-
Asian Journal of Urology Apr 2024Urolithiasis formation has been attributed to environmental and dietary factors. However, evidence is accumulating that genetic background can contribute to urolithiasis... (Review)
Review
OBJECTIVE
Urolithiasis formation has been attributed to environmental and dietary factors. However, evidence is accumulating that genetic background can contribute to urolithiasis formation. Advancements in the identification of monogenic causes using high-throughput sequencing technologies have shown that urolithiasis has a strong heritable component.
METHODS
This review describes monogenic factors implicated in a genetic predisposition to urolithiasis. Peer-reviewed journals were evaluated by a PubMed search until July 2023 to summarize disorders associated with monogenic traits, and discuss clinical implications of identification of patients genetically susceptible to urolithiasis formation.
RESULTS
Given that more than 80% of urolithiases cases are associated with calcium accumulation, studies have focused mainly on monogenetic contributors to hypercalciuric urolithiases, leading to the identification of receptors, channels, and transporters involved in the regulation of calcium renal tubular reabsorption. Nevertheless, available candidate genes and linkage methods have a low resolution for evaluation of the effects of genetic components versus those of environmental, dietary, and hormonal factors, and genotypes remain undetermined in the majority of urolithiasis formers.
CONCLUSION
The pathophysiology underlying urolithiasis formation is complex and multifactorial, but evidence strongly suggests the existence of numerous monogenic causes of urolithiasis in humans.
PubMed: 38680588
DOI: 10.1016/j.ajur.2023.03.004 -
Asian Journal of Urology Apr 2024Rheumatoid nephropathy is one of the most severe extra-articular manifestations of rheumatoid arthritis (RA) associated with a very unfavorable prognosis. This study...
OBJECTIVE
Rheumatoid nephropathy is one of the most severe extra-articular manifestations of rheumatoid arthritis (RA) associated with a very unfavorable prognosis. This study aimed to identify changes in renal function and morphological variations of kidney diseases in RA patients.
METHODS
The study enrolled patients (126 patients) between 18 and 55 years of age with a confirmed active RA of more than 12 months. Each patient underwent the following range of laboratory and instrumental research methods: general clinical analysis of blood and urine, performing urinalysis according to Nechiporenko method; determining daily proteinuria; determining the blood content of glucose, urea, creatinine, uric acid, total bilirubin, liver transaminase level, ionogram, lipidogram, and coagulogram; determining the blood content of rheumatoid factor, anti-streptolysin O, and C-reactive protein; and X-ray of the joints of hands and feet. Renal function was examined by estimating glomerular filtration rate, tubular reabsorption index, and renal functional reserve. For studying the morphological changes in the kidneys under ultrasound examination, renal biopsy was performed in 31 patients with RA with urinary syndrome (proteinuria more than 0.3 g per day and hematuria).
RESULTS
Nephropathy in RA is characterized by impaired renal function and manifested by an increased blood creatinine and a decrease in glomerular filtration rate and renal functional reserve. Among morphological variations of nephropathy at RA, mesangial proliferative glomerulonephritis prevails, accounting for 48.4% of patients. Other disorders include the secondary amyloidosis (29.0% of patients), tubulointerstitial nephritis (16.1%), membranous glomerulonephritis (3.2%), and focal-segmental glomerulosclerosis (3.2%).
CONCLUSION
Kidney damage is a common systemic manifestation of RA with a long and active course, a major nephropathy trigger.
PubMed: 38680581
DOI: 10.1016/j.ajur.2022.06.005 -
International Journal of Molecular... Apr 2024Designed ankyrin repeat protein (DARPin) G3 is an engineered scaffold protein. This small (14.5 kDa) targeting protein binds with high affinity to human epidermal growth...
