Explore the vast range of titles available.

Nitric oxide (NO) is a ubiquitous signalling molecule with widespread distribution in prokaryotes and eukaryotes where it is involved in countless physiological processes. While the mechanisms governing NO synthesis and signalling are well established in animals, the situation is less clear in the green lineage. Recent investigations have shown that NO synthase (NOS), the major enzymatic source for NO in animals, is absent in land plants but present in a limited number of algae. First detailed analysis highlighted that these new NOSs are functional but display specific structural features and probably original catalytic activities. Completing this picture, analyses were undertaken in order to investigate whether major components of the prototypic NO/cyclic GMP signalling cascades mediating many physiological effects of NO in animals were also present in plants. Only few homologues of soluble guanylate cyclases, cGMP-dependent protein kinases, cyclic nucleotide-gated channels and cGMP-regulated phosphodiesterases, were identified in some algal species and their presence did not correlate with that of NOSs. In contrast, GSNO reductase, a critical regulator of S-nitrosothiols, was recurrently found. Overall, these findings highlight that plants do not mediate NO signalling through the classical NO/cGMP-signalling module and support the concept that S-nitrosation is a ubiquitous NO-dependent signalling mechanism.

The leukotrienes, lipid mediators, have a role in gastric damage induced by ethanol. Here, the gastroprotective effect of montelukast, an antagonist of the leukotriene receptor, and the involvement of the NO-cGMP-KATP channel pathway, were evaluated in gastric damage induced by ethanol in rats. For this, l-arginine, l-NAME, methylene blue (guanylate cyclase inhibitor), sildenafil, diazoxide, or glibenclamide (ATP-sensitive potassium channel blocker) were administered 30 min before montelukast (0.1, 1, 10, and 20 mg/kg, by mouth [p.o.]). After 1 h, to induce gastric damage, the rats received absolute ethanol (4 mL/kg, p.o.), and then microscopic, macroscopic, and pro-inflammatory parameters (TNF-α and IL-1β) were assessed. Results obtained here revealed that montelukast significantly attenuated the macroscopic and microscopic lesions induced by ethanol. Montelukast also reduced IL-1β and TNF-α levels. It was also observed that NOS inhibitor (l-NAME), methylene blue, and glibenclamide inhibited the effects of montelukast in the stomach. Moreover, the NO precursor (l-arginine), the PDE-5 inhibitor (sildenafil), and a potassium channel opener (diazoxide) before montelukast produced gastroprotective effects. In conclusion, the effect of montelukast against gastric lesions induced by ethanol is mediated, at least in part, through the pathway of the NO-cGMP-KATP channel. •Montelukast produced a gastroprotective effect in ethanol-induced gastric damage.•The NO-cGMP-KATP channels pathway has an involvement in the effect of montelukast.•Montelukast attenuated TNF-α and IL-1β levels in ethanol-induced gastric damage.•Montelukast attenuated TNF-α through the NO-cGMP-KATP channels pathway.

The sperm‐specific CatSper channel controls the intracellular Ca 2+ concentration ([Ca 2+ ] i ) and, thereby, the swimming behaviour of sperm. In humans, CatSper is directly activated by progesterone and prostaglandins—female factors that stimulate Ca 2+ influx. Other factors including neurotransmitters, chemokines, and odorants also affect sperm function by changing [Ca 2+ ] i . Several ligands, notably odorants, have been proposed to control Ca 2+ entry and motility via G protein‐coupled receptors (GPCRs) and cAMP‐signalling pathways. Here, we show that odorants directly activate CatSper without involving GPCRs and cAMP. Moreover, membrane‐permeable analogues of cyclic nucleotides that have been frequently used to study cAMP‐mediated Ca 2+ signalling also activate CatSper directly via an extracellular site. Thus, CatSper or associated protein(s) harbour promiscuous binding sites that can host various ligands. These results contest current concepts of Ca 2+ signalling by GPCR and cAMP in mammalian sperm: ligands thought to activate metabotropic pathways, in fact, act via a common ionotropic mechanism. We propose that the CatSper channel complex serves as a polymodal sensor for multiple chemical cues that assist sperm during their voyage across the female genital tract. The calcium channel CatSper governs sperm swimming behaviour in response to progesterone and prostaglandins. Surprisingly, multiple types of small molecules including odorants and nucleotides directly activate CatSper‐mediated calcium influx independent of G protein‐coupled receptor (GPCR) or cAMP signalling.

