Conserved synteny between the chicken Z sex chromosome and human chromosome 9 includes the male regulatory gene DMRT1: a comparative (re)view on avian sex determination

Sex-determination mechanisms in birds and mammals evolved independently for more than 300 million years. Unlike mammals, sex determination in birds operates through a ZZ/ZW sex chromosome system, in which the female is the heterogametic sex. However, the molecular mechanism remains to be elucidated. Comparative gene mapping revealed that several genes on human chromosome 9 (HSA 9) have homologs on the chicken Z chromosome (GGA Z), indicating the common ancestry of large parts of GGA Z and HSA 9. Based on chromosome homology maps, we isolated a Z-linked chicken ortholog of DMRT1, which has been implicated in XY sex reversal in humans. Its location on the avian Z and within the sex-reversal region on HSA 9p suggests that DMRT1 represents an ancestral dosage-sensitive gene for vertebrate sex-determination. Z dosage may be crucial for male sexual differentiation/determination in birds.

Effect of immunoglobulin G from patients with Graves' ophthalmopathy and interferon gamma in intercellular adhesion molecule-1 and human leucocyte antigen-DR expression in human retroocular fibroblasts

OBJECTIVE

To detect the expression of intercellular adhesion molecule-1 (ICAM-1) and human leucocyte antigen-DR (HLA-DR) on retroocular fibroblasts (RFs) by immunoglobulin G (IgG) from patients with Graves' ophthalmopathy (GO) and interferon gamma (IFN-gamma) and to study the possible mechanism of humoral immunity and cellular immunity in the pathogenesis of GO.

METHODS

Purified IgG was obtained from 23 patients (GO 10, Graves' disease 9, toxic multinodular goiter 4) and 8 normal persons. Cytokine IFN-gamma and thyroid stimulating hormone (TSH) were incubated with normal human RF cultured in vitro. Antigen expression on RFs induced by stimulators was examined using immunofluoresence staining and a flow cytometer.

RESULTS

RFs spontaneously expressed ICAM-1, but did not express HLA-DR. All IgGs from patients with GO and other thyroid diseases as well as from normal persons could not stimulate the expression of ICAM-1 on RFs. IFN-gamma and TSH significantly enhanced the expression of ICAM-1 in dose-dependent manner (P < 0.05). Only IFN-gamma could stimulate RFs to express HLA-DR (P < 0.05).

CONCLUSIONS

IgG from patients with GO did not stimulate the expression of ICAM-1 and HLA-DR on the surface of cultured normal human RFs. IFN-gamma was the important factor for intiating and promoting autoimmune reactions in GO. We need to pay more attention to TSH, as it may possibly play a promoting role in the pathogenesis in GO.

FISH mapping of the sex-reversal region on human chromosome 9p in two XY females and in primates

Accumulating evidence suggests that haploinsufficiency of a dosage-sensitive gene(s) in human chromosome 9p24.3 is responsible for the failure of testicular development and feminisation in XY patients with monosomy for 9p. We have used molecular cytogenetic methods to characterise the sex-reversing 9p deletions in two XY females. Fluorescence in situ hybridisation (FISH) with YACs from the critical 9p region containing an evolutionarily conserved sex-determining gene, DMRT1, is a very fast and reliable assay for patient screening. Comparative YAC mapping on great ape and Old and New World monkey chromosomes demonstrated that the critical region was moved from an interstitial position on the ancestral primate chromosome to a very subtelomeric position in chimpanzee and humans by a pericentric inversion(s). Pathological 9p rearrangements may be the consequence of an evolutionary chromosome breakpoint in close proximity to the sex-reversal region.

Expression of ICAM-1, B7.1 and TPO on human thyrocytes induced by IFN-alpha

OBJECTIVE

To detect expression of intercellular adhesion molecule-1 (ICAM-1), B7.1 and thyroid peroxidase (TPO) on thyrocyte and study the possible mechanism of interferon-alpha (IFN-alpha) in the pathogenesis of autoimmune thyroid disease (AITD).

