Occupational hydrocarbon exposure and chronic nephropathy

End-stage renal disease and metalworking fluid exposure

OBJECTIVE

Despite increasing prevalence of end-stage renal disease (ESRD), little attention has been directed to how occupational exposures may contribute to risk. Our objective was to investigate the relationship between metalworking fluids (MWF) and ESRD in a cohort of 36 703 male autoworkers.

METHODS

We accounted for competing risk of death, using the subdistribution hazard approach to estimate subhazard ratios (sHRs) and 95% CIs in models with cubic splines for cumulative exposure to MWF (straight, soluble or synthetic).

RESULTS

Based on 501 ESRD cases and 13 434 deaths, we did not observe an association between MWF and ESRD overall. We observed modest associations between MWF and ESRD classification of glomerulonephritis and diabetic nephropathy. For glomerulonephritis, the 60th percentile of straight MWF was associated with an 18% increased subhazard (sHR=1.18, 95% CI: 0.99 to 1.41). For diabetic nephropathy, the subhazard increased 28% at the 60th percentile of soluble MWF (sHR=1.28, 95% CI: 1.00 to 1.64). Differences by race suggest that black males may have higher disease rates following MWF exposure.

CONCLUSIONS

Exposure to straight and soluble MWF may be related to ESRD classification, though this relationship should be further examined.

Renal injury following long-term exposure to carbon disulfide: analysis of a case series

Background

To investigate the clinicopathological characteristics of renal damage caused by long-term exposure to carbon disulfide (CS2) in nine patients.

Methods

All the patients underwent ultrasound-guided renal biopsy. All specimens were examined by light microscopy and immunohistochemistry (IHC). Samples form one patient were further analyzed using transmission electron microscopy.

Results

Similar pathological changes were observed in all patients, but the degrees of lesions were different. All cases had moderate to severe nodular mesangial hyperplasia; among these, type “Kimme1stie1-Wi1son” (K-W nodule for short) was observed in four cases, type “K - W nodule” refer to nodular hyperplasia of mesangial membrane like letter K or W. four cases had proliferative extracapillary glomerulonephritis (GN), while there were no concomitant changes in one patient. Besides, six cases had diffuse basement membrane thickening, focal segmental sclerosis or bulbar sclerosis; two cases had diffuse glomerular sclerosis, and one case had focal segmental capillary hyperplasia. Moreover, all patients had renal tubular atrophy/interstitial fibrosis with less to moderate chronic inflammatory cell infiltration, as well as renal arteriosclerosis. IHC showed that the depositions of IgA, IgM, C3d, C4d, C1q and Fib were not specific; while IgG, type III collagen, Fibronectin, Amyloid A, Igκ, Igλ, HBsAg and HBcAg were all negative.

Conclusion

Diffuse nodular mesangial hyperplasia/sclerosing glomerular nephropathy is characterized by nodular mesangial hyperplasia with type “K-W nodules” formation, which we speculate is a special pathological manifestation of renal damage caused by carbon disulfide (CS2).

Prediction of biopersistence of hydrocarbons using a single parameter

Aerobic biodegradation is an important attenuation process for petroleum hydrocarbons (PHCs) in the natural environment. It has also been frequently used in engineered systems to remediate PHC-contaminated sites. A model such as a quantitative structure property relationship (QSPR) that can predict the biodegradation rate of PHCs would be helpful prior to implementing any extensive environmental measurements and bioremediation strategies. Existing QSPRs either have a large number of predictor variables that may cause overfitting or are based on a small dataset of PHCs. The goal of this study is to develop a simple, portable QSPR that has only a few predicator variables but can accurately predict the biodegradation half-lives of a large group of PHCs. To this end, more than 500 molecular variables were screened, and candidate variables were refined by a feature selection method and fitted to biodegradation data of a group of structurally heterogeneous PHCs (n = 173). The model was established by means of hierarchical clustering and classification and regression tree algorithms, which was optimized by an internal validation procedure and validated by an external dataset. The optimal QSPR model, containing only one predictor variable (the number of bonds that do not contain hydrogen), was able to accurately predict biodegradation half-lives for a wide variety of PHCs. The internal validation test indicated an overall prediction accuracy of 93%, and predictions applied to an independent external set of 64 PHCs yielded 95% accuracy. The new model is transparent and easily portable from one user to another.

Renal pathology in patients with occupational exposure to carbon disulphide: A case series

AIM

Carbon disulphide (CS₂ ) is widely used as an organic solvent. However, there is little information available regarding the clinical manifestations and the pathological features of kidney injury caused by CS₂ . The current study aimed to describe the renal manifestations of a group of patients with long-term occupational exposure to CS₂ .