The NO-cGMP signal transduction pathway plays a crucial role in tone regulation in hepatic sinusoids and peripheral blood vessels. In a cirrhotic liver, the key enzymes endothelial NO synthase (eNOS), soluble guanylate cyclase (sGC), and phosphodiesterase-5 (PDE-5) are overexpressed, leading to decreased cyclic guanosine-monophosphate (cGMP). This results in constriction of hepatic sinusoids, contributing about 30% of portal pressure. In contrast, in peripheral arteries, dilation prevails with excess cGMP due to low PDE-5. Both effects eventually lead to circulatory dysfunction in progressed liver cirrhosis. The conventional view of portal hypertension (PH) pathophysiology has been described using the “NO-paradox”, referring to reduced NO availability inside the liver and elevated NO production in the peripheral systemic circulation. However, recent data suggest that an altered availability of cGMP could better elucidate the contrasting findings of intrahepatic vasoconstriction and peripheral systemic vasodilation than mere focus on NO availability. Preclinical and clinical data have demonstrated that targeting the NO-cGMP pathway in liver cirrhosis using PDE-5 inhibitors or sGC stimulators/activators decreases intrahepatic resistance through dilation of sinusoids, lowering portal pressure, and increasing portal venous blood flow. These results suggest further clinical applications in liver cirrhosis. Targeting the NO-cGMP system plays a role in possible reversal of liver fibrosis or cirrhosis. PDE-5 inhibitors may have therapeutic potential for hepatic encephalopathy. Serum/plasma levels of cGMP can be used as a non-invasive marker of clinically significant portal hypertension. This manuscript reviews new data about the role of the NO-cGMP signal transduction system in pathophysiology of cirrhotic portal hypertension and provides perspective for further studies.

In vitro fertilization (IVF) is currently one of the most effective methods of infertility treatment. An alternative to commonly used ovarian hyperstimulation can become extracorporeal maturation of oocytes (in vitro maturation; IVM). Fertilization and normal development of the embryo depends on the cytoplasmic, nuclear and genomic maturity of the oocyte. The microenvironment of the ovarian follicle and maternal signals, which mediate bidirectional communication between granulosa, cumulus and oocyte cells, influence the growth, maturation and acquisition of oocyte development capability. During oogenesis in mammals, the meiosis is inhibited in the oocyte at the prophase I of the meiotic division due to the high cAMP level. This level is maintained by the activity of C-type natriuretic peptide (CNP, NPPC) produced by granulosa cells. The CNP binds to the NPR2 receptor in cumulus cells and is responsible for the production of cyclic guanosine monophosphate (cGMP). The cGMP penetrating into the oocyte through gap junctions inhibits phosphodiesterase 3A (PDE3A), preventing cAMP hydrolysis responsible for low MPF activity. The LH surge during the reproductive cycle reduces the activity of the CNP/NPR2 complex, which results in a decrease in cGMP levels in cumulus cells and consequently in the oocyte. Reduced cGMP concentration unblocks the hydrolytic activity of PDE3A, which decreases cAMP level inside the oocyte. This leads to the activation of MPF and resumption of meiosis. The latest IVM methods called SPOM, NFSOM or CAPA IVM consist of two steps: prematuration and maturation itself. Taking into account the role of cAMP in inhibiting and then unblocking the maturation of oocytes, they have led to a significant progress in terms of the percentage of mature oocytes in vitro and the proportion of properly developed embryos in both animals and humans.

Hereditary retinal degeneration (RD) is often associated with excessive cGMP signalling in photoreceptors. Previous research has shown that inhibition of cGMP-dependent protein kinase G (PKG) can reduce photoreceptor loss in two different RD animal models. In this study, we identified a PKG inhibitor, the cGMP analogue CN238, which preserved photoreceptor viability and functionality in rd1 and rd10 mutant mice. Surprisingly, in explanted retinae, CN238 also protected retinal ganglion cells from axotomy-induced retrograde degeneration and preserved their functionality. Furthermore, kinase activity-dependent protein phosphorylation of the PKG target Kv1.6 was reduced in CN238-treated rd10 retinal explants. Ca2+-imaging on rd10 acute retinal explants revealed delayed retinal ganglion cell repolarization with CN238 treatment, suggesting a PKG-dependent modulation of Kv1-channels. Together, these results highlight the strong neuroprotective capacity of PKG inhibitors for both photoreceptors and retinal ganglion cells, illustrating their broad potential for the treatment of retinal diseases and possibly neurodegenerative diseases in general.

