Dynamic activation of endothelial nitric oxide synthase by Hsp90

Study on the correlation of supplementation with L-citrulline on the gastrointestinal flora and semen antifreeze performance of ram

Introduction

Cryopreservation of semen can give full play to the reproductive advantages of male animals. However, in actual production, due to the poor frost resistance of sheep semen and the low conception rate, the promotion of sheep frozen semen is greatly hindered. Therefore, it is urgent to improve the frost resistance of semen to improve the quality of frozen semen. At present, most studies on improving the quality of frozen semen are based on the improvement of semen dilutions, and few studies on improving the freezing resistance of ram semen by feeding functional amino acids.

Methods

Therefore, 24 Turpan black rams were divided into high antifreeze group (HF) and a low antifreeze group (LF) Each of these groups was further randomly divided into control and experimental subgroups. The control subgroup was fed a basal diet, while the experimental subgroup received an additional 12 g/d of L-Cit supplementation based on the control group for a duration of 90 days.

Results

The results showed that Following L-Cit supplementation, the experimental group demonstrated significantly elevated sperm density and VSL (Velocity of straight line), T-AOC, GSH-Px, and NO levels in fresh semen compared to the control group (P < 0.01). After thawing, the experimental group exhibited significantly higher levels of T-AOC, GSH-Px, and NO compared to the control group (P < 0.01). Additionally, the HFT group, after thawing frozen semen, displayed significantly higher HK1 protein expression compared to the control group. The number of spermatogonia, spermatocytes, and sperm cells in the HFT group was significantly higher than that in the HFC group. Moreover, 16S rRNA sequence analysis showed that Candidatus_Saccharimonas, Staphylococcus, Weissella, succinivbrionaceae_UcG_002, and Quinella were significantly enriched in the rumen of the HFT group, while Ureaplasma was significantly enriched in the HFC group. In the duodenum, Clostridiales_bacterium_Firm_14, Butyrivibrio, and Prevotellaceae_NK3831_group were significantly enriched in the HFT group, whereas Desulfovibrio and Quinella were significantly enriched in the HFC group.

Discussion

Under the conditions employed in this study, L-Cit supplementation was found to enhance the intestinal flora composition in rams, thereby improving semen quality, enhancing the antifreeze performance of semen, and promoting the development of testicular spermatogenic cells.

Hyperthermic shift and cell engineering increase small extracellular vesicle production in HEK293F cells

Although small extracellular vesicles (sEVs) have promising features as an emerging therapeutic format for a broad spectrum of applications, for example, blood-brain-barrier permeability, low immunogenicity, and targeted delivery, economic manufacturability will be a crucial factor for the therapeutic applicability of sEVs. In the past, bioprocess optimization and cell line engineering improved titers of classical biologics multifold. We therefore performed a design of experiments (DoE) screening to identify beneficial bioprocess conditions for sEV production in HEK293F suspension cells. Short-term hyperthermia at 40°C elevated volumetric productivity 5.4-fold while sEVs displayed improved exosomal characteristics and cells retained >90% viability. Investigating the effects of hyperthermia via transcriptomics and proteomics analyses, an expectable, cellular heat-shock response was found together with an upregulation of many exosome biogenesis and vesicle trafficking related molecules, which could cause the productivity boost in tandem with heat shock proteins (HSPs), like HSP90 and HSC70. Because of these findings, a selection of 44 genes associated with exosome biogenesis, vesicle secretion machinery, or heat-shock response was screened for their influence on sEV production. Overexpression of six genes, CHMP1A, CHMP3, CHMP5, VPS28, CD82, and EZR, significantly increased both sEV secretion and titer, making them suitable targets for cell line engineering.

Effects of pre-exercise intake of plant- and animal-based foods on arterial function and aerobic exercise capacity in healthy young men: a randomized cross-over trial

The purpose of this study was to examine the effects of plant- versus animal-based food intake before exercise on arterial function and subsequent aerobic exercise capacity. Eleven healthy adult males (mean age, 22.6 ± 1.8 years) participated in this study. A plant- or animal-based randomized meal type crossover comparison was conducted on separate days with a uniform protein, fat, and carbohydrate balance. Both carotid-femoral pulse wave velocity (cfPWV), femoral-ankle pulse wave velocity (faPWV), and brachial artery flow-mediated dilatation (FMD) were measured as indexes of aortic and peripheral arterial stiffness and vascular endothelial function, respectively, before and at 120 min after the meal. After these measurements, maximal oxygen uptake was assessed using a graded power test on an electronically braked cycle ergometer. The results revealed that cfPWV was significantly lower, whereas FMD was significantly higher, at 120 min after compared with before the plant-based meal (p = 0.01 and 0.02, respectively). By contrast, cfPWV and FMD did not change at 120 min after compared with before the animal-based meal. In addition, faPWV did not change at 120 min after compared with before the meal for either meal type. Maximal oxygen uptake was higher in the plant- than in the animal-based meal type (p = 0.02). These results suggest that pre-exercise plant-based food intake may improve central arterial stiffness and vascular endothelial function, which may have favorable implications for aerobic exercise capacity.

Identification of immune-associated signatures and potential therapeutic targets for pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) comprises a heterogeneous group of diseases with diverse aetiologies. It is characterized by increased pulmonary arterial pressure and right ventricular (RV) failure without specific drugs for treatment. Emerging evidence suggests that inflammation and autoimmune disorders are common features across all PAH phenotypes. This provides a novel idea to explore the characteristics of immunological disorders in PAH and identify immune-related genes or biomarkers for specific anti-remodelling regimens. In this study, we integrated three gene expression profiles and performed Gene Ontology (GO) and KEGG pathway analysis. CIBERSORT was utilized to estimate the abundance of tissue-infiltrating immune cells in PAH. The PPI network and machine learning were constructed to identify immune-related hub genes and then evaluate the relationship between hub genes and differential immune cells using ImmucellAI. Additionally, we implemented molecular docking to screen potential small-molecule compounds based on the obtained genes. Our findings demonstrated the density and distribution of infiltrating CD4 T cells in PAH and identified four immune-related genes (ROCK2, ATHL1, HSP90AA1 and ACTR2) as potential targets. We also listed 20 promising molecules, including TDI01953, pemetrexed acid and radotinib, for PAH treatment. These results provide a promising avenue for further research into immunological disorders in PAH and potential novel therapeutic targets.

Recovery from indomethacin-induced gastrointestinal bleeding by treatment with teprenone

BACKGROUND

Gastrointestinal injuries caused by nonsteroidal anti-inflammatory drugs (NSAIDs) is a serious side effect in patients with rheumatoid arthritis (RA). However, effective therapeutic strategies have yet to be established. In this study, we investigated the therapeutic effects of teprenone (TEP), a gastric mucosal protective drug, on NSAID-induced gastrointestinal injuries in rats with RA (AA rats).

METHODS

Gastrointestinal injury was induced by oral administration of indomethacin (IMC), a typical NSAID. TEP was orally administered after IMC-induced gastrointestinal bleeding, and the stomach, jejunum, and ileum were excised.

RESULTS

On day 14 of IMC administration, lesion areas in the stomach, jejunum, and ileum were significantly larger in AA rats than in normal rats. When TEP was orally administered to AA rats, the lesion areas in the stomach, jejunum, and ileum significantly decreased compared with those in control rats (IMC-induced AA rats). Therefore, we measured NOS2 mRNA and NO levels, which were significantly decreased in rats with IMC-induced AA after treatment with TEP.

CONCLUSIONS

These results suggest that the oral administration of TEP may be useful for the treatment of NSAID-induced gastrointestinal injuries in patients with RA.

From Stress to Sick(le) and Back Again-Oxidative/Antioxidant Mechanisms, Genetic Modulation, and Cerebrovascular Disease in Children with Sickle Cell Anemia

Sickle cell anemia (SCA) is a genetic disease caused by the homozygosity of the HBB:c.20A>T mutation, which results in the production of hemoglobin S (HbS). In hypoxic conditions, HbS suffers autoxidation and polymerizes inside red blood cells, altering their morphology into a sickle shape, with increased rigidity and fragility. This triggers complex pathophysiological mechanisms, including inflammation, cell adhesion, oxidative stress, and vaso-occlusion, along with metabolic alterations and endocrine complications. SCA is phenotypically heterogeneous due to the modulation of both environmental and genetic factors. Pediatric cerebrovascular disease (CVD), namely ischemic stroke and silent cerebral infarctions, is one of the most impactful manifestations. In this review, we highlight the role of oxidative stress in the pathophysiology of pediatric CVD. Since oxidative stress is an interdependent mechanism in vasculopathy, occurring alongside (or as result of) endothelial dysfunction, cell adhesion, inflammation, chronic hemolysis, ischemia-reperfusion injury, and vaso-occlusion, a brief overview of the main mechanisms involved is included. Moreover, the genetic modulation of CVD in SCA is discussed. The knowledge of the intricate network of altered mechanisms in SCA, and how it is affected by different genetic factors, is fundamental for the identification of potential therapeutic targets, drug development, and patient-specific treatment alternatives.

