y+LAT1 and y+LAT2 contribution to arginine uptake in different human cell models: Implications in the pathophysiology of Lysinuric Protein Intolerance

Branched-chain amino acids: physico-chemical properties, industrial synthesis and role in signaling, metabolism and energy production

Branched-chain amino acids (BCAAs)-leucine (Leu), isoleucine (Ile), and valine (Val)-are essential nutrients with significant roles in protein synthesis, metabolic regulation, and energy production. This review paper offers a detailed examination of the physico-chemical properties of BCAAs, their industrial synthesis, and their critical functions in various biological processes. The unique isomerism of BCAAs is presented, focusing on analytical challenges in their separation and quantification as well as their solubility characteristics, which are crucial for formulation and purification applications. The industrial synthesis of BCAAs, particularly using bacterial strains like Corynebacterium glutamicum, is explored, alongside methods such as genetic engineering aimed at enhancing production, detailing the enzymatic processes and specific precursors. The dietary uptake, distribution, and catabolism of BCAAs are reviewed as fundamental components of their physiological functions. Ultimately, their multifaceted impact on signaling pathways, immune function, and disease progression is discussed, providing insights into their profound influence on muscle protein synthesis and metabolic health. This comprehensive analysis serves as a resource for understanding both the basic and complex roles of BCAAs in biological systems and their industrial application.

Combination of Transcriptomics and Metabolomics Analyses Provides Insights into the Mechanisms of Growth Differences in Spotted Seabass (Lateolabrax maculatus) Fed a Low-Phosphorus Diet

To analyze the potential mechanisms of growth differences in spotted seabass (Lateolabrax maculatus) fed a low-phosphorus diet, a total of 150 spotted seabass with an initial body weight of 4.49 ± 0.01 g were used (50 fish per tank) and fed a low-phosphorus diet for eight weeks. At the end of the experiment, five of the heaviest and five of the lightest fish were selected from each tank as fast-growing spotted seabass (FG) and slow-growing spotted seabass (SG), respectively, and their livers were analyzed by metabolomics and transcriptomics. The hepatic antioxidant capacity of the FG fed a low-phosphorus diet was significantly higher than that of the SG. A total of 431 differentially expressed genes (DEGs) were determined in the two groups, and most of the DEGs were involved in metabolism-related pathways such as steroid biosynthesis, glycolysis/gluconeogenesis, and protein digestion and absorption. Substance transport-related regulators and transporters were predominantly up-regulated. Furthermore, a large number of metabolites in the liver of FG were significantly up-regulated, especially amino acids, decanoyl-L-carnitine and dehydroepiandrosterone. The integration analysis of differential metabolites and genes further revealed that the interaction between protein digestion and absorption, as well as phenylalanine metabolism pathways were significantly increased in the liver of FG compared to those of the SG. In general, FG fed a low-phosphorus diet induced an enhancement in hepatic immune response, substance transport, and amino acid metabolism. This study provides new information on genetic mechanisms and regulatory pathways underlying differential growth rate and provides a basis for the foundation of efficient utilization of low-phosphorus diets and selective breeding programs for spotted seabass.

Involvement of mammalian SoLute Carriers (SLC) in the traffic of polyamines

Polyamines interact with different molecular targets to regulate a vast range of cellular processes. A network of enzymes and transport systems is crucial for the maintenance of polyamine homeostasis. Indeed, polyamines after synthesis must be distributed to the various tissues and some intracellular organelles. Differently from the well characterized enzymes devoted to polyamine synthesis, the transport systems are not unequivocally identified or characterized. Besides some ATPases which have been identified as polyamine transporters, much less is known about solute carriers (SLC) involved in the transport of these compounds. Only two SLCs have been unequivocally identified as polyamine transporters: SLC18B1 (VPAT) and SLC22A4 (OCTN1). Transport studies have been performed with cells transfected with the cDNAs encoding the two and other SLCs or, in the case of OCTN1, also by in vitro assay using proteoliposomes harboring the recombinant human protein. According to the role proposed for OCTN1, polyamines have been associated with prolonged and quality of life. This review provides an update on the most recent findings concerning the polyamine transporters or the prediction of the putative ones.

Interstitial Lung Disease in a 14-Year-Old Boy

CASE PRESENTATION

A 14-year-old Chinese boy presented with a 7-year history of exertional dyspnea and reduced exercise tolerance. His perinatal and family histories were unremarkable. He was short and underweight for his age since childhood but had normal intellectual development. At 3 years of age, he was admitted to the ICU for severe pneumonia and anemia, and he received blood transfusion. He developed exertional dyspnea and reduced exercise tolerance at 7 years of age and became reluctant to run or jump, with poor appetite, abdominal distension, and refusal of protein-rich foods. At 13 years of age, he experienced a coma during school military training, and he was hospitalized for hyperammonemia (blood ammonia levels between 98 and 148 μmol/L; normal range, 18-72 μmol/L). Brain MRI showed no abnormalities. He improved after symptomatic treatment and was discharged, without taking any oral medication afterwards. However, his dyspnea and exercise tolerance worsened gradually. This patient was referred to Children's Hospital affiliated with Zhengzhou University for further investigation and management.