METHODS

Thyrocytes were cultured from 6 normal persons. Antigen expression on thyrocytes induced by cytokines was examined using immunofluorescence staining with flow cytometer.

RESULTS

IFN-alpha significantly stimulated the expression of ICAM-1, B7.1 and TPO, as compared with those of control group. IFN-gamma markedly enhanced the expression of HLA-DR and ICAM-1, but not B7.1. Prolactin (PRL) resulted in increased expression of ICAM-1, B7.1, as well as overexpression of TPO, which is more significant than that stimulated by IFN-alpha.

CONCLUSIONS

Thyroid autoimmunity induced by IFN-alpha is associated with the expression of ICAM-1, B7.1 and TPO. IFN-gamma could not induce the expression of B7.1, therefore it is not an initiator in AITD. In addition, we should pay more attention to PRL which possibly plays an important role in the initiation and perpetuation of postpartum thyroiditis.

[Clinical study of weishu capsule in treating precancerous lesions of chronic atrophic gastritis]

OBJECTIVE

To explore the therapeutic effect and mechanism of Weishu capsule (WSC) in treating precancerous lesions of chronic atrophic gastritis (CAG).

METHODS

Seventy-five cases of precancerous lesions of CAG were distributed to two groups randomly, the treated group (45 patients) treated with WSC by taken orally and the control group (30 patients) treated with Weining granule (WNG) orally. The treatment course of both groups were 6 months. The clinical and pathological effects and the changes in scores of atrophy, intestinal metaplasia and its subgroups, dysplasia, carcinoembryonic antigen (CEA) and proliferating cell nuclear antigen (PCNA) expression were observed before and after treatment.

RESULTS

The total effective rate was 91% and the effective rate of atrophy, intestinal metaplasia, dysplasia in the treated group were 64%, 67% and 65% respectively, and the respective scores were lowered significantly after treatment. Compared with the control group the difference between the two groups was statistically significant (P < 0.01, P < 0.05). Immunohistochemical test showed that WSC could inhibit the subgroups of intestinal metaplasia, CEA and PCNA expression significantly (P < 0.01).

CONCLUSION

WSC could significantly improve the clinical and pathological changes in the precancerous lesions of CAG. The mechanism might be related to the inducing and promoting effect of WSC on the differentiation and maturity of intestinal metaplasia cells and dysplasia cells. WSC could also inhibit and correct the abnormal proliferation of cells.

[Correlation of expression of connexin 43 and cardiomyocyte hypertrophy]

OBJECTIVE

To study the relationship between the expression of connexin 43 and cardiomyocytes hypertrophy.

METHODS

Cardiomyocytes were isolated from newborn Wistar rats. Norepinephrine (NE) or phenylephrine (PE) were added into the media to induce myocyte hypertrophy. Immunohistochemistry methods were used to identify the expression of connexin 43, proliferating cell nuclear antigen (PCNA) and cycline dependent kinases (cdc-2). The amount of connexin 43 expression was detected by computer imaging analysis system MIPS.

RESULTS

In the groups which had PE or NE added, the myocytes expressed lower connexin 43 and higher PCNA levels than the control group's. But the expression of cdc-2 was unchanged.

CONCLUSION

The reduced expression of connexin 43 was related to its entrance into S phase of the cell cycle. This may explain the mechanism of cardiomyocyte hypertrophy.