Nitric Oxide: Physiological Functions, Delivery, and Biomedical Applications

Nitric oxide (NO) is a gaseous molecule that has a central role in signaling pathways involved in numerous physiological processes (e.g., vasodilation, neurotransmission, inflammation, apoptosis, and tumor growth). Due to its gaseous form, NO has a short half-life, and its physiology role is concentration dependent, often restricting its function to a target site. Providing NO from an external source is beneficial in promoting cellular functions and treatment of different pathological conditions. Hence, the multifaceted role of NO in physiology and pathology has garnered massive interest in developing strategies to deliver exogenous NO for the treatment of various regenerative and biomedical complexities. NO-releasing platforms or donors capable of delivering NO in a controlled and sustained manner to target tissues or organs have advanced in the past few decades. This review article discusses in detail the generation of NO via the enzymatic functions of NO synthase as well as from NO donors and the multiple biological and pathological processes that NO modulates. The methods for incorporating of NO donors into diverse biomaterials including physical, chemical, or supramolecular techniques are summarized. Then, these NO-releasing platforms are highlighted in terms of advancing treatment strategies for various medical problems.

Induction of KLF2 by Exercise Activates eNOS to Improve Vasodilatation in Diabetic Mice

Diabetic endothelial dysfunction associated with diminished endothelial nitric oxide (NO) synthase (eNOS) activity accelerates the development of atherosclerosis and cardiomyopathy. However, the approaches to restore eNOS activity and endothelial function in diabetes remain limited. The current study shows that enhanced expression of Krüppel-like factor 2 (KLF2), a shear stress-inducible transcription factor, effectively improves endothelial function through increasing NO bioavailability. KLF2 expression is suppressed in diabetic mouse aortic endothelium. Running exercise and simvastatin treatment induce endothelial KLF2 expression in db/db mice. Adenovirus-mediated endothelium-specific KLF2 overexpression enhances both endothelium-dependent relaxation and flow-mediated dilatation, while it attenuates oxidative stress in diabetic mouse arteries. KLF2 overexpression increases the phosphorylation of eNOS at serine 1177 and eNOS dimerization. RNA-sequencing analysis reveals that KLF2 transcriptionally upregulates genes that are enriched in the cyclic guanosine monophosphate-protein kinase G-signaling pathway, cAMP-signaling pathway, and insulin-signaling pathway, all of which are the upstream regulators of eNOS activity. Activation of the phosphoinositide 3-kinase-Akt pathway and Hsp90 contributes to KLF2-induced increase of eNOS activity. The present results suggest that approaches inducing KLF2 activation, such as physical exercise, are effective to restore eNOS activity against diabetic endothelial dysfunction.

ARTICLE HIGHLIGHTS

Exercise and statins restore the endothelial expression of Krüppel-like factor 2 (KLF2), which is diminished in diabetic db/db mice. Endothelium-specific overexpression of KLF2 improves endothelium-dependent relaxation and flow-mediated dilation through increasing nitric oxide bioavailability. KLF2 promotes endothelial nitric oxide synthase (eNOS) coupling and phosphorylation in addition to its known role in eNOS transcription. KLF2 upregulates the expression of several panels of genes that regulate eNOS activity.

CETP expression ameliorates endothelial function in female mice through estrogen receptor-α and endothelial nitric oxide synthase pathway

Endothelial dysfunction is an early manifestation of atherosclerosis. The cholesteryl ester transfer protein (CETP) has been considered proatherogenic by reducing plasma HDL levels. However, CETP may exhibit cell- or tissue-specific effects. We have previously reported that male mice expressing the human CETP gene show impaired endothelium-mediated vascular relaxation associated with oxidative stress. Although sexual dimorphisms on the metabolic role of CETP have been proposed, possible sex differences in the vascular effects of CETP were not previously studied. Thus, here we investigated the endothelial function of female CETP transgenic mice as compared with nontransgenic controls (NTg). Aortas from CETP females presented preserved endothelium-dependent relaxation to acetylcholine and an endothelium-dependent reduction of phenylephrine-induced contraction. eNOS phosphorylation (Ser1177) and calcium-induced NO levels were enhanced, whereas reactive oxygen species (ROS) production and NOX2 and SOD2 expression were reduced in the CETP female aortas. Furthermore, CETP females exhibited increased aortic relaxation to 17β-estradiol (E2) and upregulation of heat shock protein 90 (HSP90) and caveolin-1, proteins that stabilize estrogen receptor (ER) in the caveolae. Indeed, CETP females showed an increased E2-induced relaxation in a manner sensitive to estrogen receptor-α (ERα) and HSP90 inhibitors methylpiperidinopyrazole (MPP) and geldanamycin, respectively. MPP also impaired the relaxation response to acetylcholine in CETP but not in NTg females. Altogether, the study indicates that CETP expression ameliorates the anticontractile endothelial effect and relaxation to E2 in females. This was associated with less ROS production, and increased eNOS-NO and E2-ERα pathways. These results highlight the need for considering the sex-specific effects of CETP on cardiovascular risk.NEW & NOTEWORTHY Here we demonstrated that CETP expression has a sex-specific impact on the endothelium function. Contrary to what was described for males, CETP-expressing females present preserved endothelium-dependent relaxation to acetylcholine and improved relaxation response to 17β-estradiol. This was associated with less ROS production, increased eNOS-derived NO, and increased expression of proteins that stabilize estrogen receptor-α (ERα), thus increasing E2-ERα signaling sensitivity. These results highlight the need for considering the sex-specific effects of CETP on cardiovascular risk.

Butyrate inhibits LPC-induced endothelial dysfunction by regulating nNOS-produced NO and ROS production

Lipids oxidation is a key risk factor for cardiovascular diseases. Lysophosphatidylcholine (LPC), the major component of oxidized LDL, is an important triggering agent for endothelial dysfunction and atherogenesis. Sodium butyrate, a short-chain fatty acid, has demonstrated atheroprotective properties. So, we evaluate the role of butyrate in LPC-induced endothelial dysfunction. Vascular response to phenylephrine (Phe) and acetylcholine (Ach) was performed in aortic rings from male mice (C57BL/6J). The aortic rings were incubated with LPC (10 μM) and butyrate (0.01 or 0.1 Mm), with or without TRIM (an nNOS inhibitor). Endothelial cells (EA.hy296) were incubated with LPC and butyrate to evaluate nitric oxide (NO) and reactive oxygen species (ROS) production, calcium influx, and the expression of total and phosphorylated nNOS and ERK½. We found that butyrate inhibited LPC-induced endothelial dysfunction by improving nNOS activity in aortic rings. In endothelial cells, butyrate reduced ROS production and increased nNOS-related NO release, by improving nNOS activation (phosphorylation at Ser1412). Additionally, butyrate prevented the increase in cytosolic calcium and inhibited ERk½ activation by LPC. In conclusion, butyrate inhibited LPC-induced vascular dysfunction by increasing nNOS-derived NO and reducing ROS production. Butyrate restored nNOS activation, which was associated with calcium handling normalization and reduction of ERK½ activation.

Src-Dependent NM2A Tyrosine Phosphorylation Regulates Actomyosin Remodeling

Non-muscle myosin 2A (NM2A) is a key cytoskeletal enzyme that, along with actin, assembles into actomyosin filaments inside cells. NM2A is fundamental for cell adhesion and motility, playing important functions in different stages of development and during the progression of viral and bacterial infections. Phosphorylation events regulate the activity and the cellular localization of NM2A. We previously identified the tyrosine phosphorylation of residue 158 (pTyr¹⁵⁸) in the motor domain of the NM2A heavy chain. This phosphorylation can be promoted by Listeria monocytogenes infection of epithelial cells and is dependent on Src kinase; however, its molecular role is unknown. Here, we show that the status of pTyr¹⁵⁸ defines cytoskeletal organization, affects the assembly/disassembly of focal adhesions, and interferes with cell migration. Cells overexpressing a non-phosphorylatable NM2A variant or expressing reduced levels of Src kinase display increased stress fibers and larger focal adhesions, suggesting an altered contraction status consistent with the increased NM2A activity that we also observed. We propose NM2A pTyr¹⁵⁸ as a novel layer of regulation of actomyosin cytoskeleton organization.

