Accepted

Osteoarthritis (OA) is a major cause of pain and disability worldwide. Despite the relatively high burden of the disease, the currently available non-surgical treatment options are directed towards symptomatic relief. Therefore, we propose the use of alendronate as a disease modifying agent to help slow and prevent OA. In addition, this study will utilize Whole-Organ Magnetic Resonance Imaging Score (WORMS) to evaluate the structural integrity of cartilage in the study population. High-quality evidence, limited to a few well-conducted randomized trials, highlights contradictory results on the effect of bisphosphonates on knee function and progression of OA. Therefore, a placebo-controlled, randomized trial is needed to evaluate the combined effect of alendronate and vit D on the structure of cartilage utilizing the WORMS score and its ability to treat knee pain in OA patients.

High-mobility group box 1 (HMGB1) is a nonhistone nuclear protein, the functions of which depend on its subcellular location. It is actively or passively secreted into the blood and/or cerebrospinal fluid (CSF) and can be used as a prognostic indicator of disease. HMGB1 released into the bloodstream can cause pathological reactions in distant organs, and entry into the CSF can destroy the blood-brain barrier and aggravate brain injuries. HMGB1 expression has been reported to be increased in the tissues of spinal cord injury (SCI) patients and involved in the regulation of neuroinflammation, neuronal apoptosis, and ferroptosis. SCI can lead to brain changes, resulting in neuropathic pain, depression, and cognitive dysfunction, but the specific mechanism is unknown. It remains unclear whether HMGB1 plays an important role in brain functional remodeling after SCI. Damaged cells at the site of SCI passively release HMGB1, which travels to the brain via the blood, CSF, and/or axonal transport, destroys the blood-brain barrier, and causes pathological changes in the brain. This may explain the remodeling of brain function that occurs after SCI. In this minireview, we introduce the structure and function of HMGB1 and its mechanism of action in SCI. Clarifying the functions of HMGB1 may provide insight into the links between SCI and various brain regions.

The analysis of the public interest as reflected by Internet queries has become a highly valuable tool in many fields. The Google Trends platform, providing timely and informative data, has become increasingly popular in health and medical studies. This study explores whether Internet search frequencies for the keyword "headache" have been increasing after the COVID-19 pandemic outbreak, which could signal an increased incidence of the health problem. Weekly search volume data for 5 years spanning February 2017 to February 2022 were sourced from Google Trends. Six statistical and machine-learning methods were implemented on training and testing sets via pre-set automated forecasting algorithms. Holt-Winters has been identified as overperforming in predicting web query trends through several accuracy measures and the DM test for forecasting superiority and has been employed for producing the baseline level in the estimation of excess query level over the first pandemic wave. Findings indicate that the COVID-19 pandemic resulted in an increased global incidence of headache (as proxied by related web queries) in the first 6 months after its outbreak, with an excess occurrence of 4.53% globally. However, the study also concludes that the increasing trend in headache incidence at the world level would have continued in the absence of the pandemic, but it has been accelerated by the pandemic event. Results further show mixed correlations at the country-level between COVID-19 infection rates and population web-search behavior, suggesting that the increased headache incidence is caused by pandemic-related factors (i.e. increased stress and mental health problems), rather than a direct effect of coronavirus infections. Other noteworthy findings entail that in the Philippines, the term "headache" was the most frequently searched term in the period spanning February 2020 to February 2022, indicating that headache occurrences are a significant aspect that defines population health at the country level. High relative interest is also detected in Kenya and South Africa after the pandemic outbreak. Additionally, research findings indicate that the relative interest has decreased in some countries (i.e. US, Canada, and Australia), whereas it has increased in others (i.e. India and Pakistan) after the pandemic outbreak. We conclude that observing Internet search habits can provide timely information for policymakers on collective health trends, as opposed to ex-post statistics, and can furthermore yield valuable information for the pain management drug market key players about aggregate consumer behavior.

