Nitric oxide: biological role and clinical uses

Nitric Oxide Synthase Inhibition Prevents Cell Proliferation in Glioblastoma

Glioblastoma multiforme (GBM) is a prevalent and aggressive primary brain tumor, presenting substantial treatment challenges and high relapse rates. GBM is characterized by alterations in molecular signaling and enzyme expression within malignant cells. This tumor exhibits elevated nitric oxide (NO.) levels. NO. is a crucial signaling molecule involved in the regulation of neuronal functions, synaptic transmission, and cell proliferation. It is primarily synthesized from L-arginine by nitric oxide synthase (NOS) enzymes. The increased levels of NO. in GBM stem from dysregulated activity and expression of clinically relevant NOS isoforms, particularly inducible NOS (iNOS) and neuronal NOS (nNOS). Based on this knowledge, we hypothesize that targeted pharmacological intervention with N6-(1-iminoethyl)-L-lysine (L-NIL), an iNOS inhibitor, and 7-Nitroindazole (7-NI), an nNOS inhibitor, may suggest a promising therapeutic strategy for the treatment of GBM. To test our hypothesis, we utilized the U87-MG cell line as an in vitro model of GBM. Our results showed that treatment with L-NIL and 7-NI led to a reduction in NO. levels, NOS activity, and clonogenic proliferation in U87-MG cells. These findings suggest that NO. and NOS enzymes might be prospective therapeutic targets for GBM.

Nitric oxide-mediated the therapeutic properties of induced pluripotent stem cell for paraquat-induced acute lung injury

The mortality rate associated with acute lung injury (ALI) and its severe form, acute respiratory distress syndrome, is high. Induced pluripotent stem cell (iPSC) therapy is a potential treatment method for ALI, but its therapeutic efficacy is limited in injured lungs. Nitric oxide (NO) has various physiological actions. The current study investigated the effect of iPSCs pretreated with NO donors in paraquat (PQ)-induced ALI mouse model. Male C57BL/6 mice were intraperitoneally injected with PQ, followed by infusion of phosphate-buffered saline, iPSCs, L-arginine pretreated iPSCs, or Nitro-L-arginine methylester (L-NAME) pretreated iPSCs through the tail veins. Histopathological changes, pulmonary microvascular permeability, and inflammatory cytokine levels were analyzed after 3 or 28 d. The effects on iPSC proliferation, migration, and adhesion were evaluated in vitro. More L-arginine-pretreated iPSCs were selectively trafficked into the injured pulmonary tissue of mice with LPS-induced ALI, drastically diminishing the histopathologic changes and inflammatory cytokine levels (IL-1β and IL-6). There was also markedly improved pulmonary microvascular permeability and pulmonary function. The NO inhibitor abolished the protective effects of iPSCs. In addition, the ability of L-arginine to promote the proliferation and migration of iPSCs was decreased by L-NAME pretreatment, suggesting that NO might mediate the therapeutic benefits of iPSC. The improvement of the iPSC physiological changes by the endogenous gaseous molecule NO reduces lung injury severity. L-Arginine represents a pharmacologically important strategy for enhancing the therapeutic potential of iPSCs.

Cysteine immobilisation on the polyethylene terephthalate surfaces and its effect on the haemocompatibility

Nitric oxide (NO) is an important signalling molecule involved in haemostasis. NO, present as endogenous S-nitrosothiols, is released by cysteine through a transnitrosation reaction. To exploit this mechanism, cysteine was immobilised onto the different carboxylated polyethylene terephthalate (PET) surfaces using 1-step EDC (1-ethyl-3-(3-dimethylaminopropyl) carbodiimide) crosslinking mechanism. Immobilised cysteine concentration and NO release were dependent on the surface carboxyl density. Stability studies showed that the immobilised cysteine concentration and NO release reduced within 6 h. Immobilisation of cysteine derivatives eliminated the possibility of formation of polycysteine and its electrostatic interaction with the carboxylated PET. The immobilised cysteine concentration did not recover after DTT treatment, eliminating the possibility of disulphide bond formation. Further, cysteine was immobilised using a 2-step EDC crosslinking mechanism. Although the cysteine concentration reduced during stability studies, it recovered upon DTT treatment, indicating that cysteine forms amide bonds with the carboxylated PET and the observed decrease in cysteine concentration is probably due to the formation of disulphide bonds. The haemocompatibility of the cysteine immobilised PET surfaces showed similar results compared to the carboxylated PET. The loss of thiol groups due to the disulphide bond restricts the transnitrosation reaction. Hence, these materials can be used primarily in short-term applications.

Tadalafil: Protective Action against the Development of Multiple Organ Failure Syndrome

Introduction

Multiple organ failure syndrome (MOFS) is a pathology associated to unspecified and severe trauma, characterized by elevated morbidity and mortality. The complex inflammatory MOFS-related reactions generate important ischemia-reperfusion responses in the induction of this syndrome. Nitric oxide elevation, through the activation of cyclic guanosine monophosphate (cGMP), has the potential of counteracting the typical systemic vasoconstriction, and platelet-induced hypercoagulation. Tadalafil would possibly act protectively by reducing cGMP degradation with consequent diffuse vasodilatation, besides reduction of platelet-induced hypercoagulation, thus, preventing multiple organ failure syndrome development.

Methods

The experimental protocol was previously approved by an institution animal research committee. Experimental MOFS was induced through the stereotaxic micro-neurosurgical bilateral anterior hypothalamic lesions model. Groups of 10 Wistar rats were divided into:

a) Non-operated control;

b) Operated control group;

c) 2 hours after tadalafil-treated operated group;

d) 4 hours after tadalafil-treated operated group;

e) 8 hours after post-treated operated group. The animals were sacrificed 24 hours after the neurosurgical procedure and submitted to histopathologic examination of five organs: brain, lungs, stomach, kidneys, and liver.

