Nitric oxide : biology and chemistry最新文献

As an endogenous gas signaling molecule, hydrogen sulfide (H₂S) has been proved to have a variety of biological activities. Studies have shown that in some disease state H₂S concentration in the body is lower than normal state. Based on these findings, exogenous H₂S supplementation is expected to be an effective treatment for many diseases. In recent years, a lot of H₂S-releasing substances, namely H₂S donors, have emerged as H₂S sources. Specifically, various H₂S donors also could be connected to drugs or compounds to form H₂S donor conjugates. Many studies have found that H₂S donor conjugates can not only retain the activity of the parent drug, but also reduce the adverse effects of the parent drug, this makes H₂S donor conjugates to be a new kind of drug candidates. In this article, H₂S donor conjugates will be reviewed and classified according to different diseases, such as inflammation, cardiovascular and cerebrovascular diseases, diseases of central nervous system and cancer. This review aims to provide an idea for researchers for further study of H₂S and H₂S donor conjugates.

Aim: Sepsis and septic shock remain are significant causes of mortality in the world. The inflammatory response should be at the basis of all organ dysfunction such as cardiovascular dysfunction, characterized by severe hypotension refractory to volume replacement and vasoconstrictor therapy. Nitric oxide (NO) has been implicated as a key element in both inflammatory and cardiovascular components of sepsis. In addition to activating soluble guanylate cyclase and potassium channels, NO also modifies proteins post-translationally by reacting with protein thiol groups, yielding S-nitrosothiols (RS-NO), which can act as endogenous NO reservoirs. Besides its use in quantifying free sulfhydryl groups of proteins and non-protein thiols, DTNB [5,5'-dithiobis-(2-nitrobenzoic acid)] has also been used as a pharmacological tool due to its specificity for oxidizing reactive sulfhydryl groups. Here we aimed to investigate the effects of DTNB in the inflammatory aspects of a sepsis model and to verify whether its effects can be attributed to S-denitrosylation.

Methods: Anesthetized female Swiss mice were intratracheally injected with 1 × 10⁸ CFU of K. pneumoniae. Twelve hours after pneumonia-induced sepsis, the animals were injected with vehicle (sodium bicarbonate 5 %, s.c.) or DTNB (31.5, 63 and 126 μmol/kg, s.c.). Twenty-four hours post-sepsis induction, plasma, bronchoalveolar lavage (BAL), and lung tissues were collected for assays (protein, cell count, nitrite + nitrate levels (NOx), cytokine levels, and sulfhydryl groups). In addition, lung S-nitrosylated proteins were visualized by a modified tissue assay for S-nitrosothiols.

Results: Sepsis induced a significant vascular leakage in the lungs and elevated NOx levels in BAL, both reduced by DTNB. BAL leukocytosis and elevated IL-1β induced by sepsis were also reduced by DTNB, whereas it did not affect bacterial dissemination to liver, heart and BAL. Sepsis reduced free sulfhydryl groups in BAL and lung and DTNB did not change it. On the other hand, DTNB substantially reduced protein S-nitrosylation levels in the lung parenchyma and halved sepsis-induced mortality in septic mice.

Conclusion: Our results show that the administration of DTNB 12 h after bacterial instillation reduced most of the local inflammatory parameters and, more importantly, decreased mortality. These beneficial effects may be due to S-denitrosylation of RS-NO pools carried out by DTNB. Since DTNB was effective in reducing the inflammatory process after its onset, this mechanism of action could serve as a valuable proof of concept for compounds that can be useful to interfere with sepsis outcome.

