RTN3 deficiency exacerbates cisplatin-induced acute kidney injury through the disruption of mitochondrial stability.

Reticulum 3 (RTN3) is an endoplasmic reticulum (ER) protein that has been reported to act in neurodegenerative diseases and lipid metabolism. However, the role of RTN3 in acute kidney injury (AKI) has not been explored. Here, we employed public datasets, patient data, and animal models to explore the role of RTN3 in AKI. The underlying mechanisms were studied in primary renal tubular epithelial cells and in the HK2 cell line. We found reduced expression of RTN3 in AKI patients, cisplatin-induced mice, and cisplatin-treated HK2 cells. RTN3-null mice exhibit more severe AKI symptoms and kidney fibrosis after cisplatin treatment. Mitochondrial dysfunction was also found in cells with RTN3 knockdown or knockout. A mechanistic study revealed that RTN3 can interact with HSPA9 in kidney cells. RTN3 deficiency may disrupt the RTN3-HSPA9-VDAC2 complex and affect MAMs during ER-mitochondrion contact, which further leads to mitochondrial dysfunction and exacerbates cisplatin-induced AKI. Our study indicated that RTN3 was important in the kidney and that a decrease in RTN3 in the kidney might be a risk factor for the aggravation of AKI.

Reticulon 3 regulates sphingosine-1-phosphate synthesis in endothelial cells to control blood pressure.

The discovery of the endothelium as a major regulator of vascular tone triggered intense research among basic and clinical investigators to unravel the physiologic and pathophysiologic significance of this phenomenon. Sphingosine-l-phosphate (S1P), derived from the vascular endothelium, is a significant regulator of blood pressure. However, the mechanisms underlying the regulation of S1P biosynthetic pathways in arteries remain to be further clarified. Here, we reported that Reticulon 3 (RTN3) regulated endothelial sphingolipid biosynthesis and blood pressure. We employed public datasets, patients, and mouse models to explore the pathophysiological roles of RTN3 in blood pressure control. The underlying mechanisms were studied in human umbilical vein endothelial cells (HUVECs). We reported that increased RTN3 was found in patients and that RTN3-null mice presented hypotension. In HUVECs, RTN3 can regulate migration and tube formation via the S1P signaling pathway. Mechanistically, RTN3 can interact with CERS2 to promote the selective autophagy of CERS2 and further influence S1P signals to control blood pressure. We also identified an RTN3 variant (c.116C>T, p.T39M) in a family with hypertension. Our data provided the first evidence of the association between RTN3 level changes and blood pressure anomalies and preliminarily elucidated the importance of RTN3 in S1P metabolism and blood pressure regulation.

Loss of RTN3 phenocopies chronic kidney disease and results in activation of the IGF2-JAK2 pathway in proximal tubular epithelial cells.

Reticulon 3 (RTN3) is an endoplasmic reticulum protein that has previously been shown to play roles in neurodegenerative diseases, but little is known about its function in the kidneys. The aim of the present study was to clarify the roles of RTN3 in chronic kidney disease (CKD) and kidney fibrosis. In this study, RTN3 levels were measured in kidney tissues from healthy controls and CKD or kidney fibrosis patients. An RTN3-null mouse model was generated to explore the pathophysiological roles of RTN3 in the kidneys. The underlying mechanisms were studied in primary proximal tubular epithelial cells and HEK293 cells in vitro. The results showed that (1) a reduction in RTN3 in mice induces CKD and kidney fibrosis; (2) decreased RTN3 expression is found in patients with CKD; (3) RTN3 plays critical roles in regulating collagen biosynthesis and mitochondrial function; and (4) mechanistically, RTN3 regulates these phenotypes by interacting with GC-Rich Promoter Binding Protein 1 (GPBP1), which activates the IGF2-JAK2-STAT3 pathway. Our study indicates that RTN3 might play crucial roles in CKD and kidney fibrosis and that a reduction in RTN3 in the kidneys might be a risk factor for CKD and kidney fibrosis.

Case Report: Congenital Brain Dysplasia, Developmental Delay and Intellectual Disability in a Patient With a 7q35-7q36.3 Deletion.

