A clinical-stage Nrf2 activator suppresses osteoclast differentiation via the iron-ornithine axis.

Activating Nrf2 by small molecules is a promising strategy to treat postmenopausal osteoporosis. However, there is currently no Nrf2 activator approved for treating chronic diseases, and the downstream mechanism underlying the regulation of Nrf2 on osteoclast differentiation remains unclear. Here, we found that bitopertin, a clinical-stage glycine uptake inhibitor, suppresses osteoclast differentiation and ameliorates ovariectomy-induced bone loss by activating Nrf2. Mechanistically, bitopertin interacts with the Keap1 Kelch domain and decreases Keap1-Nrf2 binding, leading to reduced Nrf2 ubiquitination and degradation. Bitopertin is associated with less adverse events than clinically approved Nrf2 activators in both mice and human subjects. Furthermore, Nrf2 transcriptionally activates ferroportin-coding gene Slc40a1 to reduce intracellular iron levels in osteoclasts. Loss of Nrf2 or iron supplementation upregulates ornithine-metabolizing enzyme Odc1, which decreases ornithine levels and thereby promotes osteoclast differentiation. Collectively, our findings identify a novel clinical-stage Nrf2 activator and propose a novel Nrf2-iron-ornithine metabolic axis in osteoclasts.

Cancer burden attributable to risk factors, 1990-2019: A comparative risk assessment.

An up-to-date comprehensive assessment of the cancer burden attributable to risk factors is essential for cancer prevention. We analyzed the population attributable fraction (PAF) of cancer disability-adjusted life years (DALYs) attributable to 11 level 2 risk factors using data from the Global Burden and Disease Study (GBD) 2019. We highlighted that almost half of the cancer DALYs can be preventable by modifying relevant risk factors. The attributable cancer DALYs increased by 60.42%-105.0 million from 1990 to 2019. Tobacco, dietary risks, alcohol use, high body-mass index, and air pollution were the top five risk factors. The PAFs attributable to high fasting plasma glucose, high body-mass index, and low physical activity have increased worldwide from 1990 to 2019. Unsafe sex was the leading risk factor for women before age of 54. Tailored prevention programs targeted at specific populations should be scaled up to reduce the cancer burden in the future.

Global Burden of Lung Cancer Attributable to Household Fine Particulate Matter Pollution in 204 Countries and Territories, 1990 to 2019.

INTRODUCTION: Household particulate matter (PM) air pollution is substantially associated with lung cancer. Nevertheless, the global burden of lung cancer attributable to household PM2.5 is still uncertain. METHODS: In this study, data from the Global Burden and Disease Study 2019 are used to thoroughly assess the burden of lung cancer associated with household PM2.5. RESULTS: The number of deaths and disability-adjusted life-years (DALYs) attributable to household PM2.5 was found to be 0.08 million and 1.94 million, respectively in 2019. Nevertheless, the burden of lung cancer attributable to household PM2.5 decreased from 1990 to 2019. At the sociodemographic index (SDI) district level, the middle SDI region had the most number of lung cancer deaths and DALYs attributable to household PM2.5. Moreover, the burden of lung cancer was mainly distributed in low-SDI regions, such as Sub-Saharan Africa. Conversely, in high-SDI regions, the age-standardized mortality rate and age-standardized DALY rate of lung cancer attributable to household PM2.5 exhibit the most rapid declines. The burden of lung cancer attributable to household PM2.5 is heavier for men than for women. The sex difference is more obvious in the elderly. CONCLUSIONS: The prevalence of lung cancer attributable to household PM2.5 has exhibited a declining trend from 1990 to 2019 owing to a concurrent decline in household PM2.5 exposure.

Sustainable production of catechol derivatives from waste tung nutshell C/G-type lignin via heterogeneous Cu-NC catalytic oxidation.

The sustainable production of catechol derivatives is a challenging task. Catechyl (C) and guaiacyl (G) lignins coexisting in waste tung nutshells are promising feedstocks to form valuable catechol derivatives, but the depolymerization of C/G lignin typically involves a catalytic reductive process that cannot produce these oxidized aromatic chemicals. Herein, we demonstrated that the sustainable production of catechol derivative aldehydes and acids from C/G lignin could be achieved through a heterogeneous copper-catalyzed oxidative process. Under optimized conditions, the Cu-NC-800 catalyst affords a 43.5 mg g-1 yield (8.9 wt%, based on Klason lignin) of aromatic aldehydes (protocatechuic aldehyde, vanillin) and acids (protocatechuic acid, vanillic acid). XRD and XPS analyses showed that CuO and Cu2O may be the active species during the heterogeneous oxidation of the Cu-NC-800 catalyst. This study opens new opportunities for the sustainable production of catechol derivatives from C/G-type lignin.