Potential use of heat shock protein 90 as a biomarker for the diagnosis of human diseases

INTRODUCTION

The heat shock protein 90 (Hsp90) is a protein involved in many different biological processes and especially in cell survival. Some of these functions require the participation of other biological molecules, so Hsp90 is a chaperone that takes part in many protein-protein interactions working as a critical signaling hub protein. As a member of the heat shock protein family, Hsp90 expression is regulated under certain environmental and/or stressful situations, therefore Hsp90 concentration can be monitored and linked to these effects.

AREAS COVERED

This review discusses the Hsp90 expression in samples from individuals affected by different diseases (from infectious to cancer origin), and the biological consequences of these disorders, including the potential use of Hsp90 as a biomarker for the diagnosis of human diseases.

EXPERT OPINION

The potential of Hsp90 as a biomarker disease has been demonstrated in several studies in relation to infectious diseases and especially cancer. However, further research in this field is still needed, mainly to validate in statistically significant clinical studies that the detection of Hsp90 protein allows the diagnosis of some cancers at an early stage and also that it can act as a biomarker for monitoring the efficacy of their therapies.

Heat stress and stallion fertility

The threat posed by increased surface temperatures worldwide has attracted the attention of researchers to the reaction of animals to heat stress. Spermatogenesis in animals such as stallions is a temperature-dependent process, ideally occurring at temperatures slightly below the core body temperature. Thus, proper thermoregulation is essential, especially because stallion spermatogenesis and the resulting spermatozoa are negatively affected by increased testicular temperature. Consequently, the failure of thermoregulation resulting in heat stress may diminish sperm quality and increase the likelihood of stallion infertility. In this review, we emphasize upon the impact of heat stress on spermatogenesis and the somatic and germ cells and describe the subsequent testicular alterations. In addition, we explore the functions and molecular responses of heat shock proteins, including HSP60, HSP70, HSP90, and HSP105, in heat-induced stress conditions. Finally, we discuss the use of various therapies to alleviate heat stress-induced reproductive harm by modulating distinct signaling pathways.

The In Vitro Evaluation of Rooster Semen Pellets Frozen with Dimethylacetamide

Sperm cryopreservation is an effective technique for conserving animal genetic diversity and transmitting superior genetic backgrounds, maintained via a non-invasive sampling and collection of huge quantities of sperm. Nevertheless, cryopreservation in avian species is not commercially viable because of the rooster sperm's susceptibility to damage. This study aims to estimate the impact of dimethylacetamide (DMA) as a cryoprotectant at different levels (3%, 6%, or 9%) on the post-thawed sperm quality, motility, antioxidant-biomarkers, and the expression of anti-freeze related genes. Semen samples were collected twice a week from twelve roosters aged 40 wk, weighing 3400 ± 70 g, and belonging to the Cairo-B2 chicken strain. Fresh semen samples were rapidly appraised, pooled, diluted with two volumes of a basic extender, and divided equally into three groups. The diluted groups were chilled at -20 °C for 7 min, then gently supplemented with 3, 6, or 9% pre-cooled DMA and equilibrated at 5 °C for a further 10 min. Semen pellets were formed by pipetting drops 7 cm above liquid nitrogen (LN₂), which were then kept inside cryovials in the LN₂. Thawing was performed 2 months later by taking 3-4 pellets of the frozen semen into a glass tube and warming it in a water bath for 8 s at 60 °C. The results showed that 3% DMA increased the proportion of total motile sperm, progressivity, viability, and plasma membrane integrity (%) compared to the 6% and 9% DMA groups. The lipid peroxidation and antioxidant enzyme activity were improved in the 3% group. At the same time, some anti-freeze-related genes' (including ras homolog family member A (RHOA), heat shock protein 70 (HSP70), and small nuclear ribonucleoprotein polypeptide A (SNRPA1)) expressions were upregulated within the 3% DMA group relative to other groups. In conclusion, the 3% DMA group maintained higher post-thawed sperm quality than the other tested groups.

Machine learning classifiers predict key genomic and evolutionary traits across the kingdoms of life

In this study, we investigate how an organism's codon usage bias can serve as a predictor and classifier of various genomic and evolutionary traits across the domains of life. We perform secondary analysis of existing genetic datasets to build several AI/machine learning models. When trained on codon usage patterns of nearly 13,000 organisms, our models accurately predict the organelle of origin and taxonomic identity of nucleotide samples. We extend our analysis to identify the most influential codons for phylogenetic prediction with a custom feature ranking ensemble. Our results suggest that the genetic code can be utilized to train accurate classifiers of taxonomic and phylogenetic features. We then apply this classification framework to open reading frame (ORF) detection. Our statistical model assesses all possible ORFs in a nucleotide sample and rejects or deems them plausible based on the codon usage distribution. Our dataset and analyses are made publicly available on GitHub and the UCI ML Repository to facilitate open-source reproducibility and community engagement.

Dynamic cycling with a unique Hsp90/Hsp70-dependent chaperone machinery and GAPDH is needed for heme insertion and activation of neuronal NO synthase

Heat shock protein 90 (Hsp90) is known to mediate heme insertion and activation of heme-deficient neuronal nitric oxide (NO) synthase (apo-nNOS) in cells by a highly dynamic interaction that has been extremely difficult to study mechanistically with the use of subcellular systems. In that the heme content of many critical hemeproteins is regulated by Hsp90 and the heme chaperone GAPDH, the development of an in vitro system for the study of this chaperone-mediated heme regulation would be extremely useful. Here, we show that use of an antibody-immobilized apo-nNOS led not only to successful assembly of chaperone complexes but the ability to show a clear dependence on Hsp90 and GAPDH for heme-mediated activation of apo-nNOS. The kinetics of binding for Hsp70 and Hsp90, the ATP and K⁺ dependence, and the absolute requirement for Hsp70 in assembly of Hsp90•apo-nNOS heterocomplexes all point to a similar chaperone machinery to the well-established canonical machine regulating steroid hormone receptors. However, unlike steroid receptors, the use of a purified protein system containing Hsp90, Hsp70, Hsp40, Hop, and p23 is unable to activate apo-nNOS. Thus, heme insertion requires a unique Hsp90-chaperone complex. With this newly developed in vitro system, which recapitulates the cellular process requiring GAPDH as well as Hsp90, further mechanistic studies are now possible to better understand the components of the Hsp90-based chaperone system as well as how this heterocomplex works with GAPDH to regulate nNOS and possibly other hemeproteins.

Effect of Dimethylacetamide Concentration on Motility, Quality, Antioxidant Biomarkers, Anti-Freeze Gene Expression, and Fertilizing Ability of Frozen/Thawed Rooster Sperm

Sperm cryopreservation is of great importance for the poultry industry but still needs to be optimized. The high susceptibility of poultry sperm to cryodamage leads to low fertility rates after cryopreservation. Therefore, the present study aimed at evaluating the effect of including a cryoprotectant, dimethylacetamide (DMA), in the chicken semen freezing extenders at a final concentration of 3%, 6%, or 9% on the post-thawed sperm motility, quality, antioxidant biomarkers, anti-freeze gene expression, and fertilizing ability. Results showed that the total motile sperm, progressivity, and viability were quadratically increased (p < 0.05) in the 6% DMA group. The antioxidant enzyme activity and lipid peroxidation were negatively (p < 0.05) affected by the increase in DMA concentration. Furthermore, some anti-freeze-associated genes such as heat shock protein 70 (HSP70) and ras homolog family member A (RHOA) were linearly and quadratically down-regulated (p < 0.05) with the high concentration of DMA. Finally, the fertility and hatchability rates did not indicate statistical differences between DMA groups. It can be concluded that using the low concentration of 3−6% DMA in the freezing semen extender is preferable to obtain acceptable results in the post-thawed sperm quality and fertility.