Microalgae are competitive and commercial sources for health-benefit carotenoids. In this study, a Chromochloris zofingiensis mutant (Cz-pkg), which does not shut off its photosystem and stays green upon glucose treatment, was generated and characterized. Cz-pkg was developed by treating the algal cells with a chemical mutagen as N-methyl-N’-nitro-N-nitrosoguanidine and followed by a color-based colony screening approach. Cz-pkg was found to contain a dysfunctional cGMP-dependent protein kinase (PKG). By cultivated with CO2 aeration under mixotrophy, the mutant accumulated lutein up to 31.93 ± 1.91 mg L−1 with a productivity of 10.57 ± 0.73 mg L−1 day−1, which were about 2.5- and 8.5-fold of its mother strain. Besides, the lutein content of Cz-pkg could reach 7.73 ± 0.52 mg g−1 of dry weight, which is much higher than that of marigold flower, the most common commercial source of lutein. Transcriptomic analysis revealed that in the mutant Cz-pkg, most of the genes involved in the biosynthesis of lutein and chlorophylls were not down-regulated upon glucose addition, suggesting that PKG may regulate the metabolisms of photosynthetic pigments. This study demonstrated that Cz-pkg could serve as a promising strain for both lutein production and glucose sensing study.

DNA damage is a causative factor in ageing of the vasculature and other organs. One of the most important vascular ageing features is reduced nitric oxide (NO)soluble guanylate cyclase (sGC)—cyclic guanosine monophosphate (cGMP) signaling. We hypothesized that the restoration of NO‐sGC‐cGMP signaling with an sGC activator (BAY 54–6544) may have beneficial effects on vascular ageing and premature death in DNA repair‐defective mice undergoing accelerated ageing. Eight weeks of treatment with a non‐pressor dosage of BAY 54–6544 restored the decreased in vivo microvascular cutaneous perfusion in progeroid Ercc1∆/− mice to the level of wild‐type mice. In addition, BAY 54–6544 increased survival of Ercc1∆/− mice. In isolated Ercc1∆/− aorta, the decreased endothelium‐independent vasodilation was restored after chronic BAY 54–6544 treatment. Senescence markers p16 and p21, and markers of inflammation, including Ccl2, Il6 in aorta and liver, and circulating IL‐6 and TNF‐α were increased in Ercc1∆/−, which was lowered by the treatment. Expression of antioxidant genes, including Cyb5r3 and Nqo1, was favorably changed by chronic BAY 54–6544 treatment. In summary, BAY 54–6544 treatment improved the vascular function and survival rates in mice with accelerated ageing, which may have implication in prolonging health span in progeria and normal ageing. DNA repair deficiency in Ercc1∆/− mice cause a disruption of NO‐sGC‐cGMP signaling and a decrease of vasodilator response. These mice die prematurely between the age of 14 and 26 weeks and can be used to test interventions in ageing. Treatment with the BAY 54–6544 improved NO‐mediated vasodilation and attenuated vascular senescence and inflammation markers. Moreover, these changes are not restricted to vascular tissue, but manifest themselves also in liver, an organ that is often used to study changes in common ageing pathways in various models. Thus, BAY 54–6544 could be a potential therapeutic treatment to attenuate vascular ageing and improve survival.

Increasing cyclic GMP activates 26S proteasomes via phosphorylation by Protein Kinase G and stimulates the intracellular degradation of misfolded proteins. Therefore, agents that raise cGMP may be useful therapeutics against neurodegenerative diseases and other diseases in which protein degradation is reduced and misfolded proteins accumulate, including Charcot Marie Tooth 1A and 1B peripheral neuropathies, for which there are no treatments. Here we increased cGMP in the S63del mouse model of CMT1B by treating for three weeks with either the phosphodiesterase 5 inhibitor tadalafil, or the brain-penetrant soluble guanylyl cyclase stimulator CYR119. Both molecules activated proteasomes in the affected peripheral nerves, reduced polyubiquitinated proteins, and improved myelin thickness and nerve conduction. CYR119 increased cGMP more than tadalafil in the peripheral nerves of S63del mice and elicited greater biochemical and functional improvements. To determine whether raising cGMP could be beneficial in other neuropathies, we first showed that polyubiquitinated proteins and the disease-causing protein accumulate in the sciatic nerves of the C3 mouse model of CMT1A. Treatment of these mice with CYR119 reduced the levels of polyubiquitinated proteins and the disease-causing protein, presumably by increasing their degradation, and improved myelination, nerve conduction, and motor coordination. Thus, pharmacological agents that increase cGMP are promising treatments for CMT1 neuropathies and may be useful against other proteotoxic and neurodegenerative diseases.