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Sodium thiosulfate, a reversible oxidation product of hydrogen sulfide, has vasodilating and anti-oxidative properties, making it an attractive agent to alleviate damaging effects of hypertension. In experimental settings, inhibition of nitric oxide synthase causes hypertension, renal dysfunction and damage. We hypothesized that thiosulfate would attenuate renal injury and improve renal function, hemodynamics and the efficiency of oxygen utilization for sodium reabsorption in hypertensive renal disease. Additionally, thiosulfate co-administration would further improve these variables when compared to inhibiting the renin-angiotensin system alone. Nitric oxide synthase was inhibited in Sprague Dawley rats by administering N-ω-nitro-L-arginine (L-NNA) in the food for three weeks. After one week, rats were split into two groups; without and with thiosulfate in the drinking water. In a parallel study, rats given N-ω-nitro-L-arginine and the angiotensin converting enzyme inhibitor lisinopril at a relatively low dose in their food were divided into two groups; without and with thiosulfate in the drinking water. Treatment with thiosulfate alleviated hypertension (mean 190 vs. 229 mmHg), lowered plasma urea (mean 11.3 vs. 20.0 mmol/L) and improved the terminal glomerular filtration rate (mean 503 vs. 260 μl/min/100 gbw), effective renal plasma flow (mean 919 vs. 514 μl/min/100 gbw) and oxygen utilization for sodium reabsorption (mean 14.3 vs. 8.6 μmol/μmol). Combining thiosulfate with lisinopril further lowered renal vascular resistance (mean 43 vs. 63 mmHg/ml/min/100 gbw) and prevented glomerulosclerosis. Thus, our results suggest that thiosulfate has therapeutic potential in hypertensive renal disease and might be of value when added to standard antihypertensive therapies., (Copyright © 2020 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

Syndecan-1, a heparan sulfate proteoglycan, has an important role in wound healing by binding several growth factors and cytokines. As these processes are also crucial in damage and repair after renal transplantation, we examined syndecan-1 expression in human control kidney tissue, renal allograft protocol biopsies, renal allograft biopsies taken at indication, and non-transplant interstitial fibrosis. Syndecan-1 expression was increased in tubular epithelial cells in renal allograft biopsies compared with control. Increased epithelial syndecan-1 in allografts correlated with low proteinuria and serum creatinine, less interstitial inflammation, less tubular atrophy, and prolonged allograft survival. Knockdown of syndecan-1 in human tubular epithelial cells in vitro reduced cell proliferation. Selective binding of growth factors suggests that syndecan-1 may promote epithelial restoration. Bilateral renal ischemia/reperfusion in syndecan-1-deficient mice resulted in increased initial renal failure and tubular injury compared with wild-type mice. Macrophage and myofibroblast numbers, tubular damage, and plasma urea levels were increased, and tubular proliferation reduced in the kidneys of syndecan-1 deficient compared with wild-type mice 14 days following injury. Hence syndecan-1 promotes tubular survival and repair in murine ischemia/reperfusion injury and correlates with functional improvement in human renal allograft transplantation.

Background: Advanced glycation end products (AGEs) contribute to diabetic and atherosclerotic end-organ damage, but the mechanisms of AGE-formation and AGE-induced damage are unclear. Glycolaldehyde (GA) is a Maillard-reaction intermediate and can be formed by reaction of L-serine with the myeloperoxidase-system. GA reacts with proteins to form AGEs, such as GA-pyridine, which is specific for protein modification by GA. GA-pyridine accumulates in human atherosclerotic lesions. As atherosclerosis and progressive glomerulosclerosis share many similarities, we hypothesized that GA-pyridine accumulates in renal diseases, especially those with prominent mesangial involvement., Methods: Paraffin-embedded renal biopsies from 55 patients with various renal diseases, as well as control tissue, obtained from the unaffected part of kidneys from 10 patients with renal cell carcinoma were immunohistochemically stained with a monoclonal antibody directed against GA-pyridine and were scored semiquantitatively. Additional sections were scored for mesangial matrix expansion (MME) and focal glomerular sclerosis (FGS)., Results: In normal human kidneys, GA-pyridine was mainly localized in tubular epithelial cells, but not in the glomerular mesangium. Significant mesangial GA-pyridine accumulation was found in disorders with mesangial involvement as a common denominator. In contrast, mesangial GA-pyridine accumulation was less prominent in renal diseases without prominent mesangial involvement. Moreover, mesangial GA-pyridine accumulation was more pronounced in kidneys with higher MME and FGS scores across the different diagnoses., Conclusion: GA-pyridine accumulates in the mesangium in human renal disease, in particular in disorders with mesangial involvement. Further studies should elucidate whether mesangial GA-pyridine plays a role in the progression of glomerular damage.

