Relationship of urinary cGMP excretion with aging and menopausal status in a general population

Menopause-Associated Depression: Impact of Oxidative Stress and Neuroinflammation on the Central Nervous System-A Review

Perimenopausal depression, occurring shortly before or after menopause, is characterized by symptoms such as emotional depression, anxiety, and stress, often accompanied by endocrine dysfunction, particularly hypogonadism and senescence. Current treatments for perimenopausal depression primarily provide symptomatic relief but often come with undesirable side effects. The development of agents targeting the specific pathologies of perimenopausal depression has been relatively slow. The erratic fluctuations in estrogen and progesterone levels during the perimenopausal stage expose women to the risk of developing perimenopausal-associated depression. These hormonal changes trigger the production of proinflammatory mediators and induce oxidative stress, leading to progressive neuronal damage. This review serves as a comprehensive overview of the underlying mechanisms contributing to perimenopausal depression. It aims to shed light on the complex relationship between perimenopausal hormones, neurotransmitters, brain-derived neurotrophic factors, chronic inflammation, oxidative stress, and perimenopausal depression. By summarizing the intricate interplay between hormonal fluctuations, neurotransmitter activity, brain-derived neurotrophic factors, chronic inflammation, oxidative stress, and perimenopausal depression, this review aims to stimulate further research in this field. The hope is that an increased understanding of these mechanisms will pave the way for the development of more effective therapeutic targets, ultimately reducing the risk of depression during the menopausal stage for the betterment of psychological wellbeing.

Swimming exercise inhibits myocardial ER stress in the hearts of aged mice by enhancing cGMP‑PKG signaling

The purpose of the present study was to explore aging‑associated cardiac dysfunction and the possible mechanism by which swimming exercise modulates cardiac dysfunction in aged mice. Aged mice were divided into two groups: i) Aged mice; and ii) aged mice subjected to swimming exercises. Another cohort of 4‑month‑old male mice served as the control group. Cardiac structure and function in mice were analyzed using hematoxylin and eosin staining, and echocardiography. The levels of oxidative stress were determined by measuring the levels of superoxide dismutase, malondialdehyde and reactive oxygen species (ROS). Levels of the endoplasmic reticulum (ER) stress‑related protein PKR‑like ER kinase, glucose‑regulated protein 78 and C/EBP homologous protein were determined to evaluate the level of ER stress. The aged group exhibited an abnormal cardiac structure and decreased cardiac function, both of which were ameliorated by swimming exercise. The hearts of the aged mice exhibited pronounced oxidative and ER stress, which were ameliorated by exercise, and was accompanied by the reactivation of myocardial cGMP and suppression of cGMP‑specific phosphodiesterase type 5 (PDE5). The inhibition of PDE5 attenuated age‑induced cardiac dysfunction, blocked ROS production and suppressed ER stress. An ER stress inducer abolished the beneficial effects of the swimming exercise on cardiac function and increased ROS production. The present study suggested that exercise restored cardiac function in mice with age‑induced cardiac dysfunction by inhibiting oxidative stress and ER stress, and increasing cGMP‑protein kinase G signaling.

cGMP-dependent protein kinase-2 regulates bone mass and prevents diabetic bone loss

NO/cGMP signaling is important for bone remodeling in response to mechanical and hormonal stimuli, but the downstream mediator(s) regulating skeletal homeostasis are incompletely defined. We generated transgenic mice expressing a partly-activated, mutant cGMP-dependent protein kinase type 2 (PKG2R242Q) under control of the osteoblast-specific Col1a1 promoter to characterize the role of PKG2 in post-natal bone formation. Primary osteoblasts from these mice showed a two- to three-fold increase in basal and total PKG2 activity; they proliferated faster and were resistant to apoptosis compared to cells from WT mice. Male Col1a1-Prkg2R242Q transgenic mice had increased osteoblast numbers, bone formation rates and Wnt/β-catenin-related gene expression in bone and a higher trabecular bone mass compared to their WT littermates. Streptozotocin-induced type 1 diabetes suppressed bone formation and caused rapid bone loss in WT mice, but male transgenic mice were protected from these effects. Surprisingly, we found no significant difference in bone micro-architecture or Wnt/β-catenin-related gene expression between female WT and transgenic mice; female mice of both genotypes showed higher systemic and osteoblastic NO/cGMP generation compared to their male counterparts, and a higher level of endogenous PKG2 activity may be responsible for masking effects of the PKG2R242Q transgene in females. Our data support sexual dimorphism in Wnt/β-catenin signaling and PKG2 regulation of this crucial pathway in bone homeostasis. This work establishes PKG2 as a key regulator of osteoblast proliferation and post-natal bone formation.

Inhaled nitric oxide increases urinary nitric oxide metabolites and cyclic guanosine monophosphate in premature infants: relationship to pulmonary outcome

OBJECTIVE

Inhaled nitric oxide (iNO) has been tested to prevent bronchopulmonary dysplasia (BPD) in premature infants, however, the role of cyclic guanosine monophosphate (cGMP) is not known. We hypothesized that levels of NO metabolites (NOx) and cGMP in urine, as a noninvasive source for biospecimen collection, would reflect the dose of iNO and relate to pulmonary outcome.

STUDY DESIGN

Studies were performed on 125 infants who required mechanical ventilation at 7 to 14 days and received 24 days of iNO at 20-2 ppm. A control group of 19 infants did not receive iNO.

