Canonical and non-canonical mechanisms of Nrf2 activation

Synthesis and pharmacological evaluation of novel N-aryl-cinnamoyl-hydrazone hybrids designed as neuroprotective agents for the treatment of Parkinson's disease

Molecular hybridization between structural fragments from the structures of curcumin (1) and resveratrol (2) was used as a designing tool to generate a new N-acyl-cinnamoyl-hydrazone hybrid molecular architecture. Twenty-eight new compounds were synthesized and evaluated for multifunctional activities related to Parkinson's disease (PD), including neuroprotection, antioxidant, metal chelating ability, and Keap1/Nrf2 pathway activation. Compounds 3b (PQM-161) and 3e (PQM-164) were highlighted for their significant antioxidant profile, acting directly as induced free radical stabilizers by DPPH and indirectly by modulating intracellular inhibition of t-BOOH-induced ROS formation in neuronal cells. The mechanism of action was determined as a result of Keap1/Nrf2 pathway activation by both compounds and confirmed by different experiments. Furthermore, compound 3e (PQM-164) exhibited a significant effect on the accumulation of α-synuclein and anti-inflammatory activity, leading to an expressive decrease in gene expression of iNOS, IL-1β, and TNF-α. Overall, these results highlighted compound 3e as a promising and innovative multifunctional drug prototype candidate for PD treatment.

Curcumin inhibits PAT-induced renal ferroptosis via the p62/Keap1/Nrf2 signalling pathway

Patulin (PAT), the most common mycotoxin, is widespread in foods and beverages which poses a serious food safety issue to human health. Our previous research confirmed that exposure to PAT can lead to acute kidney injury (AKI). Curcumin is the most abundant active ingredient in turmeric rhizome with various biological activities. The aim of this study is to investigate whether curcumin can prevent the renal injury caused by PAT, and to explore potential mechanisms. In vivo, supplementation with curcumin attenuated PAT-induced ferroptosis. Mechanically, curcumin inhibited autophagy, led to the accumulation of p62 and its interaction with Keap1, promoted the nuclear translocation of nuclear factor E2 related factor 2 (Nrf2), and increased the expression of antioxidant stress factors in the process of ferroptosis. These results have also been confirmed in HKC cell experiments. Furthermore, knockdown of Nrf2 in HKC cells abrogated the protective effect of curcumin on ferroptosis. In conclusion, we confirmed that curcumin mitigated PAT-induced AKI by inhibiting ferroptosis via activation of the p62/Keap1/Nrf2 pathway. This study provides new potential targets and ideas for the prevention and treatment of PAT.

The emerging roles of hydrogen sulfide in ferroptosis

SIGNIFICANCE

Ferroptosis, a form of regulated cell death characterized by a large amount of lipid peroxidation-mediated membrane damage, joins the evolution of multisystem diseases. For instance, neurodegenerative diseases, chronic obstructive pulmonary disease and acute respiratory distress syndrome, osteoporosis and osteoarthritis, and so on. Since being identified as the third gasotransmitter in living organisms, the intricate role of hydrogen sulfide (H2S) in ferroptosis has emerged at the forefront of research.

RECENT ADVANCES

The discovery of novel targets in the relevant metabolic pathways, including transferrin receptor 1, cystine/glutamate antiporter, and others, coupled with the exploration of new signaling pathways, particularly the p53 signaling pathway and the nitric oxide / nuclear factor erythroid 2-related factor 2 signaling pathway, and so on. Many diseases such as emphysema and airway inflammation, myocardial diseases, endothelial dysfunction in aging arteries, and traumatic brain injury have recently been found to be alleviated directly by H2S inhibition of ferroptosis. Safe, effective, and tolerable novel H2S donors have been developed and have shown promising results in phase I clinical trials.

CRITICAL ISSUES

Complicated crosstalk between ferroptosis signaling pathway and oncogenic factors results in the risk of cancer when inhibiting ferroptosis. Notably, targeted delivery of H2S is still a challenging task.

FUTURE DIRECTIONS

Discovering more reliable and stable novel H2S donors and achieving their targeted delivery will enable further clinical trials for diseases associated with ferroptosis inhibition by H2S, determining their safety, efficacy, and tolerance.

NRF2 Signaling Pathway in Chemo/Radio/Immuno-Therapy Resistance of Lung Cancer: Looking Beyond the Tip of the Iceberg

Lung cancer is one of the most common causes of cancer death in men and women worldwide. Various combinations of surgery, chemotherapy, radiation therapy and immunotherapy are currently used to treat lung cancer. However, the prognosis remains relatively poor due to the higher frequency of tumor mutational burden (TMB). Nuclear factor E2-related factor 2 (NFE2L2/NRF2) is often considered a primary regulator of the expression of antioxidant enzymes and detoxification proteins and is involved in cytoprotection. On the contrary, NRF2 is even known to induce metastasis and support tumor progression. Kelch-like ECH-associated protein 1 (KEAP1) plays an important role in negatively regulating NRF2 activity via CUL3-mediated ubiquitinylation and successive proteasomal degradation. Extensive research has shown that the genetic alterations of KEAP1/NFE2L2/CUL3 genes lead to increased expression of NRF2 and its target genes in lung cancer. Thus, these studies provide ample evidence for the dual role of NRF2 in lung cancer. In this review, we discussed the mechanistic insights into the role of NRF2 signaling in therapy resistance by focusing on cell lines, mouse models, and translational studies in lung cancer. Finally, we highlighted the potential therapeutic strategies targeting NRF2 inhibition, followed by the discussion of biomarkers related to NRF2 activity in lung cancer. Overall, our article exclusively discusses in detail the NRF2 signaling pathway in resistance to therapy, especially immunotherapy, and its therapeutic avenue in the treatment of lung cancer.

Tanshinone IIA positively regulates the Keap1-Nrf2 system to alleviate pulmonary fibrosis via the sestrin2-sqstm1 signaling axis-mediated autophagy

BACKGROUND

Activation of myofibroblasts, linked to oxidative stress, emerges as a pivotal role in the progression of pulmonary fibrosis (PF). Our prior research has underscored the therapeutic promise of tanshinone IIA (Tan-IIA) in mitigating PF by enhancing nuclear factor-erythroid 2-related factor 2 (Nrf2) activity. Nevertheless, the molecular basis through which Tan-IIA influences Nrf2 activity has yet to be fully elucidated.

METHODS

The influence of Tan-IIA on PF was assessed in vivo and in vitro models. Inhibitors, overexpression plasmids, and small interfering RNA (siRNA) were utilized to probe its underlying mechanism of action in vitro.

RESULTS

We demonstrate that Tan-IIA effectively activates the kelch-like ECH-associated protein 1 (Keap1)-Nrf2 antioxidant pathway, which in turn inhibits myofibroblast activation and ameliorates PF. Notably, the stability and nucleo-cytoplasmic shuttling of Nrf2 is shown to be dependent on augmented autophagic flux, which is in alignment with the observation that Tan-IIA induces autophagy. Inhibition of autophagy, conversely, fosters the activation of extracellular matrix (ECM)-producing myofibroblasts. Further, Tan-IIA initiates an autophagy program through the sestrin 2 (Sesn2)-sequestosome 1 (Sqstm1) signaling axis, crucial for protecting Nrf2 from Keap1-mediated degradation. Meanwhile, these findings were corroborated in a murine model of PF.

CONCLUSION

Collectively, we observed for the first time that the Sqstm1-Sesn2 axis-mediated autophagic degradation of Keap1 effectively prevents myofibroblast activation and reduces the synthesis of ECM. This autophagy-dependent degradation of Keap1 can be initiated by the Tan-IIA treatment, which solidifies its potential as an Nrf2-modulating agent for PF treatment.

Targeting Nrf2 by bioactive peptides alleviate inflammation: expanding the role of gut microbiota and metabolites

Inflammation is a complex process that usually refers to the general response of the body to the harmful stimuli of various pathogens, tissue damage, or exogenous pollutants. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor that regulates cellular defense against oxidative damage and toxicity by expressing genes related to oxidative stress response and drug detoxification. In addition to its antioxidant properties, Nrf2 is involved in many other important physiological processes, including inflammation and metabolism. Nrf2 can bind the promoters of antioxidant genes and upregulates their expressions, which alleviate oxidation-induced inflammation. Nrf2 has been shown to upregulate heme oxygenase-1 expression, which promotes NF-κB activation and is closely related with inflammation. Nrf2, as a key factor in antioxidant response, is closely related to the expressions of pro-inflammatory factors, NF-κB pathway and cell metabolism. Bioactive peptides come from a wide range of sources and have many biological functions. Increasing evidence indicates that bioactive peptides have potential anti-inflammatory activities. This article summarized the sources, absorption and utilization of bioactive peptides and their role in alleviating inflammation via Nrf2 pathway. Bioactive peptides can also regulate gut microbiota and alter metabolites, which regulates the Nrf2 pathway through novel pathway and supplement the anti-inflammatory mechanisms of bioactive peptides. This review provides a reference for further study on the anti-inflammatory effect of bioactive peptides and the development and utilization of functional foods.