Background: Plasma hemopexin has been shown to induce proteinuria after intrarenal infusion in rats, as well as glomerular alterations identical to those seen in corticosteroid-responsive nephrotic syndrome (CRNS). The question emerged whether also renal cells are potentially able to release hemopexin., Methods: Normal human mesangial cells (HMC) were incubated overnight in serum-free medium with or without tumor necrosis factor-alpha (TNF-alpha) (10 ng/mL). Parallel cultures were supplemented with prednisolone (10-3 mol/L). Concentrated supernatants were analyzed by Western blotting, using antihemopexin immunoglobulin G (IgG). Antitransferrin IgG served as control antibody. In addition, cytospins were stained using polyclonal or monoclonal antihemopexin IgG. A part of the cells was used for RNA isolation and reverse transcription-polymerase chain reaction (RT-PCR), to study hemopexin mRNA., Results: Eighty five kD bands were exclusively detected by antihemopexin IgG in the Western blots in supernatants from TNF-alpha-stimulated cultures and to a lesser extent in prednisolone-treated cultures. Cells from TNF-alpha-stimulated cultures stain positive for hemopexin in contrast to those from prednisolone-treated or nonstimulated cultures. RT-PCR data suggest that mRNA for hemopexin is up-regulated in TNF-alpha-treated versus prednisolone-treated HMC., Conclusion: Stimulated HMC are able to release hemopexin in vitro in a corticosteroid-dependent manner. As preliminary data indicate that mesangial hemopexin is able to affect glomerular anionic sites, it is conceivable that stimulated mesangium may contribute to enhanced glomerular permeability in CRNS through local hemopexin release.

Background: Control of blood pressure (BP) and optimal reduction of proteinuria (Uprot) are necessary for long-term renoprotection. Unfortunately, angiotensin-converting enzyme inhibitors (ACEI) and angiotensin II (Ang II) antagonists are not effective during sodium repletion. Vasopeptidase inhibitors (VPI) cause dual inhibition of ACE and neutral endopeptidase, the latter resulting in decreased atrial natriuretic peptide (ANP) breakdown and thus enhanced natriuresis. Therefore, in contrast with ACEI, VPI may be effective during high sodium intake., Methods: To test this hypothesis, the renoprotective actions of the new VPI gemopatrilat (GEM) were studied during low (0.05% NaCl) and high (3.0% NaCl) sodium diets in normotensive Wistar rats with established adriamycin nephrosis. The ACEI lisinopril (LIS) was used as control. Rats received either GEM (0.3 mg/g chow), an equihypotensive dose of LIS (75 mg/L drinking water), or vehicle (VEH) from week 6 (that is, established Uprot) until sacrifice. The effect of therapy was monitored by measuring systolic BP and Uprot (weekly) and structural renal damage at the end of study (week 16)., Results: During low sodium, GEM effectively reduced Uprot (-48 +/- 4%), but LIS was more effective (-80 +/- 2%), while Uprot slightly increased in VEH (+23 +/- 2%). The focal glomerulosclerosis (FGS) score after GEM (38 +/- 14) was lower than in the VEH group (79 +/- 27), although this was not significant. LIS (18 +/- 6) reduced FGS significantly. Remarkably, on high sodium, GEM was completely ineffective in reducing BP, Uprot and structural renal injury, just like LIS., Conclusions: The renoprotective actions of VPI depend on dietary sodium intake in normotensive nephrotic rats: therapeutic efficacy is fully blunted by a high sodium diet. During a low sodium diet, gemopatrilat was renoprotective, but less effective than lisinopril. Whether higher doses of the VPI could improve its renoprotective efficacy remains to be elucidated.

