Nitric oxide induces apoptosis in human gingival fibroblast through mitochondria-dependent pathway and JNK activation

Mitochondrial Dysfunction in Periodontitis and Associated Systemic Diseases: Implications for Pathomechanisms and Therapeutic Strategies

Periodontitis is a chronic infectious disorder damaging periodontal tissues, including the gingiva, periodontal ligament, cementum, and alveolar bone. It arises from the complex interplay between pathogenic oral bacteria and host immune response. Contrary to the previous view of "energy factories", mitochondria have recently been recognized as semi-autonomous organelles that fine-tune cell survival, death, metabolism, and other functions. Under physiological conditions, periodontal tissue cells participate in dynamic processes, including differentiation, mineralization, and regeneration. These fundamental activities depend on properly functioning mitochondria, which play a crucial role through bioenergetics, dynamics, mitophagy, and quality control. However, during the initiation and progression of periodontitis, mitochondrial quality control is compromised due to a range of challenges, such as bacterial-host interactions, inflammation, and oxidative stress. Currently, mounting evidence suggests that mitochondria dysfunction serves as a common pathological mechanism linking periodontitis with systemic conditions like type II diabetes, obesity, and cardiovascular diseases. Therefore, targeting mitochondria to intervene in periodontitis and multiple associated systemic diseases holds great therapeutic potential. This review provides advanced insights into the interplay between mitochondria, periodontitis, and associated systemic diseases. Moreover, we emphasize the significance of diverse therapeutic modulators and signaling pathways that regulate mitochondrial function in periodontal and systemic cells.

Physiopathology of nitric oxide in the oral environment and its biotechnological potential for new oral treatments: a literature review

OBJECTIVES

A narrative review on the NO properties and their relationship with the oral environment describing NO's molecular origin, role, and perspectives regarding oral pathological, physiological, and regenerative processes for future applications and possible use as prevention or treatment in dentistry.

MATERIALS AND METHODS

Pubmed was searched using the word "nitric oxide." Reviews, clinical studies, and experimental studies were eligible for the screening process. Similar search procedures were then performed with the additional search words "conservative dentistry," "orthodontics," "endodontics," "implants," "periodontics," "oral cancer," "pulp revascularization," and "oral surgery." Furthermore, references of included articles were examined to identify further relevant articles.

RESULTS

There is a relationship between NO production and oral diseases such as caries, periodontal diseases, pulp inflammation, apical periodontitis, oral cancer, with implants, and orthodontics. Studies on this relationship and uses of NO, in diagnosis, prevention, and treatment, are being developed. Also, some NO and oral cavity patents have already registered.

CONCLUSIONS

The understanding of how NO can interfere in oral health maintenance or disease processes can contribute to elucidate the disease development and optimize treatment approaches.

CLINICAL RELEVANCE

NO has considerable biotechnological potential and can contribute to improving diagnostics and treating the oral environment. As a biomarker, NO has an important role in the early diagnosis of diseases. Regarding treatments, NO can possibly be used as a regulator of inflammation, anti-biofilm action, replacing antibiotics, inducing apoptosis of cancerous cells, and contributing to the angiogenesis. All these studies are initial considerations regarding the relationship between NO and dentistry.

Inorganic nitrite increases the susceptibility of tilapia (Oreochromis niloticus) leucocytes to Streptococcus agalactiae

Deteriorating water quality, especially from high concentrations of nitrite, is currently largely blamed for disease outbreaks in farmed tilapia (Oreochromis niloticus). In this study, the underlying mechanism of nitrite on the susceptibility of tilapia leucocytes to Streptococcus agalactiae (S. agalactiae) was studied. We found that a high dose of heat-killed S. agalactiae decreased tilapia leucocytes cell viability, whereas nitrite decreased the cell viability of leucocytes exposed to a low dose of bacteria. Bacterial challenge increased the production of nitric oxide (NO), whereas nitrite and bacteria coexposure caused higher NO production than nitrite or bacterial exposure alone. Cell viability increased after elimination of NO, and negative correlations existed between cell viability and the NO content, suggesting that nitrite increased the susceptibility of the leucocytes against S. agalactiae was NO-dependent. For a more comprehensive understanding of the mechanism of nitrite affecting disease resistance in tilapia leucocytes, an RNA-Seq-based transcriptome was generated. The results showed that 6173 transcripts were differently expressed, and the differentially expressed transcripts (DETs) of the bacterial group, nitrite group and bacteria-nitrite co-treatment group compared to the control group were selected for GO and KEGG analyses. The DETs in the bacterial group and bacteria-nitrite cotreatment group were highly involved with the membrane component, signal transduction, and immune responses. KEGG analysis showed that the protein processing in the endoplasmic reticulum and the AMPK signaling pathway, which are related to autophagy, were significantly enriched in the cotreatment group but not in bacterial group. In addition, the mRNA expression of ten DETs and several autophagy and apoptosis related genes validated by q-PCR showed the high reliability of the RNA-seq. Taken together, the results of this study suggest that nitrite may increase the susceptibility of tilapia leucocytes to S. agalactiae by generating excess NO to affect the autophagy and apoptosis process.

