Mechanistic and Therapeutic Insights into Nrf2-Mediated Redox Regulation in Periodontitis.

Background:Mitochondrial function is implicated as a target of environmental toxicants and found in disease or injury models, contributing to acute and chronic inflammation. One mechanism by which mitochondrial damage can propagate inflammation is via activation of the nucleotide-binding oligomerization domain (NOD)-like receptor (NLR) family, pyrin domain-containing receptor (NLRP)3 inflammasome, a protein complex that processes mature interleukin . plays an important role in the innate immune response and dysregulation is associated with autoinflammatory disorders.Objective:The objective was to evaluate whether mitochondrial toxicants recruit inflammasome activation and processing.Method:Murine macrophages (RAW 264.7) exposed to tri-organotins (triethyltin bromide (TETBr), trimethyltin hydroxide (TMTOH), triphenyltin hydroxide (TPTOH), bis(tributyltin)oxide) [Bis(TBT)Ox] were examined for pro-inflammatory cytokine induction. TMTOH and TETBr were examined in RAW 264.7 and bone marrow-derived macrophages for mitochondrial bioenergetics, reactive oxygen species (ROS) production, and inflammasome activation via visualization of aggregate formation, caspase-1 flow cytometry, enzyme-linked immunosorbent assay and Western blots, and microRNA (miRNA) and mRNA arrays.Results:TETBr and TMTOH induced inflammasome aggregate formation and release in lipopolysaccharide (LPS)-primed macrophages. Mitochondrial bioenergetics and mitochondrial ROS were suppressed. Il1a and Il1b induction with LPS or challenge was diminished. Differential miRNA and mRNA profiles were observed. Lower miR-151-3p targeted cyclic adenosine monophosphate (cAMP)-mediated and AMP-activated protein kinase signaling pathways; higher miR-6909-5p, miR-7044-5p, and miR-7686-5p targeted Wnt beta-catenin signaling, retinoic acid receptor activation, apoptosis, signal transducer and activator of transcription 3, IL-22, IL-12, and IL-10 signaling. Functional enrichment analysis identified apoptosis and cell survival canonical pathways.Conclusion:Select mitotoxic tri-organotins disrupted murine macrophage transcriptional response to LPS, yet triggered inflammasome activation. The differential response pattern suggested unique functional changes in the inflammatory response that may translate to suppressed host defense or prolong inflammation. We posit a framework to examine immune cell effects of environmental mitotoxic compounds for adverse health outcomes. https://doi.org/10.1289/EHP8314

Oxidative stress, resulting from increased production of reactive oxygen species (ROS) and/or reduced antioxidant defences, has been implicated in cardiovascular disease pathophysiology for over 2 decades. Based on the concept that this drives both the genesis and progression of conditions such as heart failure, numerous clinical trials of antioxidant therapies were undertaken but were unsuccessful. Nevertheless, experimental data linking oxidative stress and heart disease remain compelling and support continued efforts to develop more effective therapies than antioxidant vitamins.1 In the current issue of Circulation , Zhao et al .2 report that cardiomyocyte-specific high-level overexpression of the ROS-generating enzyme NADPH oxidase-4 (Nox4) aggravated angiotensin II-induced cardiac remodeling and was mitigated by a small molecule Nox inhibitor. The authors propose that Nox4 inhibition may have therapeutic potential to treat cardiac remodeling. Is this proposal reasonable and how should such studies be interpreted within a pathophysiological framework for the roles of ROS in heart failure?

Nickel oxide nanoparticles (NiONPs) can trigger reactive oxygen species (ROS) production and NLRP3 inflammasome activation in macrophages as key steps in promoting lung inflammation. However, the impact of NiONP-induced lysosome membrane permeabilization (LMP) on mitochondrial ROS (mtROS) production and NLRP3 inflammasome activation is unknown. Murine ex vivo alveolar macrophages (mexAM) were exposed to NiONPs or crystalline silica (cSiO2) as a positive control particle. Imipramine was used to inhibit LMP before measuring mtROS and NLRP3 inflammasome activation and MitoTEMPO was used to block mtROS before measuring LMP and NLRP3 inflammasome activation. The ability of phagocytosed NiONPs to leach Ni2+ and stimulate ROS production was also assessed. Exposure to either particle resulted in LMP, mtROS production, and NLRP3 inflammasome activation with cSiO2 causing greater effects than NiONPs. LMP was rate-limiting in cSiO2-induced NLRP3 inflammasome activation and mtROS production, which further activated the inflammasome. Similar to cSiO2, NiONP-induced LMP was rate-limiting in NLRP3 inflammasome activation. In contrast to cSiO2, NiONP-induced mtROS was detected whether or not LMP was inhibited. Furthermore, NiONP-derived Ni2+ ions were present in the cytosol whether or not LMP occurred, and Ni2+ release was proportional to measured mtROS production and hydroxyl radical formation. The inability of MitoTEMPO to block the effects of Ni2+ ions on mtROS production suggested an alternative unclear mechanism was involved. This study demonstrates that LMP serves as a pivotal upstream trigger of NLRP3 inflammasome activation and potentially ROS production in response to cSiO2 and NiONPs—underscoring the crucial role of lysosomes in particle-induced inflammation.