Lysinuric protein intolerance with novel mutations in solute carrier family 7A member 7 in a Chinese family

Introduction

Lysinuric protein intolerance (LPI) is a rare genetic disorder caused by mutations in the solute carrier family 7A member 7 (SLC7A7) gene.

Case presentation

We presented two siblings with LPI, carrying novel mutations of c.776delT (p.L259Rfs*18) and c.155G>T (p.G52V) in SLC7A7. The younger sibling, preferring protein-rich foods, showed severe symptoms, including alveolar proteinosis, macrophage activation syndrome, severe diarrhea, and disturbance of consciousness with involuntary movements. In contrast, the elder sibling only had mild symptoms, likely due to aversion to protein-rich food since toddler age.

Conclusion

LPI is a congenital genetic metabolic disease with multi-system involvement. Initiating appropriate protein-restricted diet therapy as soon as possible could help prevent the progression of LPI.

Metabolic heterogeneity in tumor microenvironment - A novel landmark for immunotherapy

The surrounding non-cancer cells and tumor cells that make up the tumor microenvironment (TME) have various metabolic rhythms. TME metabolic heterogeneity is influenced by the intricate network of metabolic control within and between cells. DNA, protein, transport, and microbial levels are important regulators of TME metabolic homeostasis. The effectiveness of immunotherapy is also closely correlated with alterations in TME metabolism. The response of a tumor patient to immunotherapy is influenced by a variety of variables, including intracellular metabolic reprogramming, metabolic interaction between cells, ecological changes within and between tumors, and general dietary preferences. Although immunotherapy and targeted therapy have made great strides, their use in the accurate identification and treatment of tumors still has several limitations. The function of TME metabolic heterogeneity in tumor immunotherapy is summarized in this article. It focuses on how metabolic heterogeneity develops and is regulated as a tumor progresses, the precise molecular mechanisms and potential clinical significance of imbalances in intracellular metabolic homeostasis and intercellular metabolic coupling and interaction, as well as the benefits and drawbacks of targeted metabolism used in conjunction with immunotherapy. This offers insightful knowledge and important implications for individualized tumor patient diagnosis and treatment plans in the future.

A novel variant in a Chinese boy with lysinuric protein intolerance: A case report and literature review

We report a case of a 4-year-old boy with lysinuric protein intolerance in China. The patient presented with interstitial lung disease with obvious clubbing of the fingers and toes. During the course of diagnosis and treatment, we found he was averse to a high-protein diet, intolerant to activity, and had a history of diarrhea and fractures. Physical examination revealed hepatosplenomegaly and clubbing of the fingers and toes. Next-generation sequencing revealed compound heterozygous mutations (c.1387delG, c.958T > C) in SLC7A7, which was confirmed as a disease-causing gene for lysinuric protein intolerance. After a literature review, we found that c.958T > C had not been previously reported, and summarized the clinical and genetic characteristics of patients from different continents. His symptoms improved significantly after 3 months of being on a low-protein diet, supplementation with lysine, citrulline, carnitine, and trace elements, and oral corticosteroid treatment for 2 months. The patient is still under follow-up.

Comprehensive review of amino acid transporters as therapeutic targets

The solute carrier (SLC) family, with more than 400 membrane-bound proteins, facilitates the transport of a wide array of substrates such as nutrients, ions, metabolites, and drugs across biological membranes. Amino acid transporters (AATs) are membrane transport proteins that mediate transfer of amino acids into and out of cells or cellular organelles. AATs participate in many important physiological functions including nutrient supply, metabolic transformation, energy homeostasis, redox regulation, and neurological regulation. Several AATs have been found to significantly impact the progression of human malignancies, and dysregulation of AATs results in metabolic reprogramming affecting tumor growth and progression. However, current clinical therapies that directly target AATs have not been developed. The purpose of this review is to highlight the structural and functional diversity of AATs, the molecular mechanisms in human diseases such as tumors, kidney diseases, and emerging therapeutic strategies for targeting AATs.

[Enteral nutrition support for lysinuric protein intolerance: a case report and literature review]

OBJECTIVES

To summarize the clinical characteristics and nutrition therapy for children with lysinuric protein intolerance (LPI).

METHODS

The clinical manifestations, laboratory test results and enteral nutrition treatment in a girl with LPI diagnosed in Xiangya Hospital, Central South University were retrospective analyzed. Additionally, the data of the children with LPI reported in China and overseas were reviewed.

RESULTS

A case of 4-year-old girl was presented, who exhibited significant gastrointestinal symptoms, such as chronic abdominal distension, prolonged diarrhea, recurrent pneumonia, and limited growth. She had a poor response to anti-infection treatment. After receiving enteral nutrition therapy, she did not experience any gastrointestinal discomfort, and there were improvements in the levels of hemoglobin, albumin, and blood ammonia. Unfortunately, due to serious illness, she declined further treatment and later passed away. A total of 92 cases of pediatric patients with LPI have been reported to date, including one case reported in this study. Most children with LPI experienced disease onset after weaning or introduction of complementary foods, presenting with severe digestive system symptoms, malnutrition, and growth retardation. It is noteworthy that only 50% (46/92) of these cases received nutritional therapy, which effectively improved their nutritional status. Among the 92 children, 8 (9%) died, and long-term follow-up data were lacking in other reports.