Targeting the Main Sources of Reactive Oxygen Species Production: Possible Therapeutic Implications in Chronic Pain.

Humans have long been combating chronic pain. In clinical practice, opioids are first- choice analgesics, but long-term use of these drugs can lead to serious adverse reactions. Finding new, safe and effective pain relievers that are useful treatments for chronic pain is an urgent medical need. Based on accumulating evidence from numerous studies, excess reactive oxygen species (ROS) contribute to the development and maintenance of chronic pain. Some antioxidants are potentially beneficial analgesics in the clinic, but ROS-dependent pathways are completely inhibited only by scavenging ROS directly targeting cellular or subcellular sites. Unfortunately, current antioxidant treatments donot achieve this effect. Furthermore, some antioxidants interfere with physiological redox signaling pathways and fail to reverse oxidative damage. Therefore, the key upstream processes and mechanisms of ROS production that lead to chronic pain in vivo must be identified to discover potential therapeutic targets related to the pathways that control ROS production in vivo. In this review, we summarize the sites and pathways involved in analgesia based on the three main mechanisms by which ROS are generated in vivo, discuss the preclinical evidence for the therapeutic potential of targeting these pathways in chronic pain, note the shortcomings of current research and highlight possible future research directions to provide new targets and evidence for the development of clinical analgesics.

Health burden of unbalanced fatty acids intake from 1990 to 2019: A global analysis.

BACKGROUND: Unbalanced fatty acids intake is associated with a range of health outcomes; however, the impact on human health remains unclear globally. We aim to provide a comprehensive assessment of the health effect of unbalanced fatty acids intake on a global scale. METHODS: We analyzed the trends of summary exposure value (SEV) and the attributable burden of unbalanced fatty acids intake, including diet low in polyunsaturated fatty acids (low PUFAs), diet low in seafood omega-3 fatty acids (low seafood-(ω-3)-PUFAs), and diet high in trans fatty acids (high TFAs) from 1990 to 2019 using data from Global Burden of Disease Study 2019. FINDINGS: The global fatty acids intake was far from the optimal level. High-income North America had the highest SEV of diet of high TFAs, while less-developed regions located in Saharan Africa had the highest SEVs of low PUFAs and low seafood-(ω-3)-PUFAs. The attributable burden was unequally distributed to less-developed regions. Males had lower SEVs but higher attributable burden than females and this gender gap was particularly pronounced before the age of 59. The young population had a higher SEV of diet of low PUFAs, comparable SEV of low seafood-(ω-3)-PUFAs but lower SEV of high TFAs than the elderly population. CONCLUSIONS: This study underpinned the high prevalence of unbalanced fatty acids intake worldwide and provided evidence-based guidance for identifying at-risk populations and developing effective strategies to improve fatty acids intake in the future. FUNDING: The study was funded by Shanxi Province "136" Revitalization Medical Project Construction Funds and the Fundamental Research Funds for the Central Universities.

Effect of PM2.5 air pollution on the global burden of lower respiratory infections, 1990-2019: A systematic analysis from the Global Burden of Disease Study 2019.

Particulate matter (PM) air pollution is closely related to lower respiratory infections (LRIs). However, the global LRI burden attributable to PM remains unclear. Here, we provide a comprehensive assessment of the PM2.5-attributable LRI burden using data from the Global Burden and Disease Study (GBD) 2019. We found that PM2.5 air pollution contributed to approximately 0.7 million deaths and 37.6 million disability-adjusted life years (DALYs) of LRIs in 2019. The LRI burden attributable to PM2.5 has decreased from 1990 to 2019, with a more pronounced decrease in household PM2.5 than in ambient PM2.5. Unlike the decreasing trend in LRI burden due to household PM2.5 worldwide, nearly one fifth of countries experienced an increase of LRI burden due to ambient PM2.5. The burden was unevenly distributed to less developed countries, mainly in Sub-Saharan Africa. All age groups experienced a decrease in the PM2.5-attributable burden, with the most significant decrease in children younger than 10 years. Notably, individuals aged 20-84 years experienced an increase in the LRI burden attributable to ambient PM2.5. Males had higher burden than females in the elder age and higher SDI regions. This study provided an evidence-based guidance for the prevention of LRIs and control of PM2.5 air pollution.

