Mononuclear cells in glomeruli and cytokines in urine reflect the severity of experimental proliferative immune complex glomerulonephritis

Evaluation of Tubular Dysfunction Using Urine Biomarkers in Children with COVID-19

OBJECTIVE

The coronavirus disease pandemic is a major problem that the world has been facing since December 2019. It mainly affects the respiratory system; however, the disease can affect the kidneys to different degrees. This study aimed to determine the changes in tubular dysfunction and inflammation parameters in children with coronavirus disease using urine biomarkers.

MATERIALS AND METHODS

We included 36 children who tested positive for severe acute respiratory syndrome coronavirus 2 on real-time reverse transcriptase-polymerase chain reaction using respiratory specimens. Coronavirus disease-positive and -negative period parameters were evaluated. For measurement of interleukin-1β, interleukin-6, and urine β2 microglobulin levels, patients' urine samples were collected at diagnosis and 1 month after discharge. Additionally, routine urine and hematological parameters were evaluated concurrently.

RESULTS

For all patients, the median urine β2 microglobulin, serum urea, and lactate dehydrogenase levels were significantly higher in the coronavirus disease-positive period than in the coronavirus disease-negative period (P < .05). Further, serum platelet count was significantly lower in the coronavirus disease-positive period than in the coronavirus disease-negative period (P < .05). However, there was no difference in serum creatinine, interleukin-6, or interleukin-1β levels between the 2 periods (P > .05).

CONCLUSION

Our results suggest kidney involvement and tubular dysfunction in patients with asymptomatic, mild, and moderate infections. Furthermore, interleukin-1β and interleukin-6 levels were high in the urine, even in non-critically ill patients. We believe that these findings contribute to the accumulation of evidence on continued inflammation in the kidney.

AAV8-Mediated Angiotensin-Converting Enzyme 2 Gene Delivery Prevents Experimental Autoimmune Uveitis by Regulating MAPK, NF-κB and STAT3 Pathways

Renin angiotensin system (RAS) is a key hormonal system which regulates the cardiovascular function and is implicated in several autoimmune diseases. With the discovery of the angiotensin-converting enzyme 2 (ACE2), a protective axis of RAS namely ACE2/Ang-(1-7)/Mas that counteracts the deleterious ACE/AngII/AT1R axis has been established. This axis is emerging as a novel target to attenuate ocular inflammation. However, the underlying molecular mechanisms remain unclear. We investigated the hypothesis that enhancing the activity of the protective axis of RAS by subretinal delivery of an AAV8 (Y733F)-ACE2 vector would protect against the ocular inflammation in experimental autoimmune uveitis (EAU) mice through regulating the local immune responses. Our studies demonstrated that increased ACE2 expression exerts protective effects on inflammation in EAU mouse by modulating ocular immune responses, including the differentiation of Th1/Th17 cells and the polarization of M1/M2 macrophages; whereas the systemic immune responses appeared not affected. These effects were mediated by activating the Ang-(1-7)/Mas and inhibiting the MAPK, NF-κB and STAT3 signaling pathways. This proof-of-concept study suggests that activation of ocular ACE2/Ang-(1-7)/Mas axis with AAV gene transfer modulates local immune responses and may be a promising, long-lasting therapeutic strategy for refractory and recurrent uveitis, as well as other inflammatory eye diseases.

Genetic susceptibility to idiopathic membranous nephropathy in high-prevalence Area, Taiwan

Idiopathic membranous nephropathy (MN) is one common cause of idiopathic nephrotic syndrome in adults; 25% of MN patients proceed to end-stage renal disease. In adults, membranous nephropathy is a lead cause of nephrotic syndrome, with about 75% of the cases idiopathic. Secondary causes include autoimmune disease, infection, drugs and malignancy. Three hypotheses about pathogenesis have surfaced: preformed immune complex, in situ immune complex formation, and auto-antibody against podocyte membrane antigen. Pathogenesis does involve immune complex formation with later deposition in sub-epithelial sites, but definite mechanism is still unknown. Several genes were recently proven associated with primary membranous nephropathy in Taiwan: IL-6, NPHS1, TLR-4, TLR-9, STAT4, and MYH9 . These may provide a useful tool for diagnosis and prognosis. This article reviews epidemiology and lends new information on KIRREL2 (rs443186 and rs447707) polymorphisms as underlying causes of MN; polymorphisms revealed by this study warrant further investigation.

Effect of IL-6 C-572G polymorphism on idiopathic membranous nephropathy risk in a Han Chinese population

Membranous glomerulonephritis (MGN) is viewed as an immune-mediated glomerular disease, with immunologic expression occurring in genetically susceptible persons. The cytokine interleukin-6 (IL-6) gene polymorphism is known to impair intracellular signaling pathways following adaptive immune response. Our study gauged the effects of IL-6 C-572G (rs1800796) single nucleotide polymorphism (SNP) on MGN among Taiwan's Han Chinese population, as analyzed in 265 controls and 106 MGN patients. Genotyping for IL-6 C-572G SNP was performed by restriction fragment length polymorphism assay. Data showed stark differences in genotype and allele frequency distributions at IL-6 C-572G SNP between MGN patients and controls (p = 1.6E-04 and 1.7E-04, respectively). People with C allele or with CC genotype at IL-6 C-572G SNP showed higher risk of MGN (odds ratio = 2.42 and 2.71, respectively; 95% confidence interval = 1.51-3.87 and 1.60-4.60, respectively). These point to IL-6 C-572G polymorphism as the underlying cause of MGN; polymorphism merits further investigation.

Multi-glycoside of Tripterygium wilfordii Hook f. ameliorates proteinuria and acute mesangial injury induced by anti-Thy1.1 monoclonal antibody

BACKGROUND/AIMS

Multi-glycoside from Tripterygium wilfordii Hook f. (GTW) is used for various immune and inflammatory diseases including renal diseases represented by mesangial proliferative glomerulonephritis (MsPGN) in China. However, there have been no fundamental studies on the operating mechanism of GTW on MsPGN. The aim of this study is to examine as the first step the effects of GTW on acute injurious process such as mesangial injury and proteinuria in an acute and reversible Thy.1.1 glomerulonephritis (Thy1.1GN) model and then to clarify the action mechanism of GTW at molecular level by examining its effects on various injurious factors in this model.

