Aquaporins in Immune Cells and Inflammation: New Targets for Drug Development

Decreased Expression of Aquaporins as a Feature of Tubular Damage in Lupus Nephritis

Background: Tubulointerstitial hypoxia is a key factor for lupus nephritis progression to end-stage renal disease. Numerous aquaporins (AQPs) are expressed by renal tubules and are essential for their proper functioning. The aim of this study is to characterize the tubular expression of AQP1, AQP2 and AQP3, which could provide a better understanding of tubulointerstitial stress during lupus nephritis. Methods: This retrospective monocentric study was conducted at Erasme-HUB Hospital. We included 37 lupus nephritis samples and 9 healthy samples collected between 2000 and 2020, obtained from the pathology department. Immunohistochemistry was performed to target AQP1, AQP2 and AQP3 and followed by digital analysis. Results: No difference in AQP1, AQP2 and AQP3 staining location was found between healthy and lupus nephritis samples. However, we observed significant differences between these two groups, with a decrease in AQP1 expression in the renal cortex and in AQP3 expression in the cortex and medulla. In the subgroup of proliferative glomerulonephritis (class III/IV), this decrease in AQPs expression was more pronounced, particularly for AQP3. In addition, within this subgroup, we detected lower AQP2 expression in patients with higher interstitial inflammation score and lower AQP3 expression when higher interstitial fibrosis and tubular atrophy were present. Conclusions: We identified significant differences in the expression of aquaporins 1, 2, and 3 in patients with lupus nephritis. These findings strongly suggest that decreased AQP expression could serve as an indicator of tubular injury. Further research is warranted to evaluate AQP1, AQP2, and AQP3 as prognostic markers in both urinary and histological assessments of lupus nephritis.

Exploring the Shared Diagnostic Genes in IBD and Psoriasis through Bioinformatics and Experimental Assays

Background: Inflammatory bowel disease (IBD) is a persistent, non-specific inflammation affecting the intestines. Psoriasis is a long-lasting inflammatory disorder of the skin. There is a comorbidity correlation between IBD and psoriasis, but the specific pathogenesis of the comorbidity is unclear. Materials and methods: In this study, we analyzed datasets sourced from the Gene Expression Omnibus (GEO) database, and identified shared genes of IBD and psoriasis through differential expression analysis and weighted gene co-expression network analysis (WGCNA). Then three machine learning algorithms were applied to identify shared diagnostic genes. Next, the validation of shared diagnostic genes was evaluated with ROC curves, with the AUC determined. Subsequently, single sample gene set enrichment analysis (ssGSEA) and immune infiltration analysis were conducted. Furthermore, we obtained potential drugs such as securinine in the Drug Signature Database (DsigDB) and 7 traditional Chinese medicines in the Coremine database, which might have therapeutic effects on the comorbidity of IBD and psoriasis. Finally, we confirmed the expression of the shared diagnostic gene in colitis and psoriasis mice tissues through RT-PCR, Western blot and immunohistochemistry (IHC) methods. Results: The results showed that AQP9 had the highest diagnostic value for two diseases. AQP9 had AUC values of 93.681% for UC, 89.629% for CD,and 78.689% for psoriasis in the internal validation datasets. In the external validation datasets, AQP9 had AUC values of 90.394% for UC, 93.909% for CD,and 82.906% for psoriasis. Immune infiltration analysis and ssGSEA revealed that AQP9 might impact the disease process of IBD and psoriasis by participating in the NF-kappaB signaling pathway, and modulating immune cell differentiation. Furthermore, the expression levels of AQP9 were consistently validated, showing upregulation in IBD and downregulation in psoriasis, compared to the control group. Conclusions: This study revealed the shared diagnostic genes and potential mechanisms of the comorbidity of IBD and psoriasis, providing new directions for future research on exploring the comorbidity mechanisms and treatment targets.

The Expanding Role of Aquaporin-1, Aquaporin-3 and Aquaporin-5 as Transceptors: Involvement in Cancer Development and Potential Druggability

Aquaporins (AQPs) are transmembrane proteins that facilitate the transport of water and small solutes, including glycerol, hydrogen peroxide and ions, across cell membranes. Beyond their established physiological roles in water regulation and metabolic processes, AQPs also exhibit receptor-like signaling activities in cancer-associated signaling pathways, integrating the dual roles of transporters and receptors, hence functioning as transceptors. This dual functionality underpins their critical involvement in cancer biology, where AQPs play key roles in promoting cell proliferation, migration, and invasion, contributing significantly to carcinogenesis. Among the AQPs, AQP1, AQP3 and AQP5 have been consistently identified as being aberrantly expressed in various tumor types. Their overexpression is strongly associated with tumor progression, metastasis, and poor patient prognosis. This review explores the pivotal roles of AQP1, AQP3 and AQP5 as transceptors in cancer biology, underscoring their importance as pharmacological targets. It highlights the urgent need for the development of effective modulators to target these AQPs, offering a promising avenue to enhance current therapeutic approaches for cancer treatment.

Exploring Aquaporins in Human Studies: Mechanisms and Therapeutic Potential in Critical Illness

Aquaporins (AQPs) are membrane proteins facilitating water and other small solutes to be transported across cell membranes. They are crucial in maintaining cellular homeostasis by regulating water permeability in various tissues. Moreover, they regulate cell migration, signaling pathways, inflammation, tumor growth, and metastasis. In critically ill patients, such as trauma, sepsis, and patients with acute respiratory distress syndrome (ARDS), which are frequently encountered in intensive care units (ICUs), water transport regulation is crucial for maintaining homeostasis, as dysregulation can lead to edema or dehydration, with the latter also implicating hemodynamic compromise. Indeed, AQPs are involved in fluid transport in various organs, including the lungs, kidneys, and brain, where their dysfunction can exacerbate conditions like ARDS, acute kidney injury (AKI), or cerebral edema. In this review, we discuss the implication of AQPs in the clinical entities frequently encountered in ICUs, such as systemic inflammation and sepsis, ARDS, AKI, and brain edema due to different types of primary brain injury from a clinical perspective. Current and possible future therapeutic implications are also considered.

Exploring the interplay between inflammation and male fertility

Male fertility results from a complex interplay of physiological, environmental, and genetic factors. It is conditioned by the properly developed anatomy of the reproductive system, hormonal regulation balance, and the interplay between different cell populations that sustain an appropriate and functional environment in the testes. Unfortunately, the mechanisms sustaining male fertility are not flawless and their perturbation can lead to infertility. Inflammation is one of the factors that contribute to male infertility. In the testes, it can be brought on by varicocele, obesity, gonadal infections, leukocytospermia, physical obstructions or traumas, and consumption of toxic substances. As a result of prolonged or untreated inflammation, the testicular resident cells that sustain spermatogenesis can suffer DNA damage, lipid and protein oxidation, and mitochondrial dysfunction consequently leading to loss of function in affected Sertoli cells (SCs) and Leydig cells (LCs), and the formation of morphologically abnormal dysfunctional sperm cells that lay in the basis of male infertility and subfertility. This is due mainly to the production and secretion of pro-inflammatory mediators, including cytokines, chemokines, and reactive oxygen species (ROS) by local immune cells (macrophages, lymphocytes T, mast cells) and tissue-specific cells [SCs, LCs, peritubular myoid cells (PMCs) and germ cells (GCs)]. Depending on the location, duration, and intensity of inflammation, these mediators can exert their toxic effect on different elements of the testes. In this review, we discuss the most prevalent inflammatory factors that negatively affect male fertility and describe the different ways inflammation can impair male reproductive function.