Trends and risk factors of global incidence, mortality, and disability of genitourinary cancers from 1990 to 2019: Systematic analysis for the Global Burden of Disease Study 2019.

Background: The incidence of kidney, bladder, and prostate cancer ranked ninth, sixth, and third in male cancers respectively, meanwhile, the incidence of testicular cancer also increased gradually in the past 30 years. Objective: To study and present estimates of the incidence, mortality, and disability of kidney, bladder, prostate, and testicular cancer by location and age from 1990 to 2019 and reveal the mortality risk factors of them. Materials: The Global Burden of Diseases Study 2019 was used to obtain data for this research. The prediction of cancer mortality and incidence was based on mortality-to-incidence ratios (MIRs). The MIR data was processed by logistic regression and adjusted by Gaussian process regression. The association between the socio-demographic index and the incidence or disease burden was determined by Spearman's rank order correlation. Results: Globally in 2019, there were 371,700 kidney cancer cases with an age-standardized incidence rate (ASIR) of 4.6 per 100,000, 524,300 bladder cancer cases, with an ASIR of 6.5 per 100,000, 1,410,500 prostate cancer cases with an ASIR of 4.6 per 100,000 and 109,300 testicular cancer incident cases with an ASIR of 1.4 per 100,000, the ASIR of these four cancers increased by 29.1, 4, 22, and 45.5% respectively. The incidence rate of the four cancers and the burden of kidney cancer were positively correlated with the socio-demographic index (SDI), regions with a higher SDI faced more of a burden attributable to these four cancers. High body-mass index has surpassed smoking to be the leading risk factor in the past thirty years for kidney cancer mortality. Smoking remained the leading risk factor for cancer-related mortality for bladder cancer and prostate cancer and the only risk factor for prostate cancer. However, the contribution of high fasting plasma glucose to bladder cancer mortality has been increasing. Conclusion: The incidence of bladder, kidney, prostate, and testicular cancer is ever-increasing. High-income regions face a greater burden attributable to the four cancers. In addition to smoking, metabolic risk factors may need more attention.

Lignin-derived polyphenols with enhanced antioxidant activities by chemical demethylation and their structure-activity relationship.

Lignin valorization to biobased polyphenols antioxidants is increasingly attractive in the modern industry due to their inherent phenolic structures. Herein, lignin-derived polyphenols with enhanced antioxidant activities were prepared from the most available technical lignin including organosolv lignin (OL), alkali lignin (AL), and enzyme lignin (EL) by iodocyclohexane (ICH) chemical demethylation. The structural evolution of lignin indicated that the CAr-OCH3 group and the CAr-O-Calkyl side-chain could be effectively transformed into the CAr-OH group, resulting in a significant increase of the phenolic-OH content and a slight decrease of the molecular weight. The 1,1-diphenyl-2-picrylhydrazyl radical (DPPH·) scavenging activity was in the order of ICHOL-24 > ICHAL-24 > ICHEL-24 ≈ FA > BHT, and the IC50 value of ICHOL-24 was 0.56 times lower than that of BHT. The structure-activity relationship demonstrated the activities were quasi-linearly related to phenolic-OH contents and could be affected by molecular weights. The H/G/S proportions of lignin could be an indicator for accurate screening of efficient lignin-derived polyphenols antioxidants (LPA). It was preliminarily estimated to have economic feasibility for producing LPA from technical lignin by demethylation compared with synthetic or natural antioxidants. This work will help to develop efficient biobased antioxidants for lignin valorization.

Global, Regional, and National Burden of CKD due to Glomerulonephritis from 1990 to 2019: A Systematic Analysis from the Global Burden of Disease Study 2019.