In acute glomerulonephritis (GN), increased nitric oxide (NO) production occurs, suggesting a pathophysiological role for NO in the disease process. Although NO potentially could have both toxic as well as protective effects, its exact role in the pathophysiology of GN is unclear and may depend on the NOS isoform generating NO. The protective effects of NO such as prevention of leukocyte and platelet activation and adhesion have been attributed to NO generated by endothelial nitric oxide synthase (eNOS). Evidence for a beneficial role for eNOS includes the demonstration of reduced eNOS expression in experimental models of GN as well as human biopsy specimens that is mostly likely due to endothelial cell necrosis. Reduced NO production in GN also may occur through reaction of NO with superoxide anions or the myeloperoxidase (MPO)/hypochlorous acid (HOCL) system. Further evidence has been provided by the observation that in several experimental models of GN, glomerular injury is exacerbated following treatment with non-selective NO inhibitors. Finally, the development of GN is severely aggravated in mice lacking a functional gene for eNOS as compared to wild-type mice, providing direct support for a protective role of eNOS-derived NO in acute GN.

Background: The obese Zucker rat (OZR) is a model of glomerulosclerosis and renal failure in the setting of hyperlipidemia, hyperinsulinemia, and obesity. Our prior work in OZRs has shown that ovariectomy attenuates glomerulosclerosis, while added estrogen worsens it. To investigate the mechanism of estrogen's effects on glomerular disease in this model, we evaluated the effects of ovariectomy and estrogen supplementation on seven-week peripubertal OZRs. At this time point, rats exhibit no overt histologic glomerular disease, but are just beginning to show elevated urinary albumin excretion., Methods: Female OZRs fed ad libitum were ovariectomized at four weeks, with or without estrogen supplementation to raise estrogen levels to just below those of preoestral adults (mean 16.5 pg/mL). Sham-operated controls were included., Results: Ovariectomy normalized albuminuria, lowered total and very low-density lipoprotein triglycerides, and reduced glomerular fibronectin expression. Estrogen supplementation worsened albuminuria and raised total/very low-density lipoprotein triglycerides and total cholesterol. Estrogen-supplemented rats exhibited enhanced glomerular deposition of apo A-IV and apo B, increased glomerular expression of desmin and type IV collagen, and increased interstitial macrophage deposition., Conclusion: Estrogen may be permissive for the early development of renal disease in OZRs and may act by increasing triglyceride-rich lipoproteins, which then bind to glomerular cells and initiate or accelerate glomerulosclerosis.

Background: Female obese (fa/fa) Zucker rats are maximally hyperphagic from the beginning of access to solid food until 20 weeks of age and die primarily from renal failure. We documented that urinary albumin excretion (UAE) rises early in obese rats during this time of greatest hyperphagia. This study was conducted to examine if this early surge of hyperphagia is critical to the initiation of glomerular damage., Methods: Three groups of six-week-old rats were used: (a) obese females fed ad libitum (AL-obese), (b) obese females pair fed to lean controls until 21 weeks and then allowed to eat ad libitum until 57 weeks (PF. AL-obese), (c) lean (Fa/Fa) Zucker rats fed ad libitum (AL-lean). Cohorts of AL-obese and PF.AL-obese rats were allowed to continue to death or 57 weeks of age, and the rest were terminated at 21 weeks for renal histology., Results: At 21 weeks, neither PF.AL-obese nor AL-lean rats had elevated UAE or glomerular histopathology. In contrast, glomerular injury was severe in AL-obese rats. UAE increased by 10 and 29 weeks in AL- and PF.AL-obese rats, respectively. Plasma triglycerides increased prior to UAE in both PF. AL- and AL-obese rats., Conclusions: In obese rats fed ad libitum, hyperphagia is followed within a few weeks by hypertriglyceridemia and then by glomerular injury regardless of when ad libitum feeding is initiated. These events do not occur in lean rats or in obese rats pair fed to lean rats. Protective effects of pair feeding did not extend into the period of ad libitum feeding for PF.AL-obese rats. Hyperphagia quickly initiates glomerular injury in obese female Zucker rats.