The Role of Nrf2 in the Regulation of Mitochondrial Function and Ferroptosis in Pancreatic Cancer

The transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) represents the master regulator of the cellular antioxidant response and plays a critical role in tumorigenesis. This includes a preventive effect of Nrf2 on cell death through ferroptosis, which represents an essential mechanism of therapy resistance in malignant tumors, such as pancreatic ductal adenocarcinoma (PDAC) as one of the most aggressive and still incurable tumors. Addressing this issue, we provide an overview on Nrf2 mediated antioxidant response with particular emphasis on its effect on mitochondria as the organelle responsible for the execution of ferroptosis. We further outline how deregulated Nrf2 adds to the progression and therapy resistance of PDAC, especially with respect to the role of ferroptosis in anti-cancer drug mediated cell killing and how this is impaired by Nrf2 as an essential mechanism of drug resistance. Our review further discusses recent approaches for Nrf2 inhibition by natural and synthetic compounds to overcome drug resistance based on enhanced ferroptosis. Finally, we provide an outlook on therapeutic strategies based on Nrf2 inhibition combined with ferroptosis inducing drugs.

Mitigation of cisplatin-induced cardiotoxicity by Isorhamnetin: Mechanistic insights into oxidative stress, inflammation, and apoptosis modulation

The flavonoid compound Isorhamnetin (IRMN) is known for its considerable pharmacological properties, which include antioxidant and anti-inflammatory effects, as well as significant protective actions on heart health. However, the potential of IRMN to guard against heart damage caused by cisplatin (CP), a common chemotherapeutic agent, and the specific mechanisms involved, remain unexplored areas. This research was designed to investigate how IRMN counters CP-induced heart toxicity. In our study, mice were orally given IRMN at 50 or 150 mg/kg/day for a week, followed by CP injections (5 mg/kg/day) on the third and sixth days. The animals were euthanized under sodium pentobarbital anesthesia (50 mg/kg, intraperitoneally) on the eighth day to collect blood and heart tissues for further examination. Our findings reveal that IRMN administration significantly reduced the heart damage and the elevation of heart injury markers such as cardiac troponin I, creatine kinase, and lactate dehydrogenase induced by CP. IRMN also effectively lowered oxidative stress markers, including reactive oxygen species and malondialdehyde, while boosting ATP production and antioxidants like superoxide dismutase, catalase, and glutathione. The compound's capability to diminish the levels of pro-inflammatory cytokines like tumor necrosis factor-alpha and interleukin-6, alongside modulating apoptosis-regulating proteins (enhancing Bcl-2 while suppressing Bax and Caspase-3 expression), further underscores its cardioprotective effect. Notably, IRMN modulated the p62-Keap1-Nrf2 signaling pathway, suggesting a mechanism through which it exerts its protective effects against CP-induced cardiac injury. These insights underscore the potential of IRMN as an effective adjunct in cancer therapy, offering a strategy to mitigate the cardiotoxic side effects of cisplatin.

TMEM79 Ameliorates Cerebral Ischemia/Reperfusion Injury Through Regulating Inflammation and Oxidative Stress via the Nrf2/NLRP3 Pathway

BACKGROUND

Cerebral ischemia/reperfusion injury (CIRI) is still a complicated disease with high fatality rates worldwide. Transmembrane Protein 79 (TMEM79) regulates inflammation and oxidative stress in some other diseases.

METHODS

CIRI mouse model was established using C57BL/6J mice through middle cerebral artery occlusion-reperfusion (MCAO/R), and BV2 cells were subjected to oxygen and glucose deprivation/reoxygenation (OGD/R) to simulate CIRI. Brain tissue or BV2 cells were transfected or injected with lentivirus-carried TMEM79 overexpression vector. The impact of TMEM79 on CIRI-triggered oxidative stress was ascertained by dihydroethidium (DHE) staining and examination of oxidative stress indicators. Regulation of TMEM79 in neuronal apoptosis and inflammation was determined using TUNEL staining and ELISA.

RESULTS

TMEM79 overexpression mitigated neurological deficit induced by MCAO/R and decreased the extent of cerebral infarct. TMEM79 prevented neuronal death in brain tissue of MCAO/R mouse model and suppressed inflammatory response by reducing inflammatory cytokines levels. Moreover, TMEM79 significantly attenuated inflammation and oxidative stress caused by OGD/R in BV2 cells. TMEM79 facilitated the activation of Nrf2 and inhibited NLRP3 and caspase-1 expressions. Rescue experiments indicated that the Nrf2/NLRP3 signaling pathway mediated the mitigative effect of TMEM79 on CIRI in vivo and in vitro.

CONCLUSION

Overall, TMEM79 was confirmed to attenuate CIRI via regulating the Nrf2/NLRP3 signaling pathway.

Targeting cyclooxygenase-2 for chemoprevention of inflammation-associated intestinal carcinogenesis: An update

Mounting evidence from preclinical and clinical studies suggests that persistent inflammation functions as a driving force in the journey to cancer. Cyclooxygenase-2 (COX-2) is a key enzyme involved in inflammatory signaling. While being transiently upregulated upon inflammatory stimuli, COX-2 has been found to be consistently overexpressed in human colorectal cancer and several other malignancies. The association between chronic inflammation and cancer has been revisited: cancer can arise when inflammation fails to resolve. Besides its proinflammatory functions, COX-2 also catalyzes the production of pro-resolving as well as anti-inflammatory metabolites from polyunsaturated fatty acids. This may account for the side effects caused by long term use of some COX-2 inhibitory drugs during the cancer chemopreventive trials. This review summarizes the latest findings highlighting the dual functions of COX-2 in the context of its implications in the development, maintenance, and progression of cancer.

Rottlerin Enhances the Autophagic Degradation of Phosphorylated Tau in Neuronal Cells

Intra-neuronal accumulation of hyper-phosphorylated tau as neurofibrillary tangles (NFT) is a hallmark of Alzheimer's disease (AD). To prevent the aggregation of phosphorylated tau in neurons, decreasing the phosphorylated tau protein levels is important. Here, we examined the biological effects of rottlerin, a phytochemical compound extracted from the Kamala tree, Mallotus philippinensis, on phosphorylated tau levels. Notably, rottlerin decreased the levels of intracellular phosphorylated and total tau. A marked increase in the LC3-II, a hallmark of autophagy, was observed in these cells, indicating that rottlerin strongly induced autophagy. Interestingly, rottlerin induced the phosphorylation of Raptor at S792 through the activation of adenosine-monophosphate activated-protein kinase (AMPK), which likely inhibits the mammalian target of rapamycin complex 1 (mTORC1), thus resulting in the activation of transcription factor EB (TFEB), a master regulator of autophagy. In addition, nuclear factor erythroid 2-related factor 2 (Nrf2) activity increased in the presence of rottlerin. The decrease of phosphorylated tau levels in the presence of rottlerin was ameliorated by the knockdown of TFEB and partially attenuated by the knockout of the Nrf2 gene. Taken together, rottlerin likely enhances the degradation of phosphorylated tau through autophagy activated by TFEB and Nrf2. Thus, our results suggest that a natural compound rottlerin could be used as a preventive and therapeutic drug for AD.

Neuroprotective effect of acetoxypachydiol against oxidative stress through activation of the Keap1-Nrf2/HO-1 pathway

BACKGROUND

Excessive oxidative stress in the brain is an important pathological factor in neurological diseases. Acetoxypachydiol (APHD) is a lipophilic germacrane-type diterpene extracted as a major component from different species of brown algae within the genus Dictyota. There have been no previous reports on the pharmacological activity of APHD. The present research aims to explore the potential neuroprotective properties of APHD and its underlying mechanisms.

METHODS

The possible mechanism of APHD was predicted using a combination of molecular docking and network pharmacological analysis. PC12 cells were induced by H2O2 and oxygen-glucose deprivation/reoxygenation (OGD/R), respectively. Western blot, flow cytometry, immunofluorescence staining, and qRT-PCR were used to investigate the antioxidant activity of APHD. The HO-1 inhibitor ZnPP and Nrf2 gene silencing were employed to confirm the influence of APHD on the signaling cascade involving HO-1, Nrf2, and Keap1 in vitro.

RESULTS

APHD exhibited antioxidant activity in both PC12 cells subjected to H2O2 and OGD/R conditions by downregulating the release of LDH, the concentrations of MDA, and ROS, and upregulating SOD, GSH-Px, and GSH concentrations. APHD could potentially initiate the Keap1-Nrf2/HO-1 signaling cascade, according to the findings from network pharmacology evaluation and molecular docking. Furthermore, APHD was observed to increase Nrf2 and HO-1 expression at both mRNA and protein levels, while downregulating the protein concentrations of Keap1. Both Nrf2 silencing and treatment with ZnPP reversed the neuroprotective effects of APHD.

CONCLUSIONS

APHD activated antioxidant enzymes and downregulated the levels of LDH, MDA, and ROS in two cell models. The neuroprotective effect is presumably reliant on upregulation of the Keap1-Nrf2/HO-1 pathway. Taken together, APHD from brown algae of the genus Dictyota shows potential as a candidate for novel neuroprotective agents.