BACKGROUND: CKD is becoming a major human health concern. Limited quantitative assessments of the burden of CKD due to glomerulonephritis have been performed. We performed a comprehensive analysis of the disease burden to update the epidemiology of this disease. METHODS: Incidence, prevalence, deaths, and disability-adjusted life-years (DALYs) data and percent changes in these indicators were extracted from Global Burden of Disease Study 2019 to analyze the burden of CKD due to glomerulonephritis. RESULTS: Globally, there were 606,300 (95% uncertainty interval [UI], 560,100 to 658,100) incident patients, 17,300,000 (95% UI, 16,100,000 to 18,600,000) prevalent patients, 183,700 (95% UI, 146,300 to 228,900) deaths, and 6,900,000 (95% UI, 5,900,000 to 8,100,000) DALYs of CKD due to glomerulonephritis in 2019. Compared with those in 1990, the numbers of incident patients, prevalent patients, deaths, and DALYs increased by 77%, 81%, 100%, and 66%, respectively. Most of the disease burden was concentrated in countries with lower sociodemographic index. In Central Latin America, the disease burden was much higher than expected on the basis of its sociodemographic index. Decomposition analysis showed that population aging and growth were the two major drivers of the increase in DALYs. Frontier analysis revealed considerable opportunities to reduce the age-standardized DALYs in the middle of the sociodemographic-index spectrum. Although middle-aged and elderly individuals accounted for the majority of the disease burden, the highest incidence rate was observed in children aged 1-4 years. CONCLUSIONS: The disease burden of CKD due to glomerulonephritis has increased worldwide, especially in regions and countries with lower sociodemographic indexes.

What was the Epidemiology and Global Burden of Disease of Hip Fractures From 1990 to 2019? Results From and Additional Analysis of the Global Burden of Disease Study 2019.

BACKGROUND: Hip fractures are associated with a high risk of death; among those who survive a hip fracture, many experience substantial decreases in quality of life. A comprehensive understanding of the epidemiology and burden of hip fractures by country, age, gender, and sociodemographic factors would provide valuable information for healthcare policymaking and clinical practice. The Global Burden of Disease (GBD) study 2019 was a global-level study estimating the burden of 369 diseases and injuries in 204 countries and territories. An exploration and additional analysis of the GBD 2019 would provide a clearer picture of the incidence and burden of hip fractures. QUESTIONS/PURPOSES: Using data from the GBD 2019, we asked, (1) What are the global, regional, and national incidences of hip fractures, and how did they change over a recent 30-year span? (2) What is the global, regional, and national burden of hip fractures in terms of years lived with disability, and how did it change over that same period? (3) What is the leading cause of hip fractures? (4) How did the incidence and years lived with disability of patients with hip fractures change with age, gender, and sociodemographic factors? METHODS: This was a cross-sectional study. Participant data were obtained from the GBD 2019 ( http://ghdx.healthdata.org/gbd-results-tool ). The GBD study is managed by the WHO, coordinated by the Institute of Health Metrics and Evaluation, and funded by the Bill and Melinda Gates Foundation. It estimates the burden of disease and injury for 204 countries by age, gender, and sociodemographic factors, and can serve as a valuable reference for health policymaking. All estimates and their 95% uncertainty interval (UI) were produced using DisMod-MR 2.1, a Bayesian meta-regression tool in the GBD 2019. In this study, we directly pulled the age-standardized incidence rate and years lived with disability rate of hip fractures by location, age, gender, and cause from the GBD 2019. Based on these data, we analyzed the association between the incidence rate and latitude of each country. Then, we calculated the estimated annual percentage change to represent trends from 1990 to 2019. We also used the Spearman rank-order correlation analysis to determine the correlation between the incidence or burden of hip fractures and the sociodemographic index, a composite index of the income per capita, average years of educational attainment, and fertility rates in a country. RESULTS: Globally, hip fracture incidences were estimated to be 14.2 million (95% UI 11.1 to 18.1), and the associated years lived with disability were 2.9 million (95% UI 2.0 to 4.0) in 2019, with an incidence of 182 (95% UI 142 to 231) and 37 (95% UI 25 to 50) per 100,000, respectively. A strong, positive correlation was observed between the incidence rate and the latitude of each country (rho = 0.65; p < 0.001). From 1990 to 2019, the global incidence rate for both genders remained unchanged (estimated annual percentage change 0.01 [95% confidence interval -0.08 to 0.11]), but was slightly increased in men (estimated annual percentage change 0.11 [95% CI 0.01 to 0.2]). The years lived with disability rate decreased slightly (estimated annual percentage change 0.66 [95% CI -0.73 to -0.6]). These rates were standardized by age. Falls were the leading cause of hip fractures, accounting for 66% of all patients and 55% of the total years lived with disability. The incidence of hip fractures was tightly and positively correlated with the sociodemographic index (rho 0.624; p < 0.001), while the years lived with disability rate was slightly negatively correlated (rho -0.247; p < 0.001). Most hip fractures occurred in people older than 70 years, and women had higher incidence rate (189.7 [95% UI 144.2 to 247.2] versus 166.2 [95% UI 133.2 to 205.8] per 100,000) and years lived with disability (38.4 [95% UI 26.9 to 51.6] versus 33.7 [95% UI 23.1 to 45.5] per 100,000) than men. CONCLUSION: Hip fractures are common, devastating to patients, and economically burdensome to healthcare systems globally, with falls being the leading cause. The age-standardized incidence rate has slightly increased in men. Many low-latitude countries have lower incidences, possibly because of prolonged sunlight exposure. Policies should be directed to promoting public health education about maintaining bone-protective lifestyles, enhancing the knowledge of osteoporosis management in young resident physicians and those in practice, increasing the awareness of osteoporosis screening and treatment in men, and developing more effective antiosteoporosis drugs for clinical use. LEVEL OF EVIDENCE: Level III, prognostic study.