GSDMD Mediates Ang II-Induced Hypertensive Nephropathy by Regulating the GATA2/AQP4 Signaling Pathway

Aim

Hypertensive nephropathy is a common complication of hypertension. However, no effective measures are currently available to prevent the progression of renal insufficiency. Gasdermin D (GSDMD) is a crucial mediator of pyroptosis that induces an excessive inflammatory response. In the present study, we aimed to determine the effect of GSDMD on the pathogenesis of hypertensive nephropathy, which may provide new insights into the treatment of hypertensive nephropathy.

Methods

C57BL/6 (wild-type, WT) and Gsdmd knockout (Gsdmd-/-) mice were subcutaneously infused with angiotensin II (Ang II) via osmotic mini-pumps to establish a hypertensive renal injury model. Recombinant adeno-associated virus serotype 9 (AAV9) carrying GSDMD cDNA was used to overexpress GSDMD. Renal function biomarkers, histopathological changes, and inflammation and fibrosis indices were assessed. Transcriptome sequencing (RNA-seq) and cleavage under targets and mentation (CUT & Tag) experiments were performed to identify the downstream pathogenic mechanisms of GSDMD in hypertensive nephropathy.

Results

GSDMD was activated in the kidneys of mice induced by Ang II (P < 0.001). This activation was primarily observed in the renal tubular epithelial cells (P < 0.0001). GSDMD deficiency attenuated renal injury and fibrosis induced by Ang II (P < 0.0001), whereas Gsdmd overexpression promoted renal injury and fibrosis (P < 0.01). Mechanistically, GSDMD increased Ang II-induced GATA binding protein 2 (GATA2) transcription factor expression (P < 0.01). GATA2 also bound to the aquaporin 4 (Aqp4) promoter sequence and facilitated Aqp4 transcription (P < 0.001), leading to renal injury and fibrosis. Moreover, treatment with GI-Y1, an inhibitor of GSDMD, alleviated Ang II-induced renal injury and fibrosis (P < 0.01).

Conclusion

GSDMD plays an important role in the development of hypertensive nephropathy. Targeting GSDMD may be a therapeutic strategy for the treatment of hypertensive nephropathy.

Aquaporins in sepsis- an update

Aquaporins (AQPs), a family of membrane proteins that facilitate the transport of water and small solutes, have garnered increasing attention for their role in sepsis, not only in fluid balance but also in immune modulation and metabolic regulation. Sepsis, characterized by an excessive and dysregulated immune response to infection, leads to widespread organ dysfunction and significant mortality. This review focuses on the emerging roles of aquaporins in immune metabolism and their potential as therapeutic targets in sepsis, with particular attention to the modulation of inflammatory responses and organ protection. Additionally, it explores the diverse roles of aquaporins across various organ systems, highlighting their contributions to renal function, pulmonary gas exchange, cardiac protection, and gastrointestinal barrier integrity in the context of sepsis. Recent studies suggest that AQPs, particularly aquaglyceroporins like AQP3, AQP7, AQP9, and AQP10, play pivotal roles in immune cell metabolism and offer new therapeutic avenues for sepsis treatment. In the context of sepsis, immune cells undergo metabolic shifts to meet the heightened energy demands of the inflammatory response. A key adaptation is the shift from oxidative phosphorylation (OXPHOS) to aerobic glycolysis, where pyruvate is converted to lactate, enabling faster ATP production. AQPs, particularly aquaglyceroporins, may facilitate this process by transporting glycerol, a substrate that fuels glycolysis. AQP3, for example, enhances glucose metabolism by transporting glycerol and complementing glucose uptake via GLUT1, while also regulating O-GlcNAcylation, a post-translational modification that boosts glycolytic flux. AQP7 could further contributes to immune cell energy production by influencing lipid metabolism and promoting glycolysis through p38 signaling. These mechanisms could be crucial for maintaining the energy supply needed for an effective immune response during sepsis. Beyond metabolism, AQPs also regulate key immune functions. AQP9, highly expressed in septic patients, is essential for neutrophil migration and activation, both of which are critical for controlling infection. AQP3, on the other hand, modulates inflammation through the Toll-like receptor 4 (TLR4) pathway, while AQP1 plays a role in immune responses by activating the PI3K pathway, promoting macrophage polarization, and protecting against lipopolysaccharide (LPS)-induced acute kidney injury (AKI). These insights into the immunoregulatory roles of AQPs suggest their potential as therapeutic targets to modulate inflammation in sepsis. Therapeutically, AQPs present promising targets for reducing organ damage and improving survival in sepsis. For instance, inhibition of AQP9 with compounds like HTS13286 or RG100204 has been shown to reduce inflammation and improve survival by modulating NF-κB signaling and decreasing oxidative stress in animal models. AQP5 inhibition with methazolamide and furosemide has demonstrated efficacy in reducing immune cell migration and lung injury, suggesting its potential in treating acute lung injury (ALI) in sepsis. Additionally, the regulation of AQP1 through non-coding RNAs (lncRNAs and miRNAs) may offer new strategies to mitigate organ damage and inflammatory responses. Moreover, AQPs have emerged as potential biomarkers for sepsis progression and outcomes. Altered expression of AQPs, such as AQP1, AQP3, and AQP5, correlates with sepsis severity, and polymorphisms in AQP5 have been linked to better survival rates and improved outcomes in sepsis-related acute respiratory distress syndrome (ARDS). This suggests that AQP expression could be used to stratify patients and tailor treatments based on individual AQP profiles. In conclusion, AQPs play a multifaceted role in the pathophysiology of sepsis, extending beyond fluid balance to crucial involvement in immune metabolism and inflammation. Targeting AQPs offers novel therapeutic strategies to mitigate sepsis-induced organ damage and improve patient survival. Continued research into the metabolic and immune functions of AQPs will be essential for developing targeted therapies that can be translated into clinical practice.

Aquaporin Channels in Skin Physiology and Aging Pathophysiology: Investigating Their Role in Skin Function and the Hallmarks of Aging

This study examines the critical role of aquaporins (AQPs) in skin physiology and aging pathophysiology. The skin plays a vital role in maintaining homeostasis by acting as a protective barrier against external pathogens and excessive water loss, while also contributing to the appearance and self-esteem of individuals. Key physiological features, such as elasticity and repair capability, are essential for its proper function. However, with aging, these characteristics deteriorate, reducing the skin's ability to tolerate environmental stressors which contribute to external aging as well as internal aging processes, which negatively affect barrier function, immune response, and overall well-being. AQPs, primarily known for facilitating water transport, are significant for normal skin functions, including hydration and the movement of molecules like glycerol and hydrogen peroxide, which influence various cellular processes and functions. In this context, we categorized aquaporin dysfunction into several hallmarks of aging, including mitochondrial dysfunction, cellular senescence, stem cell depletion, impaired macroautophagy, dysbiosis, and inflamm-aging. Eight aquaporins (AQP1, 3, 5, 7, 8, 9, 10, and 11) are expressed in various skin cells, regulating essential processes such as cell migration, proliferation, differentiation, and also immune response. Dysregulation or altered expression of these proteins can enhance skin aging and related pathologies by activating these hallmarks. This study provides valuable insights into the potential of targeting aquaporins to mitigate skin aging and improve skin physiologic functions.

