Nitric Oxide Synthase Inhibitors into the Clinic at Last

Nicotinamide riboside, pterostilbene and ibudilast protect motor neurons and extend survival in ALS mice

Oxidative stress and neuroinflammation are major contributors to the pathophysiology of ALS. Nicotinamide riboside (a NAD+ precursor) and pterostilbene (a natural antioxidant) were efficacious in a human pilot study of ALS patients and in ALS SOD1G93A transgenic mice. Ibudilast targets different phosphodiesterases and the macrophage migration inhibitory factor, reduces neuroinflammation, and in early-phase studies improved survival and slowed progression in ALS patients. Using two ALS murine models (SOD1G93A, FUSR521C) the effects of nicotinamide riboside, pterostilbene, and ibudilast on disease onset, progression and survival were studied. In both models ibudilast enhanced the effects of nicotinamide riboside and pterostilbene on survival and neuromotor functions. The triple combination reduced microgliosis and astrogliosis, and the levels of different proinflammatory cytokines in the CSF. TNFα, IFNγ and IL1β increased H2O2 and NO generation by motor neurons, astrocytes, microglia and endothelial cells isolated from ALS mice. Nicotinamide riboside and pterostilbene decreased H2O2 and NO generation in all these cells. Ibudilast specifically decreased TNFα levels and H2O2 generation by microglia and endothelial cells. Unexpectedly, pathophysiological concentrations of H2O2 or NO caused minimal motor neuron cytotoxicity. H2O2-induced cytotoxicity was increased by NO via a trace metal-dependent formation of potent oxidants (i.e. OH and -OONO radicals). In conclusion, our results show that the combination of nicotinamide riboside, pterostilbene and ibudilast improve neuromotor functions and survival in ALS murine models. Studies on the underlying mechanisms show that motor neuron protection involves the decrease of oxidative and nitrosative stress, the combination of which is highly damaging to motor neurons.

Insights on the functional dualism of nitric oxide in the hallmarks of cancer

Nitric oxide (NO), a gaseous radical, governs a variety of physiological and pathological processes, including cancer, pro-inflammatory signalling, and vasodilation. The family of nitric oxide synthases (NOS), which comprises the constitutive forms, nNOS and eNOS, and the inducible form, iNOS, produces NO enzymatically. Additionally, NO can be generated non-enzymatically from the nitrate-nitrite-NO pathway. The anti- and pro-oxidant properties of NO and its functional dualism in cancer is due to its highly reactive nature. Numerous malignancies have NOS expression, which interferes with the tumour microenvironment to modulate the tumour's growth in both favourable and unfavourable ways. NO regulates a number of mechanisms in the tumour microenvironment, including metabolism, cell cycle, DNA repair, angiogenesis, and apoptosis/necrosis, depending on its concentration and spatiotemporal profile. This review focuses on the bi-modal impact of nitric oxide on the alteration of a few cancer hallmarks.

Neuronal Nitric Oxide Synthase and Post-Translational Modifications in the Development of Central Nervous System Diseases: Implications and Regulation

In the Central Nervous System (CNS), Nitric Oxide (NO) is mainly biosynthesized by neuronal Nitric Oxide Synthase (nNOS). The dysregulated activation of nNOS in neurons is critical in the development of different conditions affecting the CNS. The excessive production of NO by nNOS is responsible for a number of proteins' post-translational modifications (PTMs), which can lead to aberrant biochemical pathways, impairing CNS functions. In this review, we briefly revise the main implications of dysregulated nNOS in the progression of the most prevalent CNS neurodegenerative disorders, i.e., Alzheimer's disease (AD) and Parkinson's disease, as well as in the development of neuronal disorders. Moreover, a specific focus on compounds able to modulate nNOS activity as promising therapeutics to tackle different neuronal diseases is presented.

Nanowired delivery of antibodies to tau and neuronal nitric oxide synthase together with cerebrolysin attenuates traumatic brain injury induced exacerbation of brain pathology in Parkinson's disease

Concussive head injury (CHI) is one of the major risk factors for developing Parkinson's disease in later life of military personnel affecting lifetime functional and cognitive disturbances. Till date no suitable therapies are available to attenuate CHI or PD induced brain pathology. Thus, further exploration of novel therapeutic agents are highly warranted using nanomedicine in enhancing the quality of life of veterans or service members of US military. Since PD or CHI induces oxidative stress and perturbs neurotrophic factors regulation associated with phosphorylated tau (p-tau) deposition, a possibility exists that nanodelivery of agents that could enhance neurotrophic factors balance and attenuate oxidative stress could be neuroprotective in nature. In this review, nanowired delivery of cerebrolysin-a balanced composition of several neurotrophic factors and active peptide fragments together with monoclonal antibodies to neuronal nitric oxide synthase (nNOS) with p-tau antibodies was examined in PD following CHI in model experiments. Our results suggest that combined administration of nanowired antibodies to nNOS and p-tau together with cerebrolysin significantly attenuated CHI induced exacerbation of PD brain pathology. This combined treatment also has beneficial effects in CHI or PD alone, not reported earlier.