METHODS

Thy1.1 GN was induced in rats by a single intravenous injection with 500 microg of anti-Thy1.1 mAb 1-22-3. Daily oral administration of GTW and vehicle as a control was started from 3 days before injection of mAb to the day of sacrifice in each experiment. Fourteen rats were randomly divided into 2 groups, GTW-treated and vehicle-treated groups, and sacrificed on day 14 in experiment 1 or on day 7 in experiment 2 after induction of Thy1.1 GN. Proteinuria was determined on days 1, 3, 5, 7, 10 and 14 in experiment 1 or on 1, 3, 5 and 7 in experiment 2. From blood and kidneys taken at sacrifice, blood biochemical parameters, mesangial morphological changes, glomerular macrophage infiltration, and glomerular mRNA expression of cytokines were examined.

RESULTS

In experiment 1, proteinuria and mesangial matrix expansion were significantly attenuated by GTW treatment. In experiment 2, GTW treatment significantly ameliorated proteinuria, mesangial lesions and macrophage accumulation in glomerulus. In addition, it significantly reduced the glomerular expression of mRNA for PDGF, MCP-1 and IL-2.

CONCLUSION

GTW ameliorated not only proteinuria but also mesangial alterations in Thy1.1 GN most likely by reducing expression of injurious cytokines, indicating that GTW has suppressive effects on acute inflammatory changes in glomeruli.

Fractalkine expression and the recruitment of CX3CR1+ cells in the prolonged mesangial proliferative glomerulonephritis

BACKGROUND

We established the reversible and the prolonged models of mesangial proliferative glomerulonephritis (GN) with anti-Thy 1 antibody 1-22-3. However, the essential factors leading to the prolonged glomerular alterations have not been identified.

METHODS

The expressions of several chemokines and cytokines were compared in the reversible and the prolonged models. Expression of fractalkine and the number of the fractalkine receptor CX3CR1-positive cells in the glomeruli in the prolonged model were significantly higher than those in the reversible model. Then, the localization of fractalkine and the characteristics of CX3CR1+ cells were analyzed in glomeruli. To elucidate the significance of the fractalkine expression, we analyzed the expression in the model treated with angiotensin II receptor antagonist, candesartan.

RESULTS

Immunostaining of fractalkine was detected on endothelial cells on the fifth day, and fractalkine staining also was detected in the mesangial area on day 14. Major parts of the CX3CR1+ cells in the glomeruli were macrophages, especially ED3+ cells. Candesartan treatment ameliorated the glomerular morphological findings at six weeks after disease induction. Although the treatment did not ameliorate the morphological finding at two weeks, decreased expression of fractalkine and CX3CR1+ were already detected at two weeks in rats treated with candesartan.

CONCLUSIONS

Fractalkine expression and the recruitment of CX3CR1+ cells in glomeruli might play an important role in the development of the prolonged disease. These expressions could be predictors of the prolonged disease of the mesangial proliferative glomerulonephritis.

FK506 ameliorates proteinuria and glomerular lesions induced by anti-Thy 1.1 monoclonal antibody 1-22-3

BACKGROUND

We have previously reported that CD4 T lymphocytes and their cytokines contribute to development of Thy 1.1 glomerulonephritis (GN). FK506 is reported to suppress the production of Th1 cytokines. The aims of this study were to elucidate the role of Th1 cytokines on mesangial alteration and to examine whether FK506 is available for therapy of mesangial proliferative GN.

METHODS

The effects of daily treatments of FK506 from day -5 and from day +1 of Thy 1.1 GN induction on glomerular alterations were analyzed.

RESULTS

FK506 treatment with 1.0 and 0.3 mg/kg body weight (BW) daily from day 1 to day 4 significantly reduced the glomerular expression of mRNA for interferon-gamma (IFN-gamma; 1.0 mg/kg BW FK506, 32.4% to the placebo group, P < 0.01) and IL-2 (55.6%, P < 0.01) on day 5. FK506 treatment from day -5 of GN induction reduced proteinuria and glomerular alteration in a dose-dependent manner. Although no side effects were detected in rats with 0.3 mg/kg BW of FK506 treatment from day +1, the treatment also ameliorated proteinuria (day 14, 3.7 +/- 0.89 vs. 19.8 +/- 12.3 mg/100 g BW/day P < 0.05) and glomerular alterations [total cell number, 63.1 +/- 3.1 vs. 80.2 +/- 7.4, P < 0.01; matrix expansion, 0.90 +/- 0.30 vs. 1.34 +/- 0.27, P < 0.05; alpha-smooth muscle actin (alphaSMA) expression; 1.20 +/- 0.12 vs. 1.96 +/- 0.29, P < 0.01] on day 14.

CONCLUSION

Th1 cytokines may play an important role in the development of mesangial proliferative glomerulonephritis, and could be targets for therapy. FK506 might be available for clinical use.

Pentoxifylline attenuates experimental mesangial proliferative glomerulonephritis

BACKGROUND

Accumulation of glomerular macrophages, proliferation of mesangial cells (MCs), and deposition of extracellular matrix proteins are pathobiological hallmarks of glomerulonephritis. We previously reported that a clinically available nonselective inhibitor of cyclic 3',5'-nucleotide phosphodiesterase, pentoxifylline (PTX), inhibits proliferation of cultured rat MCs, as well as collagen production by these cells. In this study, we investigated the in vivo effects of PTX on rat anti-Thy1 disease, a model of mesangial proliferative nephritis.