CONCLUSIONS

LPI often involves the digestive system and may result in growth restriction with a poor prognosis. Nutritional therapy plays a crucial role in the comprehensive treatment of LPI.

The human LAT1-4F2hc (SLC7A5-SLC3A2) transporter complex: Physiological and pathophysiological implications

LAT1 and 4F2hc form a heterodimeric membrane protein complex, which functions as one of the best characterized amino acid transporters. Since LAT1-4F2hc is required for the efficient uptake of essential amino acids and hormones, it promotes cellular growth, in part, by stimulating mTORC1 (mechanistic target of rapamycin complex 1) signalling and by repressing the integrated stress response (ISR). Gain or loss of LAT1-4F2hc function is associated with cancer, diabetes, and immunological and neurological diseases. Hence, LAT1-4F2hc represents an attractive drug target for disease treatment. Specific targeting of LAT1-4F2hc will be facilitated by the increasingly detailed understanding of its molecular architecture, which provides important concepts for its function and regulation. Here, we summarize (i) structural insights that help to explain how LAT1 and 4F2hc assemble to transport amino acids across membranes, (ii) the role of LAT1-4F2hc in key metabolic signalling pathways, and (iii) how derailing these processes could contribute to diseases.

CD98 heavy chain as a prognostic biomarker and target for cancer treatment

The SLC3A2 gene encodes for a cell-surface transmembrane protein CD98hc (4F2). CD98hc serves as a chaperone for LAT1 (SLC7A5), LAT2 (SLC7A8), y+LAT1 (SLC7A7), y+LAT2 (SLC7A6), xCT (SLC7A11) and Asc1 (SLC7A10) providing their recruitment to the plasma membrane. Together with the light subunits, it constitutes heterodimeric transmembrane amino acid transporters. CD98hc interacts with other surface molecules, such as extracellular matrix metalloproteinase inducer CD147 (EMMPRIN) and adhesion receptors integrins, and regulates glucose uptake. In this way, CD98hc connects the signaling pathways sustaining cell proliferation and migration, biosynthesis and antioxidant defense, energy production, and stem cell properties. This multifaceted role makes CD98hc one of the critical regulators of tumor growth, therapy resistance, and metastases. Indeed, the high expression levels of CD98hc were confirmed in various tumor tissues, including head and neck squamous cell carcinoma, glioblastoma, colon adenocarcinoma, pancreatic ductal adenocarcinoma, and others. A high expression of CD98hc has been linked to clinical prognosis and response to chemo- and radiotherapy in several types of cancer. In this mini-review, we discuss the physiological functions of CD98hc, its role in regulating tumor stemness, metastases, and therapy resistance, and the clinical significance of CD98hc as a tumor marker and therapeutic target.

Intestinal Amino Acid Transport and Metabolic Health

Amino acids derived from protein digestion are important nutrients for the growth and maintenance of organisms. Approximately half of the 20 proteinogenic amino acids can be synthesized by mammalian organisms, while the other half are essential and must be acquired from the nutrition. Absorption of amino acids is mediated by a set of amino acid transporters together with transport of di- and tripeptides. They provide amino acids for systemic needs and for enterocyte metabolism. Absorption is largely complete at the end of the small intestine. The large intestine mediates the uptake of amino acids derived from bacterial metabolism and endogenous sources. Lack of amino acid transporters and peptide transporter delays the absorption of amino acids and changes sensing and usage of amino acids by the intestine. This can affect metabolic health through amino acid restriction, sensing of amino acids, and production of antimicrobial peptides.

Growth Arrest of Alveolar Cells in Response to Cytokines from Spike S1-Activated Macrophages: Role of IFN-γ

Acute respiratory distress syndrome (ARDS) is characterized by severe hypoxemia and high-permeability pulmonary edema. A hallmark of the disease is the presence of lung inflammation with features of diffuse alveolar damage. The molecular pathogenetic mechanisms of COVID-19-associated ARDS (CARDS), secondary to SARS-CoV-2 infection, are still not fully understood. Here, we investigate the effects of a cytokine-enriched conditioned medium from Spike S1-activated macrophage on alveolar epithelial A549 cells in terms of cell proliferation, induction of autophagy, and expression of genes related to protein degradation. The protective effect of baricitinib, employed as an inhibitor of JAK-STAT, has been also tested. The results obtained indicate that A549 exhibits profound changes in cell morphology associated to a proliferative arrest in the G0/G1 phase. Other alterations occur, such as a blockade of protein synthesis and the activation of autophagy, along with an increase of the intracellular amino acids content, which is likely ascribable to the activation of protein degradation. These changes correlate to the induction of IFN-regulatory factor 1 (IRF-1) due to an increased secretion of IFN-γ in the conditioned medium from S1-activated macrophages. The addition of baricitinib prevents the observed effects. In conclusion, our findings suggest that the IFN-γ-IRF-1 signaling pathway may play a role in the alveolar epithelial damage observed in COVID-19-related ARDS.