METHODS

Ten patients with long-term exposure to CS₂ and visiting a single centre were enrolled, with their clinical features recorded. Renal biopsies were taken from all patients, and their pathological findings were documented.

RESULTS

All patients came from the same chemical fibre factory. Their mean age at enrollment was 36.9 ± 2.4 years, and each patient had a CS₂ exposure duration exceeding 10 years. Eight patients (80%) presented with proteinuria and none had hematuria. Two patients (20%) had underlying hypertension and five (50%) had increased serum creatinine levels. Light microscopic examination of their renal biopsy specimens revealed diffuse mesangial cell proliferation and mesangial hyperplasia in all patients. Moreover, three patients (30%) had nodular hyperplasia, resembling the lesions of diabetic nephropathy. Variable degrees of tubular atrophy and interstitial infiltrations of lymphocytes and monocytes were observed in all patients. Similarly, lectron microscopic examination showed glomerular mesangial cell proliferation and mesangial hyperplasia. Immunopathological staining for IgA and IgG, complements or hepatitis B markers (hepatitis B surface antigen and e antigen-antibody) are negative in all patients.

CONCLUSION

Long-term occupational exposure to CS₂ may be associated with renal injury, although the renal pathological features are often non-specific.

Renal failure and occupational exposure to organic solvents: what work-up should be performed?

The etiological work-up of a disease with an occupational component, such as renal failure associated with exposure to organic solvents, may include several complementary investigations. The authors discussed certain elements of the etiological work-up in the light of a clinical case, particularly the individual and collective advantages and disadvantages of this work-up. Further investigations would not have provided the patient with any individual or collective benefit and were therefore not performed, whereas other investigations (environmental studies, screening of fellow workers) may provide collective rather than individual benefits, but must be decided by a multidisciplinary approach. A multidisciplinary study (general practitioner, nephrologist, occupational health physician, and specialist in toxicology) is necessary to discuss the appropriate etiological work-up, taking into account the individual and collective benefit-risk balance.

New insight into solvent-related end-stage renal disease: occupations, products and types of solvents at risk

OBJECTIVES

It has been shown that all-solvent exposure is associated with the progression of primary glomerulonephritis to end-stage renal disease (ESRD), but little is known about the type of solvents that are high risk. The aim of this study was to investigate the role of solvents by occupation, product and type.

METHODS

Using a retrospective cohort design, the authors studied 269 patients with non-end-stage and biopsy-proven primary glomerulonephritis diagnosed between 1994 and 2001 in Paris and its suburbs. Two industrial hygienists evaluated patients' exposures from lifetime occupational histories collected by interview from 2002-4, and using a list of the 30 most common solvents. The studied outcome was ESRD, defined as glomerular filtration rate <15 ml/mn/1.73 m(2) or dialysis. It was recorded during a mean follow-up of five years. Cox models were used to estimate adjusted hazard ratios (HR) of ESRD related to exposures.

RESULTS

Eighteen per cent of the patients had ever been exposed to solvents. Those with the highest risk of progression to ESRD were exposed machinery fitters and machine assemblers (HR 4.7, 95% CI 1.2 to 17.4) and plumbers/welders (HR 4.2, 95% CI 1.3 to 13.6), as compared to never exposed patients, as well as those who ever handled printing inks and petroleum products (HR 12.6 (95% CI 1.7 to 94.9) and 3.2 (95% CI 1.4 to 7.2), respectively). Among solvents, the highest risks were found for: toluene/xylene (HR 5.1, 95% CI 1.8 to 14.8), gasoline, fuel and gas-oil (HR 8.6, 95% CI 2.7 to 27.4), and ketones (HR 13.3, 95% CI 1.4 to 123.5).

CONCLUSION

This study highlights the potential nephrotoxicity of several solvents. Intervention to promote screening for proteinuria in exposed workers may prevent the progression of glomerulonephritis to ESRD.