Progression of chronic renal disease is usually more rapid in males, both in humans and in experimental animals. Estrogen-replacement studies indicate that this may be related to the beneficial effects of estrogen on the lipoprotein profile. However, in hyperlipidemic analbuminemic rats (NAR), females are more prone to develop renal injury than males, and ovariectomy tends to decrease triglyceride levels and prevent renal disease. Therefore, we studied the effects of estrogen administration on lipoproteins, and the induction of renal injury in uninephrectomized female and male NAR. Ovariectomized and orchidectomized uninephrectomized NAR were treated with estradiol implants for 24 weeks. In an additional group of ovariectomized rats, the implant was removed after 12 weeks. Both in ovariectomized and orchidectomized NAR, estradiol caused severe hypercholesterolemia (9 to 12 mmol/liter) and hypertriglyceridemia (6 to 8 mmol/liter) after six weeks. Subsequently, these rats developed severe proteinuria, reaching 209 +/- 25 and 95 +/- 43 mg/day, respectively, after 24 weeks. At this point there was severe glomerular sclerosis, with a respective score of 107 +/- 21 and 61 +/- 33. In terminal blood samples the most pronounced increase in lipid levels were observed in very low density lipoproteins (VLDL), intermediate density lipoproteins (IDL) and low density lipoproteins (LDL). In contrast, ovariectomized NAR and orchidectomized NAR without exogenous estrogen had much lower lipid levels (cholesterol 5 to 7 mmol/liter and triglycerides 1 to 2 mmol/liter) after six weeks. These rats, or ovariectomized NAR where the estrogen treatment had been withdrawn, had practically no proteinuria (4 +/- 1, 19 +/- 11, and 13 +/- 4 mg/day, respectively) or renal damage (glomerulosclerosis score 1 +/- 0.4, 5 +/- 3 and 3 +/- 1, respectively) after 24 weeks. Thus, in hypertriglyceridemic analbuminemic rats, estrogen-treatment causes further increases in both triglycerides and cholesterol. Most probably these changes contribute to the development of renal injury by estrogen in this model. This effect of estrogen, which has also been observed in the Zucker rat, is unique for the hypertriglyceridemic state and deserves further study.

Nitric oxide radicals are recognized as important mediators in various physiological and pathophysiological processes. During inflammation, increased amounts of nitric oxide (NO) are produced, but it is unclear whether NO radicals are either protective or harmful. To obtain more insight into the role of NO in glomerular inflammation, we studied the temporal expression of endothelial NO synthase (eNOS) and inducible NOS (iNOS) in conjunction with platelet aggregation, inflammatory cell influx, superoxide anion production cells, and nitrotyrosine formation in an experimental model of anti-myeloperoxidase (MPO) associated necrotizing crescentic glomerulonephritis (NCGN). Brown Norway rats were immunized with MPO in complete Freund's adjuvant (CFA) or CFA alone. After two weeks, the left kidney was perfused with a neutrophil lysosomal extract and H2O2. Rats were sacrificed at 24 hours, four days, and 10 days after perfusion. Kidney sections were stained by immunohistochemistry for eNOS, iNOS, platelets, nitrotyrosines, polymorphonuclear cells (PMN), monocytes, and T-cells. Superoxide anion producing cells were identified by enzyme cytochemistry using diaminobenzidine. Strong staining for eNOS was found in glomerular capillaries and interstitial tubular capillaries and larger vessels from non-perfused kidneys. At 24 hours after perfusion, glomerular and interstitial eNOS staining was greatly reduced, which was associated with massive platelet aggregation. At later time points, eNOS expression was absent in severely damaged glomeruli. Inducible NOS expression was found at all time points in infiltrating inflammatory cells, which by double labeling studies were identified as PMNs and monocytes. The peak in iNOS expression was observed at four days after perfusion but declined thereafter. Superoxide anion and nitrotyrosine generating cells were also found at all time points, but were most abundantly present at four days after perfusion, coinciding with the peak in iNOS expression. Double labeling experiments revealed that most nitrotyrosine generating cells also produced superoxide anions and expressed iNOS. In conclusion, these studies suggest that during the course of anti-MPO associated NCGN, loss of NO production by eNOS in conjunction with NO radical production by iNOS contribute to tissue injury. This is compatible with a protective role for eNOS contrasting with the possibly harmful effects of iNOS in anti-MPO associated NCGN.