RESULTS

In NO-treated infants there was a dose-dependent increase of both NOx and cGMP per creatinine (maximal 3.1- and 2-fold, respectively, at 10-20 ppm iNO) compared with off iNO. NOx and cGMP concentrations at both 2 ppm and off iNO were inversely related to severity of lung disease during the 1st month, and the NOx levels were lower in infants who died or developed BPD at term. NOx was higher in Caucasian compared with other infants at all iNO doses.

CONCLUSION

Urinary NOx and cGMP are biomarkers of endogenous NO production and lung uptake of iNO, and some levels reflect the severity of lung disease. These results support a role of the NO-cGMP pathway in lung development.

Soluble guanylate cyclase as a novel treatment target for osteoporosis

Osteoporosis is a major health problem leading to fractures that cause substantial morbidity and mortality. Current osteoporosis therapies have significant drawbacks, creating a need for novel bone-anabolic agents. We previously showed that the nitric oxide/cyclic GMP (cGMP)/protein kinase G pathway mediates some of the anabolic effects of estrogens and mechanical stimulation in osteoblasts and osteocytes, leading us to hypothesize that cGMP-elevating agents may have bone-protective effects. We tested cinaciguat, a prototype of a novel class of soluble guanylate cyclase activators, in a mouse model of estrogen deficiency-induced osteoporosis. Compared with sham-operated mice, ovariectomized mice had lower serum cGMP concentrations, which were largely restored to normal by treatment with cinaciguat or low-dose 17β-estradiol. Microcomputed tomography of tibiae showed that cinaciguat significantly improved trabecular bone microarchitecture in ovariectomized animals, with effect sizes similar to those obtained with estrogen replacement therapy. Cinaciguat reversed ovariectomy-induced osteocyte apoptosis as efficiently as estradiol and enhanced bone formation parameters in vivo, consistent with in vitro effects on osteoblast proliferation, differentiation, and survival. Compared with 17β-estradiol, which completely reversed the ovariectomy-induced increase in osteoclast number, cinaciguat had little effect on osteoclasts. Direct guanylate cyclase stimulators have been extremely well tolerated in clinical trials of cardiovascular diseases, and our findings provide proof-of-concept for this new class of drugs as a novel, anabolic treatment strategy for postmenopausal osteoporosis, confirming an important role of nitric oxide/cGMP/protein kinase G signaling in bone.

Age-associated increase in salt sensitivity is accompanied by a shift in the atrial natriuretic peptide modulation of the effect of marinobufagenin on renal and vascular sodium pump

BACKGROUND

Marinobufagenin (MBG) promotes natriuresis via inhibition of renotubular Na/K-ATPase (NKA) and causes vasoconstriction via inhibition of vascular NKA. Atrial natriuretic peptide (ANP), via cyclic guanosine monophosphate (cGMP)/protein kinase G (PKG)-dependent mechanism, sensitizes renal NKA to MBG but reduces MBG-induced inhibition of vascular NKA. As aging is associated with a downregulation of cGMP/PKG signaling, we hypothesized that in older rats, ANP would not potentiate renal effects of MBG and would not oppose vascular effects of MBG.

METHODS

In younger (3-month-old) and older (12-month-old) Sprague-Dawley rats, we compared SBP, natriuresis, activity of NKA in aorta and renal medulla, and levels of MBG and α-ANP at baseline and following acute NaCl loading (20%, 2.5 ml/kg, intraperitoneally), and studied modulation of MBG-induced NKA inhibition by α-ANP in vitro.

RESULTS

As compared with younger rats, NaCl-loaded older rats exhibited a greater MBG response, greater SBP elevation (25 vs. 10 mmHg, P < 0.01) and greater inhibition of NKA in aorta (39 vs. 7%, P < 0.01), 30% less natriuresis, and less inhibition of renal NKA (25 vs. 42%, P < 0.05) in the presence of comparable responses of α-ANP and cGMP. In aorta and kidney of older rats, the levels of PKG were reduced, the levels of phosphodiesterase-5 were increased compared with that in young rats, and α-ANP failed to modulate MBG-induced NKA inhibition.

CONCLUSION

Age-associated downregulation of cGMP/PKG-dependent signaling impairs the ability of ANP to modulate the effects of MBG on the sodium pump, which contributes to salt sensitivity.

cGMP level in idiopathic Parkinson's disease patients with and without cardiovascular disease - A pilot study

We have previously found that average serum cGMP level in unselected patients with Parkinson's disease (PD), particularly in patients treated with a combination of l-DOPA and the dopamine agonist pergolide mesylate, is markedly higher than that in healthy controls. Here we compared serum cGMP and total testosterone levels between l-DOPA/pergolide mesylate-treated male idiopathic PD patients without and with cardiovascular disease (iPD, n = 10, and iPD-CVD, n = 10, respectively) and age-matched healthy volunteers (n = 10). There was no difference in PD-related disability between the two patient groups as assessed by UPDRS motor score and Hoehn-Yahr staging. Whereas none of the patients showed hypoandrogenemia, PD patients compared to controls revealed significantly lower serum testosterone levels, and iPD-CVD patients showed significantly lower levels than iPD patients. Serum cGMP levels were but moderately while significantly higher in the two groups of PD patients than in the controls, and were the highest in the iPD-CVD group. For all study groups combined, there was a high negative correlation between total testosterone level and cGMP level. Our data indicate that blood total testosterone level is negatively correlated with general health status in PD patients, whereas the reverse is true for blood cGMP level.