Inhibition of cathepsin D (Cat D) sensitizes cancer cells to anticancer drugs via RNF183-mediated downregulation of Bcl-xL expression. Although NF-κB activation is involved in the upregulation of RNF183 expression, the molecular mechanism of NF-κB activation by Cat D inhibition is unknown. We conducted this study to investigate the molecular mechanism underlying Cat D-mediated NF-κB activation. Interestingly, Cat D inhibition-induced IκB degradation in an autophagy-dependent manner. Knockdown of autophagy-related genes (ATG7 and Beclin1) and lysosome inhibitors (chloroquine and bafilomycin A1) blocked IκB degradation via Cat D inhibition. Itch induced K63-linked ubiquitination of IκB and then modulated the protein stability of IκB by Cat D inhibition. Inhibition of Cat D-mediated Itch activation was modulated by the JNK signaling pathway, and phosphorylated Itch could bind to IκB, resulting in polyubiquitination of IκB. Additionally, inhibition of Cat D increased autophagy flux via activation of the LKB1-AMPK-ULK1 pathway. Therefore, our results suggested that Cat D inhibition activated NF-κB signaling via degradation of autophagy-dependent IκB, which is associated with the upregulation of RNF183, an E3 ligase of Bcl-xL. Cat D inhibition enhances TRAIL-induced apoptosis through Bcl-xL degradation via upregulation of RNF183.

Primary and secondary hyperalgesia develop in response to chronic joint inflammation due to peripheral and central mechanisms. Synovial macrophage and spinal microglia are involved in pain sensitization in arthritis. The level of angiotensin II type 2 receptor (ATR) is related to the severity of arthritis. This study aimed to determine the role of ATR in primary and secondary hyperalgesia in joint inflammatory pain in mice. After intra-articular CFA injection, primary hyperalgesia in the ipsilateral knee joint was measured by pressure application meter and gait analysis, secondary hypersensitivity in ipsilateral hind-paw was measured by von-Frey and Hargreaves tests following a combination of global ATR-deficient (Agtr2) mice and ATR pharmacological agonist C21. Synovial macrophage and spinal microglia were collected for flow cytometry. Morphological reconstruction of microglia was detected by immunostaining. ATR expression was investigated by quantitative polymerase chain reaction and western blot. Neuronal hyperactivity was evaluated by c-Fos and CGRP immunostaining. We found that pain hypersensitivity and synovial inflammation in Agtr2 mice were significantly exacerbated compared with wild-type mice; conversely, systemically administrated C21 attenuated both of the symptoms. Additionally, spinal microglia were activated, and an abundant increase of spinal ATR was expressed on activated microglia in response to peripheral joint inflammation. Intrathecally-administrated C21 reversed the secondary hypersensitivity, accompanied by alleviation of spinal microglial activation, spinal neuronal hyperactivity, and calcitonin gene-related peptide content. These findings revealed a beneficial role of ATR activating stimulation against pain hypersensitivity in joint inflammatory pain via direct modulation of synovial macrophage and spinal microglial activity.

Human pluripotent stem cells (hPSCs) show promise for studying diseases affecting cell populations that are not easily available, including sensory neurons (SNs). Here, we present a differentiation protocol in chemically defined conditions to generate peripheral SNs from hPSCs. We describe four main steps: expansion of hPSCs, neural crest cell (NCC) differentiation, NCC dissociation and replating, and sensory neuron (SN) differentiation. This protocol enables generation of a mechanoreceptor-enriched culture or a population containing all three SN subtypes (nociceptors, mechanoreceptors, and proprioceptors). For complete details on the use and execution of this protocol, please refer to Saito-Diaz et al. (2021).

The International Association for the Study of Pain (IASP) has defined pain as an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage, which also comprises a subjective component […].

Pannexin 1 (Panx1) is involved in the spinal central sensitization process in rats with neuropathic pain, but its interaction with well-known, pain-related, ligand-dependent receptors, such as NMDA receptors (NMDAR) and P2X7 purinoceptors (P2X7R), remains largely unexplored. Here, we studied whether NMDAR- and P2X7R-dependent nociceptive signaling in neuropathic rats require the activation of Panx1 channels to generate spinal central sensitization, as assessed by behavioral (mechanical hyperalgesia) and electrophysiological (C-reflex wind-up potentiation) indexes. Administration of either a selective NMDAR agonist i.t. (NMDA, 2 mM) or a P2X7R agonist (BzATP, 150 μM) significantly increased both the mechanical hyperalgesia and the C-reflex wind-up potentiation, effects that were rapidly reversed (minutes) by i.t. administration of a selective pannexin 1 antagonist (10panx peptide, 300 μM), with the scores even reaching values of rats without neuropathy. Accordingly, 300 μM 10panx completely prevented the effects of NMDA and BzATP administered 1 h later, on mechanical hyperalgesia and C-reflex wind-up potentiation. Confocal immunofluorescence imaging revealed coexpression of Panx1 with NeuN protein in intrinsic dorsal horn neurons of neuropathic rats. The results indicate that both NMDAR- and P2X7R-mediated increases in mechanical hyperalgesia and C-reflex wind-up potentiation require neuronal Panx1 channel activation to initiate and maintain nociceptive signaling in neuropathic rats.