Role of the nerve in determining fetal skeletal muscle phenotype

To determine the role of the nerve on the establishment of myofiber diversity in skeletal muscles, the lumbosacral spinal cord of 14-day gestation mice (E14) was laser ablated, and the accumulation of the myosin alkali light chains (MLC) mRNAs in crural (hindleg) muscles was evaluated just prior to birth with in situ hybridization. Numbers of molecules of each alkali MLC/ng total RNA in the extensor digitorum longus (EDL) and soleus muscles were determined with competitive polymerase chain reaction. Transcripts for all four alkali MLCs accumulate in aneural muscles. Data suggest that: (1) the absence of the nerve to either future fast or slow muscles results in less accumulation of MLC1V transcript. Moreover, the presence of the nerve is required for the enhanced accumulation of this transcript in future slow muscles; (2) the absence of innervation of future slow, but not fast, muscles decreases the accumulation of MLC1A transcript. Since increased accumulation of MLC1A and MLC1V transcripts are found in future slow muscles at birth, the nerve is necessary for the development of the slow phenotype during myogenesis; (3) MLC1F and MLC3F transcripts do not display any preferential accumulation in future fast muscles during the fetal period. Therefore, the establishment of the differential distribution of these mRNAs, based on fiber type, is a postnatal phenomenon. The nerve is required during the fetal period to allow accumulation of MLC3F messages above a basal level in future fast as well as slow muscles; whereas, the absence of the innervation to future fast, but not slow, muscles reduces the accumulation of MLC1F. Thus, the accumulation of the various alkali MLC mRNAs shows a differential, rather than coordinate, response to the absence of the nerve, and this response may vary depending on the future fiber type of the muscles.

A SPGY copy homologous to the mouse gene Dazla and the Drosophila gene boule is autosomal and expressed only in the human male gonad

We have isolated a series of human testis poly(A) cDNA clones by cross-hybridization to SPGY1, a Y gene homologous to DAZ. Their sequence analysis revealed an identical nucleotide composition in different 'full-length' clones, suggesting that all were encoded by the same gene. We mapped this gene to the short arm of chromosome 3 and designated it SPGYLA (SPGY like autosomal). Comparison of the SPGYLA cDNA sequence with the cDNA sequences of DAZ and SPGY1 revealed two prominent differences. The tandem repetitive structure of 72 bp sequence units (DAZ repeats) is absent. SPGYLA contains only one 72 bp sequence unit. Downstream of it, a specific 130 bp sequence domain is present which is absent in DAZ and SPGY1 but present in the mouse gene Dazla and in the Drosophila gene boule. SPGYLA encodes an RNA binding protein expressed only in the human male gonad. The data presented give strong evidence that not DAZ but SPGYLA is the functional human homologue of Dazla and boule.

[Effects of human interferon-alpha on periphral blood mononuclear cells of the patients with autoimmune thyroid disease]

Interferon-alpha (IFN-alpha) therapy for hepatitis and malignant tumor frequently results in autoimmune thyroid disease (AITD); this fact indicates an association of IFN-alpha with autoimmunity. In order to study the mechanism, an investigation of the effects of human IFN-alpha on T cells, T cell subpopulations, B cells, macrophages and natural killer cells of patients with AITD and normal controls was carried out. It has been found that T cells were inhibited by IFN-alpha with dosage dependency, particularly the T suppressor (CD8/CD11b) in both the patients with AITD and normal controls. An increase in number of B cells and macrophages with stimulation of IFN-alpha was also found in both groups. The results suggest that the decrease of suppressive T cells and increase B cells and macrophages may be responsible for IFN-alpha induced autoimmunity.

Morphine-induced macrophage activity modulates mesangial cell proliferation and matrix synthesis

Glomerular mesangial injury is the predominant renal lesion in patients with heroin addition. We studied the effect of morphine (an active metabolite of heroin)activated macrophages on mesangial cell (MC) proliferation and matrix synthesis. We prepared conditioned media containing either vehicle along (CSP), macrophage secretory products (MSP) and secretory products of morphine treated macrophages (M-MSP), M-MSP increased (P < 0.01) the proliferation of MC when compared with MSP alone. M-MSP increased synthesis of laminin by MC at concentrations of 10 to 50% when compared with cells treated with MSP alone (at 50% concentration, MSP, 126 +/- 19 vs. M-MSP, 312 +/- 14 ng/mg protein, P < 0.001). M-MSP also increased the synthesis of collagen type IV by MC. This effect of M-MSP was attenuated (P < 0.05) by anti-TGF-beta antibodies. Since M-MSP also increased mRNA expression for TGF-beta by MC, it appears that the effected of M-MSP on MC may be mediated through the generation of TGF-beta.