S-Ethyl-Isothiocitrullin-Based Dipeptides and 1,2,4-Oxadiazole Pseudo-Dipeptides: Solid Phase Synthesis and Evaluation as NO Synthase Inhibitors

We previously reported dipeptidomimetic compounds as inhibitors of neuronal and/or inducible NO synthases (n/iNOS) with significant selectivity against endothelial NOS (eNOS). They were composed of an S-ethylisothiocitrullin-like moiety linked to an extension through a peptide bond or a 1,2,4-oxadiazole link. Here, we developed two further series where the extension size was increased to establish more favorable interactions in the NOS substrate access channel. The extension was introduced on the solid phase by the reductive alkylation of an amino-piperidine moiety or an aminoethyl segment in the case of dipeptide-like and 1,2,4-oxadiazole compounds, respectively, with various benzaldehydes. Compared to the previous series, more potent inhibitors were identified with IC₅₀ in the micromolar to the submicromolar range, with significant selectivity toward nNOS. As expected, most compounds did not inhibit eNOS, and molecular modeling was carried out to characterize the reasons for the selectivity toward nNOS over eNOS. Spectral studies showed that compounds were interacting at the heme active site. Finally, selected inhibitors were found to inhibit intra-cellular iNOS and nNOS expressed in RAW264.7 and INS-1 cells, respectively.

Targeting Nitric Oxide: Say NO to Metastasis

Utilizing targeted therapies capable of reducing cancer metastasis, targeting chemoresistant and self-renewing cancer stem cells, and augmenting the efficacy of systemic chemo/radiotherapies is vital to minimize cancer-associated mortality. Targeting nitric oxide synthase (NOS), a protein within the tumor microenvironment, has gained interest as a promising therapeutic strategy to reduce metastatic capacity and augment the efficacy of chemo/radiotherapies in various solid malignancies. Our review highlights the influence of nitric oxide (NO) in tumor progression and cancer metastasis, as well as promising preclinical studies that evaluated NOS inhibitors as anticancer therapies. Lastly, we highlight the prospects and outstanding challenges of using NOS inhibitors in the clinical setting.

Endothelial reactive oxygen-forming NADPH oxidase 5 is a possible player in diabetic aortic aneurysm but not atherosclerosis

Atherosclerosis and its complications are major causes of cardiovascular morbidity and death. Apart from risk factors such as hypercholesterolemia and inflammation, the causal molecular mechanisms are unknown. One proposed causal mechanism involves elevated levels of reactive oxygen species (ROS). Indeed, early expression of the ROS forming NADPH oxidase type 5 (Nox5) in vascular endothelial cells correlates with atherosclerosis and aortic aneurysm. Here we test the pro-atherogenic Nox5 hypothesis using mouse models. Because Nox5 is missing from the mouse genome, a knock-in mouse model expressing human Nox5 in its physiological location of endothelial cells (eNOX5^ki/ki) was tested as a possible new humanised mouse atherosclerosis model. However, whether just on a high cholesterol diet or by crossing in aortic atherosclerosis-prone ApoE^−/− mice with and without induction of diabetes, Nox5 neither induced on its own nor aggravated aortic atherosclerosis. Surprisingly, however, diabetic ApoE^−/− x eNOX5^ki/ki mice developed aortic aneurysms more than twice as often correlating with lower vascular collagens, as assessed by trichrome staining, without changes in inflammatory gene expression, suggesting that endothelial Nox5 directly affects extracellular matrix remodelling associated with aneurysm formation in diabetes. Thus Nox5-derived reactive oxygen species are not a new independent mechanism of atherosclerosis but may enhance the frequency of abdominal aortic aneurysms in the context of diabetes. Together with similar clinical findings, our preclinical target validation opens up a first-in-class mechanism-based approach to treat or even prevent abdominal aortic aneurysms.

Recent advances on endogenous gasotransmitters in inflammatory dermatological disorders

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Endogenous gasotransmitters nitric oxide (NO), carbon monoxide (CO), hydrogen sulfide (H₂S), and potential candidates sulfur dioxide (SO₂), methane (CH₄), hydrogen gas (H₂), ammonia (NH₃) and carbon dioxide (CO₂), are generated within the human body.

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Endogenous and potential gasotransmitters regulate inflammation, vasodilation, and oxidation in inflammatory dermatological disorders.

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Endogenous and potential gasotransmitters play potential roles in psoriasis, atopic dermatitis, acne, and chronic skin ulcers.

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Further research should explore the function of these gases and gas donors and inhibitors in inflammatory dermatological disorders.

Background

Endogenous gasotransmitters are small gaseous mediators that can be generated endogenously by mammalian organisms. The dysregulation of the gasotransmitter system is associated with numerous disorders ranging from inflammatory diseases to cancers. However, the relevance of these endogenous gasotransmitters, prodrug donors and inhibitors in inflammatory dermatological disorders has not yet been thoroughly reviewed and discussed.

Aim of review

This review discusses the recent progress and will provide perspectives on endogenous gasotransmitters in the context of inflammatory dermatological disorders.

Key scientific concepts of review

Endogenous gasotransmitters nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H₂S) are signaling molecules that regulate several physiological and pathological processes. In addition, sulfur dioxide (SO₂), methane (CH₄), hydrogen gas (H₂), ammonia (NH₃), and carbon dioxide (CO₂) can also be generated endogenously and may take part in physiological and pathological processes. These signaling molecules regulate inflammation, vasodilation, and oxidative stress, offering therapeutic potential and attracting interest in the field of inflammatory dermatological disorders including psoriasis, atopic dermatitis, acne, rosacea, and chronic skin ulcers. The development of effective gas donors and inhibitors is a promising alternative to treat inflammatory dermatological disorders with controllable and precise delivery in the future.