METHODS

Anti-Thy1 nephritis was induced in Sprague-Dawley rats by injecting mouse anti-rat Thy1 antibodies intravenously. Nephritic rats were randomly assigned to receive PTX (0.1 g/kg/day) or vehicle (phosphate-buffered saline) and were sacrificed at various time points. Paraffin kidney sections were stained with hematoxylin and periodic acid-Schiff reagents for glomerular histology. Frozen kidney sections were stained by monoclonal antibodies against proliferating cell nuclear antigen, ED-1, and alpha-smooth muscle actin and were visualized by color development from a horseradish peroxidase reaction. Monocyte chemoattractant protein-1 (MCP-1), intercellular adhesion molecule-1 (ICAM-1), and various extracellular matrix mRNAs were analyzed by Northern blotting. Urine protein concentrations were determined by Lowry's method.

RESULTS

Nephritic rats treated with PTX excreted less urinary protein on day 5 of nephritis than vehicle-treated nephritic rats. In periodic acid-Schiff-stained kidneys from PTX-treated nephritic rats, there was attenuation of both glomerular cellularity and glomerular sclerosis compared with vehicle-treated nephritic rats. PTX decreased the augmented glomerular mRNA levels of MCP-1 and ICAM-1 at two hours and on day 1 of nephritis. Immunoreactive staining showed that PTX reduced the number of proliferating glomerular macrophages on days 1, 2, and 3, but not at two hours of nephritis, compared with vehicle-treated nephritic rats. On day 5, PTX decreased the number of activated proliferating MCs and attenuated the glomerular mRNA levels of type I (alpha1), type III (alpha1), and type IV (alpha1) collagen and fibronectin compared with vehicle-treated nephritic rats.

CONCLUSION

The administration of PTX to rats with anti-Thy1 disease reduces accumulation and proliferation of glomerular macrophages, attenuates proteinuria, suppresses activation and proliferation of MCs, and ameliorates glomerular sclerosis. These results suggest that PTX may have a suppressive effect in acute phases or relapses of mesangial proliferative glomerulonephritis.

Adrenergic regulation of macrophage-derived tumor necrosis factor-alpha generation during a chronic polyarthritis pain model

Increases in the levels of proinflammatory cytokines, such as TNF alpha, have been intricately linked with arthritis and the pathogenesis of several models of neuropathic pain. In addition, arthritis (as well as other types of persistent pain) is associated with increased sympathetic activity and alterations of other responses in autonomic nervous activity. Adrenergic regulation of LPS-stimulated TNF production by M phi isolated from rats with streptococcal-cell-wall (SCW)-induced arthritis has been examined. Serum TNF levels and the cellular composition of peritoneal exudates have also been assessed. M phi were obtained from: (1) normal control rats, (2) animals injected with complete Freund's adjuvant (CFA), 3 rats injected with SCW and arthritic, and (4) those injected with SCW, which failed to develop arthritis. Serum levels of TNF alpha in rats that develop arthritis are significantly greater (2.4 fold) than levels from the other groups. The proportion of OX19-positive T cell subpopulations are the same in peritoneal exudates from all groups. Immunocytochemical staining also reveals differences between M phi subgroups in the degree of activation. Peritoneal exudates from rats that develop arthritis contain a greater proportion of the high TNF producing subclass of M phi, as identified by positive ED3 staining (p < 0.001). In contrast, Ia antigen presenting M phi (OX6-positive) in the peritoneal exudate cells are only elevated in rats administered CFA. The selective blockade of adrenergic receptors by idazoxan or propranolol demonstrates that the constitutive involvement of either alpha 2 or beta-adrenergic regulation of M phi-derived TNF production is pronounced in rats with arthritis (p < 0.001). These investigations demonstrate a distinctive pattern of peripheral M phi populations in rats that develop chronic polyarthritic pain. We believe that identification of interactions between the adrenergic responses and proinflammatory cytokines will lead to the development of improved strategies to treat patients with chronic pain.

Neuronal-associated tumor necrosis factor (TNF alpha): its role in noradrenergic functioning and modification of its expression following antidepressant drug administration

Tumor necrosis factor-alpha (TNF alpha) and the alpha 2-adrenergic agonist clonidine regulate norepinephrine (NE) release from noradrenergic nerve terminals in the central nervous system (CNS). In the present study, superfusion and electrical field stimulation were applied to a series of rat hippocampal brain slices in order to investigate the regulation of [3H]-NE release. NE release had been previously determined to be decreased by TNF alpha in a concentration-dependent manner, an effect which was potentiated by the alpha 2-adrenergic antagonist idazoxan. Presently, we demonstrate that similar to alpha 2-adrenergic activation, TNF alpha regulation of NE release in a region of the brain rich in noradrenergic nerve terminals, is dependent upon the frequency of electrical stimulation applied to the hippocampal slice. Furthermore, immunoperoxidase staining has verified our previous findings of constitutive TNF alpha protein in the rat brain. Staining for TNF alpha appears to be largely localized to neurons and neuronal processes, further substantiating the proposal that TNF alpha is either synthesized de novo or is accumulated in and released by neurons. After administration of the tricyclic antidepressant desipramine, tissue sections obtained from the rat hippocampus and locus coeruleus are devoid of neuronal-associated TNF alpha immunoreactivity. TNF alpha localization in neurons and its modification of NE release comparable to alpha 2-adrenergic receptor activation, explains a functional role for the cytokine as a neuromodulator in the CNS.

Podocytes are the major source of IL-1 alpha and IL-1 beta in human glomerulonephritides

To address the question of in situ production of IL-1 alpha and IL-1 beta in proliferative and non-proliferative forms of human glomerulonephritis (GN), we performed immunocytochemical and in situ hybridization studies on renal biopsies from patients with mesangial IgA-GN (N = 38), idiopathic membranous GN (MGN; N = 12), minimal change disease (MCD; N = 9), focal segmental glomerulosclerosis (FSGS; N = 5) and acute endocapillary GN (AGN; N = 3). Normal kidneys (N = 10) served as controls. Concomitantly, the expression of IL-1 receptor type I (IL-1 RI), IL-1 receptor type II (IL-1 RII) and of IL-1 receptor antagonist (IL-1 RA) was analyzed. Antibodies against antigens expressed on podocytes (PP-44), endothelial cells (CD31) and monocytes/macrophages (CD11b, CD14, CD68) were applied to attribute the expression of IL-1/IL-1 related peptides to intrinsic glomerular and/or blood-derived infiltrating cells. Our results demonstrate that IL-1 RII is constitutively expressed on endothelial cells, and its expression can be induced in proximal tubular cells and in the interstitium. In diseased glomeruli podocytes are capable of producing IL-1 alpha/beta. In MGN and MCD/FSGS, the expression of both IL-1 forms is particularly noted in early stages of the disease and is not only accompanied by a marked reactivity for IL-1 RI, but also for IL-1 RA. In segmental sclerosing lesions in FSGS and in IgA-GN with marked glomerular proliferation and/or sclerosis, a reduced expression of the PP-44 antigen and a diminished ability of podocytes to produce IL-1/IL-1 related peptides are noted. These results suggest that intrinsic glomerular production of IL-1 may be of relevance for the protection of glomeruli from continuing injury.

