Transcriptomic changes in glomeruli in response to a high salt challenge in the Dahl SS rat

Salt sensitivity impacts a significant portion of the population and is an important contributor to the development of chronic kidney disease. One of the significant early predictors of salt-induced damage is albuminuria, which reflects the deterioration of the renal filtration barrier: the glomerulus. Despite significant research efforts, there is still a gap in knowledge regarding the molecular mechanisms and signaling networks contributing to instigating and/or perpetuating salt-induced glomerular injury. To address this gap, we used 8-wk-old male Dahl salt-sensitive rats fed a normal-salt diet (0.4% NaCl) or challenged with a high-salt diet (4% NaCl) for 3 wk. At the end of the protocol, a pure fraction of renal glomeruli obtained by differential sieving was used for next-generation RNA sequencing and comprehensive semi-automatic transcriptomic data analyses, which revealed 149 differentially expressed genes (107 and 42 genes were downregulated and upregulated, respectively). Furthermore, a combination of predictive gene correlation networks and computational bioinformatic analyses revealed pathways impacted by a high salt dietary challenge, including renal metabolism, mitochondrial function, apoptotic signaling and fibrosis, cell cycle, inflammatory and immune responses, circadian clock, cytoskeletal organization, G protein-coupled receptor signaling, and calcium transport. In conclusion, we report here novel transcriptomic interactions and corresponding predicted pathways affecting glomeruli under salt-induced stress.NEW & NOTEWORTHY Our study demonstrated novel pathways affecting glomeruli under stress induced by dietary salt. Predictive gene correlation networks and bioinformatic semi-automatic analysis revealed changes in the pathways relevant to mitochondrial function, inflammatory, apoptotic/fibrotic processes, and cell calcium transport.

β-Arrestin pathway activation by selective ATR1 agonism promotes calcium influx in podocytes, leading to glomerular damage

Angiotensin receptor blockers (ARBs) are the first-line treatment for hypertension; they act by inhibiting signaling through the angiotensin 1 receptor (AT1R). Recently, a novel biased AT1R agonist, TRV120027 (TRV), which selectively activates the β-arrestin cascade and blocks the G-protein-coupled receptor pathway has been proposed as a potential blood pressure medication. Here, we explored the effects of TRV and associated β-arrestin signaling in podocytes, essential cells of the kidney filter. We used human podocyte cell lines to determine β-arrestin's involvement in calcium signaling and cytoskeletal reorganization and Dahl SS rats to investigate the chronic effects of TRV administration on glomerular health. Our experiments indicate that the TRV-activated β-arrestin pathway promotes the rapid elevation of intracellular Ca2+ in a dose-dependent manner. Interestingly, the amplitude of β-arrestin-mediated Ca2+ influx was significantly higher than the response to similar Ang II concentrations. Single-channel analyses show rapid activation of transient receptor potential canonical (TRPC) channels following acute TRV application. Furthermore, the pharmacological blockade of TRPC6 significantly attenuated the β-arrestin-mediated Ca2+ influx. Additionally, prolonged activation of the β-arrestin pathway in podocytes resulted in pathological actin cytoskeleton rearrangements, higher apoptotic cell markers, and augmented glomerular damage. TRV-activated β-arrestin signaling in podocytes may promote TRPC6 channel-mediated Ca2+ influx, foot process effacement, and apoptosis, possibly leading to severe defects in glomerular filtration barrier integrity and kidney health. Under these circumstances, the potential therapeutic application of TRV for hypertension treatment requires further investigation to assess the balance of the benefits versus possible deleterious effects and off-target damage.

Protease-Activated Receptor 1-Mediated Damage of Podocytes in Diabetic Nephropathy

There is clinical evidence that increased urinary serine proteases are associated with the disease severity in the setting of diabetic nephropathy (DN). Elevation of serine proteases may mediate [Ca2+]i dynamics in podocytes through the protease-activated receptors (PARs) pathway, including associated activation of nonspecific cation channels. Cultured human podocytes and freshly isolated glomeruli were used for fluorescence and immunohistochemistry stainings, calcium imaging, Western blot analysis, scanning ion conductance microscopy, and patch clamp analysis. Goto-Kakizaki, Wistar, type 2 DN (T2DN), and a novel PAR1 knockout on T2DN rat background rats were used to test the importance of PAR1-mediated signaling in DN settings. We found that PAR1 activation increases [Ca2+]i via TRPC6 channels. Both human cultured podocytes exposed to high glucose and podocytes from freshly isolated glomeruli of T2DN rats had increased PAR1-mediated [Ca2+]i compared with controls. Imaging experiments revealed that PAR1 activation plays a role in podocyte morphological changes. T2DN rats exhibited a significantly higher response to thrombin and urokinase. Moreover, the plasma concentration of thrombin in T2DN rats was significantly elevated compared with Wistar rats. T2DNPar1-/- rats were embryonically lethal. T2DNPar1+/- rats had a significant decrease in glomerular damage associated with DN lesions. Overall, these data provide evidence that, during the development of DN, elevated levels of serine proteases promote an excessive [Ca2+]i influx in podocytes through PAR1-TRPC6 signaling, ultimately leading to podocyte apoptosis, the development of albuminuria, and glomeruli damage.