Morphine modulates migration of monocytes

Macrophages seem to play an important role in the development of glomerulosclerosis. In the present study we evaluated the effect of morphine, an active metabolite of heroin, on the migration of monocytes across a filter in a modified Boyden chamber. Morphine-mesangial cell interaction enhanced (p < 0.004) the migration of monocytes across the filter (control 14.2 +/- 0.6 vs. morphine 22.1 +/- 1.7 monocytes/HPF). Dimethylthiourea (DMTU), a free radical scavenger, attenuated this effect of morphine. Morphine-monocyte secretory products (MMSP) did not modulate the migration of monocytes. However, the products of interaction between mesangial cells and MMSP enhanced (p < 0.001) the passage of monocytes across the filter. Mesangial cells treated with MMSP showed mRNA expression for monocyte chemoat-tractant peptide-1 (MCP-1). Superoxide also induced mRNA expression for MCP-1 on MC. DMTU attenuated this effect of superoxide. Since morphine activates MC to produce superoxide and DMTU attenuated the effect of superoxide on MC, the effect of morphine on the migration of macrophages may be mediated through superoxide-induced generation of MCP-1. We conclude that morphine enhances the migration of monocytes. This effect of morphine may be contributing to the development of glomerulosclerosis in patients with heroin addiction.

Escherichia coli-macrophage interactions modulate mesangial cell proliferation and matrix synthesis

Patients with chronic renal interstitital diseases often develop glomerular lesions (focal segmental glomerular sclerosis). Because mesangial expansion (enhanced mesangial cell (MC) growth and matrix accumulation) has been demonstrated to precede the development of focal segmental glomerulosclerosis, we studied the effect of the interaction between bacteria such as Escherichia coli and macrophages on MC proliferation and matrix synthesis. We determined the effect of control media (CM), E. coli supernatant (ESP), serum-free macrophage supernatant (MSP), and E. coli-treated macrophage supernatants (HB101-MSP, H10-MSP) on the proliferation of MCs and synthesis of laminin (a component of mesangial matrix). ESP did not alter MC growth, whereas E. coli MSP increased the mean MC number by 5- to 6-fold when compared to cells treated with CM. Both HB101-MSP and H10-MSP stimulated greater (p < 0.05) incorporation of [3H]thymidine when compared with MSP (HB101-MSP 3.1 +/- 0.4, H10-MSP 2.7 +/- 0.3 vs. MSP 1.6 +/- 0.2 x 10(6) cpm/micrograms protein). When MC proliferation was judged by incorporation of bromodeoxyuridine, both HB101-MSP- and H10-MSP-treated cells showed a greater (p < 0.01) number of proliferating cells compared with cells treated with either MSP or CM. MC treated with H10-MSP grew in a specific pattern and showed a tendency to form hillocks (foci of cell proliferation and matrix aggregation). Both HB101-MSP and H10-MSP enhanced (p < 0.01) synthesis of laminin compared with CM. HB101-MSP-induced enhanced laminin synthesis was attenuated when MCs were treated with anti-transforming growth factor (TGF)-beta antibodies. HB101-MSP also increased mRNA expression of TGF-beta by MCs. These results indicate that E. coli-macrophage interaction has the potential to cause mesangial expansion.

Role of macrophages and colony-stimulating factor-1 in murine antiglomerular basement membrane glomerulonephritis

