[size=+1]Most of us are well aware of the beneficial mechanisms of nitric oxide however.... this thread is in response to all of the hype that accompanies these so-called.... "NO" products, and adresses the reasons why I feel that the hype is complete BS. It also nullifies the entire logic behind NO up-regulation in healthy adults.
The entire premise behind NO products, is NO up-regulation.... IF the NO products even aquired the ability to up-regulate endogenous NO production (wich they don't)....
[highlight][size=+2]It would be detrimental to our health![/size][/highlight]
In healthy adults (provided there is no shortage of the NO substrate), there is no need for NO up-regulation, and if there were a need.... it would not be possible to significantly up-regulate via the oral arginine-based "NO products", due to the p53-mediated, regulatory negative feedback loop.
I would not want to inhibit iNOS-derived, high-output NO (as it can be beneficial as well as detrimental).... I would just rather not have it up-regulated.
Here's why....[/size]
"Nitric oxide is toxic at high physiological concentration where it appears to function as a cellular effector molecule that mediates both cytostatic and cytotoxic effect." "NO is generated in the course of inflammatory and immune reactions, both by macrophages and by neutrophils. The role of these cells is quite extensive, and includes phagocytic and non-phagocytic destruction of foreign or damaged cells. These processes involve the production of large quantities of NO, which is cytotoxic."
The enhancement of the hyperglycemic effect of S-nitrosoglutathione and S-nitroso-N-acetylpenicillamine by vitamin C in an animal model | BioMed Central - Mirror @ Uni Potsdam
"Although NO can be cytotoxic to tumour cells (as it is to other cells), it can also act as a carcinogen."
http://www.clinsci.org/cs/098/0507/0980507.pdf
"NO, a chemical radical, and its toxic derivatives can cause DNA damage and cell death in a variety of cell types. NO also has the ability to directly modify intracellular targets such as proteins and lipid-peroxidation products. NO produces cytotoxicity at high concentrations, whereas NO at lower concentrations may have the opposite effect and protect against apoptotic cell death from various stimuli. Therefore, regulation of NO production is vital for both cell survival and genome integrity. DNA damage triggers p53 protein accumulation, which produces either growth arrest or apoptosis. Exposure of cells to high NO concentrations causes DNA damage and apoptosis, and recent results have shown that NO stimulates p53 accumulation and p53-mediated apoptosis."
Up-regulation of inducible nitric oxide synthase expression in cancer-prone p53 knockout mice -- Ambs et al. 95 (15): 8823 -- Proceedings of the National Academy of Sciences
"High concentrations of nitric oxide (NO) cause DNA damage and apoptosis in many cell types. Thus, regulation of NO synthase (NOS) activity is essential for minimizing effects of cytotoxic and genotoxic nitrogen oxide species." "These genetic and functional data indicate that p53 is an important transrepressor of NOS2 expression in vivo and attenuates excessive NO production in a regulatory negative feedback loop".
Up-regulation of inducible nitric oxide synthase expression in cancer-prone p53 knockout mice.
"The enzyme nitric oxide synthase 2 (NOS2), often called inducible NOS, plays a central role in the inflammatory reactions that follow infection or tissue damage. NOS2 has been detected in virtually every cell type, and the NO it produces can perform both beneficial and detrimental actions. It is thus conceivable that regulatory mechanisms exist which control the timing and intensity of NO production by NOS2 in order to outweigh protective effects against detrimental ones."
Regulation of the expression of the inflammatory nitric oxide synthase (NOS2) by cyclic AMP.
"The aberrant production of nitric oxide (NO) contributes to the pathogenesis of diseases as diverse as cancer and arthritis.
Sustained nitric oxide production in macrophages requires the arginine transporter CAT2.
"Inducible nitric oxide synthase (iNOS) is induced by inflammatory cytokines in skeletal muscle and fat. It has been proposed that chronic iNOS induction may cause muscle insulin resistance." "These findings provide genetic evidence that iNOS is involved in the development of muscle insulin resistance in diet-induced obesity."
Targeted disruption of inducible nitric oxide synthase protects against obesity-linked insulin resistance in muscle.