Verapamil Attenuates the Severity of Tendinopathy by Mitigating Mitochondrial Dysfunction through the Activation of the Nrf2/HO-1 Pathway

Tendinopathy is a prevalent condition in orthopedics patients, exerting a profound impact on tendon functionality. However, its underlying mechanism remains elusive and the efficacy of pharmacological interventions continues to be suboptimal. Verapamil is a clinically used medicine with anti-inflammation and antioxidant functions. This investigation aimed to elucidate the impact of verapamil in tendinopathy and the underlying mechanisms through which verapamil ameliorates the severity of tendinopathy. In in vitro experiments, primary tenocytes were exposed to interleukin-1 beta (IL-1β) along with verapamil at a concentration of 5 μM. In addition, an in vivo rat tendinopathy model was induced through the localized injection of collagenase into the Achilles tendons of rats, and verapamil was injected into these tendons at a concentration of 5 μM. The in vitro findings highlighted the remarkable ability of verapamil to attenuate extracellular matrix degradation and apoptosis triggered by inflammation in tenocytes stimulated by IL-1β. Furthermore, verapamil was observed to significantly suppress the inflammation-related MAPK/NFκB pathway. Subsequent investigations revealed that verapamil exerts a remediating effect on mitochondrial dysfunction, which was achieved through activation of the Nrf2/HO-1 pathway. Nevertheless, the protective effect of verapamil was nullified with the utilization of the Nrf2 inhibitor ML385. In summary, the in vivo and in vitro results indicate that the administration of verapamil profoundly mitigates the severity of tendinopathy through suppression of inflammation and activation of the Nrf2/HO-1 pathway. These findings suggest that verapamil is a promising therapeutic agent for the treatment of tendinopathy, deserving further and expanded research.

NBR1-p62-Nrf2 mediates the anti-pulmonary fibrosis effects of protodioscin

BACKGROUND

Idiopathic pulmonary fibrosis is a persistent disease of the lung interstitium for which there is no efficacious pharmacological therapy. Protodioscin, a steroidal saponin, possesses diverse pharmacological properties; however, its function in pulmonary fibrosis is yet to be established. Hence, in this investigation, it was attempted to figure out the anti-pulmonary fibrosis influences of protodioscin and its pharmacological properties related to oxidative stress.

METHODS

A mouse lung fibrosis model was generated using tracheal injections of bleomycin, followed by intraperitoneal injection of different concentrations of protodioscin, and the levels of oxidative stress and fibrosis were detected in the lungs. Multiple fibroblasts were treated with TGF-β to induce their transition to myofibroblasts. It was attempted to quantify myofibroblast markers' expression levels and reactive oxygen species levels as well as Nrf2 activation after co-incubation of TGF-β with fibroblasts and different concentrations of protodioscin. The influence of protodioscin on the expression and phosphorylation of p62, which is associated with Nrf2 activation, were detected, and p62 related genes were predicted by STRING database. The effects of Nrf2 inhibitor or silencing of the Nrf2, p62 and NBR1 genes, respectively, on the activation of Nrf2 by protodioscin were examined. The associations between p62, NBR1, and Keap1 in the activation of Nrf2 by protodioscin was demonstrated using a co-IP assay. Nrf2 inhibitor were used when protodioscin was treated in mice with pulmonary fibrosis and lung tissue fibrosis and oxidative stress levels were detected.

RESULTS

In vivo, protodioscin decreased the levels of fibrosis markers and oxidative stress markers and activated Nrf2 in mice with pulmonary fibrosis, and these effects were inhibited by Nrf2 inhibitor. In vitro, protodioscin decreased the levels of myofibroblast markers and oxidative stress markers during myofibroblast transition and promoted Nrf2 downstream gene expression, with reversal of these effects after Nrf2, p62 and NBR1 genes were silenced or Nrf2 inhibitors were used, respectively. Protodioscin promoted the binding of NBR1 to p62 and Keap1, thereby reducing Keap1-Nrf2 binding.

CONCLUSION

The NBR1-p62-Nrf2 axis is targeted by protodioscin to reduce oxidative stress and inhibit pulmonary fibrosis.

5-Methylcytosine transferase NSUN2 drives NRF2-mediated ferroptosis resistance in non-small cell lung cancer

RNA 5-methylcytosine (m5C) is an abundant chemical modification in mammalian RNAs and plays crucial roles in regulating vital physiological and pathological processes, especially in cancer. However, the dysregulation of m5C and its underlying mechanisms in non-small cell lung cancer (NSCLC) remain unclear. Here we identified that NSUN2, a key RNA m5C methyltransferase, is highly expressed in NSCLC tumor tissue. We found elevated NSUN2 expression levels strongly correlate with tumor grade and size, predicting poor outcomes for NSCLC patients. Furthermore, RNA-seq and subsequent confirmation studies revealed the antioxidant-promoting transcription factor NRF2 is a target of NSUN2, and depleting NSUN2 decreases the expression of NRF2 and increases the sensitivity of NSCLC cells to ferroptosis activators both in vitro and in vivo. Intriguingly, the methylated-RIP-qPCR assay results indicated that NRF2 mRNA has a higher m5C level when NSUN2 is overexpressed in NSCLC cells but shows no significant changes in the NSUN2 methyltransferase-deficient group. Mechanistically, we confirmed that NSUN2 upregulates the expression of NRF2 by enhancing the stability of NRF2 mRNA through the m5C modification within its 5'UTR region recognized by the specific m5C reader protein YBX1, rather than influencing its translation. In subsequent rescue experiments, we show knocking down NRF2 diminished the proliferation, migration, and ferroptosis tolerance mediated by NSUN2 overexpression. In conclusion, our study unveils a novel regulatory mechanism in which NSUN2 sustains NRF2 expression through an m5C-YBX1-axis, suggesting that targeting NSUN2 and its regulated ferroptosis pathway might offer promising therapeutic strategies for NSCLC patients.

Nrf2 activator Diethyl Maleate attenuates ROS mediated NLRP3 inflammasome activation in murine microglia

Microglia are the tissue-resident immune cells of the central nervous system. As a part of the innate immune response, NLR Family Pyrin Domain Containing Protein 3 (NLRP3) inflammasome activation leads to cleavage of caspase-1 and triggers secretion of proinflammatory cytokines and may also result in pyroptotic cell death. Inflammasome activation plays a crucial role in inflammatory conditions; aberrant activation of inflammasome contributes to the pathogenesis of neurodegenerative diseases. Diethyl Maleate (DEM) is a promising antiinflammatory chemical to alleviate inflammasome activation. In this study, NLRP3 inflammasome was activated in N9 murine microglia via 1 µg/ml LPS (Lipopolysaccharide) for 4 h and 5 mM ATP (Adenosine 5'-triphosphate) for 1 h, respectively. We demonstrated that 1 h pretreatment of DEM attenuated NLRP3 inflammasome activation in microglial cells. Besides, mitochondrial ROS decreased upon DEM pretreatment in inflammasome-induced cells. Likewise, it ameliorated pyroptotic cell death in microglia. DEM is a potent activator of Nrf2 transcription factor, the key regulator of the antioxidant response pathway. Nrf2 has been a significant target to decrease aberrant inflammasome activation through the antioxidant compounds, including DEM. Here, we have shown that DEM increased Nrf2 translocation to the nucleus, resulting in Nrf2 target gene expression in microglia. In conclusion, DEM is a promising protective agent against NLRP3 inflammasome activation.

Nanoparticles with intermediate hydrophobicity polarize macrophages to plaque-specific Mox phenotype via Nrf2 and HO-1 activation

Mox macrophages were identified recently and are closely associated with atherosclerosis. Considering the potential health risks and the impact on macrophage modulation, this study investigated the Mox polarization of macrophages induced by nanoparticles (NPs) with tunable hydrophobicity. One nanoparticle (C4NP) with intermediate hydrophobicity efficiently upregulated the mRNA expression of Mox-related genes including HO-1, Srxn1, Txnrd1, Gsr, Vegf and Cox-2 through increased accumulation of Nrf2 at a nontoxic concentration in both resting and LPS-challenged macrophages. Additionally, C4NP impaired phagocytic capacity by 20% and significantly increased the secretion of cytokines, including TNFα, IL-6 and IL-10. Mechanistic studies indicated that intracellular reactive oxygen species (ROS) were elevated by 1.5-fold and 2.6-fold in resting and LPS-challenged macrophages respectively. Phosphorylated p62 was increased by 2.5-fold in resting macrophages and maintained a high level in LPS-challenged ones, both of which partially accounted for the significant accumulation of Nrf2 and HO-1. Notably, C4NP depolarized mitochondrial membrane potential by more than 50% and switched macrophages from oxidative phosphorylation-based aerobic metabolism to glycolysis for energy supply. Overall, this study reveals a novel molecular mechanism potentially involving ROS-Nrf2-p62 signaling in mediating macrophage Mox polarization, holding promise in ensuring safer and more efficient use of nanomaterials.

Intrinsic diving reflex induces potent antioxidative response by activation of NRF2 signaling

Aims

This study aims to elucidate the underlying mechanisms of diving reflex, a powerful endogenous mechanism supporting underwater mammalian survival. Antioxidative responses, observed in marine mammals, may be contributing factors. Using a multi-organ approach, this study assesses whether acute and chronic diving reflex activate nuclear factor-erythroid-2-related factor 2 (NRF2) signaling pathways, which regulate cellular antioxidant responses.

Methods

Male Sprague-Dawley rats ( n =38) underwent either a single diving session to elicit acute diving reflex, or daily diving sessions for 4-weeks to produce chronic diving reflex. NRF2 (total, nuclear, phosphorylated), NRF2-downstream genes, and malondialdehyde were assessed via Western blot, immunofluorescence, RT-PCR, and ELISA in brain, lung, kidney, and serum.

Results

Diving reflex increased nuclear NRF2, phosphorylated NRF2, and antioxidative gene expression, in an organ-specific and exposure time-specific manner. Comparing organs, the brain had the highest increase of phosphorylated NRF2 expression, while kidney had the highest degree of nuclear NRF2 expression. Comparing acute and chronic sessions, phosphorylated NRF2 increased the most with chronic diving reflex, but acute diving reflex had the highest antioxidative gene expression. Notably, calcitonin gene-related peptide appears to mediate diving reflex' effects on NRF2 activation.