ARTICLE HIGHLIGHTS

Increased urinary serine proteases are associated with diabetic nephropathy. During the development of diabetic nephropathy in type 2 diabetes, the elevation of serine proteases could overstimulate protease-activated receptor 1 (PAR1). PAR1 signaling is involved in the development of DN via TRPC6-mediated intracellular calcium signaling. This study provides fundamental knowledge that can be used to develop efficient therapeutic approaches targeting serine proteases or corresponding PAR pathways to prevent or slow the progression of diabetes-associated kidney diseases.

NNAT is a novel mediator of oxidative stress that suppresses ER + breast cancer

BACKGROUND

Neuronatin (NNAT) was recently identified as a novel mediator of estrogen receptor-positive (ER+) breast cancer cell proliferation and migration, which correlated with decreased tumorigenic potential and prolonged patient survival. However, despite these observations, the molecular and pathophysiological role(s) of NNAT in ER + breast cancer remains unclear. Based on high protein homology with phospholamban, we hypothesized that NNAT mediates the homeostasis of intracellular calcium [Ca2+]i levels and endoplasmic reticulum (EndoR) function, which is frequently disrupted in ER + breast cancer and other malignancies.

METHODS

To evaluate the role of NNAT on [Ca2+]i homeostasis, we used a combination of bioinformatics, gene expression and promoter activity assays, CRISPR gene manipulation, pharmacological tools and confocal imaging to characterize the association between ROS, NNAT and calcium signaling.

RESULTS

Our data indicate that NNAT localizes predominantly to EndoR and lysosome, and genetic manipulation of NNAT levels demonstrated that NNAT modulates [Ca2+]i influx and maintains Ca2+ homeostasis. Pharmacological inhibition of calcium channels revealed that NNAT regulates [Ca2+]i levels in breast cancer cells through the interaction with ORAI but not the TRPC signaling cascade. Furthermore, NNAT is transcriptionally regulated by NRF1, PPARα, and PPARγ and is strongly upregulated by oxidative stress via the ROS and PPAR signaling cascades.

CONCLUSION

Collectively, these data suggest that NNAT expression is mediated by oxidative stress and acts as a regulator of Ca2+ homeostasis to impact ER + breast cancer proliferation, thus providing a molecular link between the longstanding observation that is accumulating ROS and altered Ca2+ signaling are key oncogenic drivers of cancer.

Endothelial mechanical stretch regulates the immunological synapse interface of renal endothelial cells in a sex-dependent manner

Increased mechanical endothelial cell stretch contributes to the development of numerous cardiovascular and renal pathologies. Recent studies have shone a light on the importance of sex-dependent inflammation in the pathogenesis of renal disease states. The endothelium plays an intimate and critical role in the orchestration of immune cell activation through upregulation of adhesion molecules and secretion of cytokines and chemokines. While endothelial cells are not recognized as professional antigen-presenting cells, in response to cytokine stimulation, endothelial cells can express both major histocompatibility complex (MHC) I and MHC II. MHCs are essential to forming a part of the immunological synapse interface during antigen presentation to adaptive immune cells. Whether MHC I and II are increased under increased mechanical stretch is unknown. Due to hypertension being multifactorial, we hypothesized that increased mechanical endothelial stretch promotes the regulation of MHCs and key costimulatory proteins on mouse renal endothelial cells (MRECs) in a stretch-dependent manner. MRECs derived from both sexes underwent 5%, 10%, or 15% uniaxial cyclical stretch, and immunological synapse interface proteins were determined by immunofluorescence microscopy, immunoblot analysis, and RNA sequencing. We found that increased endothelial mechanical stretch conditions promoted downregulation of MHC I in male MRECs but upregulation in female MRECs. Moreover, MHC II was upregulated by mechanical stretch in both male and female MRECs, whereas CD86 and CD70 were regulated in a sex-dependent manner. By bulk RNA sequencing, we found that increased mechanical endothelial cell stretch promoted differential gene expression of key antigen processing and presentation genes in female MRECs, demonstrating that females have upregulation of key antigen presentation pathways. Taken together, our data demonstrate that mechanical endothelial stretch regulates endothelial activation and immunological synapse interface formation in renal endothelial cells in a sex-dependent manner.NEW & NOTEWORTHY Endothelial cells contribute to the development of renal inflammation and have the unique ability to express antigen presentation proteins. Whether increased endothelial mechanical stretch regulates immunological synapse interface proteins remains unknown. We found that antigen presentation proteins and costimulatory proteins on renal endothelial cells are modulated by mechanical stretch in a sex-dependent manner. Our data provide novel insights into the sex-dependent ability of renal endothelial cells to present antigens in response to endothelial mechanical stimuli.