Our previous study has shown that hydrogen sulfide (H₂S) can attenuate cigarette smoke exposure (CSE)-induced placental injury in rats. This study investigated whether H₂S alleviates CSE-induced endothelial glycocalyx (eGC) impairment and promotes placental angiogenesis in rats. Twenty-four pregnant rats were randomly divided into four groups: control, NaHS (a donor of H₂S), CSE, and CSE + NaHS. On gestational day 21, rat placentas were collected to detect H₂S levels and protein expression of the H₂S-synthesizing enzymes, cystathionine beta synthase (CBS), cystathionine gamma-lyase (CGL), and 3-mercaptopyruvate sulfurtransferase (3-MST), using a C-7Az fluorescent probe, H₂S testing kit, and western blotting, respectively. Transmission electron microscopy and double immunofluorescence staining were performed to observe the placental eGC alterations. Placental angiogenesis, vascular endothelial proliferation and apoptosis, and protein expression levels of the PI3K/AKT/mTOR signaling pathway were assessed in rat placentas. The results showed that the administration of NaHS markedly attenuated the reduction in H₂S levels and the decrease in CBS, CGL, and 3-MST expression caused by CSE in rat placentas. Notably, NaHS treatment distinctly alleviated eGC damage and facilitated placental angiogenesis in CSE-treated rats. NaHS administration effectively promoted placental vascular endothelial proliferation and suppressed endothelial apoptosis in CSE-treated rats. Furthermore, NaHS treatment markedly elevated the phosphorylation of PI3K, AKT, and mTOR in the placenta of CSE-treated rats. Taken together, these results indicate that exogenous administration of H₂S can alleviate CSE-induced eGC damage and promote placental angiogenesis in CSE-treated rats, suggesting that H₂S may be a novel therapeutic agent for the treatment of CSE-associated vascular disease.

l-arginine derivatives (ADMA, SDMA, NMMA) are endogenous inhibitors of nitric oxide (NO֗) production, which is essential in critical brain processes including blood-brain barrier (BBB) integrity and long-term potentiation (LTP). ADMA and NMMA are degraded by dimethylarginine dimethylaminohydrolase 1 (DDAH1) and protein arginine methyltransferase 5 (PRMT5) is an emerging epigenetic enzyme that mainly represses transcription of target genes via symmetric dimethylation of arginine residues. There is no data concerning the impact of metabotropic glutamate receptors (mGlu) ligands on this aspect of brain physiology. In the present studies the impact of positive allosteric modulators (PAM) of mGlu5 (CDPPB) and mGlu2 (LY487379) receptors on l-arginine derivatives, DDAH1 and PRMT5 expression in mouse models of cognitive dysfunction induced with MK-801(0.3 mg/kg) or scopolamine (1 mg/kg), was investigated. Experiments were performed both after acute and chronic (14 days) administration of the compounds, which were administered at the doses 0.1-5 mg/kg (CDBBB) and 0.1-1 mg/kg (LY487379). The chronic administration of both compounds normalized the level of l-arginine derivatives in MK-801 model (in brain and plasma) and only low dose of CDPPB prevented scopolamine-induced changes. The expression of DDAH1 and PRMT5 was modulated by CDPPB and LY487379, both in MK-801 and scopolamine models. In the novel object recognition (NOR) test low doses of the compounds, inactive after single administration, prevented cognitive decline after chronic injections. Our findings highlight the potential of mGlu receptor modulators in treating schizophrenia and possibly dementia by normalizing l-arginine derivatives production, preventing from nitric oxide synthases uncoupling.

This study examines KLF4's role in endothelial cells (ECs), emphasizing its effects on nitric oxide (NO) production, microvascular formation, and oxidative stress regulation following ischemic stroke. Through high-throughput sequencing, we identified eight cell subpopulations in carotid artery tissues post-stroke, with KLF4 notably elevated in ECs. KLF4 overexpression in ECs promoted NO synthesis, enhanced endothelial tube formation, mitigated oxidative stress, and improved smooth muscle cells (SMCs) function, collectively boosting blood flow in ischemic regions. These findings highlight KLF4 as pivotal in vascular regeneration and oxidative stress reduction, positioning it as a promising target for cardiovascular and cerebrovascular therapies.