Conclusions

Acute and chronic diving reflex activate potent NRF2 signaling in the brain and peripheral organs. Interestingly, acute diving reflex induces higher expression of downstream antioxidative genes compared to chronic diving reflex. This result contradicts previous assumptions requiring chronic exposure to diving for induction of antioxidative effects and implies that the diving reflex has a strong translational potential during preconditioning and postconditioning therapies.

Key Points

Diving reflex activates potent NRF2 signaling via multiple mechanisms, including phosphorylation, nuclear translocation, and KEAP1 downregulation with both acute and chronic exposure.Diving reflex activates NRF2 via differential pathways in the brain and other organs; phosphorylated NRF2 increases more in the brain, while nuclear NRF2 increases more in the peripheral organs.Acute diving reflex exposure induces a more pronounced antioxidative effect than chronic diving reflex exposure, indicating that the antioxidative response activated by diving reflex is not dependent upon chronic adaptive responses and supports diving reflex as both a preconditioning and postconditioning treatment.

Trimethylamine N-Oxide Improves Exercise Performance by Reducing Oxidative Stress through Activation of the Nrf2 Signaling Pathway

Trimethylamine N-oxide (TMAO) has attracted interest because of its association with cardiovascular disease and diabetes, and evidence for the beneficial effects of TMAO is accumulating. This study investigates the role of TMAO in improving exercise performance and elucidates the underlying molecular mechanisms. Using C2C12 cells, we established an oxidative stress model and administered TMAO treatment. Our results indicate that TMAO significantly protects myoblasts from oxidative stress-induced damage by increasing the expression of Nrf2, heme oxygenase-1 (HO-1), NAD(P)H dehydrogenase (NQO1), and catalase (CAT). In particular, suppression of Nrf2 resulted in a loss of the protective effects of TMAO and a significant decrease in the expression levels of Nrf2, HO-1, and NQO1. In addition, we evaluated the effects of TMAO in an exhaustive swimming test in mice. TMAO treatment significantly prolonged swimming endurance, increased glutathione and taurine levels, enhanced glutathione peroxidase activity, and increased the expression of Nrf2 and its downstream antioxidant genes, including HO-1, NQO1, and CAT, in skeletal muscle. These findings underscore the potential of TMAO to counteract exercise-induced oxidative stress. This research provides new insights into the ability of TMAO to alleviate exercise-induced oxidative stress via the Nrf2 signaling pathway, providing a valuable framework for the development of sports nutrition supplements aimed at mitigating oxidative stress.

Rev-erbα attenuates diabetic myocardial injury through regulation of ferroptosis

Diabetes is a widespread disease that threatens the life and health of human beings, and diabetic cardiomyopathy (DCM) is one of the major complications of diabetic patients. The pathological mechanisms of DCM are complex, including inflammation, endoplasmic reticulum stress, and oxidative stress that have been reported previously. Although recent studies suggested that ferroptosis is also involved in the progression of DCM, the exact mechanism remains unclear. Rev-erbα cardiac conditional knockout mice were generated and type 2 diabetes were induced by high fat diet (HFD) and intraperitoneal injection of streptozotocin (STZ) in in vivo experiments. In parallel, our in vitro experiments entailed the introduction of elevated levels of glucose (HG) and palmitic acid (PA) to induce glycolipid toxicity in H9c2 cardiomyocytes. Further deterioration of cardiac function was detected by echocardiography after the clock gene rev-erbα was knocked out. This was accompanied by significant elevations in markers of inflammation, myocardial fibrosis, and oxidative stress. In addition, iron content, transmission electron microscopy (TEM), and RT-PCR assays confirmed significantly increased levels of ferroptosis in rev-erbα-deficient DCM. Intriguingly, Co-Immunoprecipitation (Co-IP) data uncovered an interaction between rev-erbα and nuclear factor E2-related factor 2 (NRF2) in diabetic myocardial tissues. It is worth highlighting that ferroptosis within cardiomyocytes witnessed significant mitigation upon the administration of sulforaphane (SFN), an NRF2 agonist, to HG + PA-incubated H9c2 cells. Our study demonstrates for the first time that knockdown of the clock gene rev-erbα exacerbates myocardial injury and ferroptosis in type 2 diabetic mice, which can be reversed by activating NRF2.

Hepatic Alterations in a BTBR T + Itpr3tf/J Mouse Model of Autism and Improvement Using Melatonin via Mitigation Oxidative Stress, Inflammation and Ferroptosis

Autism spectrum disorder (ASD) is a complicated neurodevelopmental disorder, and its etiology is not well understood. It is known that genetic and nongenetic factors determine alterations in several organs, such as the liver, in individuals with this disorder. The aims of the present study were to analyze morphological and biological alterations in the liver of an autistic mouse model, BTBR T + Itpr3tf/J (BTBR) mice, and to identify therapeutic strategies for alleviating hepatic impairments using melatonin administration. We studied hepatic cytoarchitecture, oxidative stress, inflammation and ferroptosis in BTBR mice and used C57BL6/J mice as healthy control subjects. The mice were divided into four groups and then treated and not treated with melatonin, respectively. BTBR mice showed (a) a retarded development of livers and (b) iron accumulation and elevated oxidative stress and inflammation. We demonstrated that the expression of ferroptosis markers, the transcription factor nuclear factor erythroid-related factor 2 (NFR2), was upregulated, and the Kelch-like ECH-associated protein 1 (KEAP1) was downregulated in BTBR mice. Then, we evaluated the effects of melatonin on the hepatic alterations of BTBR mice; melatonin has a positive effect on liver cytoarchitecture and metabolic functions.

Recent progress and applications of small molecule inhibitors of Keap1-Nrf2 axis for neurodegenerative diseases

The Kelch-like ECH-associated protein 1 (Keap1)-nuclear factor erythroid 2-related factor 2 (Nrf2) pathway serves as a crucial regulator against oxidative stress (OS) damage in various cells and organs. It has garnered significant attention as a potential therapeutic target for neurodegenerative diseases (NDD). Although progress has been achieved in strategies to regulate the Keap1-Nrf2 pathway, the availability of Nrf2 activators applicable to NDD is currently limited. Currently, the FDA has approved the Nrf2 activators dimethyl fumarate (DMF) and Omaveloxolone (Omav) as novel first-line oral drugs for the treatment of patients with relapsing forms of multiple sclerosis and Friedreich's ataxia. A promising alternative approach involves the direct inhibition of Keap1-Nrf2 protein-protein interactions (PPI), which offers numerous advantages over the use of electrophilic Nrf2 activators, primarily in avoiding off-target effects. This review examines the compelling evidence supporting the beneficial role of Nrf2 in NDD and explores the potential of Keap1 inhibitors and Keap1-Nrf2 PPI inhibitors as therapeutic agents, with the aim to provide further insights into the development of inhibitors targeting this pathway for the treatment of NDD.

The Multifaceted Roles of NRF2 in Cancer: Friend or Foe?

Physiological concentrations of reactive oxygen species (ROS) play vital roles in various normal cellular processes, whereas excessive ROS generation is central to disease pathogenesis. The nuclear factor erythroid 2-related factor 2 (NRF2) is a critical transcription factor that regulates the cellular antioxidant systems in response to oxidative stress by governing the expression of genes encoding antioxidant enzymes that shield cells from diverse oxidative alterations. NRF2 and its negative regulator Kelch-like ECH-associated protein 1 (KEAP1) have been the focus of numerous investigations in elucidating whether NRF2 suppresses tumor promotion or conversely exerts pro-oncogenic effects. NRF2 has been found to participate in various pathological processes, including dysregulated cell proliferation, metabolic remodeling, and resistance to apoptosis. Herein, this review article will examine the intriguing role of phase separation in activating the NRF2 transcriptional activity and explore the NRF2 dual impacts on tumor immunology, cancer stem cells, metastasis, and long non-coding RNAs (LncRNAs). Taken together, this review aims to discuss the NRF2 multifaceted roles in both cancer prevention and promotion while also addressing the advantages, disadvantages, and limitations associated with modulating NRF2 therapeutically in cancer treatment.

Involvement of Nrf2 Signaling in Lead-induced Toxicity

Nuclear factor erythroid 2-related factor 2 (Nrf2) is used as one of the main protective factors against various pathological processes, as it regulates cells resistant to oxidation. Several studies have extensively explored the relationship between environmental exposure to heavy metals, particularly lead (Pb), and the development of various human diseases. These metals have been reported to be able to, directly and indirectly, induce the production of reactive oxygen species (ROS) and cause oxidative stress in various organs. Since Nrf2 signaling is important in maintaining redox status, it has a dual role depending on the specific biological context. On the one hand, Nrf2 provides a protective mechanism against metal-induced toxicity; on the other hand, it can induce metalinduced carcinogenesis upon prolonged exposure and activation. Therefore, the aim of this review was to summarize the latest knowledge on the functional interrelation between toxic metals, such as Pb and Nrf2 signaling.