Abstract 015: Hypertensive Stretch On The Regulation Of The Immunological Synapse And Secretomes Of Male And Female Renal Endothelial Cells

Immune cells and inflammation contribute to the development of hypertension and renal injury. While endothelial cells are recognized as professional antigen presenting cells, they can express both Major Histocompatibility Complex (MHC) I and II and possess antigen-presenting functions. Endothelial cell activation and inflammation are critical in the development of hypertension. However, the mechanisms by which inflammatory hypertensive stimuli regulate renal endothelial immunological synapse proteins remains unknown. We hypothesize that inflammatory hypertensive mechanical stretch promotes the regulation of MHC I and II and costimulatory molecules on mouse renal endothelial cells (MRECs) in a sex-dependent manner. MRECs derived from both sexes underwent normotensive (5%; 1 Hz), hypertensive (10%, 1 Hz), and supra-hypertensive (15% 1 Hz) uniaxial cyclical stretch for 48 hours. We then assessed CD80, CD86, MHC II, MHC I, CD70, and CD40 by immunoblot analysis. A proteome multiplex assay was used to analyze male and female MREC secretomes during 5%, 10%, and 15% stretch. Hypertensive 10% stretch significantly increased only CD40 expression in males, while it upregulated CD80 and CD70 expression in females (p<0.05). Under 15% stretch, males significantly upregulated MHC I, CD70, and CD40 compared to I-Ab, CD80, CD86, and CD70 in females MRECs (p<0.05). We investigated sex differences and found that females significantly increased CD70 in both 10% and 15% stretch compared to males MRECs (p<0.05). We compared sex differences from our secretome proteomics in male and female MRECs at 10% and 15% stretch. We found that pathways associated with wound healing, Th17 activation, IL-6, and NF-κB signaling were upregulated in male MRECs undergoing 10% stretch. Interestingly, Th17 activation, natural killer cell signaling, and IL-23 signaling were downregulated in female MRECs undergoing 10% stretch. Under 15% stretch, IL-13 signaling, HMBG1 signaling, B cell signaling, and IL-13 signaling were downregulated in MRECs from both sexes. Our data provides novel insights into how inflammatory hypertensive stretch regulates immunological synapse proteins and secretomes in renal endothelial cells by stretch and sex-dependent manner.

Astrocytic responses to high glucose impair barrier formation in cerebral microvessel endothelial cells

Hyperglycemic conditions are prodromal to blood-brain barrier (BBB) impairment. The BBB comprises cerebral microvessel endothelial cells (CMECs) that are surrounded by astrocytic foot processes. Astrocytes express high levels of gap junction connexin 43 (Cx43), which play an important role in autocrine and paracrine signaling interactions that mediate gliovascular cross talk through secreted products. One of the key factors of the astrocytic "secretome" is vascular endothelial growth factor (VEGF), a potent angiogenic factor that can disrupt BBB integrity. We hypothesize that high-glucose conditions change the astrocytic expression of Cx43 and increase VEGF secretion leading to impairment of CMEC barrier properties in vitro and in vivo. Using coculture of neonatal rat astrocytes and CMEC, we mimic hyperglycemic conditions using high-glucose (HG) feeding media and show a significant decrease in Cx43 expression and the corresponding increase in secreted VEGF. This result was confirmed by the analyses of Cx43 and VEGF protein levels in the brain cortex samples from the type 2 diabetic rat (T2DN). To further characterize inducible changes in BBB, we measured transendothelial cell electrical resistance (TEER) and tight junction protein levels in cocultured conditioned astrocytes with isolated rat CMEC. The coculture monolayer's integrity and permeability were significantly compromised by HG media exposure, which was indicated by decreased TEER without a change in tight junction protein levels in CMEC. Our study provides insight into gliovascular adaptations to increased glucose levels resulting in impaired cellular cross talk between astrocytes and CMEC, which could be one explanation for cerebral BBB disruption in diabetic conditions.