Nitric oxide (NO) is a versatile endogenous molecule with multiple physiological roles, including neurotransmission, vasodilation, and immune regulation. As part of the immune response, NO exerts antimicrobial effects by producing reactive nitrogen species (RNS). These RNS combat pathogens via mechanisms such as DNA deamination, S-nitrosylation of thiol groups, and lipid peroxidation, leading to disruptions in microbial cell membranes and vital protein functions. Due to these broad actions, NO targets many pathogens, including bacteria, fungi, and viruses, with minimal risk of resistance development. Given its potent antimicrobial properties, the therapeutic potential of exogenous NO has been recently studied. Various preparations, such as NO donors, inhaled gaseous NO, and topical preparations, have shown promising results in preclinical and clinical settings. This literature review examines the antimicrobial effects of exogenous NO reported in in vitro studies, animal models, and human clinical trials. We provide an overview of the mechanisms by which NO exerts its antimicrobial activity, highlighting its efficacy against diverse pathogens. By presenting the current findings, we aim to contribute to the growing body of evidence supporting the use of NO as a versatile antimicrobial agent in clinical practice.

COVID-19, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), primarily manifests as a flu-like illness with lung injury, often necessitating supplemental oxygen. Elderly individuals and those with pre-existing cardiovascular diseases are at increased risk of mortality. The endothelial barrier disruption observed in patients indicates systemic viral invasion and widespread endotheliitis. Endothelial dysfunction, characterized by impaired nitric oxide (NO) production, contributes to vasoconstriction, inflammation, and coagulation abnormalities seen in COVID-19. In this study, we investigated the impact of COVID-19 patient-derived plasma on the endothelium through NO metabolite analysis using an in vitro 3D micro vessel model. Our experiments revealed alterations in NO metabolites in response to COVID-19 patient plasma perfusion, with BH4+BH2 supplementation improving citrulline levels in severe COVID-19 patient models. Positive correlation between arginase activity and eNOS activity was observed in the severe COVID-19 patient model but not in the mild COVID-19 patient model. These findings underscore the importance of endothelial dysfunction in COVID-19 pathogenesis and highlight potential therapeutic targets for mitigating vascular complications associated with severe infection.

Background: Osteocytes are crucial for detecting mechanical stimuli and translating them into biochemical responses within the bone. The primary cilium, a cellular 'antenna,' plays a vital role in this process. However, there is a lack of direct correlation between cilium length changes and osteocyte mechanosensitivity changes. This study aims to reveal the relationship between ciliary length and nitric oxide (NO) release in osteocytes to show how primary cilia may be involved in reducing osteocyte mechanosensitivity caused by microgravity.

Materials and methods: We used the MLO-Y4 cell line and primary osteoblasts to adjust the ciliary length using chloral hydrate (CH) for shortening and lithium ions (Li⁺) for elongation. We then examined the impact of varied ciliary lengths on osteocyte response to fluid shear stress, focusing on the PC1/PC2-Ca²⁺-NO signaling pathway. Co-culture systems assessed downstream effects on osteoblast function, including collagen secretion and mineralization.

Results: We observed a significant correlation between ciliary length and osteocyte mechanosensitivity, with longer primary cilia enhancing Ca²⁺ influx and NO release in response to fluid shear stress. However, contrary to expectations, calmodulin (CaM) expression did not increase with ciliary length, suggesting alternative pathways, such as PKC or Akt/PKB, may modulate p-eNOS activity. Co-cultured osteoblasts showed altered osteogenic functions regulated by osteocyte-derived signals influenced by primary cilia length.

Conclusion: Our findings clarify the role of primary cilia length in modulating osteocyte mechanosensitivity and their influence on osteoblast function, highlighting a complex regulatory network that may not solely rely on CaM for NO release. These insights contribute to a deeper understanding of bone mechanotransduction and could have implications for developing therapeutic targets for osteocyte-related disorders.