7q terminal deletion syndrome is a rare condition presenting with multiple congenital malformations, including abnormal brain and facial structures, developmental delay, intellectual disability, abnormal limbs, and sacral anomalies. At least 40 OMIM genes located in the 7q34-7q36.3 region act as candidate genes for these phenotypes, of which SHH, EN2, KCNH2, RHEB, HLXB9, EZH2, MNX1 and LIMR1 may be the most important. In this study, we discuss the case of a 2.5-year-old male patient with multiple malformations, congenital brain dysplasia, developmental delay, and intellectual disability. A high-resolution genome-wide single nucleotide polymorphism array and real-time polymerase chain reaction were performed to detect genetic lesions. A de novo 9.4 Mb deletion in chromosome region 7q35-7q36.3 (chr7:147,493,985-156,774,460) was found. This chromosome region contains 68 genes, some of which are candidate genes for each phenotype. To the best of our knowledge, this is a rare case report of 7q terminal deletion syndrome in a Chinese patient. Our study identifies a rare phenotype in terms of brain structure abnormalities and cerebellar sulcus widening in patients with deletion in 7q35-7q36.3.

A novel heterozygous variant of the COL4A4 gene in a Chinese family with hematuria and proteinuria leads to focal segmental glomerulosclerosis and chronic kidney disease.

BACKGROUND: Focal segmental glomerulosclerosis (FSGS), as the frequent primary glomerular diseases in adults, accounts for symptomless proteinuria or nephrotic syndrome with or without renal insufficiency. As the crucial lesion of chronic kidney disease (CKD), accumulating evidence from recent studies show that mutations in Collagen-related genes may be responsible for FSGS. The aim of this study was to identify the genetic lesion of a Chinese family with FSGS and CKD. METHODS: In this study, we recruited a Han-Chinese family with unexplained high serum creatinine, hematuria, and proteinuria. Further renal biopsy and renal pathology indicated the diagnosis of FSGS in the proband. Whole-exome sequencing and Sanger sequencing were employed to explore the pathogenic mutation of this family. RESULTS: A novel heterozygous mutation (NM_000092 c.2030G>A, p.G677D) of the collagen type IV alpha-4 gene (COL4A4) was detected. Co-segregation analysis revealed that the novel mutation was carried by all the five affected individuals and absent in other healthy members as well as in our 200 local control cohorts. Bioinformatics predication indicated that this novel mutation was pathogenic and may disrupt the structure and function of type IV collagen. Simultaneously, this variant is located in an evolutionarily conserved site of COL4A4 protein. CONCLUSION: Here, we identified a novel mutation of COL4A4 in a family with FSGS and CKD. Our study expanded the variants spectrum of the COL4A4 gene and contributed to the genetic counseling and prenatal genetic diagnosis of the family. In addition, we also recommended the new classification of collagen IV nephropathies, which may be a benefit to the diagnosis, target drug treatment, and management of patients with COL4A3/COL4A4 mutations.

Identification of a Novel Arginine Vasopressin Receptor 2 Mutation (p.V183M) in a Chinese Family with Nephrogenic Diabetes Insipidus.

Loss of function of arginine vasopressin receptor 2 (AVPR2) may affect the recognition and binding of arginine vasopressin (AVP) which, in turn, may prevent the activation of Gs/adenylate cyclase and reduce the reabsorption of water by renal tubules and combined tubes. Finally, the organism may suffer from nephrogenic diabetes insipidus (NDI), a kind of kidney disorder featured by polyuria and polydipsia, due to a break of water homeostasis. In this study, we enrolled a Chinese family with polyuria and polydipsia. The proband presented abnormal fluid intake and excessive urine output. A water deprivation and AVP stimulation test further indicated that this patient had NDI. By sequencing known causative genes for diabetes insipidus, we identified a novel mutation in AVPR2 (c.547G>A; p.V183M) in the family. This mutation, located in a conserved site of AVPR2 and predicted to be disease-causing by informatics programs, was absent in our 200 controls and other public databases. Our study not only further confirms the clinical diagnosis, but also expands the spectrum of AVPR2 mutations and contributes to genetic diagnosis and counseling of patients with NDI.

Whole exome sequencing identified a novel mutation (p.Ala1884Pro) of ß-spectrin in a Chinese family with hereditary spherocytosis.