The JAK1/2 Inhibitor Baricitinib Mitigates the Spike-Induced Inflammatory Response of Immune and Endothelial Cells In Vitro

The purpose of this study was to examine the effect of the JAK-STAT inhibitor baricitinib on the inflammatory response of human monocyte-derived macrophages (MDM) and endothelial cells upon exposure to the spike S1 protein from SARS-CoV-2. The effect of the drug has been evaluated on the release of cytokines and chemokines from spike-treated MDM, as well as on the activation of endothelial cells (HUVECs) after exposure to conditioned medium collected from spike-activated MDM. Results obtained indicate that, in MDM, baricitinib prevents the S1-dependent phosphorylation of STAT1 and STAT3, along with the induction of IP-10- and MCP-1 secretion; the release of IL-6 and TNFα is also reduced, while all other mediators tested (IL-1β, IL-8, RANTES, MIP-1α and MIP-1β) are not modified. Baricitinib is, instead, poorly effective on endothelial activation when HUVECs are exposed to supernatants from S1-activated macrophages; the induction of VCAM-1, indeed, is not affected by the drug, while that of ICAM-1 is only poorly inhibited. The drug, however, also exerts protective effects on the endothelium by limiting the expression of pro-inflammatory mediators, specifically IL-6, RANTES and IP-10. No effect of baricitinib has been observed on IL-8 synthesis and, consistently, on neutrophils chemiotaxis. Our in vitro findings reveal that the efficacy of baricitinib is limited, with effects mainly focused on the inhibition of the IL-6-mediated inflammatory loop.

Expression and Function of ABC Transporters in Human Alveolar Epithelial Cells

ATP-binding cassette (ABC) transporters are a large superfamily of membrane transporters that facilitate the translocation of different substrates. While ABC transporters are clearly expressed in various tumor cells where they can play a role in drug extrusion, the presence of these transporters in normal lung tissues is still controversial. Here, we performed an analysis of ABC transporters in EpiAlveolar^TM, a recently developed model of human alveoli, by defining the expression and activity of MDR1, BCRP, and MRPs. Immortalized primary epithelial cells hAELVi (human alveolar epithelial lentivirus-immortalized cells) were employed for comparison. Our data underline a close homology between these two models, where none of the ABC transporters here studied are expressed on the apical membrane and only MRP1 is clearly detectable and functional at the basolateral side. According to these findings, we can conclude that other thus-far-unidentified transporter/s involved in drug efflux from alveolar epithelium deserve investigations.

Organic zinc with moderate chelation strength enhances zinc absorption in the small intestine and expression of related transporters in the duodenum of broilers

Our previous study demonstrated that the absorption of zinc (Zn) from the organic Zn proteinate with moderate chelation strength was significantly higher than that of Zn from the inorganic Zn sulfate in the in situ ligated duodenal segment of broilers, but the underlying mechanisms are unknown. The present study aimed to determine the effect of organic Zn with moderate chelation strength and inorganic Zn on the Zn absorption in the small intestine and the expression of related transporters in the duodenum of broilers. The Zn-deficient broilers (13 days old) were fed with the Zn-unsupplemented basal diets (control) containing 25.72 and 25.64 mg Zn/kg by analysis or the basal diets supplemented with 60 mg Zn/kg as the Zn sulfate or the Zn proteinate with moderate chelation strength (Zn-Prot M) for 26 days. The results showed that the plasma Zn contents from the hepatic portal vein of broilers at 28 days and 39 days of age were increased (p < 0.05) by Zn addition and greater (p < 0.05) in the Zn-Prot M than in the Zn sulfate. On d 28, Zn addition upregulated (p < 0.05) mRNA expression of zinc transporter 1 (ZnT1), Zrt-irt-like protein 5 (ZIP5), y + L-type amino transporter 2 (y + LAT2) and b^0,+-type amino acid transporter (rBAT), zinc transporter 4 (ZnT4) protein expression, and zinc transporter 9 (ZnT9) mRNA and protein expression in the duodenum. Moreover, ZnT9 mRNA expression, ZnT4, ZIP5, and rBAT protein expression, zinc transporter 7 (ZnT7), and y + LAT2 mRNA and protein expression in the duodenum of broilers on 28 days were higher (p < 0.05) in the Zn-Prot M than in the Zn sulfate. On d 39, supplemental Zn increased (p < 0.05) peptide-transporter 1 (PepT1) mRNA expression and y + LAT2 protein expression, while the mRNA expression of ZnT7 and Zrt-irt-like protein 3 (ZIP3) were higher (p < 0.05) for the Zn-Prot M than for the Zn sulfate in the duodenum. It was concluded that the Zn-Prot M enhanced the Zn absorption in the small intestine partially via upregulating the expression of ZnT4, ZnT7, ZnT9, ZIP3, ZIP5, y + LAT2, and rBAT in the duodenum of broilers.