Naringenin promoted spinal microglia M2 polarization in rat model of cancer-induced bone pain via regulating AMPK/PGC-1α signaling axis.

Cancer-induced bone pain (CIBP) treatment remains a clinical challenge because the pathophysiological mechanisms are not fully understood. Recently, it was verified that shifting microglial polarization toward the M2 phenotype reveals a potential strategy for CIBP treatment. Naringenin, a natural flavone flavonoid, has been reported to have antioxidant, anti-inflammatory and neuroprotective properties. However, the role of naringenin on regulating microglial polarization in CIBP rats and the molecular mechanisms participating in this process have not been fully clarified. Herein, we investigated the potential effect of naringenin on M1/M2 microglial polarization and further explored the potential mechanisms of this action. Our study demonstrated that intraperitoneal administration of naringenin could upregulate the antioxidative molecule glutathione peroxidase 4 (GPx4) level in the spinal cord, as well as bone cancer-induced mechanical allodynia in rats. Moreover, naringenin treatment also suppressed microglia-mediated neuroinflammation by downregulating the phosphorylation of nuclear factor κB (NF-κB) p65 expression and promoting microglial polarization toward the M2 phenotype in CIBP rats. The promoting effects mediated by naringenin on M1/M2 microglial polarization are dependent on the serine/threonine protein kinase adenosine monophosphate-activated protein kinase (AMPK)/proliferator-activated receptor γ coactivator-1α (PGC-1α) signaling pathway. Inhibition of AMPK activation with the classical AMPK inhibitor Compound C attenuated this effect of naringenin. These results improved the understanding of the anti-inflammatory property of naringenin on microglial polarization, which might provide new alternative avenues for CIBP treatment.

Global, Regional, and National Burden of Low Bone Mineral Density From 1990 to 2019: Results From the Global Burden of Disease Study 2019.

Objective: We aim to explore the global spatial prevalence and temporal trends of the burden of low bone mineral density (LBMD) worldwide, due to a lack of related studies. Design: Cross-sectional study. Methods: We used data from the Global Burden of Disease Study 2019 to conduct this study. LBMD in the GBD study includes both osteopenia and osteoporosis. The estimation for the prevalence, measured by the summary exposure value (SEV), and burden of LBMD was made in DisMod-MR 2.1, a Bayesian meta-regression tool. Correlation analysis was performed using the Spearman rank order correlation methods. The temporal trends were represented by the estimated annual percentage change (EAPC). Results: In 2019, there were 438 thousand deaths and 16.6 million DALYs attributable to LBMD, increasing by 111.1% and 93.8% respectively, compared to that in 1990. From 1990 to 2019, the prevalence of LBMD has decreased worldwide, but has increased in high-income North America. Some countries, such as the United States, Australia, Canada, and China had increased disability and mortality rates of LBMD with time. Countries with low socio-demographic index (SDI) had higher incidence and mortality rate than those with high SDI. The prevalence of LBMD was lower in males, but the attributable disability and mortality were higher in males in all years from 1990 to 2019. Conclusion: With population aging, countries worldwide, especially those with low-SDI, will face increasing challenges in reducing the burden attributable to LBMD and osteoporosis. The treatment of osteoporosis has been overlooked in men for a long time. Effective measures are warranted to control the prevalence and burden of LBMD.