An orally active ETA/ETB receptor antagonist ameliorates proteinuria and glomerular lesions in rats with proliferative nephritis

The proliferation of mesangial cells and the extracellular matrix expansion constitute the most outstanding morphological aspects of the majority of progressive glomerular diseases. In vitro, endothelin-1 (ET-1) is mitogenic for mesangial cells and induces matrix protein synthesis. We studied the possible participation of ET-1 in the pathogenesis of renal damage in a normotensive model of proliferative nephritis. Coincidentally with maximal proteinuria and glomerular lesions, an increase was found in the glomerular mRNA expression of preproET-1 and the ETA receptor (10 and 6 times compared to controls, respectively), but not of the ETB receptor, and in ET-1 urinary excretion (217 +/- 33 vs. 84 +/- 4 pg ET-1/24 hr, N = 4 to 5, P < 0.05). By in situ hybridization, an increase in preproET-1 mRNA expression in glomerular endothelial, epithelial and mesangial cells, and in come tubular cells was observed. The administration of bosentan, an ETA/ETB receptor antagonist, had a beneficial effect on the evolution of nephritis preventing the appearance of intense proteinuria (76 +/- 35 vs. 380 +/- 77 mg/24 hr, N = 4 to 5, P < 0.05), the morphological lesions and the renal function impairment (creatinine clearance 367 +/- 46 vs. 268 +/- 33 microliters/min/100 g, N = 4 to 5). Simultaneously, there was a decrease in ET-1 urinary excretion (88 +/- 14 vs. 217 +/- 33 pgET-1/24 hr, N = 4,5, P < 0.05) and in the renal preproET-1 mRNA expression. The mean systolic blood pressures remained in the normal range in all animals. These data indicate that ET-1 participates in the pathogenesis of proteinuria and glomerular injury in a model of proliferative nephritis. The nonpeptidic orally active ETA/ETB receptor antagonists could be useful in the treatment of some human nephritis.

Interferon-inducible protein-10 is highly expressed in rats with experimental nephrosis

Interferon-inducible protein (IP)-10 is a small glycoprotein member of a family of chemotactic cytokines structurally related to interleukin-8. We have recently described the induction of IP-10 mRNA in mouse mesangial cells stimulated with lipopolysacharide, interferon-gamma, and tumor necrosis factor-alpha. To further evaluate a possible role for this chemokine in renal injury, we have studied IP-10 in an experimental model of nephrosis induced in rats by adriamycin. High levels of glomerular IP-10 mRNA expression and glomerular and tubulointerstitial IP-10 protein were seen on day 21, coinciding with maximal proteinuria, glomerular tumor necrosis factor mRNA expression, and interstitial cellular infiltrates. Maintenance on a low protein diet not only delayed the appearance of proteinuria and interstitial cellular infiltrate but also decreased glomerular IP-10 mRNA expression. Isolated normal glomeruli and cultured glomerular epithelial and mesangial cells from normal rats expressed IP-10 mRNA upon stimulation with 100 U/ml interferon or 1 microgram/ml lipopolysaccharide for 3 hours. IP-10 mRNA expression was also inducible by lipopolysaccharide and cytokines in NRK 49F renal interstitial fibroblasts and, to a lesser extent, in NRK 52E tubular epithelial cells. Furthermore, IP-10 protein was inducible in murine mesangial cells. We conclude that IP-10 is highly inducible in vitro and in vivo in resident glomerular and tubulointerstitial cells. IP-10 may participate in the modulation of renal damage in experimental nephrosis.

ACE inhibition reduces proteinuria, glomerular lesions and extracellular matrix production in a normotensive rat model of immune complex nephritis

We studied the effect of the angiotensin converting enzyme (ACE) inhibitor, quinapril, on the clinical and morphological lesions of a normotensive model of immune complex nephritis. Untreated rats developed massive nephrotic syndrome, intense cell proliferation and glomerular and tubulointerstitial lesions. In the renal cortex of nephritic rats there was a significant increase in gene expression of TGF-beta 1, fibronectin and collagens, and ACE activity. Systolic blood pressure remained normal with progression of the disease. Administration of quinapril for three weeks to animals with glomerular lesions (proteinuria 20 to 50 mg/day) avoided the development of intense proteinuria (79 +/- 28 vs. 589 +/- 73 mg/day, P < 0.001) and decreased cell proliferation, glomerulosclerosis, tubulointerstitial lesions, and inflammatory infiltrates. Cortical gene expression of TGF-beta 1 and matrix proteins was also diminished. ACE activity was inhibited by 68% in renal cortex. These results show that quinapril administration to normotensive rats with immune complex nephritis decreases proteinuria and glomerular and tubulointerstitial lesions, probably modulating the local angiotensin II generation and its effects on cell growth, TGF beta and matrix protein synthesis.