A reference tissue atlas for the human kidney

Kidney Precision Medicine Project (KPMP) is building a spatially specified human kidney tissue atlas in health and disease with single-cell resolution. Here, we describe the construction of an integrated reference map of cells, pathways, and genes using unaffected regions of nephrectomy tissues and undiseased human biopsies from 56 adult subjects. We use single-cell/nucleus transcriptomics, subsegmental laser microdissection transcriptomics and proteomics, near-single-cell proteomics, 3D and CODEX imaging, and spatial metabolomics to hierarchically identify genes, pathways, and cells. Integrated data from these different technologies coherently identify cell types/subtypes within different nephron segments and the interstitium. These profiles describe cell-level functional organization of the kidney following its physiological functions and link cell subtypes to genes, proteins, metabolites, and pathways. They further show that messenger RNA levels along the nephron are congruent with the subsegmental physiological activity. This reference atlas provides a framework for the classification of kidney disease when multiple molecular mechanisms underlie convergent clinical phenotypes.

STAT5A modulates CDYL2/SLC7A6 pathway to inhibit the proliferation and invasion of hepatocellular carcinoma by targeting to mTORC1

Chromodomain Y-like 2 (CDYL2), as a member of CDY family known to be involved in spermatogenesis, has been reported to participate in breast cancer development recently, but its exact biological role in hepatocellular carcinoma (HCC) remains unclear. Here, we observed that CDYL2 was down-regulated in human primary HCC tissues and the low levels of CDYL2 expression were correlated with poor survival. Gain- and loss-of-function experiments showed that CDYL2 inhibited the proliferation and metastasis of HCC cells in vitro and in vivo. Mechanistically, CDYL2 down-regulates solute carrier family 7 member 6 (SLC7A6) by decreasing the enrichment of H3K4me3 on the promoter region of SLC7A6. Additionally, we also found that signal transducer and activator of transcription 5A (STAT5A) could directly and positively regulate the expression of CDYL2. Thus, CDYL2 was regulated by STAT5A, and suppressed the amino acid transportation through down-regulation of SLC7A6, and then inhibits the mTORC1/S6K pathway, a master regulator of cell growth. Consistently, CDYL2 expression correlated significantly with STAT5A and SLC7A6 expression in HCC. Collectively, we propose a model for a STAT5A/CDYL2/SLC7A6 axis that provides novel insight into CDYL2, which may serve as a potential factor for predicting prognosis and a therapeutic target for HCC patients.

Desmopressin Stimulates Nitric Oxide Production in Human Lung Microvascular Endothelial Cells

Desmopressin (dDAVP) is the best characterized analogue of vasopressin, the endocrine regulator of water balance endowed with potent vasoconstrictive effects. Despite the use of dDAVP in clinical practice, ranging from the treatment of nephrogenic diabetes insipidus to bleeding disorders, much remains to be understood about the impact of the drug on endothelial phenotype. The aim of this study was, thus, to evaluate the effects of desmopressin on the viability and function of human pulmonary microvascular endothelial cells (HLMVECs). The results obtained demonstrate that the vasopressor had no cytotoxic effect on the endothelium; similarly, no sign of endothelial activation was induced by dDAVP, indicated by the lack of effect on the expression of inflammatory cytokines and adhesion molecules. Conversely, the drug significantly stimulated the production of nitric oxide (NO) and the expression of the inducible isoform of nitric oxide synthase, NOS2/iNOS. Since the intracellular level of cAMP also increased, we can hypothesize that NO release is consequent to the activation of the vasopressin receptor 2 (V2R)/guanylate cyclase (Gs)/cAMP axis. Given the multifaceted role of NOS2-deriving NO for many physio-pathological conditions, the meanings of these findings in HLMVECs appears intriguing and deserves to be further addressed.

Organic cation transporters (OCTs/OCTNs) in human primary alveolar epithelial cells

Alveolar epithelium, besides exerting a key role in gas exchange and surfactant production, plays important functions in host defense and inflammation. Pathological conditions associated to alveolar dysfunction include Acute Respiratory Distress Syndrome (ARDS), asthma, chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF). The use of predictive in vitro models of human alveolar epithelium is nowadays required for the study of disease mechanisms, as well as of pharmacokinetic parameters of pulmonary drugs delivery. Here, we employed a novel 3D model of human alveoli, namely EpiAlveolar™, consisting of primary alveolar epithelial cells, pulmonary endothelial cells and fibroblasts, that reflects properly the in vivo-like conditions. In EpiAlveolar™ we performed a characterization of Organic Cation Transporters (OCTs and OCTNs) expression and activity and we found that OCTN2, OCT1 and OCT3 are expressed on the basolateral membrane; instead, ATB^0,+ transporter for cationic and neutral amino acids, which shares with OCTN2 the affinity for carnitine as substrate, is readily detectable and functional at the apical side. We also show that these transporters differentially interact with anticholinergic drugs. Overall, our findings reveal close similarities of EpiAlveolar™ with the tracheal/bronchial epithelium (EpiAirway™ model) and entrust this alveolar tissue as a potential tool for the screening of biopharmaceuticals molecules.