BACKGROUND: Hereditary spherocytosis (HS) is an inherited disorder of erythrocyte. The typical feature of HS is the presence of spherical-shaped erythrocytes on the peripheral blood smear. According to previous studies, more than five candidate genes, such as ANK1, SPTB, SPTA1, SLC4A1 and EPB42 have been identified in HS patients. METHODS: In the present study, a Chinese HS family was investigated. The proband suffered from pathologic jaundice and splenomegaly. A blood test and peripheral blood smear experiment further confirmed the diagnosis of HS. We selected the proband to perform the whole exome sequencing. RESULTS: After data filtering and co-segregation analysis, we identified 12 mutations in affected members that were absent in healthy members. In consideration of the inheritance pattern, Online Mendelian Inheritance in Man clinical phenotypes, Toppgene function and American College of Medical Genetics classification, we considered the novel mutation (c.5650G > C/p.Ala1884Pro) of ß-spectrin (SPTB) to be the genetic lesion in this family. The novel mutation, resulting in a substitution of alanine by proline, may lead to transformation of the SPTB protein structure, which affects the binding between SPTB and ankyrin. CONCLUSIONS: The present study confirmed the hereditary red blood cell membrane disorders at a molecular level and expanded the spectrum of SPTB mutations. This may contribute to the clinical management and genetic counseling with respect to HS.

Whole-Exome Sequencing Identifies a Novel Mutation of Desmocollin 2 in a Chinese Family With Arrhythmogenic Right Ventricular Cardiomyopathy.

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a rare heart disorder characterized by myocyte loss and fibro-fatty tissue replacement. With the progress of ARVC, patient can present serious ventricular arrhythmias, heart failure, and even sudden cardiac death. Previous studies have revealed that the generation and development of ARVC are related to structural changes of desmosomes. To date, at least 5 genes associated with desmosomes have been identified in patients with ARVC, including Desmoplakin, Plakophilin 2, Desmoglein 2, Desmocollin 2, and Junction plakoglobin. In this study, we applied whole-exome sequencing to explore the potential causative gene in a Chinese family with suspicious ARVC. A novel missense mutation (c.1090 G > A/p.V364 M) of DSC2 was identified and co-segregated with the affected family members. This mutation leads to a substitution of valine by methionine and is predicted to be damaging by bioinformatics tools. In conclusion, our study not only expands the spectrum of DSC2 mutations and contributes to genetic counseling of families with ARVC but also improves the awareness of pathogenesis in Chinese patients with ARVC.

Long-term follow-up of an Alport syndrome patient with a novel mutation of COL4A5.

BACKGROUND: Alport syndrome (AS) is a genetic disease characterized by progressive glomerulonephritis with a high life-time risk for end-stage renal disease (ESRD), sensorineural hearing loss and ocular abnormalities. So far, a lot of mutations were reported in COL4A3, COL4A4 and COL4A5 genes, which are related to AS. METHODS: Whole-exome sequencing in combination with AS-related genes filtering strategy was applied to investigate a Chinese AS family. We also employed Sanger sequencing to confirm the family co-segregation. In addition, we also summed up a long-term follow-up data from 2003 to 2016. RESULTS: In this study, we have detected a novel insertion mutation (c.348_349insTCCGG/p.G117Sfs×40) of COL4A5, which may lead to a truncated protein in the proband. Sanger sequencing confirmed that this novel mutation was co-segregated with all the family members. The long-term follow-up data showed that the progress of chronic kidney disease become more and more serious in the proband. CONCLUSIONS: A novel mutation (c.348_349insTCCGG/p.G117Sfs×40) of COL4A5 was identified in this study. In addition, approximately 15 years long-term follow-up data was provided in this paper. Our study not only expands the spectrum of COL4A5 mutations, but also analysis the progress of AS and fills the knowledge about course and potential further complications and health risks of AS.

Whole-Exome Sequencing Identifies Two Novel TTN Mutations in Chinese Families with Dilated Cardiomyopathy.