Targeting HSP90 as a Novel Therapy for Cancer: Mechanistic Insights and Translational Relevance

Heat shock protein (HSP90), a highly conserved molecular chaperon, is indispensable for the maturation of newly synthesized poly-peptides and provides a shelter for the turnover of misfolded or denatured proteins. In cancers, the client proteins of HSP90 extend to the entire process of oncogenesis that are associated with all hallmarks of cancer. Accumulating evidence has demonstrated that the client proteins are guided for proteasomal degradation when their complexes with HSP90 are disrupted. Accordingly, HSP90 and its co-chaperones have emerged as viable targets for the development of cancer therapeutics. Consequently, a number of natural products and their analogs targeting HSP90 have been identified. They have shown a strong inhibitory effect on various cancer types through different mechanisms. The inhibitors act by directly binding to either HSP90 or its co-chaperones/client proteins. Several HSP90 inhibitors—such as geldanamycin and its derivatives, gamitrinib and shepherdin—are under clinical evaluation with promising results. Here, we review the subcellular localization of HSP90, its corresponding mechanism of action in the malignant phenotypes, and the recent progress on the development of HSP90 inhibitors. Hopefully, this comprehensive review will shed light on the translational potential of HSP90 inhibitors as novel cancer therapeutics.

Structure of the RAF1-HSP90-CDC37 complex reveals the basis of RAF1 regulation

RAF kinases are RAS-activated enzymes that initiate signaling through the MAPK cascade to control cellular proliferation, differentiation, and survival. Here, we describe the structure of the full-length RAF1 protein in complex with HSP90 and CDC37 obtained by cryoelectron microscopy. The reconstruction reveals a RAF1 kinase with an unfolded N-lobe separated from its C-lobe. The hydrophobic core of the N-lobe is trapped in the HSP90 dimer, while CDC37 wraps around the chaperone and interacts with the N- and C-lobes of the kinase. The structure indicates how CDC37 can discriminate between the different members of the RAF family. Our structural analysis also reveals that the folded RAF1 assembles with 14-3-3 dimers, suggesting that after folding RAF1 follows a similar activation as B-RAF. Finally, disruption of the interaction between CDC37 and the DFG segment of RAF1 unveils potential vulnerabilities in attempting the pharmacological degradation of RAF1 for therapeutic purposes.

Cell-To-Cell Communication in the Resistance Vasculature

The arterial vasculature can be divided into large conduit arteries, intermediate contractile arteries, resistance arteries, arterioles, and capillaries. Resistance arteries and arterioles primarily function to control systemic blood pressure. The resistance arteries are composed of a layer of endothelial cells oriented parallel to the direction of blood flow, which are separated by a matrix layer termed the internal elastic lamina from several layers of smooth muscle cells oriented perpendicular to the direction of blood flow. Cells within the vessel walls communicate in a homocellular and heterocellular fashion to govern luminal diameter, arterial resistance, and blood pressure. At rest, potassium currents govern the basal state of endothelial and smooth muscle cells. Multiple stimuli can elicit rises in intracellular calcium levels in either endothelial cells or smooth muscle cells, sourced from intracellular stores such as the endoplasmic reticulum or the extracellular space. In general, activation of endothelial cells results in the production of a vasodilatory signal, usually in the form of nitric oxide or endothelial-derived hyperpolarization. Conversely, activation of smooth muscle cells results in a vasoconstriction response through smooth muscle cell contraction. © 2022 American Physiological Society. Compr Physiol 12: 1-35, 2022.

Hsp90: From Cellular to Organismal Proteostasis

Assuring a healthy proteome is indispensable for survival and organismal health. Proteome disbalance and the loss of the proteostasis buffer are hallmarks of various diseases. The essential molecular chaperone Hsp90 is a regulator of the heat shock response via HSF1 and a stabilizer of a plethora of signaling proteins. In this review, we summarize the role of Hsp90 in the cellular and organismal regulation of proteome maintenance.

HSP90 Modulates T2R Bitter Taste Receptor Nitric Oxide Production and Innate Immune Responses in Human Airway Epithelial Cells and Macrophages

Bitter taste receptors (T2Rs) are G protein-coupled receptors (GPCRs) expressed in various cell types including ciliated airway epithelial cells and macrophages. T2Rs in these two innate immune cell types are activated by bitter products, including those secreted by Pseudomonas aeruginosa, leading to Ca2+-dependent activation of endothelial nitric oxide (NO) synthase (eNOS). NO enhances mucociliary clearance and has direct antibacterial effects in ciliated epithelial cells. NO also increases phagocytosis by macrophages. Using biochemistry and live-cell imaging, we explored the role of heat shock protein 90 (HSP90) in regulating T2R-dependent NO pathways in primary sinonasal epithelial cells, primary monocyte-derived macrophages, and a human bronchiolar cell line (H441). Immunofluorescence showed that H441 cells express eNOS and T2Rs and that the bitter agonist denatonium benzoate activates NO production in a Ca2+- and HSP90-dependent manner in cells grown either as submerged cultures or at the air-liquid interface. In primary sinonasal epithelial cells, we determined that HSP90 inhibition reduces T2R-stimulated NO production and ciliary beating, which likely limits pathogen clearance. In primary monocyte-derived macrophages, we found that HSP-90 is integral to T2R-stimulated NO production and phagocytosis of FITC-labeled Escherichia coli and pHrodo-Staphylococcus aureus. Our study demonstrates that HSP90 serves as an innate immune modulator by regulating NO production downstream of T2R signaling by augmenting eNOS activation without impairing upstream Ca2+ signaling. These findings suggest that HSP90 plays an important role in airway antibacterial innate immunity and may be an important target in airway diseases such as chronic rhinosinusitis, asthma, or cystic fibrosis.

Novel Insights on Nitric Oxide Synthase and NO Signaling in Ascidian Metamorphosis

Nitric oxide (NO) is a pivotal signaling molecule involved in a wide range of physiological and pathological processes. We investigated NOS/NO localization patterns during the different stages of larval development in the ascidia Ciona robusta and evidenced a specific and temporally controlled pattern. NOS/NO expression starts in the most anterior sensory structures of the early larva and progressively moves towards the caudal portion as larval development and metamorphosis proceeds. We here highlight the pattern of NOS/NO expression in the central and peripheral nervous system of Ciona larvae which precisely follows the progression of neural signals of the central pattern generator necessary for the control of the movements of the larva towards the substrate. This highly dynamic localization profile perfectly matches with the central role played by NO from the first phase of settlement induction to the next control of swimming behavior, adhesion to substrate and progressive tissue resorption and reorganization of metamorphosis itself.

The acute effects of passive heating on endothelial function, muscle microvascular oxygen delivery, and expression of serum HSP90α

Passive heating has been a therapeutic tool used to elevate core temperature and induce increases in cardiac output, blood flow, and shear stress. We aimed to determine the effects of a single bout of passive heating on endothelial function and serum heat shock protein 90α (HSP90α) levels in young, healthy subjects. 8 healthy subjects were recruited to participate in one bout of whole-body passive heating via immersion in a 40 °C hot tub to maintain a 1 °C increase in rectal temperature for 60 min. Twenty-four hours after heating, shear-rate corrected endothelium-dependent dilation increased (pre: 0.004 ± 0.002%SR_AUC; post: 0.006 ± 0.003%SR_AUC; p = 0.034) but serum [HSP90α] was not changed (pre: 36.7 ± 10.3 ng/mL; post: 40.6 ± 15.9 ng/mL; p = 0.39). Neither resting muscle O₂ utilization (pre: 0.17 ± 0.11 ml O₂ min^-1 (100 g)^-1; post: 0.14 ± 0.09 ml O₂ min^-1 (100 g)^-1); p = 0.28) nor mean arterial pressure (pre: 74 ± 11 mmHg; post: 73 ± 11 mmHg; p = 0.79) were influenced by the heating intervention. Finally, time to peak after cuff release was significantly delayed for % O₂ sat (TTP_pre = 39 ± 8.9 s and TTP_post = 43.5 ± 8.2 s; p = 0.007) and deoxy-[heme] (TTP_pre = 41.3 ± 18.1 s and TTP_post = 51.4 ± 16.3 s; p = 0.018), with no effect on oxy-[heme] (p = 0.19) and total-[heme] (p = 0.41). One bout of passive heating improved endothelium-dependent dilation 24 h later in young, healthy subjects. This data suggests that passive heat treatments may provide a simple intervention for improving vascular health.

Targeting mechanosensitive endothelial TXNDC5 to stabilize eNOS and reduce atherosclerosis in vivo

Although atherosclerosis preferentially develops at arterial curvatures and bifurcations where disturbed flow (DF) activates endothelium, therapies targeting flow-dependent mechanosensing pathways in the vasculature are unavailable. Here, we provided experimental evidence demonstrating a previously unidentified causal role of DF-induced endothelial TXNDC5 (thioredoxin domain containing 5) in atherosclerosis. TXNDC5 was increased in human and mouse atherosclerotic lesions and induced in endothelium subjected to DF. Endothelium-specific Txndc5 deletion markedly reduced atherosclerosis in ApoE-/- mice. Mechanistically, DF-induced TXNDC5 increases proteasome-mediated degradation of heat shock factor 1, leading to reduced heat shock protein 90 and accelerated eNOS (endothelial nitric oxide synthase) protein degradation. Moreover, nanoparticles formulated to deliver Txndc5-targeting CRISPR-Cas9 plasmids driven by an endothelium-specific promoter (CDH5) significantly increase eNOS protein and reduce atherosclerosis in ApoE-/- mice. These results delineate a new molecular paradigm that DF-induced endothelial TXNDC5 promotes atherosclerosis and establish a proof of concept of targeting endothelial mechanosensitive pathways in vivo against atherosclerosis.