Fibronectin (FN) decreases glomerular lesions and synthesis of tumour necrosis factor-alpha (TNF-alpha), platelet-activating factor (PAF) and FN in proliferative glomerulonephritis

We have studied the effect of therapy with plasma FN on glomerular synthesis of PAF, TNF-alpha and FN, in experimental proliferative glomerulonephritis. Glomerular PAF, TNF-alpha and FN production were increased in rats with nephritis. Peak glomerular PAF production preceded, while peak glomerular TNF-alpha bioactivity coincided with maximal proteinuria. Rats treated with FN (5 mg/kg per 48 h) for 15 days had less proteinuria, glomerular and interstitial cell infiltration and glomerular PAF, TNF-alpha and FN synthesis than non-treated rats. In order to characterize further the mechanisms of action of FN, healthy rats were injected with either FN or saline. Peripheral blood mononuclear cells and neutrophils from healthy rats injected with FN secreted less TNF-alpha and PAF, respectively, than those obtained from saline-treated rats. Our data suggest that the beneficial effect of FN may be related to decreased number of glomerular leucocytes and decreased synthesis of inflammatory mediators and extracellular matrix.

Biosynthesis of C3 by human mesangial cells. Modulation by proinflammatory cytokines

Deposits of complement (C) components are found in the glomeruli of patients with various glomerulonephritides without detectable immunoglobulins, thus suggesting a pathogenetic role of the locally produced proteins of this system. In the present study, we have examined human mesangial cells (HMC) for their ability to secrete C3. Three different cell lines were examined and all showed a basal production of C3, which was up-regulated following stimulation with IL-1 beta. IL-6 had no direct stimulatory effect on its own, but synergized with IL-1 to induce an increased production of C3 in the culture supernatant and its relative amount was confirmed by SDS-PAGE and immunoblot. Another agonist such as lipopolysaccharide was not able to induce any significant C3 synthesis. Analysis of C3 HMC gene expression, performed by both reverse transcription-polymerase chain reaction of isolated RNA and Northern blot, confirmed the parallel increase of the specific transcript under IL-1 beta and IL-1 beta + IL-6 stimulation. From these data we conclude that production of C3 in the mesangium could have a pathophysiologic relevance.

Non-lymphoid and lymphoid cells in acute, chronic and relapsing experimental colitis

In rodents, intracolonic administration of ethanol 30% induces an acute colitis, while administration of 2,4,6-trinitrobenzene sulphonic acid (TNBS) in ethanol induces a longer lasting colitis. In the acute and chronic stages of experimental colitis, lymphoid and non-lymphoid cells were studied in the colon by immunohistochemistry. During the acute inflammation a high damage score of the colon was observed, which was related to an increase in the number of macrophages and granulocytes. Also a change in distributional patterns of macrophage subpopulations was found. The chronic stage of TNBS-ethanol-induced colitis was characterized by an increase in the number of lymphocytes, especially T cells. These data suggest that macrophages and granulocytes are important in the acute phase of experimental colitis, while lymphocytes play a pivotal role in the chronic stage. As most inflammatory bowel disease (IBD) patients have relapses during the chronic disease, we attempted to induce a relapse during experimental colitis by giving a second i.p. or s.c. dose of TNBS. This resulted in increased damage scores of the colon, new areas of ulceration and a further increase in macrophage numbers. No effect on the number of granulocytes was seen. These results indicate that it is possible to mimic relapses in experimental colitis by a second administration of TNBS, and suggest that the rats had been sensitized by the first dose of TNBS, given into the colon.

Glomerular macrophage phagocytic activity in experimental immune complex nephritis

In rats with the proliferative immune complex glomerulonephritis of chronic serum sickness, kidney function deteriorates in three clearly distinguishable and discrete stages: mild, moderate and severe. The macrophage component of glomerular inflammation in each stage is also quantitatively and qualitatively distinct, with abnormal phenotypic markers appearing in the moderate stage and increasing in the severe stage. To determine whether there were distinct functional differences among macrophages from the three stages, Fc gamma receptor-mediated phagocytic capacity was measured. The phagocytic capacity of glomerular macrophages increased significantly in the moderate stage, then significantly decreased, as rats progressed to severe chronic serum sickness. This decline in phagocytic function was not associated with a decrease in the expression of Fc gamma receptors on the glomerular macrophage cell surface. Furthermore, the phagocytic function of peritoneal macrophages from rats with severe chronic serum sickness was not impaired. Whether or not this attenuation of glomerular macrophage phagocytic capacity is the cause, or result, of renal disease progression remains unclear. It may indicate a potentially protective role for intraglomerular macrophages, and can serve as an additional functional marker of disease progression.

Effects of glomerular macrophages on mesangial cells in rat serum sickness glomerulonephritis: a comparison of histological and co-culture studies

Effects of glomerular macrophages on mesangial cell proliferation at different stages of experimental serum sickness nephritis (SSN) in the rat were examined using a direct co-culture system. The results were compared with the manifestations of glomerular tissue at the same points in time during the course of the SSN, especially with regard to glomerular infiltration and glomerular cell proliferation. Macrophages were isolated from the glomeruli at different points in time during the course of the SSN. While the number of glomerular macrophages increased during the sensitization, the proliferating cell nuclear antigen/cyclin positivity of the glomerular tissue was increased after cessation of the antigenic sensitization. The effect of macrophages on mesangial cell proliferation was relatively diminished during the sensitization but was augmented thereafter. Proliferating cells were mostly attached by macrophages, suggesting the importance of the proximity of macrophages for mesangial proliferation. These results suggest that mesangial cell proliferation is largely influenced by macrophage function variability in the glomeruli during the course of SSN.

Tumor necrosis factor alpha from peripheral blood mononuclear cells of IgA nephropathy and mesangial cell proliferation

BACKGROUND

To investigate the role of mononuclear cells and their products on rat mesangial cell proliferation, we evaluated the effect of peripheral blood mononuclear cells (PBMC) culture supernatant of patients with IgA nephropathy on rat mesangial cells 3[H]-thymidine uptake, and measured the concentration of cytokines in the supernatant to find out which cytokine in PBMC culture supernatant has a major influence on mesangial cell 3[H]-thymidine uptake.

METHODS

In ten patients with primary IgA nephropathy and 10 normal controls, PBMC were cultured with PHA (20 micrograms/ml) and con-A (10 micrograms/ml) for 24 hours, and supernatants were collected and stored at -70 degrees C until tested. Mesangial cell was cultured for 48 hours at a concentration of 10(4) cells/well with 1:2 or 1:10 diluted PBMC culture supernatant. 3[H]-thymidine uptake into rat mesangial cell was assayed after 18 hour culture. The cytokine concentrations of PBMC culture supernatant were measured by radioimmunoassay.