Designed ankyrin repeat protein (DARPin) G3 is an engineered scaffold protein. This small (14.5 kDa) targeting protein binds with high affinity to human epidermal growth factor receptor 2 (HER2). HER2 is overexpressed in several cancers. The use of the DARPin G3 for radionuclide therapy is complicated by its high renal reabsorption after clearance via the glomeruli. We tested the hypothesis that a fusion of the DARPin G3 with an albumin-binding domain (ABD) would prevent rapid renal excretion and high renal reabsorption resulting in better tumour targeting. Two fusion proteins were produced, one with the ABD at the C-terminus (G3-ABD) and another at the N-terminus (ABD-G3). Both variants were labelled with Lu. The binding properties of the novel constructs were evaluated in vitro and their biodistribution was compared in mice with implanted human HER2-expressing tumours. Fusion with the ABD increased the retention time of both constructs in blood compared with the non-ABD-fused control. The effect of fusion with the ABD depended strongly on the order of the domains in the constructs, resulting in appreciably better targeting properties of [Lu]Lu-G3-ABD. Our data suggest that the order of domains is critical for the design of targeting constructs based on scaffold proteins.
Topics: Animals; Female; Humans; Mice; Albumins; Ankyrin Repeat; Cell Line, Tumor; Lutetium; Protein Binding; Protein Domains; Radioisotopes; Radiopharmaceuticals; Receptor, ErbB-2; Recombinant Fusion Proteins; Tissue Distribution; Molecular Targeted Therapy
PubMed: 38673831
DOI: 10.3390/ijms25084246 -
Journal of Cellular and Molecular... Apr 2024X-linked nephrogenic diabetes insipidus (X-NDI) is a rare congenital disease caused by inactivating mutations of the vasopressin type-2 receptor (AVPR2), characterized...
X-linked nephrogenic diabetes insipidus (X-NDI) is a rare congenital disease caused by inactivating mutations of the vasopressin type-2 receptor (AVPR2), characterized by impaired renal concentrating ability, dramatic polyuria, polydipsia and risk of dehydration. The disease, which still lacks a cure, could benefit from the pharmacologic stimulation of other GPCRs, activating the cAMP-intracellular pathway in the kidney cells expressing the AVPR2. On the basis of our previous studies, we here hypothesized that the β3-adrenergic receptor could be such an ideal candidate. We evaluated the effect of continuous 24 h stimulation of the β3-AR with the agonist BRL37344 and assessed the effects on urine output, urine osmolarity, water intake and the abundance and activation of the key renal water and electrolyte transporters, in the mouse model of X-NDI. Here we demonstrate that the β3-AR agonism exhibits a potent antidiuretic effect. The strong improvement in symptoms of X-NDI produced by a single i.p. injection of BRL37344 (1 mg/kg) was limited to 3 h but repeated administrations in the 24 h, mimicking the effect of a slow-release preparation, promoted a sustained antidiuretic effect, reducing the 24 h urine output by 27%, increasing urine osmolarity by 25% and reducing the water intake by 20%. At the molecular level, we show that BRL37344 acted by increasing the phosphorylation of NKCC2, NCC and AQP2 in the renal cell membrane, thereby increasing electrolytes and water reabsorption in the kidney tubule of X-NDI mice. Taken together, these data suggest that human β3-AR agonists might represent an effective possible treatment strategy for X-NDI.
Topics: Male; Animals; Mice, Inbred C57BL; Disease Models, Animal; Adrenergic beta-3 Receptor Agonists; Antidiuretic Agents; Kidney Concentrating Ability; Polydipsia
PubMed: 38652212
DOI: 10.1111/jcmm.18301 -
BioRxiv : the Preprint Server For... May 2024The mitochondrial-rich renal tubule cells are key regulators of blood homeostasis via excretion and reabsorption of metabolic waste. With age, tubules are subject to...
