Cysteine as a Multifaceted Player in Kidney, the Cysteine-Related Thiolome and Its Implications for Precision Medicine.

In this review encouraged by original data, we first provided in vivo evidence that the kidney, comparative to the liver or brain, is an organ particularly rich in cysteine. In the kidney, the total availability of cysteine was higher in cortex tissue than in the medulla and distributed in free reduced, free oxidized and protein-bound fractions (in descending order). Next, we provided a comprehensive integrated review on the evidence that supports the reliance on cysteine of the kidney beyond cysteine antioxidant properties, highlighting the relevance of cysteine and its renal metabolism in the control of cysteine excess in the body as a pivotal source of metabolites to kidney biomass and bioenergetics and a promoter of adaptive responses to stressors. This view might translate into novel perspectives on the mechanisms of kidney function and blood pressure regulation and on clinical implications of the cysteine-related thiolome as a tool in precision medicine.

Zebrafish Model as a Screen to Prevent Cyst Inflation in Autosomal Dominant Polycystic Kidney Disease.

In autosomal dominant polycystic kidney disease (ADPKD), kidney cyst growth requires the recruitment of CFTR (cystic fibrosis transmembrane conductance regulator), the chloride channel that is defective in cystic fibrosis. We have been studying cyst inflation using the zebrafish Kupffer's vesicle (KV) as model system because we previously demonstrated that knocking down polycystin 2 (PC2) induced a CFTR-mediated enlargement of the organ. We have now quantified the PC2 knockdown by showing that it causes a 73% reduction in the number of KV cilia expressing PC2. According to the literature, this is an essential event in kidney cystogenesis in ADPKD mice. Additionally, we demonstrated that the PC2 knockdown leads to a significant accumulation of CFTR-GFP at the apical region of the KV cells. Furthermore, we determined that KV enlargement is rescued by the injection of Xenopus pkd2 mRNA and by 100 µM tolvaptan treatment, the unique and approved pharmacologic approach for ADPKD management. We expected vasopressin V2 receptor antagonist to lower the cAMP levels of KV-lining cells and, thus, to inactivate CFTR. These findings further support the use of the KV as an in vivo model for screening compounds that may prevent cyst enlargement in this ciliopathy, through CFTR inhibition.

An Atypical Presentation of Thrombotic Microangiopathy After Lung Transplant: A Case Report.

Thrombotic microangiopathy (TMA) is a pathologic condition characterized by microangiopathic hemolytic anemia, thrombocytopenia, and organ injury due to microvascular endothelial lesions and thrombosis. It occurs in a variety of diseases and, unless recognized and treated, leads to severe morbidity and mortality. We present the case of a 48-year-old woman who underwent lung transplantation, initially under tacrolimus, mycophenolate mofetil (MMF), and prednisolone. Several complications emerged in the following months, including abdominal aortic and left renal artery thrombosis and cutaneous infections, although her renal function remained normal. Six months after transplant, her renal function began to deteriorate, which was assumed to be due to elevated tacrolimus levels and doses were adjusted. Due to leukopenia, MMF was changed to everolimus. One year after, she was admitted with fatigue, anemia, and renal dysfunction. Complementary exams revealed only iron deficiency, leukopenia, normal platelets, and elevated lactate dehydrogenase; her renal ultrasound was normal. A renal biopsy was performed and thrombotic microangiopathy was subsequently identified as the main cause of the renal dysfunction. Tacrolimus was therefore discontinued and MMF restarted with slow improvement of renal function. Only when everolimus was stopped did the patient's renal function show incremental improvement. TMA may be a serious complication after lung transplantation and the risk is higher when a combination of tacrolimus and everolimus is used. Renal biopsy findings are essential to confirm the final diagnosis of TMA, allowing for a change in immunosuppression to prevent permanent and severe renal damage.

Adult presentation of Bartter syndrome type IV with erythrocytosis / Apresentação tardia de síndrome de Bartter tipo IV com eritrocitose

Abstract Bartter syndrome comprises a group of rare autosomal-recessive salt-losing disorders with distinct phenotypes, but one unifying pathophysiology consisting of severe reductions of sodium reabsorption caused by mutations in five genes expressed in the thick ascending limb of Henle, coupled with increased urinary excretion of potassium and hydrogen, which leads to hypokalemic alkalosis. Bartter syndrome type IV, caused by loss-of-function mutations in barttin, a subunit of chloride channel CLC-Kb expressed in the kidney and inner ear, usually occurs in the antenatal-neonatal period. We report an unusual case of late onset presentation of Bartter syndrome IV and mild phenotype in a 20 years-old man who had hypokalemia, deafness, secondary hyperparathyroidism and erythrocytosis.

Resumo A síndrome de Bartter compreende um grupo raro de doenças autossômicas recessivas perdedoras de sal, decorrentes de mutações em genes expressos na porção ascendente espessa da alça de Henle, com fenótipos distintos, porém fisiopatogenia única, que consiste em redução severa da reabsorção de sódio, e aumento da excreção urinária de hidrogênio e potássio, levando à alcalose hipocalêmica. A síndrome de Bartter tipo IV, causada por mutações com perda de função da bartina, uma subunidade do canal de cloro CLC-Kb expressa no rim e ouvido interno, geralmente se apresenta nos períodos ante e neonatal. No presente relato, descreve-se um caso não usual de síndrome de Bartter tipo IV com apresentação tardia e fenótipo atenuado, diagnosticado por análise molecular, em um homem adulto de 20 anos que se apresentava com hipocalemia, surdez, hiperparatireoidismo secundário e eritrocitose.

Secondary amyloidosis in a patient with long duration Crohn's disease treated with infliximab.

Systemic AA amyloidosis is a serious complication of many chronic inflammatory disorders. Its association with Crohn's disease implies that the inflammatory burden is high enough for amyloid fibrils to form deposits in tissues. A case is presented in which this complication occurred while the patient was clinically well, with biological and endoscopic markers showing an inactive or mildly active disease under anti-tumor necrosis factor alpha therapy.

A novel heterozygous missense mutation in the UMOD gene responsible for Familial Juvenile Hyperuricemic Nephropathy.

BACKGROUND: Familial Juvenile Hyperuricemic Nephropathy is an autosomal dominant nephropathy, characterized by decreased urate excretion and progressive interstitial nephritis. Mutations in the uromodulin coding UMOD gene have been found responsible for the disease in some families. CASE PRESENTATION: We here describe a novel heterozygous p.K307T mutation in an affected female with hyperuricemia, renal cysts and renal failure. The proband's only son is also affected and the mutation was found to segregate with the disease. CONCLUSIONS: This mutation is the fourth reported in exon 5. Initial studies identified a mutation clustering in exon 4 and it has been recommended that sequencing this exon alone should be the first diagnostic test in patients with chronic interstitial nephritis with gout or hyperuricemia. However, regarding the increasing number of mutations being reported in exon 5, we now suggest that sequencing exon 5 should also be performed.