"Our results show that short-term NOS2 expression enhances CD95-mediated apoptosis and T cell cytotoxicity dose dependently. Furthermore, we could show that during chronic exposure to NO, besides the primary cytotoxic NO effect, there is selection of cell clones resistant to NO that show cross-resistance to CD95-induced apoptosis and the killing by CTLs. We propose that NO production could initially act as an autocrine suicide or paracrine killing mechanism in cells undergoing malignant transformation. However, once failed, the outcome is fatal. NO promotes tumor formation by enhancing the selection of cells that can evade immune attack by acquiring apoptosis resistance."
Nitric Oxide Promotes Resistance to Tumor Suppression by CTLs.
"Nitric oxide (NO.), an important mediator of inflammation, and beta-catenin, a component of the Wnt-adenomatous polyposis coli signaling pathway, contribute to the development of cancer." "These data are consistent with the hypothesis that beta-catenin up-regulates NOS2 and suggest a novel mechanism by which the Wnt/beta-catenin signaling pathway may contribute to cancer by increasing NO. production."
Regulation of Human Nitric Oxide Synthase 2 Expression by Wnt {beta}-Catenin Signaling.
"NO synthase 2 (NOS2) plays an important role in endotoxemia through overproduction of NO".
Reduction of nitric oxide synthase 2 expression by distamycin A improves survival from endotoxemia.
"Nitric oxide (NO) production in macrophages by inducible nitric oxide synthase (NOS2) has multiple tissue damaging effects and is involved in the pathogenesis of inflammation and graft rejection." "NOS2 inhibition may explain the antinflammatory effects of HmOx induction which could also be used therapeutically in situations when NO hyperproduction leads to cytotoxic effects such as inflammation or transplant rejection."
Nitric oxide synthase inhibition by haem oxygenase decreases macrophage nitric-oxide-dependent cytotoxicity: a negative feedback mechanism for the regulation of nitric oxide production.
"Recent evidence suggests that expression of inducible nitric oxide synthase (iNOS), or Nos2 gene product, in vascular smooth-muscle cells may, in part, promote atherosclerosis by increasing local oxidative stress. We therefore hypothesized that homocysteine contributes to atherosclerosis by affecting cytokine-induced production of nitric oxide (NO) by vascular smooth-muscle cells." "These data demonstrate that exposure of vascular smooth-muscle cells to pathophysiologically relevant concentrations of homocysteine prior to cytokine stimulation leads both to an increase in NO production and to an NF-kappa B-mediated increase in Nos2 transcription. Upregulation of Nos2 may contribute to the inflammatory response that characterizes early atherogenesis and may, in part, account for the adverse vascular effects of hyperhomocysteinemia."
Homocysteine-induced nitric oxide production in vascular smooth-muscle cells by NF-kappa B-dependent transcriptional activation of Nos2.
"Increased production of nitric oxide (NO) after induction of the cytokine-inducible isoform of nitric oxide synthase (iNOS or NOS2) in cardiac myocytes and other parenchymal cells within the heart may in addition to contributing to myocyte contractile dysfunction also contribute to the induction of programmed cell death (apoptosis). To investigate the mechanism(s) by which increased NO production leads to apoptosis, we examined the role of NO in primary cultures of neonatal rat ventricular myocytes"
Cytokine-mediated apoptosis in cardiac myocytes: the role of inducible nitric oxide synthase induction and peroxynitrite generation.
"Increased NOS2 expression and NO generation may be important in the pathogenesis of RA".
Increased expression of blood mononuclear cell nitric oxide synthase type 2 in rheumatoid arthritis patients.
Elevated polyamine and nitric oxide levels (both derived from arginine) promote tumorigenesis, whereas non-steroidal anti-inflammatory drugs (NSAIDs) inhibit colorectal cancer (CRC) incidence in experimental and epidemiologic studies."
Risk and risk reduction involving arginine intake and meat consumption in colorectal tumorigenesis and survival.
"The inducible nitric oxide (NO) synthase (iNOS or NOS2) generates a prolonged release of large amounts of NO which may be cytotoxic and/or inhibit myocyte contractility. It has been suggested that this mechanism specifically contributes to heart failure caused by dilated cardiomyopathy (DCM)."