Important functions and molecular mechanisms of aquaporins family on respiratory diseases: potential translational values

Aquaporins (AQPs) are a subgroup of small transmembrane transporters that are distributed in various types of tissues, including the lung, kidney, heart and central nervous system. It is evident that respiratory diseases represent a significant global health concern, with a considerable number of deaths occurring worldwide. Recent researches have demonstrated that AQPs play a pivotal role in respiratory diseases, including chronic obstructive pulmonary disease (COPD), asthma, acute respiratory distress syndrome (ARDS), and particularly non-small cell lung cancer (NSCLC). In the context of NSCLC, the overexpression of AQP1, AQP3, AQP4, and AQP5 has been demonstrated to facilitate tumor angiogenesis, as well as the proliferation, migration, and invasiveness of tumor cells. This review concisely explores the role of AQP family on respiratory diseases, to assess their clinical and translational significance for understanding molecular pathogenesis. However, the potential translation of AQPs biomarkers into clinical applications is promising and the understanding of the precise mechanisms influencing respiratory diseases is still ongoing. Addressing the challenges and outlining the future perspectives in AQPs development is essential for clinical progress in a concise manner.

The involvement of aquaporin 5 in the inflammatory response of primary Sjogren's syndrome dry eye: potential therapeutic targets exploration

Sjogren's syndrome (SS) is a chronic autoimmune disease. Mainly due to the infiltration of lymphoplasmic cells into the exocrine glands, especially the salivary glands and lacrimal glands, resulting in reduced tear and saliva secretion. Reduced tear flow can trigger Sjogren's syndrome dry eye (SSDE). Although the pathophysiology of SSDE xerosis remains incompletely understood, recent advances have identified aquaporin-5 (AQP5) as a critical factor in dysregulation of the exocrine gland and epithelium, influencing the clinical presentation of SSDE through modulation of inflammatory microenvironment and tear secretion processes. This review aims to explore AQP5 regulatory mechanisms in SSDE and analyze its potential as a therapeutic target, providing new directions for SSDE treatment.

Peroxiporins and Oxidative Stress: Promising Targets to Tackle Inflammation and Cancer

Peroxiporins are a specialized subset of aquaporins, which are integral membrane proteins primarily known for facilitating water transport across cell membranes. In addition to the classical water transport function, peroxiporins have the unique capability to transport hydrogen peroxide (H2O2), a reactive oxygen species involved in various cellular signaling pathways and regulation of oxidative stress responses. The regulation of H2O2 levels is crucial for maintaining cellular homeostasis, and peroxiporins play a significant role in this process by modulating its intracellular and extracellular concentrations. This ability to facilitate the passage of H2O2 positions peroxiporins as key players in redox biology and cellular signaling, with implications for understanding and treating various diseases linked to oxidative stress and inflammation. This review provides updated information on the physiological roles of peroxiporins and their implications in disease, emphasizing their potential as novel biomarkers and drug targets in conditions where they are dysregulated, such as inflammation and cancer.

PPAR-γ/NF-kB/AQP3 axis in M2 macrophage orchestrates lung adenocarcinoma progression by upregulating IL-6

Aquaporin 3 (AQP3), which is mostly expressed in pulmonary epithelial cells, was linked to lung adenocarcinoma (LUAD). However, the underlying functions and mechanisms of AQP3 in the tumor microenvironment (TME) of LUAD have not been elucidated. Single-cell RNA sequencing (scRNA-seq) was used to study the composition, lineage, and functional states of TME-infiltrating immune cells and discover AQP3-expressing subpopulations in five LUAD patients. Then the identifications of its function on TME were examined in vitro and in vivo. AQP3 was associated with TNM stages and lymph node metastasis of LUAD patients. We classified inter- and intra-tumor diversity of LUAD into twelve subpopulations using scRNA-seq analyses. The analysis showed AQP3 was mainly enriched in subpopulations of M2 macrophages. Importantly, mechanistic investigations indicated that AQP3 promoted M2 macrophage polarization by the PPAR-γ/NF-κB axis, which affected tumor growth and migration via modulating IL-6 production. Mixed subcutaneous transplanted tumor mice and Aqp3 knockout mice models were further utilized, and revealed that AQP3 played a critical role in mediating M2 macrophage polarization, modulating glucose metabolism in tumors, and regulating both upstream and downstream pathways. Overall, our study demonstrated that AQP3 could regulate the proliferation, migration, and glycometabolism of tumor cells by modulating M2 macrophages polarization through the PPAR-γ/NF-κB axis and IL-6/IL-6R signaling pathway, providing new insight into the early detection and potential therapeutic target of LUAD.

Aquaporins: Gatekeepers of Fluid Dynamics in Traumatic Brain Injury

Aquaporins (AQPs), particularly AQP4, play a crucial role in regulating fluid dynamics in the brain, impacting the development and resolution of edema following traumatic brain injury (TBI). This review examines the alterations in AQP expression and localization post-injury, exploring their effects on brain edema and overall injury outcomes. We discuss the underlying molecular mechanisms regulating AQP expression, highlighting potential therapeutic strategies to modulate AQP function. These insights provide a comprehensive understanding of AQPs in TBI and suggest novel approaches for improving clinical outcomes through targeted interventions.

Protective roles of peroxiporins AQP0 and AQP11 in human astrocyte and neuronal cell lines in response to oxidative and inflammatory stressors

In addition to aquaporin (AQP) classes AQP1, AQP4 and AQP9 known to be expressed in mammalian brain, our recent transcriptomic analyses identified AQP0 and AQP11 in human cortex and hippocampus at levels correlated with age and Alzheimer's disease (AD) status; however, protein localization remained unknown. Roles of AQP0 and AQP11 in transporting hydrogen peroxide (H2O2) in lens and kidney prompted our hypothesis that up-regulation in brain might similarly be protective. Established cell lines for astroglia (1321N1) and neurons (SHSY5Y, differentiated with retinoic acid) were used to monitor changes in transcript levels for human AQPs (AQP0 to AQP12) in response to inflammation (simulated with 10-100 ng/ml lipopolysaccharide [LPS], 24 h), and hypoxia (5 min N2, followed by 0 to 24 h normoxia). AQP transcripts up-regulated in both 1321N1 and SHSY5Y included AQP0, AQP1 and AQP11. Immunocytochemistry in 1321N1 cells confirmed protein expression for AQP0 and AQP11 in plasma membrane and endoplasmic reticulum; AQP11 increased 10-fold after LPS and AQP0 increased 0.3-fold. In SHSY5Y cells, AQP0 expression increased 0.2-fold after 24 h LPS; AQP11 showed no appreciable change. Proposed peroxiporin roles were tested using melondialdehyde (MDA) assays to quantify lipid peroxidation levels after brief H2O2. Boosting peroxiporin expression by LPS pretreatment lowered subsequent H2O2-induced MDA responses (∼50%) compared with controls; conversely small interfering RNA knockdown of AQP0 in 1321N1 increased lipid peroxidation (∼17%) after H2O2, with a similar trend for AQP11 siRNA. Interventions that increase native brain peroxiporin activity are promising as new approaches to mitigate damage caused by aging and neurodegeneration.