This series of debates was initiated for the Journal of Applied Physiology because we believe an important means of searching for truth is through debate where contradictory viewpoints are put forward. This dialectic process whereby a thesis is advanced, then opposed by an antithesis, with a

Interplay between survival and regulated cell death mechanisms during periodontitis progression: a systematic review

Neuroinflammation, along with activation of microglia and oxidative stress, plays an important role in the development and progression of neurodegenerative diseases. During the inflammation process, immune cells release inflammatory mediators such as cytokines and chemicals that may promote the formation and growth of cancer cells. Obtusifolin, an anthraquinone extracted from the seeds of Senna obtusifolin, has anti-inflammatory properties. However, the effect of obtusifolin on neuroinflammation and its regulatory mechanism have not been yet investigated. In the present study, BV2 microglial cells were used to investigate the effects of obtusifolin on LPS-induced inflammatory responses, NLRP3 inflammasome activation, and reactive oxygen species (ROS) production. The secretion of nitric oxide (NO) was analyzed by Griess reagent assay, and the cell viability was detected by the CCK-8 assay. The expressions of iNOS, COX-2, STAT3, ERK, JNK, and p38 were examined using Western blotting, and the production of IL-6 and TNF-α was measured by ELISA. To examine whether obtusifolin affected NLRP3 inflammasome activation, BV2 cells were pretreated with LPS and then stimulated with ATP or nigericin. The secretion of IL-1β was measured by ELISA, whereas the expression of NLRP3 inflammasome-related proteins was detected using Western blotting. The production of ROS was analyzed by flow cytometry. Our experimental results showed that obtusifolin suppressed the production of NO and the secretion of proinflammatory cytokines by LPS-induced BV2 cells under noncytotoxic concentrations. In addition, obtusifolin decreased the expression of iNOS, COX-2, phospho-STAT3, phospho-ERK, phosphor-JNK and phospho-p38, and also attenuated the expression of NLRP3 and ASC, cleaved caspase-1 and cleaved IL-1β by LPS- induced BV2 cells. Moreover, obtusifolin reduced the production of both intracellular and mitochondrial ROS by LPS-induced BV2 cells. Overall, these results demonstrated that obtusifolin attenuated LPS-induced inflammation by suppressing the activation of MAPK and NF-κB signaling pathways, inhibiting NLRP3 inflammasome activation, and reducing the production of ROS in microglia, suggesting that obtusifolin might have benefits in the treatment of neurodegenerative diseases. Citation Format: Hsin Yi Lin, Che-Hsin Lee, Chia-Yang Li. Obtusifolin attenuates LPS-induced inflammation and NLRP3 inflammasome activation by suppressing the MAPK/NF-κB signaling pathway and ROS production in BV2 cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7476.

IntroductionLupus nephritis (LN) is a representative manifestation in systemic lupus erythematosus (SLE). Some studies have shown that myeloid-derived suppressor cells (MDSCs) play a vital role in the regulation of the SLE process. MDSC infiltration in the kidney as well as inflammation and oxidative stress provokes the acceleration and deterioration of LN. Nuclear factor E2-related factor 2 (Nrf2) is thought to be a major regulator of the antioxidant response. Baicalein is a flavonoid with known anti-inflammatory effects and antioxidant response. However, the effects of baicalein on MDSCs, inflammation, and oxidative stress are not evaluated in the development of pristane-induced LN in mice.MethodsThe renoprotective effect of baicalein was detected in a pristane-induced lupus mice model. NLRP3 inflammasome activation and NF-κB phosphorylation as well as reactive oxygen species (ROS) production and Nrf2 activation were examined. The percentages and function changes of MDSCs were measured. The possible mechanisms of the underlying effects of baicalein on ROS production and signaling pathways of Nrf2/heme-oxygenase (HO)-1, NLRP3 inflammasome, and NF-κB phosphorylation in lipopolysaccharide (LPS)-primed MDSCs were analyzed.ResultsBaicalein reduced proteinuria and attenuated renal function impairment and renal histopathology including intrinsic cell proliferation, cellular crescents, and podocyte injury as well as glomerulonephritis activity in lupus mice. Moreover, baicalein downregulated the activation of NLRP3 inflammasome and levels of ROS or NF-κB phosphorylation, and it enhanced Nrf2 activation. Of note, baicalein inhibited the expansion of MDSCs and improved the function of MDSCs in lupus mice. Through analyzing LPS-primed MDSCs in vitro, baicalein was found to exhibit cytoprotective effects coincident with the induction of Nrf2/HO-1 signaling and the suppression of the NLRP3 inflammasome.ConclusionThe data show that baicalein alleviates the symptoms of pristane-induced LN and suggest that the alleviation may be attributed to inhibition of MDSC expansion and regulation of the balance of the Nrf2/HO-1 signal and NLRP3 expression in MDSCs.