Caveolin-1/Endothelial Nitric Oxide Synthase Interaction Is Reduced in Arteries From Pregnant Spontaneously Hypertensive Rats

We have investigated the role caveolae/caveolin-1 (Cav-1) plays in endothelial nitric oxide synthase (eNOS) activation and how it impacts pregnancy-induced decreased vascular reactivity in normotensive (Wistar rats) and spontaneously hypertensive rats (SHR). Wistar rats and SHR were divided into non-pregnant (NP) and pregnant (P). Nitrite levels were assessed by the Griess method in the aorta and mesenteric vascular bed. In functional studies, arteries were incubated with methyl-β-cyclodextrin (dextrin, 10mmol/L), which disrupts caveolae by depleting cholesterol, and concentration-response curves to phenylephrine (PE) and acetylcholine (ACh) were constructed. Electronic microscopy was used to determine endothelial caveolae density in the aorta and resistance mesenteric artery in the presence of vehicle or dextrin (10mmol/L). Western blot was performed to evaluate Cav-1, p-Cav-1, calmodulin (CaM), and heat shock protein 90 (Hsp90) expression. Cav-1/eNOS interaction in the aorta and mesenteric vascular bed was assessed by co-immunoprecipitation. Nitric oxide (NO) generation was greater in arteries from P groups compared to NP groups. Dextrin did not change vascular responses in the aorta from P groups or the number of caveolae in P groups compared to NP groups. Compared to NP Wistar rats, NP SHR showed smaller number of caveolae and reduced Cav-1 expression. Pregnancy did not alter Cav-1, CaM, or Hsp90 expression in the aorta or mesenteric vascular bed from Wistar rats or SHR. These results suggest that pregnancy does not alter expression of the main eNOS regulatory proteins, but it decreases Cav-1/eNOS interaction. Reduced Cav-1/eNOS interaction in the aorta and mesenteric vascular bed seems to be an important mechanism to increase eNOS activity and nitric oxide production in pregnant normotensive and hypertensive rats.

Mechanisms underlying unidirectional laminar shear stress-mediated Nrf2 activation in endothelial cells: Amplification of low shear stress signaling by primary cilia

Endothelial cells are sensitive to mechanical stress and respond differently to oscillatory flow versus unidirectional flow. This review highlights the mechanisms by which a wide range of unidirectional laminar shear stress induces activation of the redox sensitive antioxidant transcription factor nuclear factor-E2-related factor 2 (Nrf2) in cultured endothelial cells. We propose that fibroblast growth factor-2 (FGF-2), brain-derived neurotrophic factor (BDNF) and 15-Deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2) are potential Nrf2 activators induced by laminar shear stress. Shear stress-dependent secretion of FGF-2 and its receptor-mediated signaling is tightly controlled, requiring neutrophil elastase released by shear stress, αvβ3 integrin and the cell surface glycocalyx. We speculate that primary cilia respond to low laminar shear stress (<10 dyn/cm2), resulting in secretion of insulin-like growth factor 1 (IGF-1), which facilitates αvβ3 integrin-dependent FGF-2 secretion. Shear stress induces generation of heparan-binding epidermal growth factor-like growth factor (HB-EGF), which contributes to FGF-2 secretion and gene expression. Furthermore, HB-EGF signaling modulates FGF-2-mediated NADPH oxidase 1 activation that favors casein kinase 2 (CK2)-mediated phosphorylation/activation of Nrf2 associated with caveolin 1 in caveolae. Higher shear stress (>15 dyn/cm2) induces vesicular exocytosis of BDNF from endothelial cells, and we propose that BDNF via the p75NTR receptor could induce CK2-mediated Nrf2 activation. Unidirectional laminar shear stress upregulates gene expression of FGF-2 and BDNF and generation of 15d-PGJ2, which cooperate in sustaining Nrf2 activation to protect endothelial cells against oxidative damage.

The Relationship of Glutathione-S-Transferase and Multi-Drug Resistance-Related Protein 1 in Nitric Oxide (NO) Transport and Storage

Nitric oxide is a diatomic gas that has traditionally been viewed, particularly in the context of chemical fields, as a toxic, pungent gas that is the product of ammonia oxidation. However, nitric oxide has been associated with many biological roles including cell signaling, macrophage cytotoxicity, and vasodilation. More recently, a model for nitric oxide trafficking has been proposed where nitric oxide is regulated in the form of dinitrosyl-dithiol-iron-complexes, which are much less toxic and have a significantly greater half-life than free nitric oxide. Our laboratory has previously examined this hypothesis in tumor cells and has demonstrated that dinitrosyl-dithiol-iron-complexes are transported and stored by multi-drug resistance-related protein 1 and glutathione-S-transferase P1. A crystal structure of a dinitrosyl-dithiol-iron complex with glutathione-S-transferase P1 has been solved that demonstrates that a tyrosine residue in glutathione-S-transferase P1 is responsible for binding dinitrosyl-dithiol-iron-complexes. Considering the roles of nitric oxide in vasodilation and many other processes, a physiological model of nitric oxide transport and storage would be valuable in understanding nitric oxide physiology and pathophysiology.

Phosphorylation of SARS-CoV-2 Orf9b Regulates Its Targeting to Two Binding Sites in TOM70 and Recruitment of Hsp90

SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) is the causative agent of the COVID19 pandemic. The SARS-CoV-2 genome encodes for a small accessory protein termed Orf9b, which targets the mitochondrial outer membrane protein TOM70 in infected cells. TOM70 is involved in a signaling cascade that ultimately leads to the induction of type I interferons (IFN-I). This cascade depends on the recruitment of Hsp90-bound proteins to the N-terminal domain of TOM70. Binding of Orf9b to TOM70 decreases the expression of IFN-I; however, the underlying mechanism remains elusive. We show that the binding of Orf9b to TOM70 inhibits the recruitment of Hsp90 and chaperone-associated proteins. We characterized the binding site of Orf9b within the C-terminal domain of TOM70 and found that a serine in position 53 of Orf9b and a glutamate in position 477 of TOM70 are crucial for the association of both proteins. A phosphomimetic variant Orf9b_S53E showed drastically reduced binding to TOM70 and did not inhibit Hsp90 recruitment, suggesting that Orf9b–TOM70 complex formation is regulated by phosphorylation. Eventually, we identified the N-terminal TPR domain of TOM70 as a second binding site for Orf9b, which indicates a so far unobserved contribution of chaperones in the mitochondrial targeting of the viral protein.

The role of extracellular matrix in tumour angiogenesis: the throne has NOx servants

The extracellular matrix (ECM) dynamics in tumour tissue are deregulated compared to the ECM in healthy tissue along with disorganized architecture and irregular behaviour of the residing cells. Nitric oxide (NO) as a pleiotropic molecule exerts different effects on the components of the ECM driving or inhibiting augmented angiogenesis and tumour progression and tumour cell proliferation and metastasis. These effects rely on the concentration of NO within the tumour tissue, the nature of the surrounding microenvironment and the sensitivity of resident cells to NO. In this review article, we summarize the recent findings on the correlation between the levels of NO and the ECM components towards the modulation of tumour angiogenesis in different types of cancers. These are discussed principally in the context of how NO modulates the expression of ECM proteins resulting in either the promotion or inhibition of tumour growth via tumour angiogenesis. Furthermore, the regulatory effects of individual ECM components on the expression of the NO synthase enzymes and NO production were reviewed. These findings support the current efforts for developing effective therapeutics for cancers.

Alcohol-induced Hsp90 acetylation is a novel driver of liver sinusoidal endothelial dysfunction and alcohol-related liver disease

BACKGROUND & AIMS

Liver sinusoidal endothelial cell (LSEC) dysfunction has been reported in alcohol-related liver disease, yet it is not known whether LSECs metabolize alcohol. Thus, we investigated this, as well as the mechanisms of alcohol-induced LSEC dysfunction and a potential therapeutic approach for alcohol-induced liver injury.