Anethole mitigates H2 O2 -induced inflammation in HIG-82 synoviocytes by suppressing the aquaporin 1 expression and activating the protein kinase A pathway

Rheumatoid arthritis (RA) is an autoimmune inflammatory disease affecting approximately 1% of the global population, with a higher prevalence in women than in men. Chronic inflammation and oxidative stress play pivotal roles in the pathogenesis of RA. Anethole, a prominent compound derived from fennel (Foeniculum vulgare), possesses a spectrum of therapeutic properties, including anti-arthritic, anti-inflammatory, antioxidant, and tumor-suppressive effects. However, its specific impact on RA remains underexplored. This study sought to uncover the potential therapeutic value of anethole in treating RA by employing an H2 O2 -induced inflammation model with HIG-82 synovial cells. Our results demonstrated that exposure to H2 O2 induced the inflammation and apoptosis in these cells. Remarkably, anethole treatment effectively countered these inflammatory and apoptotic processes triggered by H2 O2 . Moreover, we identified the aquaporin 1 (AQP1) and protein kinase A (PKA) pathway as critical regulators of inflammation and apoptosis. H2 O2 stimulation led to an increase in the AQP1 expression and a decrease in p-PKA-C, contributing to cartilage degradation. Conversely, anethole not only downregulated the AQP1 expression but also activated the PKA pathway, effectively suppressing cell inflammation and apoptosis. Furthermore, anethole also inhibited the enzymes responsible for cartilage degradation. In summary, our findings highlight the potential of anethole as a therapeutic agent for mitigating H2 O2 -induced inflammation and apoptosis in synovial cells, offering promising prospects for future RA treatments.

Candidate Biomarkers for Targeting in Type 1 Diabetes; A Bioinformatic Analysis of Pancreatic Cell Surface Antigens

OBJECTIVE

Type 1 diabetes (T1Ds) is an autoimmune disease in which the immune system invades and destroys insulin-producing cells. Nevertheless, at the time of diagnosis, about 30-40% of pancreatic beta cells are healthy and capable of producing insulin. Bi-specific antibodies, chimeric antigen receptor regulatory T cells (CAR-Treg cells), and labeled antibodies could be a new emerging option for the treatment or diagnosis of type I diabetic patients. The aim of the study is to choose appropriate cell surface antigens in the pancreas tissue for generating an antibody for type I diabetic patients.

MATERIALS AND METHODS

In this bioinformatics study, we extracted pancreas-specific proteins from two large databases; the Human Protein Atlas (HPA) and Genotype-Tissue Expression (GTEx) Portal. Pancreatic-enriched genes were chosen and narrowed down by Protter software for the investigation of accessible extracellular domains. The immunohistochemistry (IHC) data of the protein atlas database were used to evaluate the protein expression of selected antigens. We explored the function of candidate antigens by using the GeneCards database to evaluate the potential dysfunction or activation/hyperactivation of antigens after antibody binding.

RESULTS

The results showed 429 genes are highly expressed in the pancreas tissue. Also, eighteen genes encoded plasma membrane proteins that have high expression in the microarray (GEO) dataset. Our results introduced four structural proteins, including NPHS1, KIRREL2, GP2, and CUZD1, among all seventeen candidate proteins.

CONCLUSION

The presented antigens can potentially be used to produce specific pancreatic antibodies that guide CARTreg, bi-specific, or labeling molecules to the pancreas for treatment, detection, or other molecular targeted therapy scopes for type I diabetes.

AQP3 and AQP9-Contrary Players in Sepsis?

Sepsis involves an immunological systemic response to a microbial pathogenic insult, leading to a cascade of interconnected biochemical, cellular, and organ-organ interaction networks. Potential drug targets can depict aquaporins, as they are involved in immunological processes. In immune cells, AQP3 and AQP9 are of special interest. In this study, we tested the hypothesis that these aquaporins are expressed in the blood cells of septic patients and impact sepsis survival. Clinical data, routine laboratory parameters, and blood samples from septic patients were analyzed on day 1 and day 8 after sepsis diagnosis. AQP expression and cytokine serum concentrations were measured. AQP3 mRNA expression increased over the duration of sepsis and was correlated with lymphocyte count. High AQP3 expression was associated with increased survival. In contrast, AQP9 expression was not altered during sepsis and was correlated with neutrophil count, and low levels of AQP9 were associated with increased survival. Furthermore, AQP9 expression was an independent risk factor for sepsis lethality. In conclusion, AQP3 and AQP9 may play contrary roles in the pathophysiology of sepsis, and these results suggest that AQP9 may be a novel drug target in sepsis and, concurrently, a valuable biomarker of the disease.

Intestinal polyphenol antioxidant activity involves redox signaling mechanisms facilitated by aquaporin activity

Ascertaining whether dietary polyphenols evoke an antioxidant or prooxidant activity, which translates to a functional role required to maintain intestinal cell homeostasis continues to be an active and controversial area of research for food chemists and biochemists alike. We have proposed that the paradoxical function of polyphenols to autoxidize to generate H2O2 is a required first step in the capacity of some plant phenolics to function as intracellular antioxidants. This is based on the fact that cell redox homeostasis is achieved by a balance between H2O2 formation and subsequent outcomes of antioxidant systems function. Maintaining optimal extracellular and intracellular H2O2 concentrations is required for cell survival, since low levels are important to upregulate endogenous antioxidant capacity; whereas, concentrations that go beyond homeostatic control typically result in an inflammatory response, growth arrest, or eventual cell death. Aquaporins (AQPs) are a family of water channel membrane proteins that facilitate cellular transportation of water and other small molecule-derived solutes, such as H2O2, in all organisms. In the intestine, AQPs act as gatekeepers to regulate intracellular uptake of H2O2, generated from extracellular polyphenol autoxidation, thus enabling an intracellular cell signaling responses to mitigate onset of oxidative stress and intestinal inflammation. In this review, we highlight the potential role of AQPs to control important underlying mechanisms that define downstream regulation of intestinal redox homeostasis, specifically. It has been established that polyphenols that undergo oxidation to the quinone form, resulting in subsequent adduction to a thiol group on Keap1-Nrf2 complex, trigger Nrf2 activation and a cascade of indirect intracellular antioxidant effects. Here, we propose a similar mechanism that involves H2O2 generated from specific dietary polyphenols with a predisposition to undergo autoxidation. The ultimate bioactivity is regulated and expressed by AQP membrane function and thus, by extension, represents expression of an intracellular antioxidant chemoprotection mechanism.

