Dimethyl Fumarate Attenuates Pain Behaviors in Osteoarthritis Rats via Induction of Nrf2-Mediated Mitochondrial Biogenesis

The role and intervention of mitochondrial metabolism in osteoarthritis

Osteoarthritis (OA), a prevalent degenerative joint disease, affects a substantial global population. Despite the elusive etiology of OA, recent investigations have implicated mitochondrial dysfunction as a significant factor in disease pathogenesis. Mitochondria, pivotal cellular organelles accountable for energy production, exert essential roles in cellular metabolism. Hence, mitochondrial dysfunction can exert broad-ranging effects on various cellular processes implicated in OA development. This comprehensive review aims to provide an overview of the metabolic alterations occurring in OA and elucidate the diverse mechanisms through which mitochondrial dysfunction can contribute to OA pathogenesis. These mechanisms encompass heightened oxidative stress and inflammation, perturbed chondrocyte metabolism, and compromised autophagy. Furthermore, this review will explore potential interventions targeting mitochondrial metabolism as means to impede or decelerate the progression of OA. In summary, this review offers a comprehensive understanding of the involvement of mitochondrial metabolism in OA and underscores prospective intervention strategies.

Intraarticular monomethyl fumarate as a perspective therapy for osteoarthritis by macrophage polarization

BACKGROUND

Osteoarthritis (OA) is a chronic disease that may lead to joint structure degeneration, cartilage destruction, osteophyte formation, subchondral bone disruption, and pain. In this scenario, a higher proportion of the proinflammatory macrophage type 1 (M1) than the anti-inflammatory macrophage type 2 (M2) could be highlighted as a hallmark of OA progression. The balance between these two macrophage types emerges as a new therapeutic target in OA. This study aimed to evaluate the analgesia and macrophage profile in the treatment of experimental osteoarthritis (EOA) with systemic dimethyl fumarate (DMF) or local intra-articular monomethyl fumarate (MMF).

RESULTS

DMF via gavage or MMF via intra-articular in the right knee of EOA rats showed improvements in gait parameters and the nociceptive recovery of the mechanical threshold assessment by adapted electronic von Frey treatment on the twenty-first day (long-lasting phase). DMF treatment decreased proinflammatory TNF-α while increasing anti-inflammatory IL-10 cytokines from the macerated capsule on the fifth day (inflammatory phase). MMF treatment showed joint capsule mRNA extraction downregulating iNOS and TNF-α gene expression while upregulating IL-10 and MCP-1. However, CD206 was not significant but higher than untreated EOA rats' joints on the seventh day (inflammatory phase).

CONCLUSIONS

Our studies with EOA model induced by MIA suggest a new perspective for human treatment committed with OA based on macrophage polarization as a therapeutic target, switching the proinflammatory profile M1 to the anti-inflammatory profile M2 with DMF systematic or by MMF locally treatment according to the OA severity.

PGC-1α activation ameliorates cancer-induced bone pain via inhibiting apoptosis of GABAergic interneurons

Cancer-induced bone pain (CIBP) stands out as one of the most challenging issues in clinical practice due to its intricate and not fully elucidated pathophysiological mechanisms. Existing evidence has pointed toward the significance of peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) down-regulation in contributing to pain behaviors in various rodent models of neuropathic pain. In our current study, we aimed to investigate the role of PGC-1α in CIBP. Our results unveiled a reduction in PGC-1α expression within the spinal cord of CIBP rats, particularly in GABAergic interneurons. Notably, intrathecal administration of the PGC-1α activator ZLN005 suppressed the loss of spinal GABAergic interneurons. This suppression was achieved by inhibiting caspase-3-mediated apoptosis, ultimately leading to the alleviation of mechanical allodynia in CIBP rats. Further exploration into the mechanism revealed that PGC-1α activation played a pivotal role in mitigating ATP depletion and reactive oxygen species accumulation linked to mitochondrial dysfunction. This was achieved through the restoration of mitochondrial biogenesis and the activation of the SIRT3-SOD2 pathway. Impressively, the observed effects were prominently reversed upon the application of SR18292, a specific PGC-1α inhibitor. In conclusion, our findings strongly suggest that PGC-1α activation acts as a potent inhibitor of apoptosis in spinal GABAergic interneurons. This inhibition is mediated by the improvement of mitochondrial function, facilitated in part through the enhancement of mitochondrial biogenesis and the activation of the SIRT3-SOD2 pathway. The results of our study shed light on potential therapeutic avenues for addressing CIBP.

Anti-Osteoarthritis Mechanism of the Nrf2 Signaling Pathway

Osteoarthritis (OA) is a chronic degenerative disease and the primary pathogenic consequence of OA is inflammation, which can affect a variety of tissues including the synovial membrane, articular cartilage, and subchondral bone. The development of the intra-articular microenvironment can be significantly influenced by the shift of synovial macrophages between pro-inflammatory and anti-inflammatory phenotypes. By regulating macrophage inflammatory responses, the NF-κB signaling route is essential in the therapy of OA; whereas, the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway appears to manage the relationship between oxidative stress and inflammation. Additionally, it has been demonstrated that under oxidative stress and inflammation, there is a significant interaction between transcriptional pathways involving Nrf2 and NF-κB. Studying how Nrf2 signaling affects inflammation and cellular metabolism may help us understand how to treat OA by reprogramming macrophage behavior because Nrf2 signaling is thought to affect cellular metabolism. The candidates for treating OA by promoting an anti-inflammatory mechanism by activating Nrf2 are also reviewed in this paper.

