Anna Siekierzycka

Background/Objectives: The aim of the study was to evaluate the effects of positive allosteric modulators (PAMs) of metabotropic glutamate (mGlu2, mGlu5) and muscarinic (M1, M4) receptors on nitric oxide (NO֗)-dependent pathways. Scopolamine-induced cognitive impairment model reflecting cholinergic dysfunction characteristic of Alzheimer’s disease was used. Methods: The experiments were performed in vivo in Albino Swiss mice and in vitro in astrocytic cell lines (C8D1A, 1321N1). Chronic (14 days) scopolamine and mGlu2 (LY487379), mGlu5 (CDPPB), M1 (VU0357017), and M4 (VU0152100) PAMs were administered in vivo. In brain tissue samples (frontal cortex or hippocampus) cGMP levels (ELISA), total and protein-specific S-nitrosylation (biotin switch assay), and neuronal (nNOS) or endothelial (eNOS) synthase-dependent (NO֗) release (nanoelectrochemical detection) were measured. In vitro oxidative stress (NBT assay) was performed. Results: Significantly reduced cGMP levels, decreased both nNOS- and eNOS-dependent (NO֗) release, and lowered total protein S-nitrosylation in brain tissue were observed. mGlu2 and mGlu5 PAMs prevented the reduction in nNOS-related (NO֗) release and restored total S-nitrosylation. CDPPB did not protect against eNOS-related impairment. Muscarinic receptors modulators effectively counteracted eNOS dysfunction. All investigated compounds attenuated oxidative stress, with particularly pronounced effects in human astrocytes. Conclusions: mGlu and muscarinic receptor PAMs differentially modulate (NO֗)-related signaling pathways, demonstrating both therapeutic potential and potential safety limitations. None of the tested compounds fully restored neurochemical balance, suggesting that combination strategies (e.g., with (NO֗) donors or modulators of the (NO֗)-cGMP pathway) may represent a promising direction for future Alzheimer’s disease treatments.

Habitual physical activity is known to support cardiovascular health. However, when intensive exercise is performed for long durations, it can negatively affect the cardiovascular system. We evaluated the exercise-induced physiological responses of cardiac markers in male marathon runners based on basal plasma trimethylamine-N-oxide (TMAO) levels, a metabolite related to major adverse cardiovascular events. Blood samples from 28 marathon runners were collected two weeks before the marathon run (baseline), after finishing the race (post-marathon), and two weeks after the race (2 weeks post-marathon). Serum cardiac troponin I (cTnI), endothelin-1 (ET-1), galectin-3, pentraxin-3, human growth differentiation factor 15, and neopterin were determined by the enzyme immunoassay method. Plasma trimethylamine (TMA) and TMAO were measured by the ultra-high-performance liquid chromatography-mass spectrometry method. Running a marathon increased levels of circulating biomarkers. A greater post-marathon elevation of cTnI and ET-1 was associated with baseline plasma TMAO levels (R ​= ​0.400, p ​= ​0.035 and R ​= ​0.476, p ​= ​0.012, respectively). Moreover, we observed an increase in post-marathon TMA levels. Greater post-marathon elevation of cTnI and ET-1 was associated with higher baseline plasma TMAO levels. Therefore, TMAO could potentially serve as a new marker in assessing the response of cardiovascular stress biomarkers to marathon running.

The role of endothelial nitric oxide synthase (eNOS) in the regulation of a variety of biological processes is well established, and its dysfunction contributes to brain pathologies, including schizophrenia or Alzheimer’s disease (AD). Positive allosteric modulators (PAMs) of metabotropic glutamate (mGlu) receptors were shown to be effective procognitive compounds, but little is known about their impact on eNOS expression and stability. Here, we investigated the influence of the acute and chronic administration of LY487379 or CDPPB (mGlu2 and mGlu5 PAMs), on eNOS expression in the mouse brain and the effect of the joint administration of the ligands with nitric oxide (NO) releasers, spermineNONOate or DETANONOate, in different combinations of doses, on MK-801- or scopolamine-induced amnesia in the novel object recognition (NOR) test. Our results indicate that both compounds provoked eNOS monomer formation, and CDPPB at a dose of 5 mg/kg exaggerated the effect of MK-801 or scopolamine. The coadministration of spermineNONOate or DETANONOate enhanced the antiamnesic effect of CDPPB or LY487379. The best activity was observed for ineffective or moderate dose combinations. The results indicate that treatment with mGluR2 and mGluR5 PAMs may be burdened with the risk of promoting eNOS uncoupling through the induction of dimer dissociation. Administration of the lowest possible doses of the compounds with NO^• donors, which themselves have procognitive efficacy, may be proposed for the treatment of schizophrenia or AD.