Evaluation of dual potentiality of 2,4,5-trisubstituted oxazole derivatives as aquaporin-4 inhibitors and anti-inflammatory agents in lung cells

Inflammation is a multifaceted "second-line" adaptive defense mechanism triggered by exo/endogenous threating stimuli and inter-communicated by various inflammatory key players. Unresolved or dysregulated inflammation in lungs results in manifestation of diseases and leads to irreparable damage. Aquaporins (AQPs) are a ubiquitously expressed superfamily of intrinsic transmembrane water channel proteins that modulate the fluid homeostasis. In addition to their conventional functions, AQPs have clinical relevance to inflammation prevailing under the infectious conditions of various lung diseases and this proclaims them as appropriate biomarkers to be targeted. Hence an endeavor was undertaken to identify potential ligands to target AQP4 for the treatment of lung diseases. Oxazole being a versatile bio-potent core, a series of 2,4,5-trisubstituted oxazoles 3a-j were synthesized by a Lewis acid mediated reaction of aroylmethylidene malonates with nitriles. In silico studies conducted using the protein data bank (PDB) structure 3gd8 for AQP4 revealed that compound 3a would serve as a suitable candidate to inhibit AQP4 in human lung cells (NCI-H460). Further, in vitro studies demonstrated that compound 3a could effectively inhibit AQP4 and inflammatory cytokines in lung cells and hence it may be considered as a viable drug candidate for the treatment of various lung diseases.

Deficiency of Caspase-1 Attenuates HIV-1-Associated Atherogenesis in Mice

Within arterial plaque, HIV infection creates a state of inflammation and immune activation, triggering NLRP3/caspase-1 inflammasome, tissue damage, and monocyte/macrophage infiltration. Previously, we documented that caspase-1 activation in myeloid cells was linked with HIV-associated atherosclerosis in mice and people with HIV. Here, we mechanistically examined the direct effect of caspase-1 on HIV-associated atherosclerosis. Caspase-1-deficient (Casp-1-/-) mice were crossed with HIV-1 transgenic (Tg26+/-) mice with an atherogenic ApoE-deficient (ApoE-/-) background to create global caspase-1-deficient mice (Tg26+/-/ApoE-/-/Casp-1-/-). Caspase-1-sufficient (Tg26+/-/ApoE-/-/Casp-1+/+) mice served as the controls. Next, we created chimeric hematopoietic cell-deficient mice by reconstituting irradiated ApoE-/- mice with bone marrow cells transplanted from Tg26+/-/ApoE-/-/Casp-1-/- (BMT Casp-1-/-) or Tg26+/-/ApoE-/-/Casp-1+/+ (BMT Casp-1+/+) mice. Global caspase-1 knockout in mice suppressed plaque deposition in the thoracic aorta, serum IL-18 levels, and ex vivo foam cell formation. The deficiency of caspase-1 in hematopoietic cells resulted in reduced atherosclerotic plaque burden in the whole aorta and aortic root, which was associated with reduced macrophage infiltration. Transcriptomic analyses of peripheral mononuclear cells and splenocytes indicated that caspase-1 deficiency inhibited caspase-1 pathway-related genes. These results document the critical atherogenic role of caspase-1 in chronic HIV infection and highlight the implication of this pathway and peripheral immune activation in HIV-associated atherosclerosis.

The multifaceted role of aquaporins in physiological cell migration

Cell migration is an essential process that underlies many physiological processes, including the immune response, organogenesis in the embryo, and angiogenesis, as well as pathological processes such as cancer metastasis. Cells have at their disposal a variety of migratory behaviors and mechanisms that seem to be specific to cell type and the microenvironment. Research over the past two decades has elucidated the water channel protein family of aquaporins (AQPs) as a regulator of many cell migration-related processes, from physical phenomena to biological signaling pathways. The roles that AQPs play in cell migration are both cell type- and isoform-specific; thus, a large swath of information has accumulated as researchers seek to identify the responses across these distinct variables. There does not seem to be a universal role that AQPs play in cell migration; the complex interplay between AQPs and cell volume management, signaling pathway activation, and in a few identified circumstances, gene expression regulation, has shown the intricate, and perhaps paradoxical, role of AQPs in cell migration. The objective of this review is to provide an organized and integrated collection of recent work that has elucidated the many mechanisms by which AQPs regulate cell migration.NEW & NOTEWORTHY Research has elucidated the water channel protein family of aquaporins (AQPs) as a regulator of many cell migration-related processes, from physical phenomena to biological signaling pathways. The roles that AQPs play in cell migration are both cell type- and isoform-specific; thus, a large swath of information has accumulated as researchers seek to identify the responses across these distinct variables. This review compiles insights into the recent findings linking AQPs to physiological cell migration.

T cells go with the flow: aquaporin 4 is required for full T-cell activation

Proximal T-cell receptor signaling and subsequent T cell activation was reduced downstream of anti-CD3/CD28 ligation through small molecule inhibition of the water channel aquaporin 4.

Role of aquaporins in corneal healing post chemical injury

Aquaporins (AQPs) are transmembrane water channel proteins that regulate the movement of water through the plasma membrane in various tissues including cornea. The cornea is avascular and has specialized microcirculatory mechanisms for homeostasis. AQPs regulate corneal hydration and transparency for normal vision. Currently, there are 13 known isoforms of AQPs that can be subclassified as orthodox AQPs, aquaglyceroporins (AQGPs), or supraquaporins (SAQPs)/unorthodox AQPs. AQPs are implicated in keratocyte function, inflammation, edema, angiogenesis, microvessel proliferation, and the wound-healing process in the cornea. AQPs play an important role in wound healing by facilitating the movement of corneal stromal keratocytes by squeezing through tight stromal matrix and narrow extracellular spaces to the wound site. Deficiency of AQPs can cause reduced concentration of hepatocyte growth factor (HGF) leading to reduced epithelial proliferation, reduced/impaired keratocyte migration, reduced number of keratocytes in the injury site, delayed and abnormal wound healing process. Dysregulated AQPs cause dysfunction in osmolar homeostasis as well as wound healing mechanisms. The cornea is a transparent avascular tissue that constitutes the anterior aspect of the outer covering of the eye and aids in two-thirds of visual light refraction. Being the outermost layer of the eye, the cornea is prone to injury. Of the 13 AQP isoforms, AQP1 is expressed in the stromal keratocytes and endothelial cells, and AQP3 and AQP5 are expressed in epithelial cells in the human cornea. AQPs can facilitate wound healing through aid in cellular migration, proliferation, migration, extracellular matrix (ECM) remodeling and autophagy mechanism. Corneal wound healing post-chemical injury requires an integrative and coordinated activity of the epithelium, stromal keratocytes, endothelium, ECM, and a battery of cytokines and growth factors to restore corneal transparency. If the chemical injury is mild, the cornea will heal with normal clarity, but severe injuries can lead to partial and/or permanent loss of corneal functions. Currently, the role of AQPs in corneal wound healing is poorly understood in the context of chemical injury. This review discusses the current literature and the role of AQPs in corneal homeostasis, wound repair, and potential therapeutic target for acute and chronic corneal injuries.