The Inhibition of Neuropathic Pain Incited by Nerve Injury and Accompanying Mood Disorders by New Heme Oxygenase-1 Inducers: Mechanisms Implicated

Neuropathic pain is a type of pain that persists for a long time and becomes pathological. Additionally, the anxiodepressive disorders derived from neuropathic pain are difficult to palliate with the current treatments and need to be resolved. Then, using male mice with neuropathic pain provoked by chronic constriction of the sciatic nerve (CCI), we analyzed and compared the analgesic actions produced by three new heme oxygenase 1 (HO-1) inducers, 1m, 1b, and 1a, with those performed by dimethyl fumarate (DMF). Their impact on the anxiety- and depressive-like comportments and the expression of the inflammasome NLRP3, Nrf2, and some antioxidant enzymes in the dorsal root ganglia (DRG) and amygdala (AMG) were also investigated. Results revealed that the administration of 1m, 1b, and DMF given orally for four days inhibited the allodynia and hyperalgesia caused by CCI, while 1a merely reduced the mechanical allodynia. However, in the first two days of treatment, the antiallodynic effects produced by 1m were higher than those of 1a and DMF, and its antihyperalgesic actions were greater than those produced by 1b, 1a, and DMF, revealing that 1m was the most effective compound. At four days of treatment, all drugs exerted anxiolytic and antidepressant effects, decreased the NLRP3 levels, and increased/normalized the Nrf2, HO-1, and superoxide dismutase 1 levels in DRG and AMG. Data indicated that the dual modulation of the antioxidant and inflammatory pathways produced by these compounds, especially 1m, is a new promising therapeutic approach for neuropathic pain and related emotional illnesses.

Novel Heme Oxygenase-1 Inducers Palliate Inflammatory Pain and Emotional Disorders by Regulating NLRP3 Inflammasome and Activating the Antioxidant Pathway

Chronic pain caused by persistent inflammation is current in multiple diseases and has a strong negative impact on society. It is commonly associated with several mental illnesses, which can exert a negative influence on pain perception, and needs to be eradicated. Nevertheless, actual therapies are not sufficiently safe and effective. Recent reports demonstrate that the induction of heme oxygenase-1 (HO-1) enzyme produces analgesic effects in animals with osteoarthritis pain and reverses the grip strength loss caused by sciatic nerve crush. In this research, we evaluated the potential use of three new HO-1 inducers, 1m, 1a, and 1b, as well as dimethyl fumarate (DMF), for treating persistent inflammatory pain induced by the subplantar injection of complete Freud's adjuvant and the functional deficits and emotional sickness associated. The modulator role of these treatments on the inflammatory and antioxidant pathways were also assessed. Our findings revealed that repeated treatment, for four days, with 1m, 1a, 1b, or DMF inhibited inflammatory pain, reversed grip strength deficits, and reversed the linked anxious- and depressive-like behaviors, with 1m being the most effective. These treatments also suppressed the up-regulation of the inflammasome NLRP3 and activated the expression of the Nrf2 transcription factor and the HO-1 and superoxide dismutase 1 enzymes in the paw and/or amygdala, thus revealing the anti-inflammatory and antioxidant capacity of these compounds during inflammatory pain. Results suggest the use of 1m, 1a, 1b, and DMF, particularly 1m, as promising therapies for inflammatory pain and the accompanying functional disabilities and emotional diseases.

Dioscin alleviates the progression of osteoarthritis: an in vitro and in vivo study

Osteoarthritis (OA) is a common joint disease and is the main cause of physical disability in the elderly. Currently, there is no adequate therapeutic strategy to reverse the progression of OA. Many natural plant extracts have received attention in the treatment of OA due to their potential anti-inflammatory properties, and reduced incidence of adverse events. Dioscin (Dio), a natural steroid saponin, has been demonstrated to inhibit the release of inflammatory cytokines in mouse and rat models of various diseases, and has a protective effect in chronic inflammatory diseases. However, whether Dio alleviates OA progression remains to be explored. In this research, our purposes were to investigate the therapeutic potential of Dio in OA. The results demonstrated that Dio exerted anti-inflammatory effects by repressing NO, PGE₂, iNOS and COX-2. Moreover, the application of Dio could repress IL-1β-induced overexpression of matrix metalloproteinases (MMPs, including MMP1, MMP3, and MMP13) and ADAMTS-5, and improve the synthesis of collagen II and aggrecan, which contribute to the maintenance of chondrocyte matrix homeostasis. The underlying mechanism involved the inhibition of the MAPK and NF-κB signaling pathways by Dio. Furthermore, the treatment of Dio significantly improved the pain behaviors of rat OA models. The in vivo study revealed that Dio could ameliorate cartilage erosion and degradation. These results collectively indicate that Dio can be used as a promising and effective agent for the therapy of OA.

PGC-1α in osteoarthritic chondrocytes: From mechanism to target of action

Osteoarthritis (OA) is one of the most common degenerative joint diseases, often involving the entire joint. The degeneration of articular cartilage is an important feature of OA, and there is growing evidence that the mitochondrial biogenesis master regulator peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) exert a chondroprotective effect. PGC-1α delays the development and progression of OA by affecting mitochondrial biogenesis, oxidative stress, mitophagy and mitochondrial DNA (mtDNA) replication in chondrocytes. In addition, PGC-1α can regulate the metabolic abnormalities of OA chondrocytes and inhibit chondrocyte apoptosis. In this paper, we review the regulatory mechanisms of PGC-1α and its effects on OA chondrocytes, and introduce potential drugs and novel nanohybrid for the treatment of OA which act by affecting the activity of PGC-1α. This information will help to further elucidate the pathogenesis of OA and provide new ideas for the development of therapeutic strategies for OA.