RESULTS

When 1:2 diluted PBMC culture supernatant was added, the supernatant of IgA nephropathy induced higher 3[H]-thymidine uptake into mesangial cell compared with that of normal controls. 3[H]-thymidine uptake induced by 1:2 diluted PBMC culture supernatant was significantly higher than that induced by 1:10 diluted supernatant of IgA nephropathy. The concentration of TNF-alpha in PBMC culture supernatant of the patients with IgA nephropathy was higher than that of normal controls and showed a good correlation with the mesangial cell 3[H]-thymidine uptake.

CONCLUSION

It is suggested that the mononuclear cell of IgA nephropathy may have the intrinsic property to produce more TNF-alpha which may be mitogenic to mesangial cells when stimulated with mitogens, and it may be related to the mesangial cell proliferation in IgA nephropathy.

Macrophage populations in different stages of induced hepatic metastases in rats: an immunohistochemical analysis

Macrophages play a role in the host defence against cancer. Little is known about changes in macrophage populations during early metastatic growth. To evaluate the distribution, number and phenotype of macrophages in the development of hepatic metastases in a rat model (Wag/Rij rats and syngeneic CC531 colon carcinoma cell line), an immunohistochemical study was performed with the monoclonal antibodies ED1 (monocytes, and all macrophages), ED2 (resident tissue macrophages, like Kupffer cells) and ED3 (a subpopulation of macrophages which may play a role in the recruitment of lymphocytes). OX19 and His14 were used to identify lymphocytes. In this study a new monoclonal antibody CC52 is described, which recognizes the CC531 tumour cell line. Liver metastases were induced by injection of CC531 colon carcinoma cells into a mesenteric vein. Rats were killed at various intervals. Results show three major macrophage populations during hepatic tumour growth: (1) on day 3, infiltrates are observed around the micrometastases, which contain mainly newly recruited macrophages (ED1+ and ED2-); (2) after 7 days, ED3-positive (ED3+) macrophages together with T lymphocytes are found in the infiltrates; (3) an increase in the number of ED2-positive (ED2+) Kupffer cells is observed in the liver parenchyma after 14 days. In conclusion, the present results suggest that various populations of macrophages, newly recruited (ED1+) as well as resident Kupffer cells (ED2+), are involved in the immune response against tumour cell deposits in the liver.

Elevated levels of tumor necrosis factor-alpha in the nephrotic syndrome in humans

To investigate the possible role of cytokines in the mediation of glomerular injury in the nephrotic syndrome, the levels of interleukin (IL)-1 beta, IL-2, interferon (IFN)-alpha, IFN-gamma, and tumor necrosis factor-alpha (TNF-alpha) were measured in patients with primary nephrotic syndrome. These patients had minimal change nephropathy (MCN), focal and segmental glomerulosclerosis (FSGS), or membranous nephropathy (MN) on biopsy. Cytokine levels were assessed by immunoradiometric assays, and specimens consisted of plasma, urine, and the culture supernate of mitogen-stimulated peripheral blood mononuclear cells (PBMC). Only TNF-alpha was found to be significantly elevated, in the plasma and urine of patients with FSGS and MN, above that found in healthy control subjects and patients with MCN. The elevation of TNF-alpha could not be shown to correlate with the length or severity of the nephrotic syndrome or with loss of body mass. IL-1 beta, IL-2, IFN-alpha, and IFN-gamma levels were not elevated. In culture, mitogen-stimulated PBMC from all three groups of nephrotic subjects released an excess of TNF-alpha compared with controls, a response not consistently observed for the other cytokines measured. The findings of this survey of cytokine levels in nephrotic patients support the possibility that TNF-alpha may play a pathogenic role in the induction or maintenance of glomerular barrier dysfunction in humans.

Immunohistology of joint inflammation induced in rats by cell wall fragments of Eubacterium aerofaciens

After a single intraperitoneal injection of cell wall fragments of Eubacterium aerofaciens, a main resident from the human intestinal flora, an acute arthritis develops within 2 days which is followed by a chronic arthritis that lasts at least 90 days. In an earlier report the histological appearance of the joint inflammation during this period has been described. In this study we investigated in more detail the cell types that are involved in the development of arthritis by using cell-type-specific monoclonal antibodies in an immunohistological assay. In the acute phase of arthritis, T-helper cells appeared in the synovial tissue together with ED1-positive (ED1+) and ED3-positive (ED3+) macrophages. After a temporary decline at day 12 all macrophage subsets, as well as T-helper cells, reappeared or increased again at day 33. Later, in the chronic phase (days 47-90), an increased number of ED1-positive (ED1+) cells in the synovial tissue and a decreased number of ED2-positive (ED2+) cells in the synovial lining was the most prominent finding when compared with control rats. These results indicate that, apart from T lymphocytes, macrophages also play an important role in the development and continuation of chronic arthritis in this model.

Adhesion promotes transcellular leukotriene biosynthesis during neutrophil-glomerular endothelial cell interactions: inhibition by antibodies against CD18 and L-selectin

Eicosanoid formation by transcellular routes can amplify the levels and types of lipid mediators within a local milieu. To evaluate the role of adhesion in this process, we assessed the influence of mAb against adhesion molecules on LTC4 generation by PMN-endothelial cell interaction. Transcellular LTC4 generation was initiated by addition of fMLP to coincubations of GM-CSF-primed PMN and TNF-activated endothelial cells cultured from kidney glomeruli. Both PMN-endothelial cell adhesion and transcellular LTC4 generation were inhibited by mAb against leukocyte L-selectin and CD18. These results indicate that cytokine-treated PMN and endothelial cells generate LTC4 via transcellular routes by receptor-triggered mechanisms. They suggest that adhesion promotes transcellular eicosanoid biosynthesis and that adhesion molecules may also be targets for blockade of transcellular biosynthesis of lipid mediators.