Novel Discoveries in Immune Dysregulation in Inborn Errors of Immunity

With the expansion of our knowledge on inborn errors of immunity (IEI), it gradually becomes clear that immune dysregulation plays an important part. In some cases, autoimmunity, hyperinflammation and lymphoproliferation are far more serious than infections. Thus, immune dysregulation has become significant in disease monitoring and treatment. In recent years, the wide application of whole-exome sequencing/whole-genome sequencing has tremendously promoted the discovery and further studies of new IEI. The number of discovered IEI is growing rapidly, followed by numerous studies of their pathogenesis and therapy. In this review, we focus on novel discovered primary immune dysregulation diseases, including deficiency of SLC7A7, CD122, DEF6, FERMT1, TGFB1, RIPK1, CD137, TET2 and SOCS1. We discuss their genetic mutation, symptoms and current therapeutic methods, and point out the gaps in this field.

Endothelial Cell Activation by SARS-CoV-2 Spike S1 Protein: A Crosstalk between Endothelium and Innate Immune Cells

Background. Emerging evidences suggest that in severe COVID-19, multi-organ failure is associated with a hyperinflammatory state (the so-called “cytokine storm”) in combination with the development of a prothrombotic state. The central role of endothelial dysfunction in the pathogenesis of the disease is to date accepted, but the precise mechanisms underlying the associated coagulopathy remain unclear. Whether the alterations in vascular homeostasis directly depend upon the SARS-CoV-2 infection of endothelial cells or, rather, occur secondarily to the activation of the inflammatory response is still a matter of debate. Here, we address the effect of the SARS-CoV-2 spike S1 protein on the activation of human lung microvascular endothelial cells (HLMVEC). In particular, the existence of an endothelium-macrophage crosstalk in the response to the spike protein has been explored. Methods and Results. The effect of the spike protein is addressed in human lung microvascular endothelial cells (HLMVEC), either directly or after incubation with a conditioned medium (CM) of human monocyte-derived macrophages (MDM) previously activated by the spike S1 protein (CM-MDM). Both MDM and HLMVEC are activated in response to the S1 protein, with an increased expression of pro-inflammatory mediators. However, when HLMVEC are exposed to CM-MDM, an enhanced cell activation occurs in terms of the expression of adhesion molecules, pro-coagulant markers, and chemokines. Under this experimental condition, ICAM-1 and VCAM-1, the chemokines CXCL8/IL-8, CCL2/MCP1, and CXCL10/IP-10 as well as the protein tissue factor (TF) are markedly induced. Instead, a decrease of thrombomodulin (THBD) is observed. Conclusion. Our data suggest that pro-inflammatory mediators released by spike-activated macrophages amplify the activation of endothelial cells, likely contributing to the impairment of vascular integrity and to the development of a pro-coagulative endothelium.

Urine-Derived Epithelial Cells as Models for Genetic Kidney Diseases

Epithelial cells exfoliated in human urine can include cells anywhere from the urinary tract and kidneys; however, podocytes and proximal tubular epithelial cells (PTECs) are by far the most relevant cell types for the study of genetic kidney diseases. When maintained in vitro, they have been proven extremely valuable for discovering disease mechanisms and for the development of new therapies. Furthermore, cultured patient cells can individually represent their human sources and their specific variants for personalized medicine studies, which are recently gaining much interest. In this review, we summarize the methodology for establishing human podocyte and PTEC cell lines from urine and highlight their importance as kidney disease cell models. We explore the well-established and recent techniques of cell isolation, quantification, immortalization and characterization, and we describe their current and future applications.

Effects of underwater and semi-aquatic environments on gut tissue and microbiota of the mudskipper Boleophthalmus pectinirostris

In both underwater and semi-aquatic environments, the gut microbiota is of particular physiological importance for amphibious animals, given that the gut tract is among those organs in direct communication with the external environment. In this study, we examined the effects of these contrasting environments on the dominant bacteria in the guts of the amphibious mudskipper Boleophthalmus pectinirostris. Compared with the guts of normal mudskippers, in which the dominant bacteria were identified as Vibrio and Faecalibacterium, we found that Acinetobacter, Shigella, and Bacillus predominated in their guts after exposure to the semi-aquatic environment, whereas Escherichia, Bacteroides, and Bacillus were more prevalent in the guts in the underwater environment. The total number of cultured gut bacteria decreased significantly in the semi-aquatic environment. In semi-aquatic mudskippers, we also detected reductions and increases in the length and width of gut villi, respectively, whereas the width of gut villi declined and the number of goblet cells increased significantly in mudskippers maintained underwater. The mRNA expression of multiple gut transporters for glucose, long-chain fatty acids, and amino acids was found to increase markedly in both underwater and semi-aquatic environments, with the expression of most transporters being significantly higher in those mudskippers exposed to an underwater environment. Furthermore, we detected significant increases in the mRNA expression of pro-inflammatory cytokine transcripts in the guts of both underwater and semi-aquatic mudskippers on days 2, 4, and 6 of exposure, whereas the expression of IL-10 and TGFβ mRNA was more pronounced on days 4 and 8, respectively. Comparatively, we found that expression levels of cytokines in the guts of underwater mudskipper were substantially higher than those in the guts of semi-aquatic mudskippers. Collectively, our findings revealed notable differences in the gut microbiota and energy metabolism requirements of mudskippers exposed to underwater and semi-aquatic conditions, thereby providing a theoretical basis explaining the maintenance of a homeostatic state in mudskippers that constantly transition between these contrasting amphibious habitats.