Macrophages have been shown to mediate glomerular injury in antiglomerular basement membrane (anti-GBM) glomerulonephritis in rats and rabbits. To evaluate the role of macrophages and the macrophage-related cytokines, colony stimulating factor-1 (CSF-1), monocyte chemoattractant protein-1 (MCP-1) and RANTES, accelerated anti-GBM nephritis was studied in op/op mutant mice, which lack CSF-1 and are severely macrophage deficient, and in heterozygous op/+ control mice. Observations were made 24 h and 3 days after the injection of rabbit anti-mouse GBM antibody in mice preimmunized with rabbit immunoglobulin G. Proteinuria rose progressively in both groups but did not differ between them (urine protein/creatinine ratio at 3 days: 1.01 +/- 0.38 in op/op versus 1.45 +/- 0.43 in op/+; P, not significant). In both op/op and op/+ mice, anti-GBM nephritis was associated with renal expression of mRNA for RANTES and MCP-1 and barely detectable levels of mRNA for CSF-1. In contrast, these cytokines were not expressed in sham-injected mice. Morphologic lesions appeared earlier in op/op mice but were comparable by Day 3. Glomerular injury consisted of capillary thrombosis and endothelial cell damage associated with mild to moderate leukocyte infiltration. Despite enhanced expression of mRNA for RANTES and MCP-1, glomerular macrophage infiltration was not increased in op/+ mice. It was concluded that, in mice, in contrast to rats and rabbits, accelerated anti-GBM nephritis may develop in the absence of both CSF-1 and macrophage infiltration.

Intracellular glutathione influences collagen generation by mesangial cells

The cellular redox state is altered in a number of pathological conditions, including various forms of glomerular injury and diabetes. For example, glucose, via the pentose phosphate pathway generates NADPH, which maintains glutathione (GSH) (part of a major intracellular reducing system) in its reduced state. GSH in turn influences the activity of transcription factors on gene expression. We therefore examined whether changes in cellular GSH influence total collagen synthesis and mRNA levels for collagen I, collagen IV and TGF-beta in SV-40 transformed mouse mesangial cells (MC) maintained in either 5 or 25 mM glucose media. Total intracellular GSH was increased by N-acetylcysteine (NAC; 10 mM) or decreased with the GSH synthesis inhibitor buthionine sulfoximine (BSO; 0.2 mM) in MC. NAC increased 3H-proline incorporation into collagenase-sensitive protein while BSO decreased it under both glucose conditions. The presence of BSO did not reverse the increased collagen synthesis seen in the NAC stimulated cells. Northern blot analysis showed increased mRNA levels for collagen I, collagen IV and TGF-beta in cells grown in high glucose (25 mM). NAC increased the mRNA for all three compounds while BSO alone had no effect on these mRNA levels. However, BSO reversed the increased mRNA levels for collagen I, IV and TGF-beta seen in the presence of NAC. These findings suggest that the cellular redox state may influence gene transcription in MC, and may have implications in explaining injury-associated alterations of mesangial matrix generation.

Oxygen radicals as second messengers for expression of the monocyte chemoattractant protein, JE/MCP-1, and the monocyte colony-stimulating factor, CSF-1, in response to tumor necrosis factor-alpha and immunoglobulin G. Evidence for involvement of reduced nicotinamide adenine dinucleotide phosphate (NADPH)-dependent oxidase

The potential involvement of reactive oxygen species in the expression of genes involved in immune response was examined in mesangial cells. Tumor necrosis factor (TNF-alpha) and aggregated (aggr.) IgG increased mRNA levels for the monocyte chemoattractant protein, JE/MCP-1, and the colony-stimulating factor, CSF-1. Scavengers for free radicals such as di- and tetra-methylthiourea (DMTU and TMTU) attenuated the increase in mRNA levels in response to TNF-alpha and aggr. IgG. Generation of superoxide anion by xanthine oxidase and hypoxanthine increased mRNA levels of these genes, but exogenous H2O2 did not. Addition of NADPH to activate a membrane-bound NADPH-oxidase generated superoxide and caused a dose-dependent increase in mRNA levels and further enhanced the stimulation by TNF-alpha or aggr. IgG. An inhibitor of NADPH-dependent oxidase 4'-hydroxy-3'-methoxy-acetophenone attenuated the rise in mRNA levels in response to TNF-alpha and aggr. IgG. By nuclear run-on experiments TNF-alpha, aggr. IgG and NADPH increased the transcription rates for JE/MCP-1 and CSF-1, effects inhibited by TMTU. We conclude that generation of reactive oxygen species, possibly by NADPH-dependent oxidase, are involved in the induction of the JE/MCP-1 and CSF-1 genes by TNF-alpha and IgG complexes. The concerted expression of leukocyte-directed cytokines represents a general response to tissue injury.