The lack of homology domain and leucine rich repeat protein phosphatase 2 ameliorates visual impairment in rats with diabetic retinopathy through regulation of the AKT-GSK-3β-Nrf2 signal cascade

Pleckstrin homology domain and leucine rich repeat protein phosphatase 2 (PHLPP2) is an emerging player in diverse disorders. Our previous findings have documented that reducing PHLPP2 levels in cultured retinal ganglion cells protects against cellular damage caused by high glucose, indicating a possible link between PHLPP2 and diabetic retinopathy (DR). The present work was dedicated to the investigation of PHLPP2 in DR through in vivo experiments with rat models induced by intraperitoneal injection of streptozotocin. Compared to normal rats, the retinas of rats with DR exhibited a notable increase in the level of PHLPP2. The reduction of PHLPP2 levels in the retina was achieved by the intravitreal administration of adeno-associated viruses expressing specific shRNA targeting PHLPP2. Decreasing the expression of PHLPP2 ameliorated visual function impairment and improved the pathological changes of retina in DR rats. Moreover, decreasing the expression of PHLPP2 repressed the apoptosis, oxidative stress and proinflammatory response in the retinas of rats with DR. Reduction of PHLPP2 levels led to an increase in the levels of phosphorylated AKT and glycogen synthase kinase-3β (GSK-3β). Decreasing the expression of PHLPP2 resulted in increased activation of nuclear factor erythroid 2-related factor 2 (Nrf2), which was reversed by suppressing AKT. Notably, the protective effect of reducing PHLPP2 on DR was eliminated when Nrf2 was restrained. These observations show that the down-regulation of PHLPP2 has protective effects on DR by preserving the structure and function of the retina by regulating the AKT-GSK-3β-Nrf2 signal cascade. Therefore, targeting PHLPP2 may hold promise in the treatment of DR.

Dendrobium offificinale polysaccharides prevents glucocorticoids-induced osteoporosis by destabilizing KEAP1-NRF2 interaction

Glucocorticoid-induced osteoporosis (GIOP) represents the foremost cause of secondary osteoporosis and fragility fractures. Novel therapeutic strategies for GIOP are needed, with improved safety profiles and reduced costs compared to current options. Dendrobium officinale (D. officinale) is a traditional Chinese medicine that has been reported to have beneficial effects on bone metabolism. Here, we sought to investigate the impacts of D. officinale polysaccharides (DOP), the main active constituents of D. officinale, on GIOP in vivo models and dexamethasone (DEX)-treated osteoblast lineage cells. We found that low concentrations of DOP are relatively safe in vitro and in vivo, respectively. Importantly, we found that DOP treatment significantly inhibited DEX-induced osteoporosis in two in vivo models, zebrafish and mice, while boosting osteogenic differentiation of hBMSCs exposed to DEX. Futhermore, our data reveal that DOP elevates nuclear Nrf2 levels under DEX treatment, by suppressing of Nrf2 ubiquitination. Leveraging Keap1b knockout zebrafish and RNAi approach, we demonstrated that DOP disrupts the association of Nrf2/Keap1, resulting in the inhibition of Nrf2 ubiquitination. Taken together, these results illuminate that DOP stimulates osteogenesis in the presence of DEX by destabilizing the Nrf2/Keap1 interaction. These findings suggest that DOP may serve as a novel drug against osteoporosis caused by glucocorticoids.

In Vivo and In Silico Studies of the Hepatoprotective Activity of Tert-Butylhydroquinone

Tert-butylhydroquinone (TBHQ) is a synthetic food antioxidant with biological activities, but little is known about its pharmacological benefits in liver disease. Therefore, this work aimed to evaluate TBHQ during acute liver damage induced by CCl4 (24 h) or BDL (48 h) in Wistar rats. It was found that pretreatment with TBHQ prevents 50% of mortality induced by a lethal dose of CCl4 (4 g/kg, i.p.), and 80% of BDL+TBHQ rats survived, while only 50% of the BDL group survived. Serum markers of liver damage and macroscopic and microscopic (H&E staining) observations suggest that TBHQ protects from both hepatocellular necrosis caused by the sublethal dose of CCl4 (1.6 g/kg, i.p.), as well as necrosis/ductal proliferation caused by BDL. Additionally, online databases identified 49 potential protein targets for TBHQ. Finally, a biological target candidate (Keap1) was evaluated in a proof-of-concept in silico molecular docking assay, resulting in an interaction energy of -5.5491 kcal/mol, which was higher than RA839 and lower than monoethyl fumarate (compounds known to bind to Keap1). These findings suggest that TBHQ increases the survival of animals subjected to CCl4 intoxication or BDL, presumably by reducing hepatocellular damage, probably due to the interaction of TBHQ with Keap1.

Advances in the regulatory mechanisms of mTOR in necroptosis

The mammalian target of rapamycin (mTOR), an evolutionarily highly conserved serine/threonine protein kinase, plays a prominent role in controlling gene expression, metabolism, and cell death. Programmed cell death (PCD) is indispensable for maintaining homeostasis by removing senescent, defective, or malignant cells. Necroptosis, a type of PCD, relies on the interplay between receptor-interacting serine-threonine kinases (RIPKs) and the membrane perforation by mixed lineage kinase domain-like protein (MLKL), which is distinguished from apoptosis. With the development of necroptosis-regulating mechanisms, the importance of mTOR in the complex network of intersecting signaling pathways that govern the process has become more evident. mTOR is directly responsible for the regulation of RIPKs. Autophagy is an indirect mechanism by which mTOR regulates the removal and interaction of RIPKs. Another necroptosis trigger is reactive oxygen species (ROS) produced by oxidative stress; mTOR regulates necroptosis by exploiting ROS. Considering the intricacy of the signal network, it is reasonable to assume that mTOR exerts a bifacial effect on necroptosis. However, additional research is necessary to elucidate the underlying mechanisms. In this review, we summarized the mechanisms underlying mTOR activation and necroptosis and highlighted the signaling pathway through which mTOR regulates necroptosis. The development of therapeutic targets for various diseases has been greatly advanced by the expanding knowledge of how mTOR regulates necroptosis.

DPP9 Stabilizes NRF2 to Suppress Ferroptosis and Induce Sorafenib Resistance in Clear Cell Renal Cell Carcinoma

The KEAP1-NRF2 axis is the principal regulator of cellular responses to oxidative and electrophilic stressors. NRF2 hyperactivation is frequently observed in many types of cancer and promotes cancer initiation, progression, metastasis, and resistance to various therapies. Here, we determined that dipeptidyl peptidase 9 (DPP9) is a regulator of the KEAP1-NRF2 pathway in clear cell renal cell carcinoma (ccRCC). DPP9 was markedly overexpressed at the mRNA and protein levels in ccRCC, and high DPP9 expression levels correlated with advanced tumor stage and poor prognosis in patients with ccRCC. Protein affinity purification to identify functional partners of DPP9 revealed that it bound to KEAP1 via a conserved ESGE motif. DPP9 disrupted KEAP1-NRF2 binding by competing with NRF2 for binding to KEAP1 in an enzyme-independent manner. Upregulation of DPP9 led to stabilization of NRF2, driving NRF2-dependent transcription and thereby decreasing cellular reactive oxygen species levels. Moreover, DPP9 overexpression suppressed ferroptosis and induced resistance to sorafenib in ccRCC cells, which was largely dependent on the NRF2 transcriptional target SLC7A11. Collectively, these findings indicate that the accumulation of DPP9 results in hyperactivation of the NRF2 pathway to promote tumorigenesis and intrinsic drug resistance in ccRCC.

SIGNIFICANCE

DPP9 overcomes oxidative stress and suppresses ferroptosis in ccRCC by binding to KEAP1 and promoting NRF2 stability, which drives tumor development and sorafenib resistance.

Neuroprotective Effects of Sinomenine on Experimental Autoimmune Encephalomyelitis via Anti-Inflammatory and Nrf2-Dependent Anti-Oxidative Stress Activity

Multiple sclerosis (MS) is an autoimmune inflammatory disease of the central nervous system (CNS). Sinomenine (SIN), a bioactive alkaloid extracted from the Chinese medicinal plant Sinomenium acutum, has powerful anti-inflammatory and immunosuppressive therapeutic benefits. In our previous research, we found that SIN increased resistance to oxidative stress via the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway in PC12 neuronal cells. However, whether SIN can improve the symptoms and pathological features of experimental autoimmune encephalomyelitis (EAE), a murine model of MS, via the Nrf2 signaling pathway remains unclear. EAE was immunized followed by SIN treatment. Then we evaluated the effects of SIN in EAE. Subsequently, primary microglia were cultured to explore the effect of SIN on microglia activation. Further, the levels of Nrf2 and its downstream molecules were detected to assess the molecular mechanisms of SIN. We demonstrated that SIN effectively ameliorated the severity of EAE, accompanied by a reduction in the demyelination, axonal damage and inhibition of inflammatory cell infiltration. Mechanistically, SIN decreased the inflammatory cytokines expression, and suppressed microglia and astrocytes activation in EAE mice. Furthermore, SIN suppressed lipopolysaccharide (LPS)-induced microglial activation and the production of pro-inflammatory factors in vitro. Moreover, SIN inhibited oxidative stress via the activation of the Nrf2 signaling pathway. Our work proves that SIN exerts its neuroprotective effects by the Nrf2-dependent anti-oxidative stress and diminishing neuroinflammation, suggesting that the "antioxiflammation" effect of SIN is expected to be an ideal treatment strategy for MS/EAE.