NAADP-Evoked Ca2+ Signaling: The DUOX2-HN1L/JPT2-Ryanodine Receptor 1 Axis

Nicotinic acid adenine dinucleotide phosphate (NAADP) is the most potent Ca²⁺ mobilizing second messenger known to date. Major steps elucidating metabolism and Ca²⁺ mobilizing activity of NAADP are reviewed, with emphasis on a novel redox cycle between the inactive reduced form, NAADPH, and the active oxidized form, NAADP. Oxidation from NAADPH to NAADP is catalyzed in cell free system by (dual) NADPH oxidases NOX5, DUOX1, and DUOX2, whereas reduction from NAADP to NAADPH is catalyzed by glucose 6-phosphate dehydrogenase. Using different knockout models for NOX and DUOX isozymes, DUOX2 was identified as NAADP forming enzyme in early T-cell activation.Recently, receptors or binding proteins for NAADP were identified: hematological and neurological expressed 1-like protein (HN1L)/Jupiter microtubule associated homolog 2 (JPT2) and Lsm12 are small cytosolic proteins that bind NAADP. In addition, they interact with NAADP-sensitive Ca²⁺ channels, such as ryanodine receptor type 1 (RYR1) or two-pore channels (TPC).Due to its role as Ca²⁺ mobilizing second messenger in T cells, NAADP's involvement in inflammation is also reviewed. In the central nervous system (CNS), NAADP regulates autoimmunity because NAADP antagonism affects a couple of T-cell migration and re-activation events, e.g. secretion of the pro-inflammatory cytokine interleukin-17. Further, the role of NAADP in transdifferentiation of IL-17-producing Th17 cells into T regulatory type 1 cells in vitro and in vivo is discussed.

Aquaporins in Immune System

Recent studies have shown that at least six aquaporins (AQPs), including AQP1, AQP3, AQP4, AQP5, AQP7, and AQP9, are expressed in immune system. These AQPs distribute in lymphocytes, macrophages, dendritic cells, and neutrophils, and mediate water and glycerol transportation in these cells, which play important roles in innate and adaptive immune functions. Immune system plays important roles in body physiological functions and health. Therefore, understanding the association between AQPs and immune system may provide approaches to prevent and treat related diseases. Here we will discuss the expression and physiological functions of AQPs in immune system and summarize recent researches on AQPs in immune diseases.

Gene Expression of Aquaporins (AQPs) in Cumulus Oocytes Complex and Embryo of Cattle

Aquaporins (AQPs) are proteins with various functions related to proper cell function and early development in mammals. The aim of this study was to evaluate the presence of AQPs and determine their mRNA levels in the cumulus oocyte complex (COC) of four bovine breeds and in blastocysts of five bovine crosses. Grade I, II and III COCs were collected by ovum pick up from non-lactating heifers of the Brahaman, Holstein, Gir and Romosinuano breeds. Embryos were produced in vitro up to the blastocyst stage of the bovine ♀Gir × ♂Holstein, ♀Holstein × ♂Gir, ♀Brahman × ♂Holstein, ♀Holstein × ♂Brahman, and ♀Romosinuano × ♂Holstein crosses. mRNA expression of AQP1-AQP12b was estimated in COC and embryos by real-time-PCR. The presence of the twelve AQPs in the COCs and bovine embryos was established. Additionally, significant differences were determined in the expression of AQP6 and AQP12b in COCs, as well as in transcripts levels of AQP4, AQP8 and AQP9 from bovine embryos. Gene expression of AQPs in COCs and bovine embryos is consistent with the previously described biological functions. This is the first report of AQPs in COC of Gir, Brahman, Holstein and Romosinuano and embryos of five crossbreeds between Bos indicus and B. taurus.

Cell volume restriction by mercury chloride reduces M1-like inflammatory response of bone marrow-derived macrophages

Dysregulation of macrophages in the pro-inflammatory (M1) and anti-inflammatory (M2) sub-phenotypes is a crucial element in several inflammation-related diseases and injuries. We investigated the role of aquaporin (AQP) in macrophage polarization using AQP pan-inhibitor mercury chloride (HgCl₂). Lipopolysaccharides (LPSs) induced the expression of AQP-1 and AQP-9 which increased the cell size of bone marrow-derived macrophages. The inhibition of AQPs by HgCl₂ abolished cell size changes and significantly suppressed M1 polarization. HgCl₂ significantly reduced the activation of the nuclear factor kappa B (NF-κB) and p38 mitogen-activated protein kinase (MAPK) pathways and inhibited the production of IL-1β. HgCl₂ attenuated LPS-induced activation of mitochondria and reactive oxygen species production and autophagy was promoted by HgCl₂. The increase in the light chain three II/light chain three I ratio and the reduction in PTEN-induced kinase one expression suggests the recycling of damaged mitochondria and the restoration of mitochondrial activity by HgCl₂. In summary, the present study demonstrates a possible mechanism of the AQP inhibitor HgCl₂ in macrophage M1 polarization through the restriction of cell volume change, suppression of the p38 MAPK/NFκB pathway, and promotion of autophagy.

Molecular Mechanisms Linking Inflammation to Autoimmunity in Sjögren's Syndrome: Identification of New Targets

Sjögren's syndrome (SS) is a systemic autoimmune rheumatic disorder characterized by the lymphocytic infiltration of exocrine glands and the production of autoantibodies to self-antigens. The involvement of the exocrine glands drives the pathognomonic manifestations of dry eyes (keratoconjunctivitis sicca) and dry mouth (xerostomia) that define sicca syndrome. To date, the molecular mechanisms mediating pathological salivary gland dysfunction in SS remain to be elucidated, despite extensive studies investigating the underlying cause of this disease, hampering the development of novel therapeutic strategies. Many researchers have identified a multifactorial pathogenesis of SS, including environmental, genetic, neuroendocrine, and immune factors. In this review, we explore the latest developments in understanding the molecular mechanisms involved in the pathogenesis of SS, which have attracted increasing interest in recent years.

Aquaporins: New players in breast cancer progression and treatment response

Aquaporins (AQPs) are a family of small transmembrane proteins that selectively transport water and other small molecules and ions following an osmotic gradient across cell plasma membranes. This enables them to regulate numerous functions including water homeostasis, fat metabolism, proliferation, migration, and adhesion. Previous structural and functional studies highlight a strong biological relationship between AQP protein expression, localization, and key biological functions in normal and cancer tissues, where aberrant AQP expression correlates with tumorigenesis and metastasis. In this review, we discuss the roles of AQP1, AQP3, AQP4, AQP5, and AQP7 in breast cancer progression and metastasis, including the role of AQPs in the tumor microenvironment, to highlight potential contributions of stromal-derived to epithelial-derived AQPs to breast cancer. Emerging evidence identifies AQPs as predictors of response to cancer therapy and as targets for increasing their sensitivity to treatment. However, these studies have not evaluated the requirements for protein structure on AQP function within the context of breast cancer. We also examine how AQPs contribute to a patient's response to cancer treatment, existing AQP inhibitors and how AQPs could serve as novel predictive biomarkers of therapy response in breast cancer. Future studies also should evaluate AQP redundancy and compensation as mechanisms used to overcome aberrant AQP function. This review highlights the need for additional research into how AQPs contribute molecularly to therapeutic resistance and by altering the tumor microenvironment.