Personalized medicine is emerging as a new goal in the diagnosis and treatment of diseases. This approach aims to establish differences between patients suffering from the same disease, which allows to choose the most effective treatment. Molecular imaging (MI) enables advanced insight into molecule interactions and disease pathology, improving the process of diagnosis and therapy and, for that reason, plays a crucial role in personalized medicine. Nanoparticles are widely used in MI techniques due to their size, high surface area to volume ratio, and multifunctional properties. After conjugation to specific ligands and drugs, nanoparticles can transport therapeutic compounds directly to their area of action and therefore may be used in theranostics—the simultaneous implementation of treatment and diagnostics. This review summarizes different MI techniques, including optical imaging, ultrasound imaging, magnetic resonance imaging, nuclear imaging, and computed tomography imaging with theranostics nanoparticles. Furthermore, it explores the potential use of constructs that enables multimodal imaging and track diseases in real time.

MK-801, an NMDA receptor antagonist, and scopolamine, a cholinergic receptor blocker, are widely used as tool compounds to induce learning and memory deficits in animal models to study schizophrenia or Alzheimer-type dementia (AD), respectively. Memory impairments are observed after either acute or chronic administration of either compound. The present experiments were performed to study the nitric oxide (NO)-related mechanisms underlying memory dysfunction induced by acute or chronic (14 days) administration of MK-801 (0.3 mg/kg, i.p.) or scopolamine (1 mg/kg, i.p.). The levels of L-arginine and its derivatives, L-citrulline, L-glutamate, L-glutamine and L-ornithine, were measured. The expression of constitutive nitric oxide synthases (cNOS), dimethylaminohydrolase (DDAH1) and protein arginine N-methyltransferases (PMRTs) 1 and 5 was evaluated, and the impact of the studied tool compounds on cGMP production and NMDA receptors was measured. The studies were performed in both the cortex and hippocampus of mice. S-nitrosylation of selected proteins, such as GLT-1, APP and tau, was also investigated. Our results indicate that the availability of L-arginine decreased after chronic administration of MK-801 or scopolamine, as both the amino acid itself as well as its level in proportion to its derivatives (SDMA and NMMA) were decreased. Additionally, among all three methylamines, SDMA was the most abundant in the brain (~70%). Administration of either compound impaired eNOS-derived NO production, increasing the monomer levels, and had no significant impact on nNOS. Both compounds elevated DDAH1 expression, and slight decreases in PMRT1 and PMRT5 in the cortex after scopolamine (acute) and MK-801 (chronic) administration were observed in the PFC, respectively. Administration of MK-801 induced a decrease in the cGMP level in the hippocampus, accompanied by decreased NMDA expression, while increased cGMP production and decreased NMDA receptor expression were observed after scopolamine administration. Chronic MK-801 and scopolamine administration affected S-nitrosylation of GLT-1 transport protein. Our results indicate that the analyzed tool compounds used in pharmacological models of schizophrenia or AD induce changes in NO-related pathways in the brain structures involved in cognition. To some extent, the changes resemble those observed in human samples.

Cardiovascular diseases (CVDs) are the leading cause of death worldwide. The initial stage of CVDs is characterized by endothelial dysfunction, defined as the limited bioavailability of nitric oxide (NO). Thus, any factors that interfere with the synthesis or metabolism of NO in endothelial cells are involved in CVD pathogenesis. It is well established that hypoxia is both the triggering factor as well as the accompanying factor in cardiovascular disease, and diminished tissue oxygen levels have been reported to influence endothelial NO bioavailability. In endothelial cells, NO is produced by endothelial nitric oxide synthase (eNOS) from L-Arg, with tetrahydrobiopterin (BH₄) as an essential cofactor. Here, we discuss the mechanisms by which hypoxia affects NO bioavailability, including regulation of eNOS expression and activity. What is particularly important is the fact that hypoxia contributes to the depletion of cofactor BH₄ and deficiency of substrate L-Arg, and thus elicits eNOS uncoupling—a state in which the enzyme produces superoxide instead of NO. eNOS uncoupling and the resulting oxidative stress is the major driver of endothelial dysfunction and atherogenesis. Moreover, hypoxia induces impairment in mitochondrial respiration and endothelial cell activation; thus, oxidative stress and inflammation, along with the hypoxic response, contribute to the development of endothelial dysfunction.

Inflammatory response to a marathon run in amateur athletes. Background While moderate physical exercise has positive effects on the cardiovascular system, the data regarding intensive endurance sports is bi...