Nitric-Oxide-Mediated Signaling in Podocyte Pathophysiology

Nitric oxide (NO) is a potent signaling molecule involved in many physiological and pathophysiological processes in the kidney. NO plays a complex role in glomerular ultrafiltration, vasodilation, and inflammation. Changes in NO bioavailability in pathophysiological conditions such as hypertension or diabetes may lead to podocyte damage, proteinuria, and rapid development of chronic kidney disease (CKD). Despite the extensive data highlighting essential functions of NO in health and pathology, related signaling in glomerular cells, particularly podocytes, is understudied. Several reports indicate that NO bioavailability in glomerular cells is decreased during the development of renal pathology, while restoring NO level can be beneficial for glomerular function. At the same time, the compromised activity of nitric oxide synthase (NOS) may provoke the formation of peroxynitrite and has been linked to autoimmune diseases such as systemic lupus erythematosus. It is known that the changes in the distribution of NO sources due to shifts in NOS subunits expression or modifications of NADPH oxidases activity may be linked to or promote the development of pathology. However, there is a lack of information about the detailed mechanisms describing the production and release of NO in the glomerular cells. The interaction of NO and other reactive oxygen species in podocytes and how NO-calcium crosstalk regulates glomerular cells’ function is still largely unknown. Here, we discuss recent reports describing signaling, synthesis, and known pathophysiological mechanisms mediated by the changes in NO homeostasis in the podocyte. The understanding and further investigation of these essential mechanisms in glomerular cells will facilitate the design of novel strategies to prevent or manage health conditions that cause glomerular and kidney damage.

The role played by the Umba fish hatchery in artificial reproduction and conservation of water biological resources in the Murmansk region

The article provides information on the need for artificial reproduction of water biological resources. It is shown that the conservation of biological diversity of fish, maintaining stocks of valuable fish species, preserving the natural habitat is impossible without effective measures in the field of artificial reproduction. A brief description of the activities of the Murmansk branch «Glavrybvod» is given. The greatest attention is paid to the oldest enterprise in the Murmansk region – the Umba fish hatchery. The historical information about the activity of this enterprise is given. An assessment of the current state of the Atlantic salmon stocks in the Umba River basin is given. The main problems of the fish-breeding enterprise are identified and analyzed: a high level of illegal fishing, the consequences of molten timber rafting and the influence of the activities of enterprises of the mining complex. Measures aimed at solving these problems are proposed. It has been proved that thanks to the fish breeders of the Umba fish hatchery, the stocks of the Atlantic salmon population of the Umba River are replenished. It is shown that a promising direction of the plant's activity is the cultivation of other valuable fish species (whitefish, pink salmon, brown trout), which will significantly contribute to the replenishment of valuable fish stocks in the water bodies of the Murmansk region. The role and importance of artificial reproduction and conservation of water biological resources will increase more and more as the anthropogenic impact on the environment intensifies. This type of activity will be the only way to preserve the commercial value of valuable species of fish and other biological resources, which makes artificial reproduction artificial reproduction one of the highest priorities in development of fishery system of the Russian Federation.

Details of artificial reproduction of Atlantic salmon (Semga) at the Umba fish hatchery

The world's demand for fish products for food and industrial purposes has already significantly exceeded the reproduction capacity of wild fish. Further increasing exploitation of natural fish populations leads to a sharp reduction in their numbers and degradation of population biodiversity. The only way to solve the problem is to develop artificial reproduction of fish. This applies primarily to salmon, which are the most valuable and popular types of fish. In the Murmansk region, there are three fish hatcheries that carry out artificial reproduction of Atlantic salmon. Factory reproduction at the Umba Fish Hatchery (URZ) is currently an important and necessary process, since the plant is the only fish hatchery for reproductive purposes in the Tersk district. The article reveals the peculiarities of reproduction of Atlantic salmon (salmon) in the URZ. A brief description of the Umba River is given. The main fish-breeding activities are covered: catching and keeping of producers, collection of sexual products and fertilization, incubation of eggs, keeping of larvae and their transfer to external nutrition, factory tagging of juveniles, release of juveniles in the Umba River and its tributaries. The peculiarity of the Umba plant in contrast to the other two fish hatcheries of the Kola Peninsula is shown. The question of the necessity of the existence of the Umba fish hatchery and the prospects for its development is highlighted. The reasons for the decline in the number of salmon in Umba are listed. Recommendations for restoring the abundance and preserving the intraspecific biodiversity of the Umba River salmon are provided.