Schweda, F. | Search bioRxiv

bioRxiv2026

Gut and Glomerular Barriers Determine Nanoplastic Fate and Systemic Impact

Nanoplastics (NPs) are increasingly recognized as pervasive environmental toxicants, however, their interactions with gut and renal barriers, and the resulting systemic consequences remain poorly understood. Here, we studied the uptake of 50 nm polystyrene (PS) nanoparticles using a multi-scale approach integrating zebrafish models, isolated perfused mouse kidneys, and in vitro assays to delineate uptake and barrier-dependent organ distribution. In zebrafish larvae, PS-NPs were efficiently absorbed via the intestinal tract, as visualized by confocal and label-free stimulated Raman scattering (SRS) microscopy, leading to gut microbiota dysbiosis and systemic inflammatory responses. Despite widespread systemic dissemination, renal accumulation was minimal under physiological conditions, whereas both zebrafish and isolated perfused mouse kidneys exhibited substantial PS-NPs retention only when the glomerular filtration barrier was disrupted. In vitro glomerular endothelial cells and podocytes readily internalized PS-NPs without altering key glomerular identity markers, highlighting their intrinsic uptake capacity that is normally restricted in vivo by barrier integrity. Our findings establish the glomerular filtration barrier as a crucial gatekeeper that prevents renal nanoplastic deposition. Furthermore, we revealed a microbiota-mediated axis that may prime the kidney for the environmentally induced stressing in long term.

systems biology↗

bioRxiv2022

Prorenin from renal tubules is a major driver of diabetic kidney disease

The renin-angiotensin-system (RAS) plays a critical role in diabetic nephropathy, and inhibitors of the RAS are central components in its therapy. Renin circulates in the blood in its active form but also in the form of its enzymatically inactive precursor prorenin. In humans, the plasma prorenin concentration exceeds that of active renin several times. While the plasma concentration of active renin is unchanged or even reduced in diabetic patients, the prorenin concentration increases significantly and it has been shown that high prorenin levels are associated with diabetic microvascular damage. Why prorenin increases in diabetes while active renin is reduced is unclear. Previous studies suggest that there may be formation of prorenin in the tubular system of diabetic kidneys. To investigate the functional consequences of possible tubular renin formation in diabetes, we generated mice with inducible tubule-specific deletion of the renin gene (tubule-renin KO). Under control conditions, tubule-renin KO had no apparent phenotype and plasma and tissue levels of renin and prorenin were similar to those of mice with intact tubular renin (control mice). In control mice type-1 diabetes (streptozotocin, STZ) for 8 to 12 weeks stimulated tubular renin mRNA and protein expression, especially in distal nephron segments including collecting ducts. This increase in renin synthesis in renal tubules was markedly attenuated or even absent in tubule-renin KO mice. Similar to diabetic patients, plasma prorenin was markedly elevated in diabetic control mice. This stimulation of plasma prorenin was absent in mice with tubule-specific deletion of the renin gene. Moreover, the high prorenin levels in renal tissue, which were observed in diabetic control mice, were markedly reduced in tubule-renin KO. Noteworthy, plasma renin activity was not reduced in tubule-renin KO compared with controls, suggesting that renal tubules of diabetic mice mainly release prorenin. Kidneys of control mice with intact tubular renin showed classical signs of diabetic renal damage, such as albuminuria, mesangial expansion, fibrosis, inflammation and capillary rarefaction. All of these parameters were significantly ameliorated in tubule-renin KO, indicating that tubular renin, most likely in its prorenin form, significantly aggravates renal damage in diabetes. These data provide clear evidence for the first time that the tubular renin system is an additional source for circulating prorenin in diabetes, hereby providing an explanation for the paradox regulation of active renin and prorenin in diabetes. Moreover, the data show that tubular renin markedly contributes to the progression of diabetic nephropathy.

physiology↗