Extrarenal cytokines modulate the glomerular response to IgA immune complexes

Clinical episodes of IgA nephropathy coincide recurrently with microbial infections. Cytokines produced during such infections may play a role in the pathogenesis of IgA-associated glomerulonephritis. To test this hypothesis, we examined the influence of passively administered proinflammatory cytokines (IL-1, IFN-gamma and IL-6) on the development of glomerulonephritis in an experimental model of IgA nephropathy. Glomerular IgA immune deposits were induced in mice by administration of IgA anti-phosphorylcholine (PC) with either a PC-containing carbohydrate antigen of Pneumococcal C polysaccharide (PnC) or a protein antigen of PC-conjugated bovine serum albumin (PC-BSA). The effect of IL-1 on the IgA-PC-BSA induced glomerular changes resulted in an increase of mesangial hypercellularity that was associated with mild proteinuria and hematuria. Mice treated with IL-1 and IgA-PnC developed diffuse proliferative glomerulonephritis with proteinuria and hematuria. In contrast, IL-6 treatment with IgA-PC-BSA of IgA-PnC failed to exert any significant renal effect. The combination of IL-6 and IL-1, however, intensified the mesangial hypercellularity of the IgA-PC-BSA, and induced severe proliferative glomerulonephritis with inflammatory monocytes and neutrophils infiltrates in the IgA-PnC treated mice. These glomerular changes were also accompanied by increased proteinuria and hematuria. Similarly, the combination of IFN with IL-1 produced histologic changes and compromised renal function more than IFN or IL-1 exerted independently. These results suggest that extrarenal cytokines influence the renal response to IgA immune deposits. We also conclude that a synergy of multiple cytokines and nephritogenic antigens immobilized in glomerular IgA immune deposits may lead to rapid progression of IgA-associated glomerulonephritis.

Macrophage subpopulations and reticulum cells in rat placenta. An immunohistochemical study

The placenta is a unique mixture of histoincompatible cells derived from mother and fetus. The aim of the present study was to obtain information on the development of macrophage subpopulations and reticulum cells during pregnancy in the placenta. Placentas of Wistar rats were removed at several stages of gestation, and were studied by immunohistochemical techniques applying monoclonal antibodies against macrophage subpopulations, lymphoid cells and reticulum cells. The expression of MHC class-II antigens was also studied. Throughout gestation macrophages were demonstrable in large numbers in the endometrium, in the myometrium and in the metrial gland, which is a compartment developing in the myometrium of pregnant rodents. In the labyrinth, a placenta compartment consisting of fetal cells, macrophages (probably of fetal origin) were already found on day 15. In the spongiotrophoblast and decidua basalis, which are layers of the placenta containing both maternal and fetal cells, only a few macrophages were recognized throughout gestation. The monoclonal antibody ED11, raised against reticulum cells, recognized fiber-like structures lining the blood sinuses of the spongiotrophoblast, in which only maternal blood is circulating. As the antigen recognized by ED11 is believed to play a role in the trapping of immune complexes, the spongiotrophoblast may play a role in the protection of the fetus from circulating immune complexes.

Expression of the ED3 antigen on rat macrophages in relation to experimental autoimmune diseases

Susceptibility to experimental autoimmune diseases (EAD) is rat strain dependent. Susceptible animals are reported to have a defective glucocorticoid response. Although many EAD are regarded as preferentially T cell-mediated, macrophages (M phi) play an important role in several different stages of these diseases. In this study we have investigated the possible effect of the disturbed hypothalamic-pituitary (HPA) axis on M phi phenotype. Therefore we studied M phi differentiation in several different rat strains, especially with regard to the M phi specific differentiation antigen as recognized by monoclonal antibody (mAb) ED3. This mAb is, in normal healthy rats, reactive with very restricted M phi subpopulations present in the lymphoid organs only. However, in autoimmune diseased tissues many of the infiltrated M phi are also ED3-positive. It appeared that M phi, in vitro derived from monocytes out of susceptible rat strains, showed a high ED3 expression in contrast to monocyte-derived M phi out of resistant rat strains. This difference in ED3 expression appeared to be T cell-mediated. Our results are suggestive for the fact that the impaired HPA-axis in EAD susceptible rat strains affects M phi differentiation. The relevance of the observed differences with respect to disease induction, maintenance, or suppression is discussed and obviously needs further investigation.

Increased excretion of soluble interleukin 2 receptors and free light chain immunoglobulins in the urine of patients with active lupus nephritis

Samples of protein from the urine of 23 patients with lupus nephropathy and 15 patients with proteinuria who did not have systemic lupus erythematosus (SLE) were studied for the presence of cytokines, soluble interleukin 2 receptors (sIL-2R), and free light chain immunoglobulins. The patients with lupus nephropathy were divided into two groups with active (nephritis) and inactive inflammation (nephrosis) based on the results of the analysis of urine samples and renal histology. The crude urine proteins (5 mg/ml) after precipitation by 80% ammonium sulphate from 14 patients with lupus nephritis contained higher concentrations of sIL-2R (4.88 (SEM 1.27 ng/ml) than those from nine patients with nephrosis (1.11 (0.52) ng/ml) or 15 patients without SLE (1.31 (0.87) ng/ml). The concentration of sIL-2R in protein from urine samples was not correlated with the concentration in plasma and was inversely correlated with the excretion of protein in urine over 24 hours in patients with SLE. It is suggested that, in addition to leakage from the circulation, the local production of sIL-2R by inflamed kidneys is possible. The crude proteins in urine were further fractionated by gel filtration on Sephacryl S-200. Arbitrarily, four fractions could be obtained from urine from patients with SLE but only three fractions were found in the urine of patients without SLE. Fraction IV derived from patients with nephritis or nephrosis augmented the pokeweed mitogen induced [3H]thymidine uptake of mononuclear cells. In addition, the positive rates of free kappa (kappa) (35.7%) and lambda (lambda) (42.9%) chains in proteins in urine from nephritic patients were higher than those in the other two groups. These results suggest that the severity of inflammation in the kidneys of patients with lupus can be reflected by the increased excretion of sIL-2R, free light chain immunoglobulins, and cytokine-like molecules in urine.