Melatonin and ferroptosis: Mechanisms and therapeutic implications

Ferroptosis, a regulated form of cell death, is characterized by iron-dependent lipid peroxidation leading to oxidative damage to cell membranes. Cell sensitivity to ferroptosis is influenced by factors such as iron overload, lipid metabolism, and the regulation of the antioxidant system. Melatonin, with its demonstrated capacity to chelate iron, modulate iron metabolism proteins, regulate lipid peroxidation, and regulate antioxidant systems, has promise as a potential therapeutic agent in mediating ferroptosis. The availability of approved drugs targeting ferroptosis is limited; therefore, melatonin is a candidate for broad application due to its safety and efficacy in attenuating ferroptosis in noncancerous diseases. Melatonin has been demonstrated to attenuate ferroptosis in cellular and animal models of noncancerous diseases, showcasing effectiveness in organs such as the heart, brain, lung, liver, kidney, and bone. This review outlines the molecular mechanisms of ferroptosis, investigates melatonin's potential effects on ferroptosis, and discusses melatonin's therapeutic potential as a promising intervention against diseases associated with ferroptosis. Through this discourse, we aim to lay a strong foundation for developing melatonin as a therapeutic strategy to modulate ferroptosis in a variety of disease contexts.

Reactive Oxygen Species and Strategies for Antioxidant Intervention in Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is a life-threatening pulmonary condition characterized by the sudden onset of respiratory failure, pulmonary edema, dysfunction of endothelial and epithelial barriers, and the activation of inflammatory cascades. Despite the increasing number of deaths attributed to ARDS, a comprehensive therapeutic approach for managing patients with ARDS remains elusive. To elucidate the pathological mechanisms underlying ARDS, numerous studies have employed various preclinical models, often utilizing lipopolysaccharide as the ARDS inducer. Accumulating evidence emphasizes the pivotal role of reactive oxygen species (ROS) in the pathophysiology of ARDS. Both preclinical and clinical investigations have asserted the potential of antioxidants in ameliorating ARDS. This review focuses on various sources of ROS, including NADPH oxidase, uncoupled endothelial nitric oxide synthase, cytochrome P450, and xanthine oxidase, and provides a comprehensive overview of their roles in ARDS. Additionally, we discuss the potential of using antioxidants as a strategy for treating ARDS.

The protective effects of uric acid against myocardial ischemia via the Nrf2 pathway

Uric acid (UA) possesses both pro- and anti-oxidative properties in ischemic heart disease, but the underlying mechanism remains unclear. We aimed to investigate UA's protective effect on myocardial ischemia by examining its effects on ECG Ischemic Alterations (EIA) and H2O2-induced oxidative stress in H9C2 myocardial cells. The incidence of EIA decreased over time and was more prevalent among women than men. A U-shaped relationship was observed between UA levels and EIA incidence, with the third quartile exhibiting a protective association. Addition of 237.9 μmol/L UA improved cellular damage and oxidative stress in H2O2-treated H9C2 cells, as determined by cell viability, LDH release, ROS levels, and total antioxidant capacity assays. UA activated the Nrf2 pathway, evidenced by increased expression of Nrf2, GCLC, and HO-1 proteins. By reversing cell cycle blockage, promoting wound healing ability, improving colony-forming capacity, and increasing angiogenesis in H2O2-treated cells, UA exhibited positive effects on cardiomyocyte growth characteristics. Additionally, use of Nrf2 inhibitor ML385 confirmed the involvement of the Nrf2 pathway by negating UA's effects on oxidatively damaged cardiomyocytes. Our findings suggest that UA induces downstream antioxidant factors to ameliorate oxidative stress by activating the Nrf2 pathway, which could be one of the targets responsible for UA's beneficial effects in myocardial ischemia.

NRF2 signaling pathway and telomere length in aging and age-related diseases

The transcription factor nuclear factor erythroid 2-related factor 2 (NRF2) is well recognized as a critical regulator of redox, metabolic, and protein homeostasis, as well as the regulation of inflammation. An age-associated decline in NRF2 activity may allow oxidative stress to remain unmitigated and affect key features associated with the aging phenotype, including telomere shortening. Telomeres, the protective caps of eukaryotic chromosomes, are highly susceptible to oxidative DNA damage, which can accelerate telomere shortening and, consequently, lead to premature senescence and genomic instability. In this review, we explore how the dysregulation of NRF2, coupled with an increase in oxidative stress, might be a major determinant of telomere shortening and age-related diseases. We discuss the relevance of the connection between NRF2 deficiency in aging and telomere attrition, emphasizing the importance of studying this functional link to enhance our understanding of aging pathologies. Finally, we present a number of compounds that possess the ability to restore NRF2 function, maintain a proper redox balance, and preserve telomere length during aging.

Ferroptosis of macrophages facilitates bone loss in apical periodontitis via NRF2/FSP1/ROS pathway

Apical periodontitis (AP) is an infectious disease that causes periapical tissue inflammation and bone destruction. Ferroptosis, a novel type of regulated cell death, is closely associated with inflammatory diseases and the regulation of bone homeostasis. However, the exact involvement of ferroptosis in the bone loss of AP is not fully understood. In this study, human periapical tissues were collected, and a mouse model was established to investigate the role of ferroptosis in AP. Colocalization staining revealed that ferroptosis in macrophages contributes to the inflammatory bone loss associated with AP. A cell model was constructed using RAW 264.7 cells stimulated with LPS to further explore the mechanism underlying ferroptosis in macrophages upon inflammatory conditions, which exhibited ferroptotic characteristics. Moreover, downregulation of NRF2 was observed in ferroptotic macrophages, while overexpression of NRF2 upregulated the level of FSP1, leading to a reduction in reactive oxygen species (ROS) in macrophages. Additionally, ferroptotic macrophages released TNF-α, which activated the p38 MAPK signaling pathway and further increased ROS accumulation in macrophages. In vitro co-culture experiments demonstrated that the osteogenic ability of mouse bone marrow stromal cells (BMSCs) was suppressed with the stimulation of TNF-α from ferroptotic macrophages. These findings suggest that the TNF-α autocrine-paracrine loop in ferroptotic macrophages can inhibit osteogenesis in BMSCs through the NRF2/FSP1/ROS signaling pathway, leading to bone loss in AP. This study highlights the potential therapeutic value of targeting ferroptosis in the treatment of inflammatory bone diseases.

Oxidative stress sensor Keap1 recognizes HBx protein to activate the Nrf2/ARE signaling pathway, thereby inhibiting hepatitis B virus replication

IMPORTANCE

The Kelch-like ECH-associated protein 1 (Keap1)/NF-E2-related factor 2 (Nrf2)/antioxidant response element (ARE) signaling pathway is one of the most important defense mechanisms against oxidative stress. We previously reported that a cellular hydrogen peroxide scavenger protein, peroxiredoxin 1, a target gene of transcription factor Nrf2, acts as a novel HBV X protein (HBx)-interacting protein and negatively regulates hepatitis B virus (HBV) propagation through degradation of HBV RNA. This study further demonstrates that the Nrf2/ARE signaling pathway is activated during HBV infection, eventually leading to the suppression of HBV replication. We provide evidence suggesting that Keap1 interacts with HBx, leading to Nrf2 activation and inhibition of HBV replication via suppression of HBV core promoter activity. This study raises the possibility that activation of the Nrf2/ARE signaling pathway is a potential therapeutic strategy against HBV. Our findings may contribute to an improved understanding of the negative regulation of HBV replication by the antioxidant response.

Sohlh2 promotes pulmonary fibrosis via repression of p62/Keap1/Nrf2 mediated anti-oxidative signaling pathway

Disturbance in the redox balance of alveolar epithelial cells (AECs) was considered as a causal factor for pulmonary fibrosis. The regulatory mechanisms of redox hemostasis in the development of pulmonary fibrosis remain largely unknown. Using a type II AEC-specific Sohlh2 conditional knock-in (CKI) mouse model, we found that Sohlh2, a basic HLH transcription factor, accelerated age-related pulmonary fibrosis. High-fat diet (HFD) resulted in a tremendous increase in lung inflammation and fibrotic changes in the lung tissues of Sohlh2 CKI mice. Sohlh2 overexpression led to a significant rise of intracellular ROS and apoptosis in the lung, mouse primary AECIIs, and human A549 cells, which was attenuated by ROS inhibitor (NAC). Sohlh2 enhanced oxidative stress via repressing p62/Keap1/Nrf2 mediated anti-oxidative signaling pathway. p62, a direct target of Sohlh2, mediated Sohlh2 effects on ROS generation and apoptosis in A549 cells. Hence, our findings elucidate a pivotal mechanism underlying oxidative stress-induced pulmonary fibrosis, providing a framework for aging-related disorder interventions.

JNK regulates the Nrf2/NQO1-ARE pathway against Microcystins-Induced oxidative stress in freshwater mussel Cristaria plicata

In response to stress, cells can utilize several processes, such as the activation of the Nrf2/Keap1 pathway as a critical regulator of oxidative stress to protect against oxidative damage. C-Jun N-terminal kinase (JNK), a member of the mitogen-activated protein kinase (MAPK) family, is involved in regulating the NF-E2-related nuclear factor 2 (Nrf2)/antioxidant response element (ARE) signaling pathway. NAD(P)H quinone redox enzyme-1 (NQO1), a downstream target gene of the Nrf2 pathway, plays a vital role in removing peroxide and providing resistance to oxidative injury. We found that microcystins (MCs) stimulated CpNrf2 to express and increase anti-oxidative enzyme activities in a previous experiment. In our current study, the full-length cDNAs of JNK and NQO1 from Cristaria plicata (designated CpJNK and CpNQO1) were cloned. The relative levels of CpJNK and CpNQO1 were high in hepatopancreas. Upon MCs induction, the relative level of CpNQO1 was increased, whereas that of CpJNK was decreased significantly. In contrast, CpNrf2 knockdown upregulated the expression of CpJNK mRNA and phosphorylation of CpJNK protein (Cpp-JNK), but inhibited CpNQO1 expression. Additionally, we found that JNK inhibitor SP600125 stimulated expression of CpNQO1 and CpNrf2 upon exposure to MCs, and we further confirmed that CpNrf2 protein combined with the ARE element in CpNQO1 gene promoter in vitro, and increased CpNQO1-ARE-luciferase activity in a CpNrf2-dependent manner. These findings indicated C. plicata effectively alleviated MC-induced oxidative injury through JNK participated in regulating the Nrf2/NQO1-ARE pathway.