METHODS

Primary human, rat and mouse LSECs were used. Histone deacetylase 6 (HDAC6) was overexpressed specifically in liver ECs via adeno-associated virus (AAV)-mediated gene delivery to decrease heat shock protein 90 (Hsp90) acetylation in ethanol-fed mice.

RESULTS

LSECs expressed CYP2E1 and alcohol dehydrogenase 1 (ADH1) and metabolized alcohol. Ethanol induced CYP2E1 in LSECs, but not ADH1. Alcohol metabolism by CYP2E1 increased Hsp90 acetylation and decreased its interaction with endothelial nitric oxide synthase (eNOS) leading to a decrease in nitric oxide (NO) production. A non-acetylation mutant of Hsp90 increased its interaction with eNOS and NO production, whereas a hyperacetylation mutant decreased NO production. These results indicate that Hsp90 acetylation is responsible for decreases in its interaction with eNOS and eNOS-derived NO production. AAV8-driven HDAC6 overexpression specifically in liver ECs deacetylated Hsp90, restored Hsp90's interaction with eNOS and ameliorated alcohol-induced liver injury in mice.

CONCLUSION

Restoring LSEC function is important for ameliorating alcohol-induced liver injury. To this end, blocking acetylation of Hsp90 specifically in LSECs via AAV-mediated gene delivery has the potential to be a new therapeutic strategy.

LAY SUMMARY

Alcohol metabolism in liver sinusoidal endothelial cells (LSECs) and the mechanism of alcohol-induced LSEC dysfunction are largely unknown. Herein, we demonstrate that LSECs can metabolize alcohol. We also uncover a mechanism by which alcohol induces LSEC dysfunction and liver injury, and we identify a potential therapeutic strategy to prevent this.

Portal hypertension in cirrhosis: Pathophysiological mechanisms and therapy

Portal hypertension, defined as increased pressure in the portal vein, develops as a consequence of increased intrahepatic vascular resistance due to the dysregulation of liver sinusoidal endothelial cells (LSECs) and hepatic stellate cells (HSCs), frequently arising from chronic liver diseases. Extrahepatic haemodynamic changes contribute to the aggravation of portal hypertension. The pathogenic complexity of portal hypertension and the unsuccessful translation of preclinical studies have impeded the development of effective therapeutics for patients with cirrhosis, while counteracting hepatic and extrahepatic mechanisms also pose a major obstacle to effective treatment. In this review article, we will discuss the following topics: i) cellular and molecular mechanisms of portal hypertension, focusing on dysregulation of LSECs, HSCs and hepatic microvascular thrombosis, as well as changes in the extrahepatic vasculature, since these are the major contributors to portal hypertension; ii) translational/clinical advances in our knowledge of portal hypertension; and iii) future directions.

Dysregulation of nitric oxide synthases during early and late pathophysiological conditions of diabetes mellitus leads to amassing of microvascular impedement

Diabetes is a major killer worldwide and its unprecedented rise poses a serious threat to mankind. According to recent estimation, 387 million people worldwide are affected from the disease with a prevalence rate of 8.3 and 46.3 % still remains undiagnosed. Important characteristics of diabetes are abnormalities of the physiological signalling functions of reactive oxygen species and reactive nitrogen species. Increased oxidative stress contributes to the activation of stress-sensitive intracellular signalling pathways and the development of gene products that trigger cellular damage and contribute to the vascular complications of diabetes. Growing evidence from studies into many diseases suggests that the pathogenesis of diabetes, obesity, cancer, ageing, inflammation, neurodegenerative disorders, hypertension, apoptosis, cardiovascular diseases, and heart failure are correlated with oxidative stress. This leads to cell metabolism and cell-cell homeostasis to be complexly dysregulated. This review focuses to investigate the status of oxidative stress, nitric oxide and reactive species in early and diabetes. Significance of nitric oxide synthases Evidences has accumulated indicating that the generation of reactive oxygen species (oxidative stress) may play an important role in the etiology of diabetic complications thus attention was given on the reactive oxygen and reactive nitrogen species and their potential role in pathogenesis. Additionally, the therapeutic advances in diabetes management are included. Nanotechnology, statins and stem cell technology are some techniques which can be considered to have a possible future in the treatment sector of diabetes.

mTOR Attenuation with Rapamycin Reverses Neurovascular Uncoupling and Memory Deficits in Mice Modeling Alzheimer's Disease

Vascular dysfunction is a universal feature of aging and decreased cerebral blood flow has been identified as an early event in the pathogenesis of Alzheimer's disease (AD). Cerebrovascular dysfunction in AD includes deficits in neurovascular coupling (NVC), a mechanism that ensures rapid delivery of energy substrates to active neurons through the blood supply. The mechanisms underlying NVC impairment in AD, however, are not well understood. We have previously shown that mechanistic/mammalian target of rapamycin (mTOR) drives cerebrovascular dysfunction in models of AD by reducing the activity of endothelial nitric oxide synthase (eNOS), and that attenuation of mTOR activity with rapamycin is sufficient to restore eNOS-dependent cerebrovascular function. Here we show mTOR drives NVC impairments in an AD model through the inhibition of neuronal NOS (nNOS)- and non-NOS-dependent components of NVC, and that mTOR attenuation with rapamycin is sufficient to restore NVC and even enhance it above WT responses. Restoration of NVC and concomitant reduction of cortical amyloid-β levels effectively treated memory deficits in 12-month-old hAPP(J20) mice. These data indicate that mTOR is a critical driver of NVC dysfunction and underlies cognitive impairment in an AD model. Together with our previous findings, the present studies suggest that mTOR promotes cerebrovascular dysfunction in AD, which is associated with early disruption of nNOS activation, through its broad negative impact on nNOS as well as on non-NOS components of NVC. Our studies highlight the potential of mTOR attenuation as an efficacious treatment for AD and potentially other neurologic diseases of aging.SIGNIFICANCE STATEMENT Failure of the blood flow response to neuronal activation [neurovascular coupling (NVC)] in a model of AD precedes the onset of AD-like cognitive symptoms and is driven, to a large extent, by mammalian/mechanistic target of rapamycin (mTOR)-dependent inhibition of nitric oxide synthase activity. Our studies show that mTOR also drives AD-like failure of non-nitric oxide (NO)-mediated components of NVC. Thus, mTOR attenuation may serve to treat AD, where we find that neuronal NO synthase is profoundly reduced early in disease progression, and potentially other neurologic diseases of aging with cerebrovascular dysfunction as part of their etiology.

Heat therapy: mechanistic underpinnings and applications to cardiovascular health

Cardiovascular diseases (CVD) are the leading cause of death worldwide, and novel therapies are drastically needed to prevent or delay the onset of CVD to reduce the societal and healthcare burdens associated with these chronic diseases. One such therapy is "heat therapy," or chronic, repeated use of hot baths or saunas. Although using heat exposure to improve health is not a new concept, it has received renewed attention in recent years as a growing number of studies have demonstrated robust and widespread beneficial effects of heat therapy on cardiovascular health. Here, we review the existing literature, with particular focus on the molecular mechanisms that underscore the cardiovascular benefits of this practice.

Vasculopathy in Sickle Cell Disease: From Red Blood Cell Sickling to Vascular Dysfunction

Sickle cell disease (SCD) is a hereditary disorder that leads to the production of an abnormal hemoglobin, hemoglobin S (HbS). HbS polymerizes in deoxygenated conditions, which can prompt red blood cell (RBC) sickling and leaves the RBCs more rigid, fragile, and prone to hemolysis. SCD patients suffer from a plethora of complications, ranging from acute complications, such as characteristic, frequent, and debilitating vaso-occlusive episodes to chronic organ damage. While RBC sickling is the primary event at the origin of vaso-occlusive processes, other factors that can further increase RBC transit times in the microcirculation may also be required to precipitate vaso-occlusive processes. The adhesion of RBC and leukocytes to activated endothelium and the formation of heterocellular aggregates, as well as increased blood viscosity, are among the mechanisms involved in slowing the progress of RBCs in deoxygenated vascular areas, favoring RBC sickling and promoting vascular occlusion. Chronic inflammatory processes and oxidative stress, which are perpetuated by hemolytic events and ischemia-reperfusion injury, result in this pan cellular activation and some acute events, such as stroke and acute chest syndrome, as well as chronic end-organ damage. Furthermore, impaired vasodilation and vasomotor hyperresponsiveness in SCD also contribute to vaso-occlusive processes. Treating SCD as a vascular disease in addition to its hematological perspective, the present article looks at the interplay between abnormal RBC physiology/integrity, vascular dysfunction and clinical severity in SCD, and discusses existing therapies and novel drugs in development that may ameliorate vascular complications in the disease. © 2021 American Physiological Society. Compr Physiol 11:1785-1803, 2021.