Macrophages in experimental autoimmune diseases in the rat: a review

In the pathogenesis of most experimental autoimmune diseases T lymphocytes play a crucial role in the initiation, whereas macrophages are essential in the effector phase. This review deals with several methods to elucidate the exact role macrophages play in different stages of autoimmune models in the rat. By using monoclonal antibodies an inventory has been made on the different macrophage subsets that are present in the infiltrates of the affected tissues. That macrophages play a decisive role in provoking the clinical signs has been shown by several macrophage elimination studies. The severe tissue damage caused by macrophages is brought about by the release of inflammatory mediators. Especially interference with the production or action of these products could provide new therapeutical means.

Progressive glomerular injury after recovery from acute glomerulonephritis in rats

To determine if an acute immunologic injury resembling poststreptococcal nephritis could lead to chronic renal injury, rats with immune-complex glomerulonephritis produced with cationic human gammaglobulin were followed for 48 weeks. During Week 1, animals developed severe proteinuria, hypoalbuminemia, and a diffuse proliferative/exudative glomerulitis. Substantial recovery, characterized by a significant decline in urinary protein excretion and normalization of plasma albumin concentration, occurred by Week 4. Subsequently, rats developed significantly elevated blood pressures and increasing proteinuria. Glomerular histology at Week 48 revealed minimal inflammation, significant hypertrophy, and considerable sclerosis. We conclude that chronic, progressive renal disease can evolve after apparent recovery from an acute immunologic insult. Further study of this model should provide clinically relevant information about the mechanisms underlying this process.

Urinary IL-6: a marker for mesangial proliferative glomerulonephritis?

A prospective study of plasma and urinary interleukin-6 (IL-6) levels was performed in 54 patients undergoing renal biopsy to determine whether detectable urinary IL-6 was a reliable marker for mesangial proliferation. Interleukin-6 was found in both the urine and plasma of seven patients, the urine alone of 15 patients, and the plasma alone of two patients. Interleukin-6 was not detected in the urine or the plasma of the remaining 30 patients, the urine of 10 healthy controls or the urine of 10 patients with rheumatoid arthritis with raised plasma IL-6. Interleukin-6 was found in the urine of only one out of an additional seven patients with lupus nephritis. Urinary IL-6 was associated with a variety of renal abnormalities and was not restricted to those with mesangial hypercellularity. Furthermore, many patients with mesangial hypercellularity did not have detectable urinary IL-6. There was no correlation between urinary IL-6 and plasma IL-6, urinary albumin excretion or urinary creatinine. These results suggest that IL-6 detected in the urine is a marker of renal IL-6 production, but not specifically of mesangial hypercellularity. The patients with IL-6 in the urine had a mean serum creatinine significantly higher than those without IL-6. It is not possible to distinguish at present whether IL-6 contributes to renal dysfunction or whether it reflects renal damage.

Glomerular macrophage proliferation in experimental immune complex nephritis

In immune complex nephritis, glomerular hypercellularity is known to result from the proliferation of intrinsic cells and from the infiltration of mononuclear cells, primarily macrophages. An immunohistochemical double-labeling procedure was used to determine whether macrophages were among the cells which may undergo mitosis within the glomerular tuft. The monoclonal antibody ED1 served as a macrophage marker; cells in the S-phase of mitosis were recognized by uptake of bromodeoxyuridine. Glomerular proliferation was studied in chronic serum sickness of LEW rats, an animal model of immune complex nephritis for which the relationship between immunopathology and pathophysiology has been well described. In normal glomeruli, resident mesangial macrophages accounted for an unexpectedly large proportion (greater than or equal to one-third) of the total mitotic activity. In immune complex glomerulonephritis, the rate of glomerular macrophage proliferation increased rapidly just at the onset of proteinuria and remained high throughout the remaining course of disease. Glomerular macrophages from rats with proliferative nephritis also divided more vigorously than normal in short term culture in vitro, while persistently expressing abnormal surface marker phenotypes. The proliferation of mesangial macrophages appears to be a prominent feature of the normal process of glomerular cell renewal. In hypercellular glomeruli, vigorous local proliferation could greatly amplify the potential of macrophages to cause damage.

Enalapril and renal injury in spontaneously hypertensive rats

Rats of the spontaneously hypertensive strain develop kidney damage that resembles the nephropathy seen in some cases of human essential hypertension. Previous studies with a triple drug antihypertensive regimen indicated that proteinuria and glomerular histopathology in spontaneously hypertensive rats might develop despite long-term effective control of systemic blood pressure. To investigate further the relation between hypertension and kidney disease, a group of spontaneously hypertensive rats were treated with enalapril at 15 weeks of age. Blood pressure, protein excretion, and kidney function were measured in those rats at regular intervals during the next year and a half and were compared with untreated spontaneously hypertensive rats and the normotensive Wistar-Kyoto parent strain. Kidney tissue samples from all three groups, collected at autopsy, were stained by immunohistochemical and conventional methods to assess the relative severity and nature of kidney damage. Although enalapril therapy was completely effective in controlling the blood pressure of spontaneously hypertensive rats, it only postponed the onset of kidney disease. Enalapril-treated spontaneously hypertensive rats eventually exhibited albuminuria as severe as that found in hypertensive rats. Kidney vessel pathology was completely prevented with enalapril, but the abnormal accumulation of mononuclear cells in tubulointerstitial and periglomerular sites was the same as in untreated spontaneously hypertensive rats. We have concluded that elevated protein excretion in rats of the spontaneously hypertensive rat strain is not a secondary consequence of systemic hypertension. Structural abnormalities of renal vessels also do not appear to contribute significantly to the pathogenesis of albuminuria in spontaneously hypertensive rats. Other explanations must be sought to account for the close link between spontaneous hypertension and kidney damage in this animal model. The clear dissociation of kidney disease from systemic hypertension exhibited by spontaneously hypertensive rats may also be relevant for human disease.