OBJECTIVES: Dilated cardiomyopathy (DCM) is a leading cause of sudden cardiac death. So far, only 127 mutations of Titin(TTN) have been reported in patients with different phenotypes such as isolated cardiomyopathies, purely skeletal muscle phenotypes or complex overlapping disorders of muscles. METHODS: We applied whole-exome sequencing (WES) to investigate cardiomyopathy patients and a cardiomyopathy-related gene-filtering strategy was used to analyze the disease-causing mutations. Sanger sequencing was applied to confirm the mutation cosegregation in the affected families. RESULTS: A nonsense mutation (c.12325C>T/p.R4109X) and a missense mutation (c.17755G>C/p.G5919R) of TTN were identified in 2 Chinese DCM families, respectively. Both mutations were cosegregated in all affected members of both families. The nonsense mutation is predicted to result in a truncated TTN protein and the missense mutation leads to a substitution of glycine by arginine. Both variants may cause the structure changes of titin protein. CONCLUSIONS: We employed WES to detect the mutations of DCM patients and identified 2 novel mutations. Our study expands the spectrum of TTN mutations and offers accurate genetic testing information for DCM patients who are still clinically negative.

Fluorofenidone protects against renal fibrosis by inhibiting STAT3 tyrosine phosphorylation.

Signaling through the Janus kinase/signal transducers and activators of transcription (JAK/STAT) pathway, especially JAK2/STAT3, is involved in renal fibrosis. Fluorofenidone (FD), a novel pyridone agent, exerts anti-fibrotic effects in vitro and in vivo. Herein, we sought to investigate whether FD demonstrates its inhibitory function through preventing JAK2/STAT3 pathway. In this study, we examined the effect of FD on activation of rat renal interstitial fibroblasts, glomerular mesangial cells (GMC), and expression of JAK2/STAT3. Moreover, we explored the histological protection effects of FD in UUO rats, db/db mice, and phosphorylation of JAK2/STAT3 cascade. Our studies found that pretreatment with FD resulted in blockade of activation of fibroblast and GMC manifested by fibronectin (FN) and α-smooth muscle actin (α-SMA) protein expression and decline of STAT3 tyrosine phosphorylation induced by IL-6 or high glucose. In unilateral ureteral obstruction rats and a murine model of spontaneous type 2 diabetes (db/db mice), treatment with FD blocked the expression of FN and α-SMA, prevented renal fibrosis progression, and attenuated STAT3 activation. However, FD administration did not interfere with JAK2 activation both in vivo and in vitro. In summary, the molecular mechanism by which FD exhibits renoprotective effects appears to involve the inhibition of STAT3 phosphorylation.

Application of GC-MS coupled with chemometrics for scanning serum metabolic biomarkers from renal fibrosis rat.

Renal interstitial fibrosis closely relates to chronic kidney disease and is regarded as the final common pathway in most cases of end-stage renal disease. Metabolomic biomarkers can facilitate early diagnosis and allow better understanding of the pathogenesis underlying renal fibrosis. Gas chromatography-mass spectrometry (GC/MS) is one of the most promising techniques for identification of metabolites. However, the existence of the background, baseline offset, and overlapping peaks makes accurate identification of the metabolites unachievable. In this study, GC/MS coupled with chemometric methods was successfully developed to accurately identify and seek metabolic biomarkers for rats with renal fibrosis. By using these methods, seventy-six metabolites from rat serum were accurately identified and five metabolites (i.e., urea, ornithine, citric acid, galactose, and cholesterol) may be useful as potential biomarkers for renal fibrosis.

Pharmacokinetics of single-dose morinidazole in patients with severe renal impairment.

OBJECTIVE: To evaluate the pharmacokinetics of morinidazole in individuals with severe renal impairment (RI). METHODS: This open-label Phase I study enrolled healthy volunteers and patients with severe RI aged 18 - 65 years. All subjects received a single infusion of sodium chloride injection with 500 mg morinidazole. Plasma and urine concentration of morinidazole and one of its metabolites (M4-1) were evaluated by using HPLC-UV and HPLC-MS/MS respectively. Pharmacokinetic parameters were calculated by Phoenix WinNonlin 6.0 software. RESULTS: 22 individuals (healthy: n = 11, severe RI: n = 11) received morinidazole. In both groups, maximum plasma concentration of morinidazole was reached within 1 hour, while the tmax of M4-1 differed greatly. Both AUC0-t and AUC0-∞ of morinidazole were 1.4 times higher in patients with severe RI, while M4-1 were over 7 times higher than healthy groups. Renal excretion of unchanged morinidazole was decreased by 65% in patients with RI, and M4-1 was decreased by 72%. Apparent correlation between CLcr and CL, AUC, t1/2 and CLr were seen in two groups. CONCLUSIONS: A single dose of 500 mg morinidazole is well tolerated. Changes in pharmacokinetic parameters of morinidazole and M4-1 are seen in patients with RI and may be clinically important.