Targeting TNF-α for COVID-19: Recent Advanced and Controversies.

Recent advances in the pathophysiologic understanding of coronavirus disease 2019 (COVID-19) suggests that cytokine release syndrome (CRS) has an association with the severity of disease, which is characterized by increased tumor necrosis factor α (TNF-α), interleukin (IL)-6, IL-2, IL-7, and IL-10. Hence, managing CRS has been recommended for rescuing severe COVID-19 patients. TNF-α, one of the pro-inflammatory cytokines commonly upregulated in acute lung injury, triggers CRS and facilitates SARS-CoV-2 interaction with angiotensin-converting enzyme 2 (ACE2). TNF-α inhibitors, therefore, may serve as an effective therapeutic strategy for attenuating disease progression in severe SARS-CoV-2 infection. Below, we review the possibilities and challenges of targeting the TNF-α pathway in COVID-19 treatment.

Clinical Applications of Liquid Biopsy in Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) is a common malignant tumor with high mortality and poor prognosis in the world. The low rate of early diagnosis, as well as the high risk of postoperative metastasis and recurrence, led to the poor clinical prognosis of HCC patients. Currently, it mainly depends on serum markers, imaging examination, and tissue biopsy to diagnose and determine the recurrence and metastasis of HCC after treatments. Nevertheless, the accuracy and sensitivity of serum markers and imaging for early HCC diagnosis are suboptimal. Tissue biopsy, containing limited tissue samples, is insufficient to reveal comprehensive tumor biology information and is inappropriate to monitor dynamic tumor progression due to its invasiveness. Thus, low invasive diagnostic methods and novel biomarkers with high sensitivity and reliability must be found to improve HCC detection and prediction. As a non-invasive, dynamic, and repeatable detection method, "liquid biopsy", has attracted much attention to early diagnosis and monitoring of treatment response, which promotes the progress of precision medicine. This review summarizes the clinical applications of liquid biopsy in HCC, including circulating tumor cells (CTCs), circulating tumor DNA (ctDNA), and exosome in early diagnosis, prognostic evaluation, disease monitoring, and guiding personalized treatment.

Galectin-3 in Microglia-Mediated Neuroinflammation: Implications for Central Nervous System Diseases.

Microglial activation is one of the common hallmarks shared by various central nervous system (CNS) diseases. Based on surrounding circumstances, activated microglia play either detrimental or neuroprotective effects. Galectin-3 (Gal-3), a group of ß-galactoside-binding proteins, has been cumulatively revealed to be a crucial biomarker for microglial activation after injuries or diseases. In consideration of the important role of Gal-3 in the regulation of microglial activation, it might be a potential target for the treatment of CNS diseases. Recently, Gal-3 expression has been extensively investigated in numerous pathological processes as a mediator of neuroinflammation, as well as in cell proliferation. However, the underlying mechanisms of Gal-3 involved in microgliamediated neuroinflammation in various CNS diseases remain to be further investigated. Moreover, several clinical studies support that the levels of Gal-3 are increased in the serum or cerebrospinal fluid of patients with CNS diseases. Thus, we summarized the roles and underlying mechanisms of Gal-3 in activated microglia, thus providing a better insight into its complexity expression pattern, and contrasting functions in CNS diseases.

Wnt signaling: A prospective therapeutic target for chronic pain.