Resveratrol protects against sodium nitroprusside induced nucleus pulposus cell apoptosis by scavenging ROS

Oxidative stress induced disc cell apoptosis plays an important role in intervertebral disc (IVD) degeneration. The present study aims to investigate effects of resveratrol (RV), a natural polyphenol compound, on sodium nitroprusside (SNP) induced nucleus pulposus (NP) cell apoptosis and related mechanism. Rat NP cells were pretreated with RV, N-acetyl cysteine (NAC) and carboxy-PTIO (PTIO) before SNP treatment. Cell Counting Kit-8 assay was carried out for cell viability evaluation. Annexin V/propidium iodide (PI), Hoechst 33258 and Actin‑Tracker Green and Tubulin-Tracker Red staining were conducted to detect NP cell apoptosis and apoptotic structural changes. Mitochondrial membrane potential (ΔΨm) was analyzed with tetramethylrhodamine methyl ester staining. DCFH-DA and DAF-FM DA staining was used to determine intracellular reactive oxygen species (ROS) and nitric oxide (NO) levels. An ex vivo experiment was also carried out followed by TUNEL assay of sections of discs. SNP induced NP cell apoptosis, excessive production of intracellular ROS and NO, reduction of ΔΨm as well as disruption of cytoskeletal and morphological structure. Meanwhile, organ culture results showed that SNP induced NP cell apoptosis ex vivo. RV and NAC siginificantly inhibited SNP induced NP cell apoptosis, production of intracellular ROS, deline of ΔΨm as well as disruption of cytoskeletal and morphological structure, while RV did not suppress NO production. RV and NAC could also suppress SNP induced NP cell apoptosis ex vivo. However, PTIO did not prevent SNP induced NP cell apoptosis, though it scavenged NO significantly. In conclusion, RV protects against SNP induced NP cell apoptosis by scavenging ROS but not NO, suggesting a promising prospect of RV in IVD degeneration retardation.

Nitric oxide mediates apoptosis and mitochondrial dysfunction and plays a role in growth hormone deficiency by nivalenol in GH3 cells

Nivalenol (NIV), a type B trichothecenes commonly found in cereal crops, can cause growth impairment in animals. However, limited information about its mechanisms is available. Trichothecenes have been characterized as an inhibitor of protein synthesis and induce apoptosis in cells. Oxidative stress is considered an underlying mechanism. However, whether NIV can induce oxidative stress and apoptosis in rat pituitary cells line GH3 is unclear. The present study showed that NIV significantly reduced the viability of cells and caused oxidative stress in GH3 cells. Further experiments showed that nitric oxide (NO), but not ROS, mediated NIV-induced oxidative stress. Additionally, NIV induced caspase-dependent apoptosis, decrease in mitochondrial membrane potential and mitochondrial ultrastructural changes. However, NIV-induced caspase activation, mitochondrial damage and apoptosis were partially alleviated by Z-VAD-FMK or NO scavenger hemoglobin. Finally, NIV changed the expression of growth-associated genes and pro-inflammatory cytokines. NIV also reduced the GH secretion in GH3 cells, which was reversed by hemoglobin. Taken together, these results suggested that NIV induced apoptosis in caspase-dependent mitochondrial pathway in GH3 cells, which might be an underlying mechanism of NIV-induced GH deficiency. Importantly, NO played a critical role in the induction of oxidative stress, apoptosis and GH deficiency in NIV-treated GH3 cells.

Immunobiology of Nitric Oxide and Regulation of Inducible Nitric Oxide Synthase

Nitric oxide (NO) is a bioactive gas that has multiple roles in innate and adaptive immune responses. In macrophages, nitric oxide is produced by inducible nitric oxide synthase upon microbial and cytokine stimulation. It is needed for host defense against pathogens and for immune regulation. This review will summarize the role of NO and iNOS in inflammatory and immune responses and will discuss the regulatory mechanisms that control inducible nitric oxide synthase expression and activity.