Nonenzymatic glycation of mesangial matrix and prolonged exposure of mesangial matrix to elevated glucose reduces collagen synthesis and proteoglycan charge

Expansion of the mesangial matrix in diabetes occurs after prolonged exposure to the diabetic milieu. To mimic the long-term hyperglycemia of diabetes mellitus we developed tissue culture systems that might approximate the chronic state. This was accomplished in two ways: (1) by growing mesangial cells on extracellular matrix glycated and crosslinked in vitro and (2) by continuously growing cells on their own matrix on filters in elevated glucose medium (500 mg/dl) for up to eight weeks without passage. Synthesis of collagen and proteoglycans was evaluated in cells grown under these conditions. In both these situations, 3H-proline incorporation into collagenase sensitive protein and 35S incorporation into sulfated proteins were reduced compared to control cultures. Despite reduction in 35S incorporation into proteoglycans in the high glucose cultures, total glycosaminoglycan content was unchanged. However, proteoglycans generated by mesangial cells grown in elevated glucose media were of a lower negative charge than controls. In mesangial cells continuously grown on filters, the levels of messenger RNA for collagen types I and IV, biglycan and TGF-beta were not different in cells grown at elevated or standard glucose concentrations for two and four weeks. We conclude that crosslinking of mesangial matrix or continuous culture of cells for prolonged periods of time in high glucose medium, which may also crosslink matrix, suppresses collagen synthesis and reduces the negative charges on matrix proteoglycans without altering mRNA levels.

Regulation of monocyte chemoattractant protein-1 and macrophage colony-stimulating factor-1 by IFN-gamma, tumor necrosis factor-alpha, IgG aggregates, and cAMP in mouse mesangial cells

The interaction of mesangial cells and monocyte-macrophages plays an important role in renal glomerular immune injury. We have, therefore, examined the regulation of two monocyte-specific cytokines, i.e., macrophage CSF-1 and monocyte chemoattractant protein (MCP-1), the product of the mouse JE gene, in mouse mesangial cells. TNF-alpha, IFN-gamma, and aggregates of IgG increased the synthesis of CSF-1 (determined by RIA) and of MCP-1 (determined by biolabeling and immunoprecipitation). Stimulation of cAMP generation by forskolin or PGE2 decreased basal CSF-1 synthesis and attenuated the responses to TNF-alpha, IFN-gamma, and IgG. Forskolin and PGE2 also decreased biolabeled MCP-1 generation after stimulation with IFN-gamma, TNF-alpha, or IgG. By Northern blot analysis steady state levels of mRNA for CSF-1 and JE/MCP-1 were increased after incubation with IFN-gamma, TNF-alpha, or IgG, and these effects were attenuated by forskolin. By using nuclear run-on assays the decrease in CSF-1 and JE/MCP-1 mRNA levels induced by stimulation of cAMP generation with forskolin was attributed to decreased transcription of these genes. Thus, agents stimulating cAMP generation, including PGE2, counterbalance the generation of CSF-1 and JE/MCP-1 in response to IFN-gamma, TNF-alpha, and IgG complexes. The locally produced CSF-1 and MCP-1 may in turn influence the interaction between mesangial cells and monocyte-macrophages in glomerular injury.