Extra-Nuclear Functions of the Transcription Factor Grainyhead-Like 3 in the Endothelium-Interaction with Endothelial Nitric Oxide Synthase

We previously demonstrated that the transcription factor Grainyhead-like 3 (GRHL3) has essential functions in endothelial cells by inhibiting apoptosis and promoting migration as well as activation of endothelial nitric oxide synthase (eNOS). We now show that a large portion of the protein is localized to myo-endothelial projections of murine arteries suggesting extra-nuclear functions. Therefore, we generated various deletion mutants to identify the nuclear localization signal (NLS) of GRHL3 and assessed potential extra-nuclear functions. Several large-scale deletion mutants were incapable of activating a GRHL3-dependent reporter construct, which could either be due to deficiencies in transcriptional activation or to impaired nuclear import. One of these mutants encompassed a predicted bipartite NLS whose deletion led to the retention of GRHL3 outside the nucleus. Interestingly, this mutant retained functions of the full-length protein as it could still inhibit pathways inducing endothelial cell apoptosis. As apoptosis protection by GRHL3 depends on NO-production, we examined whether GRHL3 could interact with eNOS and showed a direct interaction, which was enhanced with the extra-nuclear GRHL3 variant. The observation that endogenous GRHL3 also interacts with eNOS in intact murine arteries corroborated these findings and substantiated the notion that GRHL3 has important extra-nuclear functions in the endothelium.

Pravastatin suppresses inflammatory cytokines and endothelial activation in patients at risk of developing preeclampsia: INOVASIA study

INTRODUCTION

The Indonesian INOVASIA study is an ongoing multicentre randomized, open controlled trial of pravastatin for the prevention of preeclampsia in patients deemed to be high risk. Here we evaluate the effects of pravastatin on circulating inflammatory and endothelial markers, i.e. Vascular Endothelial Growth Factor (VEGF), Interleukin-6 (IL-6), Endothelin-1 (ET-1), and Nitric Oxide (NO).

METHODS

Pregnant women deemed to be at a high risk of developing preeclampsia women were recruited based on the Fetal Medicine Foundation preeclampsia screening test or a history of preterm preeclampsia, or clinical risk factors in combination with an abnormal uterine artery Doppler flow pattern at 11-20 week's gestation. This is a nested cohort study within the larger trial (INOVASIA); 38 patients were consecutively recruited and assigned to the pravastatin group and the control group. Participants in the pravastatin group received pravastatin (2 × 20 mg p.o) in addition to a standard regimen of aspirin (80 mg p.o) and calcium (1 g p.o), from 14 to 20 weeks until delivery. Blood samples to measure the various biomarkers were obtained in consecutive patients before starting the research medication and just before delivery (pre and post-test examination).

RESULT

The number of samples on the 2 time points for the various biomarkers was: VEGF: 38, IL-6: 30, ET-1: 38, and NO: 35. IL-6 levels decreased significantly in the pravastatin group (mean ± SD): (191.87 ± 82.99 vs. 151.85 + 48.46, p = .013), while levels in the control group did not change significantly (median (interquartile range)) (144.17 (53.91) vs. 140.82 (16.18), p = .177). ET-1 levels decreased significantly in the pravastatin group (3.64 ± 0.85 vs. 3.01 ± 0.74, p = .006) while the control group had more or less stable levels (3.57 ± 1.12 vs. 3.78 ± 0.73 p = .594). NO was the only serum marker that showed significant changes in both groups. NO levels increased in pravastatin group (11.30 (17.43) vs. 41.90 (53.18), p = .044) and decreased in control group (38.70 (34.80) vs. 10.03 (26.96), p = .002). VEGF levels appeared to follow opposite trends in the 2 groups (NS) (Pravastatin: 3.22 (0.62) vs. 3.28 (0.75), p = .402. Control: 3.38 (0.83) vs. 3.06 (0.74), p = .287).

CONCLUSION

Administration of 40 mg pravastatin resulted in an improvement in NO levels, and a decrease in IL-6 and endothelin (ET-1) levels. The direction of the effect of pravastatin on these biomarkers appears to underpin the potential for a beneficial effect of pravastatin in the prevention of preeclampsia.

Heat Shock Proteins in Oxidative Stress and Ischemia/Reperfusion Injury and Benefits from Physical Exercises: A Review to the Current Knowledge

Heat shock proteins (HSPs) are molecular chaperones produced in response to oxidative stress (OS). These proteins are involved in the folding of newly synthesized proteins and refolding of damaged or misfolded proteins. Recent studies have been focused on the regulatory role of HSPs in OS and ischemia/reperfusion injury (I/R) where reactive oxygen species (ROS) play a major role. ROS perform many functions, including cell signaling. Unfortunately, they are also the cause of pathological processes leading to various diseases. Biological pathways such as p38 MAPK, HSP70 and Akt/GSK-3β/eNOS, HSP70, JAK2/STAT3 or PI3K/Akt/HSP70, and HSF1/Nrf2-Keap1 are considered in the relationship between HSP and OS. New pathophysiological mechanisms involving ROS are being discovered and described the protein network of HSP interactions. Understanding of the mechanisms involved, e.g., in I/R, is important to the development of treatment methods. HSPs are multifunctional proteins because they closely interact with the antioxidant and the nitric oxide generation systems, such as HSP70/HSP90/NOS. A deficiency or excess of antioxidants modulates the activation of HSF and subsequent HSP biosynthesis. It is well known that HSPs are involved in the regulation of several redox processes and play an important role in protein-protein interactions. The latest research focuses on determining the role of HSPs in OS, their antioxidant activity, and the possibility of using HSPs in the treatment of I/R consequences. Physical exercises are important in patients with cardiovascular diseases, as they affect the expression of HSPs and the development of OS.

Endothelial caveolin and its scaffolding domain in cancer

Since the initial reports implicating caveolin-1 (CAV1) in neoplasia, the scientific community has made tremendous strides towards understanding how CAV1-dependent signaling and caveolae assembly modulate solid tumor growth. Once a solid neoplastic tumor reaches a certain size, it will increasingly rely on its stroma to meet the metabolic demands of the rapidly proliferating cancer cells, a limitation typically but not exclusively addressed via the formation of new blood vessels. Landmark studies using xenograft tumor models have highlighted the importance of stromal CAV1 during neoplastic blood vessel growth from preexisting vasculature, a process called angiogenesis, and helped identify endothelium-specific signaling events regulated by CAV1, such as vascular endothelial growth factor (VEGF) receptors as well as the endothelial nitric oxide (NO) synthase (eNOS) systems. This chapter provides a glimpse into the signaling events modulated by CAV1 and its scaffolding domain (CSD) during endothelial-specific aspects of neoplastic growth, such as vascular permeability, angiogenesis, and mechanotransduction.

The vital role for nitric oxide in intraocular pressure homeostasis

Catalyzed by endothelial nitric oxide (NO) synthase (eNOS) activity, NO is a gaseous signaling molecule maintaining endothelial and cardiovascular homeostasis. Principally, NO regulates the contractility of vascular smooth muscle cells and permeability of endothelial cells in response to either biochemical or biomechanical cues. In the conventional outflow pathway of the eye, the smooth muscle-like trabecular meshwork (TM) cells and Schlemm's canal (SC) endothelium control aqueous humor outflow resistance, and therefore intraocular pressure (IOP). The mechanisms by which outflow resistance is regulated are complicated, but NO appears to be a key player as enhancement or inhibition of NO signaling dramatically affects outflow function; and polymorphisms in NOS3, the gene that encodes eNOS modifies the relation between various environmental exposures and glaucoma. Based upon a comprehensive review of past foundational studies, we present a model whereby NO controls a feedback signaling loop in the conventional outflow pathway that is sensitive to changes in IOP and its oscillations. Thus, upon IOP elevation, the outflow pathway tissues distend, and the SC lumen narrows resulting in increased SC endothelial shear stress and stretch. In response, SC cells upregulate the production of NO, relaxing neighboring TM cells and increasing permeability of SC's inner wall. These IOP-dependent changes in the outflow pathway tissues reduce the resistance to aqueous humor drainage and lower IOP, which, in turn, diminishes the biomechanical signaling on SC. Similar to cardiovascular pathogenesis, dysregulation of the eNOS/NO system leads to dysfunctional outflow regulation and ocular hypertension, eventually resulting in primary open-angle glaucoma.