RG100204, A Novel Aquaporin-9 Inhibitor, Reduces Septic Cardiomyopathy and Multiple Organ Failure in Murine Sepsis

Sepsis is caused by systemic infection and is a major health concern as it is the primary cause of death from infection. It is the leading cause of mortality worldwide and there are no specific effective treatments for sepsis. Gene deletion of the neutral solute channel Aquaporin 9 (AQP9) normalizes oxidative stress and improves survival in a bacterial endotoxin induced mouse model of sepsis. In this study we described the initial characterization and effects of a novel small molecule AQP9 inhibitor, RG100204, in a cecal ligation and puncture (CLP) induced model of polymicrobial infection. In vitro, RG100204 blocked mouse AQP9 H2O2 permeability in an ectopic CHO cell expression system and abolished the LPS induced increase in superoxide anion and nitric oxide in FaO hepatoma cells. Pre-treatment of CLP-mice with RG100204 (25 mg/kg p.o. before CLP and then again at 8 h after CLP) attenuated the hypothermia, cardiac dysfunction (systolic and diastolic), renal dysfunction and hepatocellular injury caused by CLP-induced sepsis. Post-treatment of CLP-mice with RG100204 also attenuated the cardiac dysfunction (systolic and diastolic), the renal dysfunction caused by CLP-induced sepsis, but did not significantly reduce the liver injury or hypothermia. The most striking finding was that oral administration of RG100204 as late as 3 h after the onset of polymicrobial sepsis attenuated the cardiac and renal dysfunction caused by severe sepsis. Immunoblot quantification demonstrated that RG100204 reduced activation of the NLRP3 inflammasome pathway. Moreover, myeloperoxidase activity in RG100204 treated lung tissue was reduced. Together these results indicate that AQP9 may be a novel drug target in polymicrobial sepsis.

The Effect of Nutritional Ketosis on Aquaporin Expression in Apolipoprotein E-Deficient Mice: Potential Implications for Energy Homeostasis

Ketogenic diets (KDs) are very low-carbohydrate, very high-fat diets which promote nutritional ketosis and impact energetic metabolism. Aquaporins (AQPs) are transmembrane channels that facilitate water and glycerol transport across cell membranes and are critical players in energy homeostasis. Altered AQP expression or function impacts fat accumulation and related comorbidities, such as the metabolic syndrome. Here, we sought to determine whether nutritional ketosis impacts AQPs expression in the context of an atherogenic model. To do this, we fed ApoE^−/− (apolipoprotein E-deficient) mice, a model of human atherosclerosis, a KD (Kcal%: 1/81/18, carbohydrate/fat/protein) or a control diet (Kcal%: 70/11/18, carbohydrate/fat/protein) for 12 weeks. Plasma was collected for biochemical analysis. Upon euthanasia, livers, white adipose tissue (WAT), and brown adipose tissue (BAT) were used for gene expression studies. Mice fed the KD and control diets exhibited similar body weights, despite the profoundly different fat contents in the two diets. Moreover, KD-fed mice developed nutritional ketosis and showed increased expression of thermogenic genes in BAT. Additionally, these mice presented an increase in Aqp9 transcripts in BAT, but not in WAT, which suggests the participation of Aqp9 in the influx of excess plasma glycerol to fuel thermogenesis, while the up-regulation of Aqp7 in the liver suggests the involvement of this aquaporin in glycerol influx into hepatocytes. The relationship between nutritional ketosis, energy homeostasis, and the AQP network demands further investigation.

Aquaporin-3 and Aquaporin-5 Facilitate Migration and Cell-Cell Adhesion in Pancreatic Cancer by Modulating Cell Biomechanical Properties

BACKGROUND

Aquaporins are membrane channels responsible for the bidirectional transfer of water and small non-charged solutes across cell membranes. AQP3 and AQP5 are overexpressed in pancreatic ductal adenocarcinoma, playing key roles in cell migration, proliferation, and invasion. Here, we evaluated AQP3 and AQP5 involvement in cell biomechanical properties, cell-cell adhesion, and cell migration, following a loss-of-function strategy on BxPC-3 cells.

RESULTS

Silencing of AQP3 and AQP5 was functionally validated by reduced membrane permeability and had implications on cell migration, slowing wound recovery. Moreover, silenced AQP5 and AQP3/5 cells showed higher membrane fluidity. Biomechanical and morphological changes were assessed by atomic force microscopy (AFM), revealing AQP5 and AQP3/5 silenced cells with a lower stiffness than their control. Through cell-cell adhesion measurements, the work (energy) necessary to detach two cells was found to be lower for AQP-silenced cells than control, showing that these AQPs have implications on cell-cell adhesion.

CONCLUSION

These findings highlight AQP3 and AQP5 involvement in the biophysical properties of cell membranes, whole cell biomechanical properties, and cell-cell adhesion, thus having potential implication in the settings of tumor development.

Molecular mechanisms governing aquaporin relocalisation

The aquaporins (AQPs) form a family of integral membrane proteins that facilitate the movement of water across biological membrane by osmosis, as well as facilitating the diffusion of small polar solutes. AQPs have been recognised as drug targets for a variety of disorders associated with disrupted water or solute transport, including brain oedema following stroke or trauma, epilepsy, cancer cell migration and tumour angiogenesis, metabolic disorders, and inflammation. Despite this, drug discovery for AQPs has made little progress due to a lack of reproducible high-throughput assays and difficulties with the druggability of AQP proteins. However, recent studies have suggested that targetting the trafficking of AQP proteins to the plasma membrane is a viable alternative drug target to direct inhibition of the water-conducting pore. Here we review the literature on the trafficking of mammalian AQPs with a view to highlighting potential new drug targets for a variety of conditions associated with disrupted water and solute homeostasis.

Computer-Aided Drug Design of Anti-inflammatory Agents Targeting Microsomal Prostaglandin E2 Synthase-1 (mPGES-1)

Inflammation is a natural process in response to external stimuli associated with organism protection. However, this reaction could be exaggerated, leading to severe damages related to physiopathological processes, such as rheumatoid arthritis, cancer, diabetes, allergies, infections, among others. Inflammation is mainly characterized by pain, increased temperature, flushing, and edema, which can be controlled using anti-inflammatory drugs. In this context, prostaglandin E2 (PGE2) inhibition has been targeted for designing new compounds with anti-inflammatory properties. It is a bioactive lipid overproduced during an inflammatory process, in which its increased production is carried out mainly by COX-1, COX-2, and microsomal prostaglandin E2 synthase-1 (mPGES-1). Recently, studies have demonstrated that mPGES-1 inhibition is a safe strategy to develop anti-inflammatory agents, which could protect against pain, acute inflammation, arthritis, autoimmune diseases, and different types of cancers. To decrease production costs and increase the probability of discovering active substances, computer-aided drug design (CADD) approaches have been increasingly used for designing new inhibitors. Thus, this review will cover all aspects involving high-throughput virtual screening, molecular docking, dynamics, fragment-based drug design, quantitative structure-activity relationship in seeking new promising mPGES-1 inhibitors.

Aquaglyceroporin Modulators as Emergent Pharmacological Molecules for Human Diseases

Aquaglyceroporins, a sub-class of aquaporins that facilitate the diffusion of water, glycerol and other small uncharged solutes across cell membranes, have been recognized for their important role in human physiology and their involvement in multiple disorders, mostly related to disturbed energy homeostasis. Aquaglyceroporins dysfunction in a variety of pathological conditions highlighted their targeting as novel therapeutic strategies, boosting the search for potent and selective modulators with pharmacological properties. The identification of selective inhibitors with potential clinical applications has been challenging, relying on accurate assays to measure membrane glycerol permeability and validate effective functional blockers. Additionally, biologicals such as hormones and natural compounds have been revealed as alternative strategies to modulate aquaglyceroporins via their gene and protein expression. This review summarizes the current knowledge of aquaglyceroporins’ involvement in several pathologies and the experimental approaches used to evaluate glycerol permeability and aquaglyceroporin modulation. In addition, we provide an update on aquaglyceroporins modulators reported to impact disease, unveiling aquaglyceroporin pharmacological targeting as a promising approach for innovative therapeutics.