Results

The electrolytic hypothalamic lesions resulted in a full picture of MOFS with disseminated multiple-organs lesions, provoked primarily by diffusely spread micro-thrombi. The treatment with tadalafil 2 hours after the micro-neurosurgical lesions reduced the experimental MOFS lesions development, in a highly significant level (P<0.01) of 58.75%. The treatment with tadalafil, 4 hours after the micro-neurosurgically-induced MOFS lesions, also reduced in 49.71%, in a highly significant level (P<0.01). Finally, the treatment with tadalafil 8 hours after the neurosurgical procedure resulted in a statistically significant reduction of 30.50% (P<0.05) of the experimentally-induced MOFS gravity scores.

Conclusion

The phosphodiesterase 5 inhibitor, tadalafil, in the doses and timing utilized, showed to protect against the experimentally-induced MOFS.

The protective effect of L-arginine, tadalafil, and their combination in rat testes after ischemia and reperfusion injury

INTRODUCTION

Nitric oxide (NO) plays an important role in the ischemia and reperfusion process. In this study, we aimed to examine the effect of L-arginine, tadalafil, and their combination for prevention of the ischemia reperfusion injury after testis torsion in rats.

METHODS

A total of 40 adult, male Sprague-Dawley rats were allocated into five groups. Three hours of left testicular torsion was performed in each group, excluding the control group. While the ischemia reperfusion (I/R) group had no treatment, I/R + Arg group received L-arginine, I/R + Td group received tadalafil and I/R + Arg + Td group received tadalafil and L-arginine 30 minutes before the detorsion. Then the left testis was untwisted for four hours of reperfusion. After bilateral orchiectomy, lipid peroxidation (LPx) and glutathione (GSH) activities were examined in testicular tissue. Spermatogenesis was evaluated with Johnsen's score.

RESULTS

LPx levels of the I/R group were found to be significantly higher than for groups that received drugs for both testes (p<0.001). GSH levels of the combination group were higher than I/R group in ipsilateral testis (p<0.01) and it was significantly higher than other groups for contralateral testis (p<0.001 for I/R group, p<0.01 for I/R + Arg, p<0.05 for I/R + Td). Mean Johnsen's score of the I/R group was found to be significantly lower than treatment groups in ipsilateral testis (p<0.001 for I/R + Arg + Td group, p<0.01 for other treatment goups) and contralateral testis (p<0.001). The mean Johnsen score of the combination group was significantly higher than that of other treatment groups in ipsilateral testis (p<0.05) and it was significantly higher than in the I/R + Td group in the contralateral testis (p<0.05).

CONCLUSIONS

L-arginine, tadalafil, and combination of these two molecules showed protective effect against ischemia/reperfusion injury for both testes after unilateral testis torsion.

Nitric oxide-releasing polyurethane–PEG copolymer containing the YIGSR peptide promotes endothelialization with decreased platelet adhesion

Thrombosis and intimal hyperplasia are the principal causes of small-diameter vascular graft failure. To improve the long-term patency of polyurethane vascular grafts, we have incorporated both poly(ethylene glycol) and a diazeniumdiolate nitric oxide (NO) donor into the backbone of polyurethane to improve thromboresistance. Additionally, we have incorporated the laminin-derived cell adhesive peptide sequence YIGSR to encourage endothelial cell adhesion and migration, while NO release encourages endothelial cell proliferation. NO production by polyurethane films under physiological conditions demonstrated biphasic release, in which an initial burst of 70% of the incorporated NO was released within 2 days, followed by sustained release over 2 months. Endothelial cell proliferation in the presence of the NO-releasing material was increased as compared to control polyurethane, and platelet adhesion to polyethylene glycol-containing polyurethane was decreased significantly with the addition of the NO donor.

The effect of nitric oxide in testicular ischemia-reperfusion injury

This experiment was carried out to investigate the effect of endogenous nitric oxide (NO) on the ischemia-reperfusion injury of testis. Testicular ischemia was achieved by twisting the right testis and spermatic cord 1080 counter-clockwise for 30 minutes and reperfusion was allowed for 30 minutes after detorsion of 33 rats. Animals were treated with normal saline in controls just before detorsion, NG-nitro-L-arginine methyl ester (L-NAME), and L-arginine (L-arg) in others. The tissue damage was evaluated with light microscopy, malondialdehyde (MDA) level in tissue, and the blood flow measurement using 133xenon (Xe) clearence technique. MDA indicator of reperfusion injury increased 25% after detorsion when only normal saline was given, L-NAME further increased MDA, L-arginin decreased MDA to control level.

CONCLUSION

L-arginin infusion during the detorsion reduced the reperfusion injury of testis and improved the testicular blood flow after the detorsion.

Neuro-immune-endocrine functional system and vascular pathology

A new interpretation of the response to injury by the nervous, immune and endocrine system is proposed, in order to integrate biochemical knowledge into the respective clinical areas. The discovery that the signaling molecules of the classical nervous, immune and endocrine systems, that is, the neurotransmitters, cytokines and hormones, respectively, are expressed and perceived by the three systems, has enabled us to establish a functional concept of these systems. The hypothetical integration of different pathological processes in a functional response made up by three phases, the immediate or nervous, intermediate or immune and late or endocrine ones, makes it possible to consider that all of them represent different forms of expression of a functional response whose meaning is always the same, that is, inflammation. If the functions that characterize each one of these three phases represent the activity of the nervous, immune and endocrine systems, the biochemical knowledge could be integrated into the functional meaning of each system.