Dietary flavanols improve cerebral cortical oxygenation and cognition in healthy adults

Cocoa flavanols protect humans against vascular disease, as evidenced by improvements in peripheral endothelial function, likely through nitric oxide signalling. Emerging evidence also suggests that flavanol-rich diets protect against cognitive aging, but mechanisms remain elusive. In a randomized double-blind within-subject acute study in healthy young adults, we link these two lines of research by showing, for the first time, that flavanol intake leads to faster and greater brain oxygenation responses to hypercapnia, as well as higher performance only when cognitive demand is high. Individual difference analyses further show that participants who benefit from flavanols intake during hypercapnia are also those who do so in the cognitive challenge. These data support the hypothesis that similar vascular mechanisms underlie both the peripheral and cerebral effects of flavanols. They further show the importance of studies combining physiological and graded cognitive challenges in young adults to investigate the actions of dietary flavanols on brain function.

Location, Location, Location: How Vascular Specialization Influences Hematopoietic Fates During Development

During embryonic development, sequential waves of hematopoiesis give rise to blood-forming cells with diverse lineage potentials and self-renewal properties. This process must accomplish two important yet divergent goals: the rapid generation of differentiated blood cells to meet the needs of the developing embryo and the production of a reservoir of hematopoietic stem cells to provide for life-long hematopoiesis in the adult. Vascular beds in distinct anatomical sites of extraembryonic tissues and the embryo proper provide the necessary conditions to support these divergent objectives, suggesting a critical role for specialized vascular niche cells in regulating disparate blood cell fates during development. In this review, we will examine the current understanding of how organ- and stage-specific vascular niche specialization contributes to the development of the hematopoietic system.

Heat shock protein 90α increases superoxide generation from neuronal nitric oxide synthases

Neuronal nitric oxide synthase (nNOS) generates superoxide, particularly at sub-optimal l-arginine (l-Arg) substrate concentrations. Heat shock protein 90 (Hsp90) was reported to inhibit superoxide generation from nNOS protein. However, commercially available Hsp90 product from bovine brain tissues with unspecified Hsp90α and Hsp90β contents and an undefined Hsp90 protein oligomeric state was utilized. These two Hsp90s can have opposite effect on superoxide production by NOS. Importantly, emerging evidence indicates that nNOS splice variants are involved in different biological functions by functioning distinctly in redox signaling. In the present work, purified recombinant human Hsp90α, in its native dimeric state, was used in electron paramagnetic resonance (EPR) spin trapping experiments to study the effects of Hsp90α on superoxide generation from nNOS splice variants nNOSμ and nNOSα. Human Hsp90α was found to significantly increase superoxide generation from nNOSμ and nNOSα proteins under l-Arg-depleted conditions and Hsp90α influenced superoxide production by nNOSμ and nNOSα at varying degrees. Imidazole suppressed the spin adduct signal, indicating that superoxide was produced at the heme site of nNOS in the presence of Hsp90α, whereas l-Arg repletion diminished superoxide production by the nNOS-Hsp90α. Moreover, NADPH consumption rate values exhibited a similar trend/difference as a function of Hsp90α and l-Arg. Together, these EPR spin trapping and NADPH oxidation kinetics results demonstrated noticeable Hsp90α-induced increases in superoxide production by nNOS and a distinguishable effect of Hsp90α on nNOSμ and nNOSα proteins.

Functional implications of vascular endothelium in regulation of endothelial nitric oxide synthesis to control blood pressure and cardiac functions

The endothelium is the innermost vascular lining performing significant roles all over the human body while maintaining the blood pressure at physiological levels. Malfunction of endothelium is thus recognized as a biomarker linked with many vascular diseases including but not limited to atherosclerosis, hypertension and thrombosis. Alternatively, prevention of endothelial malfunctioning or regulating the functions of its associated physiological partners like endothelial nitric oxide synthase can prevent the associated vascular disorders which account for the highest death toll worldwide. While many anti-hypertensive drugs are available commercially, a comprehensive description of the key physiological roles of the endothelium and its regulation by endothelial nitric oxide synthase or vice versa is the need of the hour to understand its contribution in vascular homeostasis. This, in turn, will help in designing new therapeutics targeting endothelial nitric oxide synthase or its interacting partners present in the cellular pool. This review describes the central role of vascular endothelium in the regulation of endothelial nitric oxide synthase while outlining the emerging drug targets present in the vasculature with potential to treat vascular disorders including hypertension.

Modulatory effects of BPC 157 on vasomotor tone and the activation of Src-Caveolin-1-endothelial nitric oxide synthase pathway

BPC 157-activated endothelial nitric oxide synthase (eNOS) is associated with tissue repair and angiogenesis as reported in previous studies. However, how BPC 157 regulates the vasomotor tone and intracellular Src-Caveolin-1 (Cav-1)-eNOS signaling is not yet clear. The present study demonstrated a concentration-dependent vasodilation effect of BPC 157 in isolated rat aorta. Attenuation of this vasodilation effect in the absence of endothelium suggested an endothelium-dependent vasodilation effect of BPC 157. Although slightly increased vasorelaxation in aorta without endothelium was noticed at high concentration of BPC 157, there was no direct relaxation effect on three-dimensional model made of vascular smooth muscle cells. The vasodilation effect of BPC 157 was nitric oxide mediated because the addition of L-NAME or hemoglobin inhibited the vasodilation of aorta. Nitric oxide generation was induced by BPC 157 as detected by intracellular DFA-FM DA labeling which was capable of promoting the migration of vascular endothelial cells. BPC 157 enhanced the phosphorylation of Src, Cav-1 and eNOS which was abolished by pretreatment with Src inhibitor, confirming the upstream role of Src in this signal pathway. Activation of eNOS required the released binding with Cav-1 in advance. Co-immunoprecipitation analysis revealed that BPC 157 could reduce the binding between Cav-1 and eNOS. Together, the present study demonstrates that BPC 157 can modulate the vasomotor tone of an isolated aorta in a concentration- and nitric oxide-dependent manner. BPC 157 can induce nitric oxide generation likely through the activation of Src-Cav-1-eNOS pathway.

Targeting the phosphoinositide-3-kinase/protein kinase B pathway in airway innate immunity

The airway innate immune system maintains the first line of defense against respiratory infections. The airway epithelium and associated immune cells protect the respiratory system from inhaled foreign organisms. These cells sense pathogens via activation of receptors like toll-like receptors and taste family 2 receptors (T2Rs) and respond by producing antimicrobials, inflammatory cytokines, and chemokines. Coordinated regulation of fluid secretion and ciliary beating facilitates clearance of pathogens via mucociliary transport. Airway cells also secrete antimicrobial peptides and radicals to directly kill microorganisms and inactivate viruses. The phosphoinositide-3-kinase/protein kinase B (Akt) kinase pathway regulates multiple cellular targets that modulate cell survival and proliferation. Akt also regulates proteins involved in innate immune pathways. Akt phosphorylates endothelial nitric oxide synthase (eNOS) enzymes expressed in airway epithelial cells. Activation of eNOS can have anti-inflammatory, anti-bacterial, and anti-viral roles. Moreover, Akt can increase the activity of the transcription factor nuclear factor erythroid 2 related factor-2 that protects cells from oxidative stress and may limit inflammation. In this review, we summarize the recent findings of non-cancerous functions of Akt signaling in airway innate host defense mechanisms, including an overview of several known downstream targets of Akt involved in innate immunity.

A novel "hot spring"-mimetic hydrogel with excellent angiogenic properties for chronic wound healing

The treatment of chronic wounds is a major challenge in regenerative medicine, and angiogenesis is known to be critical for chronic wound healing. Hot springs with temperature in the range of 30-45 °C can promote blood circulation, and some hot spring elements including iron and silicon are also known to be active in promoting angiogenesis. Inspired by the hot spring function, we designed a novel bioactive photothermal hydrogel with "hot spring effect" based on fayalite (FA) and N, O-carboxymethyl chitosan (NOCS), which releases bioactive ions and has heating function to create hot ion environment in wound area. The hot spring-mimetic hydrogel showed significant enhancement of angiogenesis and chronic wound healing in vivo due to the in situ heating through photothermal effect combined with the bioactive ions (Fe²⁺ and SiO₄^4-) released from the hydrogel. It is further confirmed that the synergetic effect of the mild heating and bioactive ions on angiogenesis was mainly because of the activation of different angiogenic factors and signaling pathways. Our study suggests that the hot spring-mimetic approach may be an effective strategy to design bioactive materials for promoting angiogenesis and tissue regeneration.