Decreasing REDD1 expression protects against high glucose-induced apoptosis, oxidative stress and inflammatory injury in podocytes through regulation of the AKT/GSK-3β/Nrf2 pathway

OBJECTIVE

Our goal in this work was to investigate the possible role and mechanism of regulated in development and DNA damage response 1 (REDD1) in mediating high glucose (HG)-induced podocyte injury in vitro.

MATERIALS AND METHODS

Mouse podocytes were stimulated with HG to establish HG injury model. Protein expression was examined by Western blotting. Cell viability was measured by cell counting kit-8 assay. Cell apoptosis was assessed by annexin V-FITC/propidium iodide and TUNEL apoptotic assays. Levels of reactive oxygen species (ROS), malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione peroxidase (GPx) were quantified by commercial kits. Concentrations of tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-1β were measured by ELISA.

RESULTS

A marked increase in REDD1 expression was observed in podocytes stimulated with HG. Reduced REDD1 expression strikingly restrained HG-induced increases in apoptosis, oxidative stress, and inflammation response in cultured podocytes. Decreasing REDD1 expression enhanced nuclear factor erythroid 2-related factor 2 (Nrf2) activation in HG-exposed podocytes via regulation of the AKT/glycogen synthase kinase-3 beta (GSK-3β) pathway. Inhibition of AKT or reactivation of GSK-3β prominently abolished Nrf2 activation induced by decreasing REDD1 expression. Pharmacological repression of Nrf2 markedly reversed the protective effects of decreasing REDD1 expression in HG-injured podocytes.

CONCLUSION

Our data demonstrate that decreasing REDD1 expression protects cultured podocytes from HG-induced injuries by potentiating Nrf2 signaling through regulation of the AKT/GSK-3β pathway. Our work underscores the potential role of REDD1-mediated podocyte injury during the development of diabetic kidney disease.

The effects of alpha-pinene on the Nrf2-HO1 signaling pathway in gastric damage in rats

BACKGROUND

Alpha-pinene (α-pinene) is a monoterpene with gastroprotective activity. We evaluated the gastroprotective effect of α-pinene in the gastric damage model with ethanol.

METHODS

We evaluated the macroscopic evaluation of the stomach cavity, alteration in pH, mRNA expression of nuclear factor erythroid 2- related factor 2 (Nrf2) and heme oxygenase-1 (HO-1), total antioxidant capacity (TAC) levels, and histopathological changes.

RESULTS

Pretreatment with α-pinene (10, 50 and 100 mg/kg i.p.) before oral administration of ethanol reduced gastric mucosal damage by increasing the percentage of ulcer inhibition. Alpha-pinene also increased gastric pH similar to omeprazole. In addition, the histopathological examination showed that in the groups pretreated with α-pinene 50 and 100 mg/kg, and omeprazole20 mg/kg, the lesions were less than the control group. Moreover, α- pinene 10, 50, 100, and omeprazole 20 mg/kg upregulated the NRF2 and HO1.

CONCLUSIONS

Our results show that pretreatment with α-pinene is effective in reducing ethanol-induced gastric damage through regulation of Nrf2/HO-1.

Involvement of DPP3 in modulating oncological features and oxidative stress response in esophageal squamous cell carcinoma

Resistance to therapy in esophageal squamous cell carcinoma (ESCC) is a critical clinical problem and identification of novel therapeutic targets is highly warranted. Dipeptidyl peptidase III (DPP3) is a zinc-dependent aminopeptidase and functions in the terminal stages of the protein turnover. Several studies have reported overexpression and oncogenic functions of DPP3 in numerous malignancies. The present study aimed to determine the expression pattern and functional role of DPP3 in ESCC. DPP3 expression was assessed in normal and tumor tissues using quantitative real-time (qRT)-PCR and corroborated with ESCC gene expression datasets from Gene Expression Omnibus (GEO) and The cancer genome atlas (TCGA). DPP3 stable knockdown was performed in ESCC cells by shRNA and its effect on cell proliferation, migration, cell cycle, apoptosis, and activation of nuclear factor erythroid 2-related factor 2 (NRF2) pathway was assessed. The results suggested that DPP3 is overexpressed in ESCC and its knockdown leads to reduced proliferation, increased apoptosis, and inhibited migration of ESCC cells. Additionally, DPP3 knockdown leads to down-regulation of the NRF2 pathway proteins, such as NRF2, G6PD, and NQO1 along with increased sensitivity toward oxidative stress-induced cell death and chemotherapy. Conclusively, these results demonstrate critical role of DPP3 in ESCC and DPP3/NRF2 axis may serve as an attractive therapeutic target against chemoresistance in this malignancy.

Mild sleep restriction increases endothelial oxidative stress in female persons

Sleep restriction is associated with increased cardiovascular risk, which is more pronounced in female than male persons. We reported recently first causal evidence that mild, prolonged sleep restriction mimicking "real-life" conditions impairs endothelial function, a key step in the development and progression of cardiovascular disease, in healthy female persons. However, the underlying mechanisms are unclear. In model organisms, sleep restriction increases oxidative stress and upregulates antioxidant response via induction of the antioxidant regulator nuclear factor (erythroid-derived 2)-like 2 (Nrf2). Here, we assessed directly endothelial cell oxidative stress and antioxidant responses in healthy female persons (n = 35) after 6 weeks of mild sleep restriction (1.5 h less than habitual sleep) using randomized crossover design. Sleep restriction markedly increased endothelial oxidative stress without upregulating antioxidant response. Using RNA-seq and a predicted protein-protein interaction database, we identified reduced expression of endothelial Defective in Cullin Neddylation-1 Domain Containing 3 (DCUN1D3), a protein that licenses Nrf2 antioxidant responses, as a mediator of impaired endothelial antioxidant response in sleep restriction. Thus, sleep restriction impairs clearance of endothelial oxidative stress that over time increases cardiovascular risk.Trial Registration: NCT02835261 .

Denervation aggravates renal ischemia reperfusion injury via BMAL1-mediated Nrf2/ARE pathway

AIM

To explore the change of clock gene rhythm under renal denervation (RDN) and its effect on renal function and oxidative stress during renal ischemia-reperfusion (IR) injury.

METHOD

C57/BL6 mice were randomly divided into 4 groups at daytime 7 A M (zeitgeber time [ZT] 0) or at nighttime 7 P M (ZT12) in respectively: Sham (S) group, RDN group, IR group and RDN + IR (DIR) group. Renal pathological and functional changes were assessed by H&E staining, and serum creatinine, urea nitrogen and neutrophil gelatinase-associated lipocalin levels. Renal oxidative stress was detected by SOD and MDA levels, and renal inflammation was measured by IL-6, IL-17 A F and TNF-ɑ levels. BMAL1, CLOCK, Nrf2 and HO-1 mRNA and protein expressions were tested by qPCR and Western Blot.

RESULT

Compared with S groups, the rhythm of BMAL1, CLOCK and Nrf2 genes in the kidney were disordered in RDN groups, while renal pathological and functional indexes did not change significantly. Compared with IR groups, renal pathological and functional indexes were significantly higher in the DIR groups, as well as oxidative stress and inflammation in renal tissues. The nocturnal IR injury in the RDN kidney was the worst while the BMAL1, Nrf2 and HO-1 expressions were the highest. In DIR groups, renal injury was aggravated after the Brusatol treatment, but there was no significant improvement after the t-BHQ treatment at night, which might be consistent with the changes of Nrf2 and HO-1 protein expressions.

CONCLUSION

RDN lead to the disruption of BMAL1-mediated Nrf2 rhythm accumulation in the kidney, which reduced the renal ability to resist oxidative stress and inflammation, due to the impaired effect of activating Nrf2/ARE pathway in renal IR injury at nighttime.

Ozone pretreatment alleviates ischemiareperfusion injury-induced myocardial ferroptosis by activating the Nrf2/Slc7a11/Gpx4 axis

Myocardial ischemiareperfusion injury (MIRI) is defined as the additional damage that occurs during the process of restoring blood flow to the heart tissue after ischemia-induced damage. Ozone is a powerful oxidizer, but low concentrations of ozone can protect various organs from oxidative stress. Some studies have demonstrated a link between ozone and myocardioprotection, but the mechanism remains unclear. To establish an in vivo animal model of ischemiareperfusion injury (I/R), this study utilized C57 mice, while an in vitro model of hypoxia-reoxygenation (H/R) injury was developed using H9c2 cardiomyocytes to simulate ischemiareperfusion injury. Ozone pretreatment was used in in vitro and in vivo experiments. Through this research, we found that ozone therapy can reduce myocardial injury, and further studies found that ozone regulates the expression levels of these ferroptosis-related proteins and transcription factors in the H/R model, which were screened by bioinformatics. In particular, nuclear translocation of Nrf2 was enhanced by pretreatment with ozone, inhibited ferroptosis and ameliorated oxidative stress by initiating the expression of Slc7a11 and Gpx4. Significantly, Nrf2 gene silencing reverses the protective effects of ozone in the H/R model. In summary, our results suggest that ozone protects the myocardium from I/R damage through the Nrf2/Slc7a11/Gpx4 signaling pathway, highlighting the potential of ozone as a new coronary artery disease therapy.