The mitochondrial-rich renal tubule cells are key regulators of blood homeostasis via excretion and reabsorption of metabolic waste. With age, tubules are subject to increasing mitochondrial dysfunction and declining nicotinamide adenine dinucleotide (NAD+) levels, both hampering ATP production efficiency. We tested two mitochondrial interventions in young (6-mo) and aged (26-mo) adult male mice: elamipretide (ELAM), a tetrapeptide in clinical trials that improves mitochondrial structure and function, and nicotinamide mononucleotide (NMN), an NAD+ intermediate and commercially available oral supplement. Kidneys were analyzed from young and aged mice after eight weeks of treatment with ELAM (3 mg/kg/day), NMN (300 mg/kg/day), or from aged mice treated with the two interventions combined (ELAM+NMN). We hypothesized that combining pharmacologic treatments to ameliorate mitochondrial dysfunction and boost NAD+ levels, would more effectively reduce kidney aging than either intervention alone. Unexpectedly, in aged kidneys, NMN increased expression of genetic markers of inflammation (IL-1-beta; and Ccl2) and tubule injury (Kim-1). Metabolomics of endpoint sera showed that NMN-treated aged mice had higher circulating levels of uremic toxins than either aged controls or young NMN-treated mice. ELAM+NMN-treated aged mice accumulated uremic toxins like NMN-only aged mice, but reduced IL-1-beta; and Ccl2 kidney mRNA. This suggests that pre-existing mitochondrial dysfunction in aged kidney underlies susceptibility to inflammatory signaling with NMN supplementation in aged, but not young, mice. These findings demonstrate age and tissue dependent effects on downstream metabolic accumulation from NMN and highlight the need for targeted analysis of aged kidneys to assess the safety of anti-aging supplements in older populations.
PubMed: 38645109
DOI: 10.1101/2024.04.09.588624 -
Frontiers in Physiology 2024Osteoporosis after bariatric surgery is an increasing health concern as the rate of bariatric surgery has risen. In animal studies mimicking bariatric procedures, bone...
Osteoporosis after bariatric surgery is an increasing health concern as the rate of bariatric surgery has risen. In animal studies mimicking bariatric procedures, bone disease, together with decreased serum levels of Ca, Mg and the gastric hormone Ghrelin were described. Ghrelin regulates metabolism by binding to and activating the growth hormone secretagogue receptor (GHSR) which is also expressed in the kidney. As calcium and magnesium are key components of bone, we tested the hypothesis that Ghrelin-deficiency contributes to osteoporosis via reduced upregulation of the renal calcium channel TRPV5 and the heteromeric magnesium channel TRPM6/7. We expressed GHSR with TRPV5 or TRPM6/7 channel in HEK293 cells and treated them with purified Ghrelin. Whole-cell current density was analyzed by patch-clamp recording. Nephron-specific gene expression was performed by tubular microdissection followed by qPCR in wild-type (WT) mice, and immunofluorescent imaging of GHSR-eGFP mice. Tubular magnesium homeostasis was analyzed in GHSR-null and WT mice at baseline and after caloric restriction. After Ghrelin exposure, whole-cell current density did not change for TRPV5 but increased for TRPM6/7 in a dose-dependent fashion. Applying the Ghrelin-mimetic (D-Trp, Ala,D-Phe)-α-MSH (6-11) amide without and with the GHSR antagonist (D-Lys)-GHRP6, we confirmed the stimulatory role of Ghrelin towards TRPM6/7. As GHSR initiates downstream signaling via protein kinase A (PKA), we found that the PKA inhibitor H89 abrogated TRPM6/7 stimulation by Ghrelin. Similarly, transfected Gα, but not the Gα mutant Q227L, nor Gα, Gα, or Gα upregulated TRPM6/7 current density. In microdissected TALs and DCTs similar levels of GHSR mRNA were detected. In contrast, TRPM6 mRNA was expressed in the DCT and also detected in the TAL at 25% expression compared to DCT. Immunofluorescent studies using reporter GHSR-eGFP mice showed a strong eGFP signal in the TAL but surprisingly displayed no eGFP signal in the DCT. In 3-, 6-, and 9-month-old GHSR-null and WT mice, baseline serum magnesium was not significantly different, but 24-h urinary magnesium excretion was elevated in 9-month-old GHSR-null mice. In calorically restricted GHSR-null mice, we detected excess urinary magnesium excretion and reduced serum magnesium levels compared to WT mice. The kidneys from calorically restricted WT mice showed upregulated gene expression of magnesiotropic genes , , , , and compared to GHSR-null mice. Our studies show that Ghrelin stimulates TRPM6/7 via GHSR and Gα-PKA signaling. The murine studies are consistent with Ghrelin-GHSR signaling inducing reduced urinary magnesium excretion, particularly in calorically restricted mice when Ghrelin levels are elevated. This effect may be mediated by Ghrelin-upregulation of TRPM6 in the TAL and/or upregulation of other magnesiotropic genes. We postulate that rising Ghrelin levels with hunger contribute to increased renal Mg reabsorption to compensate for lack of enteral Mg uptake.