Renal failure is the primary cause of death in obese Zucker rats (OZR). We previously found that renal injury occurred earlier and with greater severity in female OZR; also, prevention of hyperphagia decreased renal damage in females more than males. To examine the relationship between estrogen (E), hyperphagia, hyperlipidemia, and renal injury in female OZR, we studied four groups from 5 to 10 or 21 weeks of age: Sham-operated (Sham), ovariectomized (Ovx), Ovx with estrogen treatment (Ovx + E), and since Ovx increases food intake, Ovx pair-fed to sham (Ovx-PF). By only six weeks of age, albumin excretion (UAE) increased significantly in Ovx + E (9.9 +/- 4.1 mg/day). Ovx + E also ate least and gained the least weight, but had the highest plasma lipid levels. In contrast, UAE in Ovx did not increase by 10 weeks of age, despite a significantly greater food consumption. The hyperlipidemia of Ovx + E was due primarily to triglycerides. Both plasma triglycerides and renal injury, judged from either histology or UAE, were greatest in the Ovx + E group Fasting plasma glucose was lower and insulin was higher in Ovx + E compared to Ovx rats at 15 weeks of age. Estrogen may promote renal injury in female OZR by increasing the plasma concentration of triglyceride-rich lipoproteins.

Abnormal lipid accumulation in glomeruli is a recognized early event in the development of glomerulosclerosis. The presence of LDL and scavenger receptors has recently been demonstrated in glomerular cells, including the visceral epithelial cells. To explore the possible molecular mechanisms of lipid-induced glomerular injury, the present investigation was conducted to examine the effects of oxidized LDL (ox-LDL) on the expression of transforming growth factor (TGF)-beta and fibronectin by cultured human glomerular epithelial cells (GEC). Cultured GEC were exposed to human ox-LDL (0 to 100 micrograms/ml) for various time points. Ox-LDL induced a dose- and time-dependent increase in the expression of TGF-beta mRNA. Actinomycin D, a transcriptional inhibitor, but not cycloheximide, a protein synthesis inhibitor, inhibited the response. GEC exposed to ox-LDL also demonstrated elevated levels of fibronectin mRNA. In addition, treatment of GEC with ox-LDL resulted in increased TGF-beta and fibronectin protein expression as detected by immunocytochemistry. Addition of anti-TGF-beta antibody significantly inhibited the increase in fibronectin message level induced by ox-LDL. These data suggest that ox-LDL stimulates matrix protein fibronectin in GEC by a mechanism involving expression of TGF-beta. Thus, accumulation of lipids in human glomerular epithelial cells may contribute to the pathogenesis of glomerulosclerosis through TGF-beta mediated mechanism(s).

To elucidate the pathogenetic role of hyperlipidemia per se in the development of glomerulosclerosis, severely hyperlipidemic female analbuminemic rats (NAR) and mildly hyperlipidemic male NAR were studied for a period of 37 weeks after uninephrectomy (UNX). Plasma cholesterol increased from 6.3 +/- 0.4 (week 4) to 11.9 +/- 0.6 mmol/liter (week 37) in the female NAR, and from 4.3 +/- 0.1 to 6.4 +/- 0.5 mmol/liter in the male NAR in the same period. Plasma protein concentration was also consistently higher in female NAR (60 +/- 1 g/liter) as compared to male NAR (52 +/- 1 g/liter). Plasma viscosity was higher in female NAR than in male NAR, but there were no differences in blood viscosity. Proteinuria increased progressively in the UNX female NAR from 25 weeks after surgery, reaching a final value of 141 +/- 37 mg/day. No proteinuria occurred in the UNX male NAR (final value 15 +/- 2 mg/day). Glomerular capillary pressure, measured prior to the onset of proteinuria, was not significantly different in UNX female NAR and UNX male NAR. At the end of the study glomerulosclerosis and lipid deposition was only found in the UNX female NAR. Throughout the study hyperfiltration and hyperperfusion, relative to the one-kidney clearances of the sham-operated (2K) animals, were not different in UNX male and female NAR. No differences were observed in blood pressure. Hypertrophy, evaluated by glomerular diameters, was less pronounced in UNX female NAR (174 +/- 3 microns) than in UNX male NAR (190 +/- 7 microns). Glomerular diameters in 2K female and male NAR were similar (respectively 158 +/- 2 and 157 +/- 4 microns). Plasma apo B levels were similar (2K female NAR: 204 +/- 8 U; 2K male NAR 204 +/- 13 U), but cholesterol and triglyceride content of apo B-containing lipoproteins, namely VLDL, IDL and LDL, was increased twofold in the female NAR as compared to the male NAR, implying a larger particle size in the female NAR. Deposition of apo B and apo E was observed in the glomerular mesangium of UNX female NAR, particularly in sclerotic lesions. Glomerular apo A-I deposits were localized primarily in visceral epithelial cells and were not associated with sclerotic lesions. The development of proteinuria and glomerulosclerosis after UNX in female NAR but not in male NAR may depend upon differences in plasma lipoprotein composition, but is apparently not related to differences in whole kidney hyperfiltration and hyperperfusion, glomerular capillary pressure, or blood viscosity.