Periodontitis is an inflammatory disease accompanied by alveolar bone loss. Moreover, M1 macrophages play a critical role in the development of periodontal disease. Uncoupling protein-2 (UCP2) is a mitochondrial transporter protein that controls M1 macrophage activation by modulating reactive oxygen species (ROS) production. We investigated the role of UCP2 in M1 macrophage infiltration in gingival tissues with periodontitis. We found that the expression of UCP2 was upregulated in M1 macrophages infiltrating human periodontal tissues with periodontitis. Macrophage-specific knockout of UCP2 could increase the infiltration of macrophage and exacerbate inflammatory response in a mouse gingiva affected with periodontitis, induced by Porphyromonas gingivalis-LPS (Pg-LPS) injection. The loss of UCP2 may contribute to the enhanced abilities of proliferation, migration, pro-inflammatory cytokine secretion, and ROS production in Pg-LPS-treated macrophages. Our results indicate that UCP2 has an important role in M1 macrophage polarization in the periodontal tissue with periodontitis. It might be helpful to provide theoretical basis for design of new therapeutic strategies for periodontitis.

Inhibition of cytochrome P450 2E1 and activation of transcription factor Nrf2 are renoprotective in myoglobinuric acute kidney injury

Lipopolysaccharide-Induced Epithelial Monoamine Oxidase Mediates Alveolar Bone Loss in a Rat Chronic Wound Model

Tubulointerstitial inflammation plays a key role in the pathogenesis of diabetic nephropathy (DN). Interleukin-1β (IL-1β) is the key proinflammatory cytokine associated with tubulointerstitial inflammation. The NLRP3 inflammasome regulates IL-1β activation and secretion. Reactive oxygen species (ROS) represents the main mediator of NLRP3 inflammasome activation. We previously reported that CD36, a class B scavenger receptor, mediates ROS production in DN. Here, we determined whether CD36 is involved in NLRP3 inflammasome activation and explored the underlying mechanisms. We observed that high glucose induced-NLRP3 inflammasome activation mediate IL-1β secretion, caspase-1 activation, and apoptosis in HK-2 cells. In addition, the levels of CD36, NLRP3, and IL-1β expression (protein and mRNA) were all significantly increased under high glucose conditions. CD36 knockdown resulted in decreased NLRP3 activation and IL-1β secretion. CD36 knockdown or the addition of MitoTempo significantly inhibited ROS production in HK-2 cells. CD36 overexpression enhanced NLRP3 activation, which was reduced by MitoTempo. High glucose levels induced a change in the metabolism of HK-2 cells from fatty acid oxidation (FAO) to glycolysis, which promoted mitochondrial ROS (mtROS) production after 72 h. CD36 knockdown increased the level of AMP-activated protein kinase (AMPK) activity and mitochondrial FAO, which was accompanied by the inhibition of NLRP3 and IL-1β. The in vivo experimental results indicate that an inhibition of CD36 could protect diabetic db/db mice from tubulointerstitial inflammation and tubular epithelial cell apoptosis. CD36 mediates mtROS production and NLRP3 inflammasome activation in db/db mice. CD36 inhibition upregulated the level of FAO-related enzymes and AMPK activity in db/db mice. These results suggest that NLRP3 inflammasome activation is mediated by CD36 in renal tubular epithelial cells in DN, which suppresses mitochondrial FAO and stimulates mtROS production.

Drugs to Inhibit the NLRP3 Inflammasome: Not Always On Target.

reactive oxygen species (ROS), such as superoxide or hydrogen peroxide, are usually thought of as damaging agents that nonspecifically disrupt proteins, lipids, and nucleic acids ([1][1]). However, there is now considerable evidence that ROS also act as signaling agents in a range of biological

Selenocysteine is inserted into selenoproteins via the translational recoding of a UGA codon, normally used as a stop signal. This process depends on the nature of the selenocysteine insertion sequence element located in the 3' UTR of selenoprotein mRNAs, selenium bioavailability, and, possibly, exogenous stimuli. To further understand the function and regulation of selenoproteins in antioxidant defense and redox homeostasis, we investigated how oxidative stress influences selenoprotein expression as a function of different selenium concentrations. We found that selenium supplementation of the culture media, which resulted in a hierarchical up-regulation of selenoproteins, protected HEK293 cells from reactive oxygen species formation. Furthermore, in response to oxidative stress, we identified a selective up-regulation of several selenoproteins involved in antioxidant defense (Gpx1, Gpx4, TR1, SelS, SelK, and Sps2). Interestingly, the response was more efficient when selenium was limiting. Although a modest change in mRNA levels was noted, we identified a novel translational control mechanism stimulated by oxidative stress that is characterized by up-regulation of UGA-selenocysteine recoding efficiency and relocalization of SBP2, selenocysteine-specific elongation factor, and L30 recoding factors from the cytoplasm to the nucleus.

Role of Phagocyte Oxidase in UVA-Induced Oxidative Stress and Apoptosis in Keratinocytes