Fluorofenidone attenuates diabetic nephropathy and kidney fibrosis in db/db mice.

BACKGROUND/AIMS: Fluorofenidone [1-(3-fluorophenyl)-5-methyl-2-(1H)-pyridone, AKF-PD], a novel pyridone agent, showed potent antifibrotic properties. The aim of the present study was to investigate the effects of AKF-PD on diabetic nephropathy and kidney fibrosis, and to obtain an insight into its mechanisms of action. METHODS: We administered AKF-PD to diabetic db/db mice for 12 weeks. Moreover, we performed in vitro cultures using murine mesangial cells exposed to high ambient glucose concentrations. RESULTS: AKF-PD reduced renal hypertrophy, mesangial matrix expansion and albuminuria in the db/db mice. The upregulated expression of α1(I)- and α1(IV)-collagen and fibronectin mRNAs, transforming growth factor-ß1 (TGF-ß1), α-smooth muscle actin (α-SMA), and tissue inhibitors of metalloproteinase 1 (TIMP-1) mRNAs and proteins was inhibited by AKF-PD treatment in the renal cortex of db/db mice. The maximal effective dose of AKF-PD was about 500 mg/kg body weight. AKF-PD inhibited the upregulated expression of α1(I)- and α1(IV)-collagens, TGF-ß1, TIMP-1 and α-SMA induced by high glucose concentrations in cultured mesangial cells. CONCLUSIONS: Our data indicate that AKF-PD diminishes the abnormal accumulation of mesangial matrix through the inhibition of upregulated expression of TGF-ß target genes in kidneys of db/db mice, resulting in attenuation of renal fibrosis and amelioration of renal dysfunction despite persistent hyperglycemia. Therefore, AKF-PD, a potent antifibrotic agent, holds great promise in the treatment of diabetic nephropathy.

[The effect of losartan on glomerular sclerosis in rats with diabetic nephropathy].

OBJECTIVE: To explore the degradation mechanism of losartan on extracellular matrix in rats with diabetic nephropathy. METHODS: The rat model of diabetic nephropathy was established by streptozotozin(STZ) injection, and the rats were randomly divided into 3 groups: (a normal group, a model group and a losartan group). For 16 weeks, the serum creatinine and urea nitrogen were measured, and glomerular sclerosis index(GSI) were caculated. The expression of collagen Type IV,connective tissue growth factor and transforming growth factor-beta1 were examined by Western blot and real time-PCR respectively. RESULTS: Blood urea nitrogen, GSI and the expressions of collagen Type IV and CTGF protein in the losartan group were lower than those in the model group(all P<0.05), and the expressions of collagen Type IV mRNA,TGF-beta1 mRNA and CTGF mRNA were lower than those in the model group (all P<0.05). CONCLUSION: Losartan modulates glomerular sclerosis and decreases the accumulation of collagen Type IV by inhibiting TGF-beta1 and CTGF.

[Expression of p27 and TGF-beta in rat kidney with unilateral ureteral obstruction and the relationship between TGF-beta and p27].

AIM: To explore the expression of p27 and the changes of TGF-beta in the renal tubule on the process of renal interstitial fibrosis caused by unilateral ureteral obstruction (UUO) in rats and to investigate the relationship between TGF-beta and p27 in renal interstitial fibrosis rats. METHODS: Sixty rats were randomly divided into sham-operated group (SOR) and UUO group. Ten rats from each group were sacrificed on days 7, 14 and 21 after operation respectively. The renal pathological changes were dynamically observed by HE . The expression and dynamic changes of p27 were detected by immunohistochemistry. The levels of p27 mRNA and TGF-beta mRNA were detected by RT-PCR. RESULTS: The expression of p27 in renal tubular epithelial cells and p27mRNA was strongly positive in SOR group. With the aggravation of interstitial fibrosis, the expression of p27 gradually decreased in UUO group while the expression of TGF-beta increased. There was a negative correlation between TGF-beta and p27. CONCLUSION: P27 is involved in the fibrosis of renal mesenchyme in rats with UUO. The mechanism of TGF-beta accelerating fibrosis may relate to the reduction of p27 expression in UUO rats.