Inducible nitric oxide synthase (iNOS) in the human heart: expression and localization in congestive heart failure.
The entire premise behind NO products, is NO up-regulation.... IF the NO products even aquired the ability to up-regulate endogenous NO production (wich they don't)....
[highlight][size=+2]It would be detrimental to our health![/size][/highlight]
In healthy adults (provided there is no shortage of the NO substrate), there is no need for NO up-regulation, and if there were a need.... it would not be possible to significantly up-regulate via the oral arginine-based "NO products", due to the p53-mediated, regulatory negative feedback loop.
I would not want to inhibit iNOS-derived, high-output NO (as it can be beneficial as well as detrimental).... I would just rather not have it up-regulated.
Here's why....[/size]
"Nitric oxide is toxic at high physiological concentration where it appears to function as a cellular effector molecule that mediates both cytostatic and cytotoxic effect." "NO is generated in the course of inflammatory and immune reactions, both by macrophages and by neutrophils. The role of these cells is quite extensive, and includes phagocytic and non-phagocytic destruction of foreign or damaged cells. These processes involve the production of large quantities of NO, which is cytotoxic."
The enhancement of the hyperglycemic effect of S-nitrosoglutathione and S-nitroso-N-acetylpenicillamine by vitamin C in an animal model | BioMed Central - Mirror @ Uni Potsdam
"Although NO can be cytotoxic to tumour cells (as it is to other cells), it can also act as a carcinogen."
http://www.clinsci.org/cs/098/0507/0980507.pdf
"NO, a chemical radical, and its toxic derivatives can cause DNA damage and cell death in a variety of cell types. NO also has the ability to directly modify intracellular targets such as proteins and lipid-peroxidation products. NO produces cytotoxicity at high concentrations, whereas NO at lower concentrations may have the opposite effect and protect against apoptotic cell death from various stimuli. Therefore, regulation of NO production is vital for both cell survival and genome integrity. DNA damage triggers p53 protein accumulation, which produces either growth arrest or apoptosis. Exposure of cells to high NO concentrations causes DNA damage and apoptosis, and recent results have shown that NO stimulates p53 accumulation and p53-mediated apoptosis."
Up-regulation of inducible nitric oxide synthase expression in cancer-prone p53 knockout mice -- Ambs et al. 95 (15): 8823 -- Proceedings of the National Academy of Sciences
"High concentrations of nitric oxide (NO) cause DNA damage and apoptosis in many cell types. Thus, regulation of NO synthase (NOS) activity is essential for minimizing effects of cytotoxic and genotoxic nitrogen oxide species." "These genetic and functional data indicate that p53 is an important transrepressor of NOS2 expression in vivo and attenuates excessive NO production in a regulatory negative feedback loop".
Up-regulation of inducible nitric oxide synthase expression in cancer-prone p53 knockout mice.
"The enzyme nitric oxide synthase 2 (NOS2), often called inducible NOS, plays a central role in the inflammatory reactions that follow infection or tissue damage. NOS2 has been detected in virtually every cell type, and the NO it produces can perform both beneficial and detrimental actions. It is thus conceivable that regulatory mechanisms exist which control the timing and intensity of NO production by NOS2 in order to outweigh protective effects against detrimental ones."
Regulation of the expression of the inflammatory nitric oxide synthase (NOS2) by cyclic AMP.
"The aberrant production of nitric oxide (NO) contributes to the pathogenesis of diseases as diverse as cancer and arthritis.
Sustained nitric oxide production in macrophages requires the arginine transporter CAT2.
"Inducible nitric oxide synthase (iNOS) is induced by inflammatory cytokines in skeletal muscle and fat. It has been proposed that chronic iNOS induction may cause muscle insulin resistance." "These findings provide genetic evidence that iNOS is involved in the development of muscle insulin resistance in diet-induced obesity."
Targeted disruption of inducible nitric oxide synthase protects against obesity-linked insulin resistance in muscle.