Regulation of monocyte chemoattractant protein-1 and macrophage colony-stimulating factor-1 by IFN-gamma, tumor necrosis factor-alpha, IgG aggregates, and cAMP in mouse mesangial cells

The interaction of mesangial cells and monocyte-macrophages plays an important role in renal glomerular immune injury. We have, therefore, examined the regulation of two monocyte-specific cytokines, i.e., macrophage CSF-1 and monocyte chemoattractant protein (MCP-1), the product of the mouse JE gene, in mouse mesangial cells. TNF-alpha, IFN-gamma, and aggregates of IgG increased the synthesis of CSF-1 (determined by RIA) and of MCP-1 (determined by biolabeling and immunoprecipitation). Stimulation of cAMP generation by forskolin or PGE2 decreased basal CSF-1 synthesis and attenuated the responses to TNF-alpha, IFN-gamma, and IgG. Forskolin and PGE2 also decreased biolabeled MCP-1 generation after stimulation with IFN-gamma, TNF-alpha, or IgG. By Northern blot analysis steady state levels of mRNA for CSF-1 and JE/MCP-1 were increased after incubation with IFN-gamma, TNF-alpha, or IgG, and these effects were attenuated by forskolin. By using nuclear run-on assays the decrease in CSF-1 and JE/MCP-1 mRNA levels induced by stimulation of cAMP generation with forskolin was attributed to decreased transcription of these genes. Thus, agents stimulating cAMP generation, including PGE2, counterbalance the generation of CSF-1 and JE/MCP-1 in response to IFN-gamma, TNF-alpha, and IgG complexes. The locally produced CSF-1 and MCP-1 may in turn influence the interaction between mesangial cells and monocyte-macrophages in glomerular injury.

Interactions of LDL and modified LDL with mesangial cells and matrix

Hyperlipidemia may play a role in the progression of diabetic and other renal diseases. Low density lipoprotein (LDL) and other proteins including extracellular matrix components undergo nonenzymatic glycation in vivo. We examined the effects of glycation of LDL as occurs in diabetes (4 to 8%) on binding and uptake by mesangial cells and their proliferation. The glycation of LDL (g-LDL) significantly decreased its binding and uptake by mesangial cells by 15 to 20%, indicating that glycated LDL binds to the LDL receptor, but with lower affinity than LDL. Both LDL and g-LDL modestly stimulated [3H] thymidine incorporation into mesangial cells at 5 to 10 micrograms/ml. Native, oxidized (Ox-LDL) and glycated LDL all bound to the extracellular matrix generated by rat mesangial cells in culture. The binding of LDL, Ox-LDL and g-LDL to mesangial matrix was two to four times higher than to mesangial cells. Binding of LDL and g-LDL was significantly higher to glycolaldehyde modified matrix, which serves as an in vitro model for nonenzymatic glycation end-product cross-linking of matrix which occurs in long-standing diabetes. Based on these findings, we propose that glycation of LDL decreases its binding and uptake by the LDL receptor of mesangial cells and may slow its catabolism. Furthermore, LDL bound to extracellular mesangial matrix can undergo oxidation and generate cytotoxic LDL components. This process may be further enhanced by advanced glycation of the mesangial matrix in diabetes, contributing to glomerular pathology.

Receptors for IgG complexes activate synthesis of monocyte chemoattractant peptide 1 and colony-stimulating factor 1

The chemotactic factors responsible for complement-independent macrophage accumulation in immune-complex diseases such as glomerulonephritis remain unknown. Fc receptors for IgG complexes are found on mesangial cells of the kidney, which produce the macrophage growth factor colony-stimulating factor 1 (CSF-1). We therefore investigated the possible stimulation of mesangial-cell expression of CSF-1 and the recently identified monocyte-specific chemoattractant protein 1 (MCP-1) by IgG complexes. IgG complexes, but not monomeric IgG or F(ab')2 fragments of IgG, rapidly (2-8 h) increased mRNA for both CSF-1 (10-fold) and MCP-1 (20-fold) in cultured mouse mesangial cells. The increase of mRNA for CSF-1 and MCP-1 was not reduced by either cytochalasin B or D, indicating that Fc receptor occupancy is sufficient for signaling and that phagocytosis is not required to elicit this response. IgG complexes also caused a 10-fold increase in the secretion of CSF-1 and a 3- to 5-fold increase in secretion of MCP-1 into the cell culture medium. The synthesis and release of CSF-1 and MCP-1 by mesangial cells as a consequence of Fc receptor occupancy may be responsible for macrophage recruitment and activation at sites of immune-complex deposition.