Despite the rapid advance over the past decades to design effective therapeutic pharmacological interventions, chronic pain remains to be an unresolved healthcare concern. Long term use of opioids, the first line analgesics, often causes detrimental side effects. Therefore, a profound understanding of the mechanisms underlying the development and maintenance of chronic pain states is urgently needed for the management of chronic pain. Substantial evidence indicates aberrant activation of Wnt signaling pathways in sciatic nerve, dorsal root ganglia and spinal cord dorsal horn in rodent models of chronic pain. Moreover, growing evidence shows that pharmacological blockage of aberrant activation of Wnt signaling pathways attenuates pain behaviors in animal models of chronic pain. Importantly, both intrathecal injection of Wnt agonists and Wnt ligands to naïve rats lead to the development of mechanical allodynia, which was inhibited by Wnt inhibitors. In this review, we summarized and discussed the therapeutic potential of pharmacological inhibitors of Wnt signaling in chronic pain in preclinical studies. These evidence showed that aberrant activation of Wnt signaling pathways contributed to chronic pain via enhancing neuroinflammation, regulating synaptic plasticity and reducing intraepidermal nerve fiber density. However, these findings raise further questions. Overall, despite the future challenges, these pioneering studies suggest that Wnt signaling is a promising therapeutic target for chronic pain.

STING/NF-κB/IL-6-Mediated Inflammation in Microglia Contributes to Spared Nerve Injury (SNI)-Induced Pain Initiation.

Innate immune response acts as the first line of host defense against damage and is initiated following the recognition of pathogen-associated molecular patterns (PAMPs). For double-stranded DNA (dsDNA) sensing, interferon gene stimulator (STING) was discovered to be an integral sensor and could mediate the immune and inflammatory response. Selective STING antagonist C-176 was administered and pain behaviors were assessed following spared nerve injury (SNI)-induced neuropathic pain. The level of serum dsDNA following neuropathic pain was assessed using Elisa analysis. STING signaling pathway, microglia activation, and proinflammatory cytokines were assessed by qPCR, western blots, Elisa, and immunofluorescence staining. STING agonist DMXAA was introduced into BV-2 cells to assess the inflammatory response in microglial cells. dsDNA was significantly increased following SNI and STING/TANK-binding kinase 1 (TBK1)/nuclear factor-kappa B (NF-κB) pathway was activated in vivo and vitro. Early but not the late intrathecal injection of C-176 attenuated SNI-induced pain hypersensitivity, microglia activation, proinflammatory factors, and phosphorylated JAK2/STAT3 in the spinal cord dorsal horn, and the analgesic effect of C-176 was greatly abolished by recombinant IL-6 following SNI. We provided evidence clarifying dsDNA mediated activation of microglia STING signaling pathway, after which promoting expression of proinflammatory cytokines that are required for hyperalgesia initiation in the spinal cord dorsal horn of SNI model. Further analysis showed that microglial STING/TBK1/NF-κB may contribute to pain initiation via IL-6 signaling. Pharmacological blockade of STING may be a promising target in the treatment of initiation of neuropathic pain.

ß2-adrenoreceptor agonist ameliorates mechanical allodynia in paclitaxel-induced neuropathic pain via induction of mitochondrial biogenesis.

Chemotherapy-induced neuropathic pain is a debilitating and common side effect of cancer treatment and so far no effective drug is available for treatment of the serious side effect. Previous studies have demonstrated ß2-adrenoreceptor (ADRB2) agonists can attenuate neuropathic pain. However, the role of ADRB2 in paclitaxel -induced neuropathic pain (PINP) remains unclear. In this study, we investigated the effect of formoterol, a long-acting ADRB2 agonist, and related mechanisms in PINP. A rat model of PINP was established by intraperitoneal injection of paclitaxel (2 mg/kg) every other day with a final cumulative dose of 8 mg/kg. Hind paw withdrawal thresholds (PWTs) in response to von Frey filament stimuli were used to evaluate mechanical allodynia. Western blot was used to examine the expression of ADRB2, peroxisome proliferator-activated receptor coactivator-1α (PGC-1α), nuclear respiratory factors 1 (NRF1) and mitochondrial transcription factor A (TFAM) and the immunofluorescence was to detect the cellular localization of ADRB2 and PGC-1α in the spinal cord. Moreover, we measured mitochondrial DNA (mtDNA) copy number by qPCR. In our study, formoterol attenuated established PINP and delayed the onset of PINP. Formoterol restored ADRB2 expression as well as mtDNA copy number and PGC-1α, NRF1, and TFAM protein expression, which are major genes involved in mitochondrial biogenesis, in the spinal cord of PINP rats. Moreover, we found the analgesic effect of formoterol against PINP was partially abolished by PGC-1α inhibitor SR-18292. Collectively, these results demonstrated the activation of ADRB2 with formoterol ameliorates PINP at least partially through induction of mitochondrial biogenesis.