Omentin-1 ameliorates experimental inflammatory bowel disease via Nrf2 activation and redox regulation

AIMS

Omentin-1 production is decreased in patients with IBD. However, the specific role of Omentin-1 in IBD has not been fully elucidated. This study aimed to investigate the expression and role of Omentin-1 in IBD and the potential mechanisms.

MAIN METHODS

We collected human serum and colon biopsy samples at the Wuhan Union Hospital. Omentin-1 recombinant protein was injected intraperitoneally in a DSS-induced experimental IBD mouse model. Omentin-1 levels were measured in IBD patients, colitis mice, and LPS-induced HT-29 cells. Omentin-1 and/or a Nrf2 specific inhibitor (ML385) were administered to DSS mice and LPS-induced HT-29 cells. The effects of Omentin-1 on inflammation, intestinal barrier function, Nrf2 pathway, oxidative stress, and NF-κB signaling were detected in vivo and in vitro.

KEY FINDINGS

Serum Omentin-1 levels were significantly reduced in UC and CD patients compared with controls (173.7 (IQR, 120.1-221.2) ng/ml, 80.8 (43.8-151.8) ng/ml, and 270.7 (220.7-306.5) ng/ml, respectively). The levels of Omentin-1 were also significantly lower in colitis mice and LPS-induced HT-29 cells. Omentin-1 treatment effectively ameliorated inflammation and impaired intestinal barrier, decreased ROS and MDA levels, and increased GSH and SOD production in the DSS-induced colitis mice and LPS-induced HT-29 cells. Mechanically, Omentin-1 repaired the intestinal barrier by activating Nrf2, then improving oxidative stress and inhibiting NF-κB signaling. Furthermore, the interaction between Omentin-1 and Nrf2 was identified.

SIGNIFICANCE

Omentin-1 activates the Nrf2 pathway to regulate redox balance, ultimately protecting intestinal barrier function and reducing intestinal inflammation. In general, Omentin-1 can be used as a promising therapeutic target for IBD.

High-Frequency Repetitive Magnetic Stimulation Activates Bactericidal Activity of Macrophages via Modulation of p62/Keap1/Nrf2 and p38 MAPK Pathways

The effects of repetitive magnetic stimulation (rMS) have predominantly been studied in excitable cells, with limited research in non-excitable cells. This study aimed to investigate the impact of rMS on macrophages, which are crucial cells in the innate immune defense. THP-1-derived macrophages subjected to a 5 min session of 10 Hz rMS exhibited increased Nrf2 activation and decreased Keap1 expression. We found that activation of the Nrf2 signaling pathway relied on rMS-induced phosphorylation of p62. Notably, rMS reduced the intracellular survival of Staphylococcus aureus in macrophages. Silencing Nrf2 using siRNA in THP-1-derived macrophages or utilizing Nrf2 knockout in alveolar macrophages abolished this effect. Additionally, rMS attenuated the expression of IL-1β and TNF-α inflammatory genes by S. aureus and inhibited p38 MAPK activation. These findings highlight the capacity of rMS to activate the non-canonical Nrf2 pathway, modulate macrophage function, and enhance the host's defense against bacterial infection.

Microglia Sirt6 modulates the transcriptional activity of NRF2 to ameliorate high-fat diet-induced obesity

BACKGROUND

Microglia play a pivotal role in neuroinflammation, while obesity triggers hypothalamic microglia activation and inflammation. Sirt6 is an important regulator of energy metabolism in many peripheral tissues and hypothalamic anorexic neurons. However, the exact mechanism for microglia Sirt6 in controlling high-fat diet-induced obesity remain unknown.

METHODS

Microglia Sirt6 expression levels under various nutritional conditions were measured in the hypothalamus of mice. Also, microglia Sirt6-deficient mice were provided various diets to monitor metabolic changes and hypothalamic inflammatory response. Besides, RNA-seq and Co-IP of microglia with Sirt6 alterations were conducted to further investigate the detailed mechanism by which Sirt6 modulated microglia activity.

RESULTS

We found that Sirt6 was downregulated in hypothalamic microglia in mice given a high-fat diet (HFD). Additionally, knockout of microglia Sirt6 exacerbated high-fat diet-induced hypothalamic microglial activation and inflammation. As a result, mice were more prone to obesity, exhibiting a decrease in energy expenditure, impaired glucose tolerance, insulin and leptin resistance, and increased food intake. In vitro, Sirt6 overexpression in BV2 cells displayed protective effects against oleic acid and palmitic acid treatment-derived inflammatory response. Mechanically, Sirt6 deacetylated and stabilised NRF2 to increase the expression of anti-oxidative genes and defend against reactive oxygen species overload. Pharmacological inhibition of NRF2 eliminated the beneficial modulating effects of Sirt6 on microglial activity.

CONCLUSION

Collectively, our results revealed that microglial Sirt6 was a primary contributor of microglial activation in the central regulation of obesity. Thus, microglial Sirt6 may be an important therapeutic target for obesity.

Interferon Gamma Enhances Cytoprotective Pathways via Nrf2 and MnSOD Induction in Friedreich's Ataxia Cells

Friedreich's ataxia (FRDA) is a rare monogenic disease characterized by multisystem, slowly progressive degeneration. Because of the genetic defect in a non-coding region of FXN gene, FRDA cells exhibit severe deficit of frataxin protein levels. Hence, FRDA pathophysiology is characterized by a plethora of metabolic disruptions related to iron metabolism, mitochondrial homeostasis and oxidative stress. Importantly, an impairment of the antioxidant defences exacerbates the oxidative damage. This appears closely associated with the disablement of key antioxidant proteins, such as the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) and the mitochondrial superoxide dismutase (MnSOD). The cytokine interferon gamma (IFN-γ) has been shown to increase frataxin expression in FRDA cells and to improve functional deficits in FRDA mice. Currently, IFN-γ represents a potential therapy under clinical evaluation in FRDA patients. Here, we show that IFN-γ induces a rapid expression of Nrf2 and MnSOD in different cell types, including FRDA patient-derived fibroblasts. Our data indicate that IFN-γ signals two separate pathways to enhance Nrf2 and MnSOD levels in FRDA fibroblasts. MnSOD expression increased through an early transcriptional regulation, whereas the levels of Nrf2 are induced by a post-transcriptional mechanism. We demonstrate that the treatment of FRDA fibroblasts with IFN-γ stimulates a non-canonical Nrf2 activation pathway through p21 and potentiates antioxidant responses under exposure to hydrogen peroxide. Moreover, IFN-γ significantly reduced the sensitivity to hydrogen peroxide-induced cell death in FRDA fibroblasts. Collectively, these results indicate the presence of multiple pathways triggered by IFN-γ with therapeutic relevance to FRDA.

Chemical mitophagy modulators: Drug development strategies and novel regulatory mechanisms

Maintaining mitochondrial homeostasis is a potential therapeutic strategy for various diseases, including neurodegenerative diseases, cardiovascular diseases, metabolic disorders, and cancer. Selective degradation of mitochondria by autophagy (mitophagy) is a fundamental mitochondrial quality control mechanism conserved from yeast to humans. Indeed, small-molecule modulators of mitophagy are valuable pharmaceutical tools that can be used to dissect complex biological processes and turn them into potential drugs. In the past few years, pharmacological regulation of mitophagy has shown promising therapeutic efficacy in various disease models. However, with the increasing number of chemical mitophagy modulator studies, frequent methodological flaws can be observed, leading some studies to draw unreliable or misleading conclusions. This review attempts (a) to summarize the molecular mechanisms of mitophagy; (b) to propose a Mitophagy Modulator Characterization System (MMCS); (c) to perform a comprehensive analysis of methods used to characterize mitophagy modulators, covering publications over the past 20 years; (d) to provide novel targets for pharmacological intervention of mitophagy. We believe this review will provide a panorama of current research on chemical mitophagy modulators and promote the development of safe and robust mitophagy modulators with therapeutic potential by introducing high methodological standards.

Medicinal Chemistry Insights into the Development of Small-Molecule Kelch-Like ECH-Associated Protein 1-Nuclear Factor Erythroid 2-Related Factor 2 (Keap1-Nrf2) Protein-Protein Interaction Inhibitors

Oxidative stress has been implicated in a wide range of pathological conditions. The transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) exerts a central role in regulating the cellular defense system against oxidative and electrophilic insults. Nonelectrophilic inhibition of the protein-protein interaction (PPI) between Kelch-like ECH-associated protein 1 (Keap1) and Nrf2 has become a promising approach to activate Nrf2. Recently, multiple drug discovery strategies have facilitated the development of small-molecule Keap1-Nrf2 PPI inhibitors with potent activity and favorable drug-like properties. In this Perspective, we summarize the latest progress of small-molecule Keap1-Nrf2 PPI inhibitors from medicinal chemistry insights and discuss future prospects and challenges in this field.