The mechanisms underlying glomerular capillary wall injury in Wegener's granulomatosis (WG) are not well understood. Anti-neutrophil cytoplasmic antibodies (ANCA), present in sera from patients with WG, are known to stimulate respiratory burst and degranulation of primed polymorphonuclear neutrophils (PMN) in vitro. Experimental studies have shown that oxygen radical production and lysosomal enzymes are important mediators of glomerular capillary wall injury. In the present study we investigated the presence of activated PMN and the extracellular localization of lysosomal enzymes in 28 consecutive renal biopsies from patients with WG. The presence of activated PMN within the renal biopsies was compared with the capacity of ANCA, isolated from simultaneously drawn serum samples, to activate primed PMN obtained from a normal donor. Both parameters were also related to renal function. Renal biopsies were obtained from newly diagnosed WG patients before therapy had started. Activation of PMN in the biopsies was assessed by measuring hydrogen peroxide production in situ. The number of activated PMN in the biopsy correlated with the extent of impairment of renal function. Proteinase 3, myeloperoxidase, and elastase, all targets of ANCA, were localized extracellularly in renal tissue and were also found within tubular epithelial cells. All ANCA positive samples were capable of activating primed PMN. The amount of activation correlated with the ANCA titer in those samples. No correlation, however, was found between the in vitro capacity of ANCA-positive IgG fractions to activate primed PMN and the number of activated PMN present in the renal biopsy. We conclude that activated PMN producing toxic oxygen metabolites and releasing lysosomal enzymes, are present in renal biopsies from patients with WG. The amount of activated PMN present within the kidney, and not the capacity of the corresponding ANCA to activate PMN, correlates with renal tissue damage as assessed by serum creatinine levels.

Administration of puromycin aminonucleoside (PAN) to Wistar rats induces proteinuria and enhanced mesangial deposition of circulating macromolecules. After proteinuria of longer duration focal and segmental glomerular hyalinosis and sclerosis (FSGHS) develops. The present report analyzes these aspects of PAN nephrosis in PVG/c rats, a strain previously shown to be remarkably resistant to proteinuria and FSGHS with aging or after uninephrectomy. In Wistar rats multiple injections of PAN during five months resulted in sustained severe proteinuria and FSGHS lesions in 8.1 +/- 1.0% (mean +/- 1 SEM) of their glomeruli (N = 6). In PVG/c rats a 1.3-fold higher dose of PAN was needed to induce chronic proteinuria similar to the Wistar rats. After five months 3.3 +/- 0.9% of their glomeruli showed FSGHS (N = 6, P less than 0.01) and the glomerular lesions were considerably less advanced. In acute PAN nephrosis induced by a single intravenous injection of PAN the mesangium of Wistar rats contained large amounts of lipid in contrast to a few small mesangial lipid droplets in nephrotic PVG/c rats. After injection of colloidal carbon in nephrotic PVG/c rats no enhanced carbon accumulation was found in the mesangium when compared to nonproteinuric controls. This result clearly differs from the increased mesangial sequestration of circulating material in nephrotic Wistar, and most other rat strains. The unchanged mesangial traficking of macromolecules in nephrotic PVG/c rats and the low incidence of FSGHS lesions in the presence of sustained glomerular proteinuria may reflect a relative resistance to PAN-induced glomerular damage in this particular rat strain.