PubMed: 38638279
DOI: 10.3389/fphys.2024.1363708 -
Nefrologia 2024The association of hypouricemia and hypercalciuria is rare. In 1974 a new syndrome named Hypouricemia with hypercalciuria and decreased bone density was described.... (Review)
Review
BACKGROUND AND OBJECTIVE
The association of hypouricemia and hypercalciuria is rare. In 1974 a new syndrome named Hypouricemia with hypercalciuria and decreased bone density was described. Afterwards, some cases with such association were published in which the fractional excretion of urate was higher than 20ml/100ml FGR. We have analyzed a series of children who were diagnosed with hypouricemia and hypercalciuria and who were monitored. The aim of this study was to determine whether our patients could be affected by the aforementioned syndrome or be carriers of a variant of idiopathic hypercalciuria.
PATIENTS AND METHODS
Retrospective longitudinal study in which the medical records of eight patients (5V, 3M) diagnosed with hypouricemia and hypercalciuria in childhood. Clinical features at diagnosis, ultrasound and densitometric findings and selected biochemical variables were noted, with special emphasis on renal tubular handling of urate. Results were compared with 36 children with idiopathic hypercalciuria without hypouricemia (14V, 22M).
RESULTS
In the hypouricemia group baseline urate levels were 1.9 (0.3) mg/dl (range: 1.5-2) and first day urine calcium/creatinine ratio 0.27 (0.05) mg/mg (range: 0.23-0.31). In all cases fractional urate excretion was less than 20ml/100ml FGR. The z-DMO values were less than -1 in 4/8 cases. At the last follow-up only three cases still had an elevated calcium/creatinine ratio and in all of them the urates levels was greater than 2mg/dl. The z-DMO value had improved in five cases and worsened in three others. In relation to the group without hypouricemia, no differences were observed between the various parameters studied including the z-DMO value, with the exception of fractional excretion and tubular urate reabsorption although plasmatic uric acid levels were still significantly lower.
CONCLUSION
Our patients with hypercalciuria and hypouricemia would be affected by a variant of idiopathic hypercalciuria in which, due to an unknown cause, the proximal tubular reabsorption of urate is modestly reduced and improves over time. Hypouricemia with hypercalciuria and decreased bone density may not be a specific entity.
Topics: Humans; Hypercalciuria; Longitudinal Studies; Retrospective Studies; Female; Male; Child; Child, Preschool; Uric Acid; Adolescent; Infant; Bone Density
PubMed: 38631961
DOI: 10.1016/j.nefroe.2024.03.023 -
The Journal of Pharmacology and... Apr 2024Organic anions (OA) are compounds including drugs or toxicants that are negatively charged at physiological pH and are typically transported by Organic Anion...