Signaling Mechanisms and Pharmacological Modulators Governing Diverse Aquaporin Functions in Human Health and Disease

The aquaporins (AQPs) are a family of small integral membrane proteins that facilitate the bidirectional transport of water across biological membranes in response to osmotic pressure gradients as well as enable the transmembrane diffusion of small neutral solutes (such as urea, glycerol, and hydrogen peroxide) and ions. AQPs are expressed throughout the human body. Here, we review their key roles in fluid homeostasis, glandular secretions, signal transduction and sensation, barrier function, immunity and inflammation, cell migration, and angiogenesis. Evidence from a wide variety of studies now supports a view of the functions of AQPs being much more complex than simply mediating the passive flow of water across biological membranes. The discovery and development of small-molecule AQP inhibitors for research use and therapeutic development will lead to new insights into the basic biology of and novel treatments for the wide range of AQP-associated disorders.

Dual NADPH oxidases DUOX1 and DUOX2 synthesize NAADP and are necessary for Ca2+ signaling during T cell activation

The formation of Ca2+ microdomains during T cell activation is initiated by the production of nicotinic acid adenine dinucleotide phosphate (NAADP) from its reduced form NAADPH. The reverse reaction—NAADP to NAADPH—is catalyzed by glucose 6-phosphate dehydrogenase (G6PD). Here, we identified NADPH oxidases NOX and DUOX as NAADP-forming enzymes that convert NAADPH to NAADP under physiological conditions in vitro. T cells express NOX1, NOX2, and, to a minor extent, DUOX1 and DUOX2. Local and global Ca2+ signaling were decreased in mouse T cells with double knockout of Duoxa1 and Duoxa2 but not with knockout of Nox1 or Nox2. Ca2+ microdomains in the first 15 s upon T cell activation were significantly decreased in Duox2−/− but not in Duox1−/− T cells, whereas both DUOX1 and DUOX2 were required for global Ca2+ signaling between 4 and 12 min after stimulation. Our findings suggest that a DUOX2- and G6PD-catalyzed redox cycle rapidly produces and degrades NAADP through NAADPH as an inactive intermediate.

Human genetic polymorphisms and risk of viral infection after solid organ transplantation

The immune system plays a key role in the host defense against viral pathogens. A signaling cascade is activated upon infection involving a variety of molecules such as pattern-recognition receptors (PRRs), interleukins or antiviral interferons. Long-term immunosuppression after solid organ transplantation (SOT) mainly abrogates adaptive T-cell-mediated responses, thus highlighting the relative contribution of innate immunity. Single-nucleotide polymorphisms (SNPs) within genes coding for PRRs or soluble mediators have been associated with differential susceptibility to viral infections among SOT recipients. A protective effect against cytomegalovirus (CMV) infection or disease has been attributed to certain SNPs in TLR9 or IFNL3 genes, whereas the opposite effect has been attributed to genetic polymorphisms in TLR2, MBL2, DC-SIGN, IL10 or IFNG. The presence of SNPs in other molecules not directly involved in innate or adaptive immune responses such as aquaporins or pregnane X appear to modulate the risk of CMV or BK polyomavirus infection, respectively. Little information is available on the genetic determinants of the post-transplant susceptibility to herpesviruses causing clinical infection (herpes simplex virus or varicella zoster virus) or the replication kinetics of components of the human blood virome used as immune surrogates (Torque teno virus). The present review critically summarizes the current knowledge on how SNP genotyping would be useful to stratify SOT recipients according to the individual risk of viral infection and proposes next research steps. Genetic susceptibility testing may improve personalized medicine and contribute to minimize the risk of viral infection after SOT.

Mechanisms of irreversible aquaporin-10 inhibition by organogold compounds studied by combined biophysical methods and atomistic simulations

The inhibition of glycerol permeation via human aquaporin-10 (hAQP10) by organometallic gold complexes has been studied by stopped-flow fluorescence spectroscopy, and its mechanism has been described using molecular modelling and atomistic simulations. The most effective hAQP10 inhibitors are cyclometalated Au(III) C^N compounds known to efficiently react with cysteine residues leading to the formation of irreversible C-S bonds. Functional assays also demonstrate the irreversibility of the binding to hAQP10 by the organometallic complexes. The obtained computational results by metadynamics show that the local arylation of Cys209 in hAQP10 by one of the gold inhibitors is mapped into a global change of the overall free energy of glycerol translocation across the channel. Our study further pinpoints the need to understand the mechanism of glycerol and small molecule permeation as a combination of local structural motifs and global pore conformational changes, which are taking place on the scale of the translocation process and whose study, therefore, require sophisticated molecular dynamics strategies.

Organ Specific Differences in Alteration of Aquaporin Expression in Rats Treated with Sennoside A, Senna Anthraquinones and Rhubarb Anthraquinones

Senna and rhubarb are often used as routine laxatives, but there are differences in mechanism of action and potential side effects. Here, we studied metabolites of senna anthraquinones (SAQ), rhubarb anthraquinones (RAQ) and their chemical marker, sennoside A (SA), in a rat diarrhea model. In in vitro biotransformation experiments, SAQ, RAQ and SA were incubated with rat fecal flora solution and the metabolites produced were analyzed using HPLC. In in vivo studies, the same compounds were investigated for purgation induction, with measurement of histopathology and Aqps gene expression in six organs. The results indicated that SAQ and RAQ had similar principal constituents but could be degraded into different metabolites. A similar profile of Aqps down-regulation for all compounds was seen in the colon, suggesting a similar mechanism of action for purgation. However, in the kidneys and livers of the diarrhea-rats, down-regulation of Aqps was found in the RAQ-rats whereas up-regulation of Aqps was seen in the SAQ-rats. Furthermore, the RAQ-rats showed lower Aqp2 protein expression in the kidneys, whilst the SA-rats and SAQ-rats had higher Aqp2 protein expression in the kidneys. This may have implications for side effects of SAQ or RAQ in patients with chronic kidney or liver diseases.

Recent Update on the Molecular Mechanisms of Gonadal Steroids Action in Adipose Tissue

The gonadal steroids, including androgens, estrogens and progestogens, are involved in the control of body fat distribution in humans. Nevertheless, not only the size and localization of the fat depots depend on the sex steroids levels, but they can also highly affect the functioning of adipose tissue. Namely, the gonadocorticoids can directly influence insulin signaling, lipid metabolism, fatty acid uptake and adipokine production. They may also alter energy balance and glucose homeostasis in adipocytes in an indirect way, e.g., by changing the expression level of aquaglyceroporins. This work presents the recent advances in understanding the molecular mechanism of how the gonadal steroids influence the functioning of adipose tissue leading to a set of detrimental metabolic consequences. Special attention is given here to highlighting the sexual dimorphism of adipocyte functioning in terms of health and disease. Particularly, we discuss the molecular background of metabolic disturbances occurring in consequence of hormonal imbalance which is characteristic of some common endocrinopathies such as the polycystic ovary syndrome. From this perspective, we highlight the potential drug targets and the active substances which can be used in personalized sex-specific management of metabolic diseases, in accord with the patient's hormonal status.