1 as an immunosuppressive mechanism, offer new paths to targeting HMGB1 for inflammation, pain, and cancer.

Mesencephalic astrocyte-derived neurotrophic factor restores blood-brain barrier integrity of aged mice after ischaemic stroke/reperfusion through anti-inflammation via TLR4/MyD88/NF-κB pathway

Ischaemic stroke remains a leading cause of disability and mortality worldwide and ageing-associated inflammation for the aged patients specifically leads to worse post-stroke blood-brain barrier (BBB) disruption than young subjects. Accordingly, suppression of excessive inflammation can alleviate BBB injury, which provides potential therapeutic treatment for ischaemic stroke of the aged. Prior studies revealed that mesencephalic astrocyte-derived neurotrophic factor (MANF) regulated inflammatory response and alleviated liver injury in ageing. However, it is unclear whether MANF confer similar benefit to BBB of aged mice suffered from ischaemic stroke. Transient cerebral ischaemia induced by middle cerebral artery occlusion (MCAO) was conducted in aged mice (18-20 months old). MANF was injected into the right lateral ventricle 2 h after MCAO. BBB integrity, tight junctional proteins, ultrastructure of microvessels, infarct volume, neurological scores, brain water content, pro-inflammatory cytokines and neutrophil infiltration rate were determined 72 h after MCAO. H₂O₂-induced senescent bEnd.3 cells were applied in the in vitro study to investigate the possible mechanism. First, we confirmed that ischaemic stroke/reperfusion in senescent condition promoted the over-expression of MANF on brain endothelial cells. Then, MANF supplement could suppress the pro-inflammatory factor production, restore BBB integrity and then alleviate infarct volume, neurological scores, brain water content and neutrophil infiltration rate. In addition, MANF maintained BBB integrity after ischaemic stroke of aged condition dependent on TLR4/MyD88/NF-κB pathway via intervention of pro-inflammatory factors production. In summary, the recognition of MANF in the process of BBB breakdown at aged condition may offer novel therapeutic approaches for ischaemic stroke.

Intrathecal implantation surgical considerations in rodents; a review

Intrathecal access in humans is a routine clinical intervention. However, intrathecal access is limited to drug delivery purposes in rodents, and intrathecal implantation is not a common surgical practice. Preclinically, we have successfully adopted different intrathecal implantation surgical methods for different implant materials in rodents. However, employing the appropriate intrathecal implantation method is a challenging process for surgeons, which includes several steps such as preoperative evaluations and postoperative care. The aim of this review is to define and compare the major documented surgical approaches applicable for intrathecal implantation in rodents along with the associated side effects, as well as highlighting the critical preoperative and postoperative considerations. Overall, this review will provide surgeons with the principles of intrathecal implantation approaches applicable for different implant materials.