Transport of L-Arginine Related Cardiovascular Risk Markers

L-arginine and its derivatives, asymmetric and symmetric dimethylarginine (ADMA and SDMA) and L-homoarginine, have emerged as cardiovascular biomarkers linked to cardiovascular outcomes and various metabolic and functional pathways such as NO-mediated endothelial function. Cellular uptake and efflux of L-arginine and its derivatives are facilitated by transport proteins. In this respect the cationic amino acid transporters CAT1 and CAT2 (SLC7A1 and SLC7A2) and the system y⁺L amino acid transporters (SLC7A6 and SLC7A7) have been most extensively investigated, so far, but the number of transporters shown to mediate the transport of L-arginine and its derivatives is constantly increasing. In the present review we assess the growing body of evidence regarding the function, expression, and clinical relevance of these transporters and their possible relation to cardiovascular diseases.

Expression and roles of system L amino acid transporters in human embryonal carcinoma cells

BACKGROUND

Testicular germ cell tumors (TGCTs) are the most common malignant cancer in young men. Although TGCTs are generally responsive to platinum-based chemotherapy particularly cisplatin, acquired resistance in patients with metastasis still occurs resulting in poor prognosis. Specifically, differentiation of embryonal carcinoma (EC) cells, the stem cells of TGCTs, can lead to the reduction of cisplatin responsiveness. Therefore, novel therapeutic strategies for TGCTs are needed. System L amino acid transporters have been reported to be up-regulated and to play an important role in tumorigenesis. However, expression and role of system L amino acid transporters in TGCTs remain elusive.

MATERIALS AND METHODS

Expression of system L amino acid transporters was analyzed in TGCT samples from The Cancer Genome Atlas (TCGA). Expression of LAT1, LAT2, and 4F2hc was examined in human embryonal carcinoma cell line NTERA2. Roles of system L amino acid transporters on NTERA2 cell survival, cell proliferation, pluripotency, and cisplatin sensitivity were evaluated.

RESULTS

Based upon TCGA datasets, we found that two isoforms of system L (LAT1 and LAT2) and their chaperone protein 4F2hc are highly expressed in EC samples compared with other groups. Treatment with the system L inhibitor BCH significantly suppressed leucine uptake into the pluripotent EC cell line NTERA2. The malignant phenotypes including cell viability, cell proliferation, and clonal ability were decreased following BCH treatment. Nonetheless, system L inhibition did not alter expression of stemness genes in NTERA2 cells. After NTERA2 differentiation, expressions of LAT1 and LAT2 were decreased. Finally, co-administration of BCH enhanced cisplatin sensitivity in both undifferentiated and differentiated cells. These effects were associated with the reduction in p70S6K phosphorylation.

CONCLUSION

Taken together, these results shed light on the roles of system L amino acid transporters in TGCTs. Therefore, system L amino acid transporters could provide novel therapeutic targets for treatment against TGCTs.

Organic Cation Transporters (OCTs) in EpiAirway™, A Cellular Model of Normal Human Bronchial Epithelium

Organic cation transporters (OCTs) and novel organic cation transporters (OCTNs) are responsible for drug delivery in the intestine and kidney; in the lung, OCTs mediate inhaled drugs’ transport, although their physiological role in airways remains poorly understood. The studies addressing OCTs/OCTNs in human airways were mostly performed in immortal or transformed cell lines; here, we studied OCTs in EpiAirway™, a recently developed in vitro model of normal bronchial epithelium. Calu-3 monolayers were used for comparison. The activity of OCTs was evaluated by measuring the uptake of 1-methyl-4-phenylpyridinium (MPP⁺) at the apical and basolateral side of monolayers and protein expression through Western Blot analysis. OCTs and OCTNs expression, along with that of Amino acid Transporter B^0,+ (ATB^0,+)transporter, was determined by measuring the number of mRNA molecules through quantitative Polymerase Chain Reaction (qPCR). The interaction of the transporters with bronchodilators was also assessed. Results highlight significant differences between Calu-3 cells and EpiAirway™, since, in the latter, OCTs are active only on the basolateral membrane where they interact with the bronchodilator ipratropium. No activity of OCTs is detectable at the apical side; there, the most abundant carrier is, instead, SLC6A14/ATB^0,+, that can thus be potentially listed among organic cation transporters responsible for drug delivery in the lung.