Structure Determinants of Lagunamide A for Anticancer Activity and Its Molecular Mechanism of Mitochondrial Apoptosis

Marine natural products are served as attractive source of anticancer therapeutics, with the great success of "first-in-class" drugs, such as Yondelis, Halaven, and Brentuximab vendotin. Lagunamides A-C from marine cyanobacterium, Lyngbya majuscula, exhibit exquisite growth inhibitory activities against cancer cells. In this study, we have systematically investigated the structure-activity relationships (SARs) of a concise collection of lagunamide A and its analogues constructed by total chemical synthesis against a broad panel of cancer cells derived from various tissues or organs, including A549, HeLa, U2OS, HepG2, BEL-7404, BGC-823, HCT116, MCF-7, HL-60, and A375. The R configuration of lagunamide A at C-39 position was found to be the structure determinant for anticancer activity. Further molecular mechanism study in A549 cells revealed that lagunamide A induced caspase-mediated mitochondrial apoptosis. Accompanied with the dissipation of mitochondrial membrane potential (Δφm) and overproduction of reactive oxygen species (ROS), lagunamide A led to mitochondrial dysfunction and finally caused cell death. Moreover, both anti- and pro-apoptotic B-cell lymphoma 2 (Bcl-2) family proteins participated in lagunamide A-induced mitochondrial apoptosis, especially myeloid cell leukemia-1 (Mcl-1). Overexpression of Mcl-1 partly rescued A549 cells from lagunamide A-induced apoptosis. This study suggests that lagunamide A may exert anticancer property through mitochondrial apoptosis. Together, our findings would provide insightful information for the design of new anticancer drugs derived from lagunamides.

EBP50 induces apoptosis in macrophages by upregulating nitric oxide production to eliminate intracellular Mycobacterium tuberculosis

Mycobacterium bovis BCG is known to have the capacity to inhibit the positioning of iNOS on BCG-containing phagosomes by interfering with EBP50, a scaffolding protein that controls the recruitment of inducible nitric oxide synthase (iNOS) at the vicinity of phagosomes in macrophages. However, knockdown of the expression of EBP50 still facilitates the intracellular survival of BCG, which suggested that EBP50 may have some other unknown antimycobacterial properties. In this study we show that overexpression of EBP50 by a recombinant lentivirus had no effect on the iNOS recruitment to M.tuberculosis-containing phagosomes, but significantly promoted the elimination of intracellular M.tuberculosis. We revealed in the present study that the enhancement of intracellular killing to M. tuberculosis upon EBP50 overexpression was due to the increased level of apoptosis in macrophages. We showed that EBP50 overexpression significantly increased the expression of iNOS and generation of nitric oxide (NO), and EBP50-induced apoptosis was NO-dependent and mediated by Bax and caspase-3. We found that M. tuberculosis decreases while Mycobacterium smegmatis increases the expression of EBP50 in RAW264.7 cells, which suggested that virulent mycobacteria are capable of modulating the antimycobacterial properties of macrophages by inhibiting the expression and interfering with the function of EBP50.

Involvement of nitric oxide in the induction of interleukin-1 beta in microglia

In response to in vitro stimulation with lipopolysaccharide (LPS), microglia induce the production of the inflammatory cytokine interleukin-1 beta (IL-1β) together with nitric oxide (NO) and superoxide anion (O2(-)). Here we investigated the role of NO and O2(-) in the signaling mechanism by which IL-1β is induced in microglia. The LPS-inducible IL-1β was significantly suppressed by pretreatment with the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide, but not by pretreatment with the O2(-) scavenger N-acetyl cysteine, suggesting the close association of NO with IL-1β induction. The pretreatment of microglia with the inducible NO synthase inhibitor 1400W prior to LPS stimulation significantly reduced the production of IL-1β, and the addition of the NO donor S-nitroso-N-acetyl-DL-penicillamine (SNAP) into microglia led to the induction of IL-1β. These results suggested that NO induces IL-1β through a specific signaling cascade. LPS-dependent IL-1β induction was significantly suppressed by inhibitors of extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK) and nuclear factor kappaB (NFκB), indicating that ERK/JNK and NFκB serve in the cascade of IL-1β induction. As expected, ERK/JNK and NFκB were all activated in the SNAP-stimulated microglia. Taken together, these results indicate that NO is an important signaling molecule for the ERK/JNK and NFκB activations, which are requisite to the induction of IL-1β in microglia.