Organic anions (OA) are compounds including drugs or toxicants that are negatively charged at physiological pH and are typically transported by Organic Anion Transporters (OATs). Human OAT4 (SLC22A11) is expressed in the apical membrane of renal proximal tubules. Although there is no rodent ortholog of hOAT4, rodents express Oat5 (Slc22a19), an anion exchanger that is also localized to the apical membrane of renal proximal tubule cells. The purpose of this study was to determine the functional similarity between mouse Oat5 and human OAT4. Chinese hamster ovary (CHO) cells expressing SLC22A11 or Slc22a19 were used to assess the transport characteristics of radiolabeled ochratoxin (OTA). We determined the kinetics of OTA transport; the resulting K and J values were very similar for both hOAT4 and mOat5: K 3.9 and 7.2 µM, respectively, & J 4.4 and 3.9 pmol/cm, respectively. For the profile of OTA inhibition by OAs, IC values were determined for several clinically important drugs and toxicants. The resulting IC values ranged from 9 µM for indomethacin to ~600 µM for the diuretic hydrochlorothiazide. We measured the efflux of OTA from preloaded cells; both hOAT4 and mOat5 supported the efflux of OTA. These data support the hypothesis that OAT4 and Oat5 are functional orthologs and share selectivity for OTA both for reabsorption and secretion. This study compares the selectivity profile between human OAT4 and mouse Oat5. Our data revealed a similar selectivity profile for OTA reabsorption and secretion by these two transporters, thereby supporting the hypothesis that hOAT4 and mOat5, while not genetic orthologs, behave as functional orthologs for both uptake and efflux. These data will be instrumental in selecting an appropriate animal model when studying the renal disposition of anionic drugs and toxicants.
PubMed: 38627096
DOI: 10.1124/jpet.123.001979 -
Drug Metabolism and Disposition: the... Apr 2024models that can faithfully replicate critical aspects of kidney tubule function such as directional drug transport are in high demand in pharmacology and toxicology....
Comparative Analysis of the Physiological and Transport Functions of Various Sources of Renal Proximal Tubule Cells Under Static and Fluidic Conditions in PhysioMimix{trade mark, serif} T12 Platform.
models that can faithfully replicate critical aspects of kidney tubule function such as directional drug transport are in high demand in pharmacology and toxicology. Accordingly, development and validation of new models is underway. The objective of this study was to characterize physiological and transport functions of various sources of human renal proximal tubule epithelial cells (RPTECs). We tested TERT1-immortalized RPTEC, including OAT1-, OCT2- or OAT3-overexpressing variants, and primary RPTECs. Cells were cultured on transwell membranes in static (24-well transwells) and fluidic (transwells in PhysioMimix{trade mark, serif} T12 organ-on-chip with 2 mL/s flow) conditions. Barrier formation, transport, and gene expression were evaluated. We show that two commercially available primary RPTECs were not suitable for studies of directional transport on transwells because they formed a substandard barrier even though they exhibited higher expression of transporters, especially under flow. TERT1-parent, -OAT1 and -OAT3 cells formed robust barriers, but were unaffected by flow. TERT1-OAT1 cells exhibited inhibitable para-aminohippurate transport, it was enhanced by flow. However, efficient tenofovir secretion and perfluorooctanoic acid reabsorption by TERT1-OAT1 cells were not modulated by flow. Gene expression showed that TERT1 and TERT1-OAT1 cells were most correlated with human kidney than other cell lines, but that flow did not have noticeable effects. Overall, our data show that addition of flow to studies of the renal proximal tubule may afford benefits in some aspects of modeling kidney function, but that careful consideration of the impact such adaptations would have on the cost and throughput of the experiments is needed. The topic of reproducibility and robustness of the complex microphysiological systems is looming large in the field of biomedical research; therefore, the uptake of these new models by the end-users is slow. This study systematically compared various RPTEC sources and experimental conditions, aiming to identify the level of model complexity needed for testing renal tubule transport. We demonstrate that while tissue chips may afford some benefits, their throughput and complexity need careful consideration in each context of use.
PubMed: 38626992
DOI: 10.1124/dmd.124.001488