Characterization of ABC Transporters in EpiAirway™, a Cellular Model of Normal Human Bronchial Epithelium

The ATP-binding cassette (ABC) transporters P-glycoprotein (MDR1/ABCB1), multidrug resistance-associated protein 1 (MRP1/ABCC1), and breast cancer resistance protein (BCRP/ABCG2) play a crucial role in the translocation of a broad range of drugs; data about their expression and activity in lung tissue are controversial. Here, we address their expression, localization and function in EpiAirway™, a three-dimensional (3D)-model of human airways; Calu-3 cells, a representative in vitro model of bronchial epithelium, are used for comparison. Transporter expression has been evaluated with RT-qPCR and Western blot, the localization with immunocytochemistry, and the activity by measuring the apical-to-basolateral and basolateral-to-apical fluxes of specific substrates in the presence of inhibitors. EpiAirway™ and Calu-3 cells express high levels of MRP1 on the basolateral membrane, while they profoundly differ in terms of BCRP and MDR1: BCRP is detected in EpiAirway™, but not in Calu-3 cells, while MDR1 is expressed and functional only in fully-differentiated Calu-3; in EpiAirway™, MDR1 expression and activity are undetectable, consistently with the absence of the protein in specimens from human healthy bronchi. In summary, EpiAirway™ appears to be a promising tool to study the mechanisms of drug delivery in the bronchial epithelium and to clarify the role of ABC transporters in the modulation of the bioavailability of administered drugs.

Functional analysis of OCTN2 and ATB0,+ in normal human airway epithelial cells

In human, OCTN2 (SLC22A5) and ATB0,+ (SLC6A14) transporters mediate the uptake of L-carnitine, essential for the transport of fatty acids into mitochondria and the subsequent degradation by β-oxidation. Aim of the present study was to characterize L-carnitine transport in EpiAirway™, a 3D organotypic in vitro model of primary human tracheal-bronchial epithelial cells that form a fully differentiated, pseudostratified columnar epithelium at air-liquid interface (ALI) condition. In parallel, Calu-3 monolayers grown at ALI for different times (8d or 21d of culture) were used as comparison. OCTN2 transporter was equally expressed in both models and functional at the basolateral side. ATB0,+ was, instead, highly expressed and active on the apical membrane of EpiAirway™ and only in early-cultures of Calu-3 (8d but not 21d ALI). In both cell models, L-carnitine uptake on the apical side was significantly inhibited by the bronchodilators glycopyrrolate and tiotropium, that hence can be considered substrates of ATB0,+; ipratropium was instead effective on the basolateral side, indicating its interaction with OCTN2. Inflammatory stimuli, such as LPS or TNFα, caused an induction of SLC6A14/ATB0,+ expression in Calu-3 cells, along with a 2-fold increase of L-carnitine uptake only at the apical side; on the contrary SLC22A5/OCTN2 was not affected. As both OCTN2 and ATB0,+, beyond transporting L-carnitine, have a significant potential as delivery systems for drugs, the identification of these transporters in EpiAirway™ can open new fields of investigation in the study of drug inhalation and pulmonary delivery.

y+LAT1 and y+LAT2 contribution to arginine uptake in different human cell models: Implications in the pathophysiology of Lysinuric Protein Intolerance

y+LAT1 (encoded by SLC7A7), together with y+LAT2 (encoded by SLC7A6), is the alternative light subunits composing the heterodimeric transport system y+L for cationic and neutral amino acids. SLC7A7 mutations cause lysinuric protein intolerance (LPI), an inherited multisystem disease characterized by low plasma levels of arginine and lysine, protein-rich food intolerance, failure to thrive, hepatosplenomegaly, osteoporosis, lung involvement, kidney failure, haematologic and immunological disorders. The reason for the heterogeneity of LPI symptoms is thus far only poorly understood. Here, we aimed to quantitatively compare the expression of SLC7A7 and SLC7A6 among different human cell types and evaluate y+LAT1 and y+LAT2 contribution to arginine transport. We demonstrate that system y+L-mediated arginine transport is mainly accounted for by y+LAT1 in monocyte-derived macrophages (MDM) and y+LAT2 in fibroblasts. The kinetic analysis of arginine transport indicates that y+LAT1 and y+LAT2 share a comparable affinity for the substrate. Differences have been highlighted in the expression of SLC7A6 and SLC7A7 mRNA among different cell models: while SLC7A6 is almost equally expressed, SLC7A7 is particularly abundant in MDM, intestinal Caco-2 cells and human renal proximal tubular epithelial cells (HRPTEpC). The characterization of arginine uptake demonstrates that system y+L is operative in renal cells and in Caco-2 where, at the basolateral side, it mediates arginine efflux in exchange with leucine plus sodium. These findings explain the defective absorption/reabsorption of arginine in LPI. Moreover, y+LAT1 is the prevailing transporter in MDM sustaining a pivotal role in the pathogenesis of immunological complications associated with the disease.