"Our results show that short-term NOS2 expression enhances CD95-mediated apoptosis and T cell cytotoxicity dose dependently. Furthermore, we could show that during chronic exposure to NO, besides the primary cytotoxic NO effect, there is selection of cell clones resistant to NO that show cross-resistance to CD95-induced apoptosis and the killing by CTLs. We propose that NO production could initially act as an autocrine suicide or paracrine killing mechanism in cells undergoing malignant transformation. However, once failed, the outcome is fatal. NO promotes tumor formation by enhancing the selection of cells that can evade immune attack by acquiring apoptosis resistance."
Nitric Oxide Promotes Resistance to Tumor Suppression by CTLs.
"Nitric oxide (NO.), an important mediator of inflammation, and beta-catenin, a component of the Wnt-adenomatous polyposis coli signaling pathway, contribute to the development of cancer." "These data are consistent with the hypothesis that beta-catenin up-regulates NOS2 and suggest a novel mechanism by which the Wnt/beta-catenin signaling pathway may contribute to cancer by increasing NO. production."
Regulation of Human Nitric Oxide Synthase 2 Expression by Wnt {beta}-Catenin Signaling.
"NO synthase 2 (NOS2) plays an important role in endotoxemia through overproduction of NO".
Reduction of nitric oxide synthase 2 expression by distamycin A improves survival from endotoxemia.
"Nitric oxide (NO) production in macrophages by inducible nitric oxide synthase (NOS2) has multiple tissue damaging effects and is involved in the pathogenesis of inflammation and graft rejection." "NOS2 inhibition may explain the antinflammatory effects of HmOx induction which could also be used therapeutically in situations when NO hyperproduction leads to cytotoxic effects such as inflammation or transplant rejection."
Nitric oxide synthase inhibition by haem oxygenase decreases macrophage nitric-oxide-dependent cytotoxicity: a negative feedback mechanism for the regulation of nitric oxide production.
"Recent evidence suggests that expression of inducible nitric oxide synthase (iNOS), or Nos2 gene product, in vascular smooth-muscle cells may, in part, promote atherosclerosis by increasing local oxidative stress. We therefore hypothesized that homocysteine contributes to atherosclerosis by affecting cytokine-induced production of nitric oxide (NO) by vascular smooth-muscle cells." "These data demonstrate that exposure of vascular smooth-muscle cells to pathophysiologically relevant concentrations of homocysteine prior to cytokine stimulation leads both to an increase in NO production and to an NF-kappa B-mediated increase in Nos2 transcription. Upregulation of Nos2 may contribute to the inflammatory response that characterizes early atherogenesis and may, in part, account for the adverse vascular effects of hyperhomocysteinemia."
Homocysteine-induced nitric oxide production in vascular smooth-muscle cells by NF-kappa B-dependent transcriptional activation of Nos2.
"Increased production of nitric oxide (NO) after induction of the cytokine-inducible isoform of nitric oxide synthase (iNOS or NOS2) in cardiac myocytes and other parenchymal cells within the heart may in addition to contributing to myocyte contractile dysfunction also contribute to the induction of programmed cell death (apoptosis). To investigate the mechanism(s) by which increased NO production leads to apoptosis, we examined the role of NO in primary cultures of neonatal rat ventricular myocytes"
Cytokine-mediated apoptosis in cardiac myocytes: the role of inducible nitric oxide synthase induction and peroxynitrite generation.
"Increased NOS2 expression and NO generation may be important in the pathogenesis of RA".
Increased expression of blood mononuclear cell nitric oxide synthase type 2 in rheumatoid arthritis patients.
Elevated polyamine and nitric oxide levels (both derived from arginine) promote tumorigenesis, whereas non-steroidal anti-inflammatory drugs (NSAIDs) inhibit colorectal cancer (CRC) incidence in experimental and epidemiologic studies."
Risk and risk reduction involving arginine intake and meat consumption in colorectal tumorigenesis and survival.
"The inducible nitric oxide (NO) synthase (iNOS or NOS2) generates a prolonged release of large amounts of NO which may be cytotoxic and/or inhibit myocyte contractility. It has been suggested that this mechanism specifically contributes to heart failure caused by dilated cardiomyopathy (DCM)."
Inducible nitric oxide synthase (iNOS) in the human heart: expression and localization in congestive heart failure.