Effect of organic solvent exposure on chronic kidney disease progression: the GN-PROGRESS cohort study

It has been suggested that solvent exposure may have a role in the progression of glomerulonephritis (GN) to ESRD, but this has never been tested with an appropriate cohort study design. A total of 338 non-ESRD patients with a first biopsy for primary GN between 1994 and 2001 were included: 194 IgA nephropathies (IgAN), 75 membranous nephropathies (MN), and 69 FSGS. ESRD, defined as an estimated GFR <15 ml/min per 1.73 m2 or dialysis, was registered during a mean follow-up period of 5 yr. Patients' lifelong solvent exposures before and after diagnosis were recorded by interview and assessed by industrial hygienist experts. Cox models were used to estimate adjusted hazard ratios (HR) of ESRD related to exposures. Overall, 15 and 14% of the patients had been exposed at a low and a high level before diagnosis, respectively. Forty-two with IgAN, 12 with MN, and 22 with FSGS reached ESRD. A graded relationship was observed for MN (age- and gender-adjusted HR [95% confidence interval] for low exposure versus none was 3.1 [0.5 to 18.2] and for high exposure versus none was 8.2 [1.9 to 34.7]) and for IgAN (1.6 [0.7 to 3.9] and 2.2 [1.0 to 4.8]) but not for FSGS. Solvent risk was mediated only partly by baseline proteinuria: Adjusted HR for high exposure versus none was 5.5 (1.3 to 23.9) for MN and 1.8 (0.8 to 3.9) for IgAN. In patients with IgAN, there was a trend in increasing HR with exposure duration before and its persistence after diagnosis. These findings support the hypothesized association of solvent exposure with the progression of GN to ESRD. They should prompt clinicians to give greater attention to patients' occupational exposures and possibly to consider professional reclassification.

Streptozotocin (STZ) diabetes enhances benzo(alpha)pyrene induced renal injury in Sprague Dawley rats

Information is lacking regarding the biological response to environmental chemicals in the context of pre-existing disease. Benzo(alpha)pyrene (BaP), a polycyclic aromatic hydrocarbon, is a byproduct of combustion that causes renal injury and elicits a nephropathic response. This study evaluated the nephrotoxicity of BaP in normoglycemic and diabetic rats. Female Sprague Dawley rats were divided into four groups: normoglycemic-vehicle (NV), normoglycemic-BaP (N-BaP), diabetic-vehicle (DV) and diabetic-BaP (D-BaP). Diabetes was induced by intraperitoneal (ip) injection of streptozotocin (60 mg/kg, 1 ml/kg). Rats were injected (ip) with vehicle or 10 mg/kg BaP (1 ml/kg) once per week for 5 weeks. Urinary protein and albumin, plasma creatinine and light microscopy were performed to assess the effects of BaP on kidney function. Diabetes was confirmed by plasma glucose levels >400 mg/dl in the DV and D-BaP groups. BaP increased kidney weight and blood urea nitrogen (BUN) levels in the D-BaP relative to the DV group. No change in BUN was observed following 5 weeks of BaP treatment in the normoglycemic animals, however, kidney weight was increased (p=0.013) in the N-BaP relative to the NV animals. STZ diabetes increased susceptibility to BaP mediated renal damage following repeated treatment for 5 weeks when compared to age matched normoglycemic rats.

Experimental glomerulonephritis induced by hydrocarbon exposure: a systematic review

BACKGROUND

Much epidemiological evidence suggests that hydrocarbon exposure may induce glomerulonephritis and worsen its course in many patients. The mechanisms are unknown, however, no specific microscopic pattern has been identified, and it has also been argued that hydrocarbon exposure causes tubular damage mainly. Studying experimental animals may best answer these questions, and as no systematic review of glomerulonephritis produced experimentally by hydrocarbon exposure has been performed previously, I found it relevant to search for and analyse such studies.

METHODS

Animal experiments having mimicked human glomerulonephritis by hydrocarbon exposure were sought on Medline and Toxnet

RESULTS

Twenty-six experiments using thirteen different hydrocarbons were identified. Several human subtypes were observed including IgA nephritis, mesangial, proliferative and extracapillary glomerulonephritis, focal and focal-segmental sclerosis, minimal change nephropathy, anti-GBM and anti-TBM nephritis, and glomerulonephritis associated with peiarteritis nodosa. Glomerular proteinuria was seen in 10/12 experiments that included urine analyses, and renal failure in 5/8 experiments that included measurements of glomerular function. All experiments resulted in various degrees of tubular damage as well. In most studies, where the animals were examined at different times during or after the exposure, the renal microscopic and functional changes were seen immediately, whereas deposits of complement and immunoglobulins appeared late in the course, if at all.

CONCLUSION

These experiments are in accord with epidemiological evidence that hydrocarbon exposure may cause glomerulonephritis and worsen renal function. Probable mechanisms include an induction of autologous antibodies and a disturbance of normal immunological functions. Also, tubular damage may increase postglomerular resistance, resulting in a glomerular deposition of macromolecules. In most models a causal role of glomerular immune complex formation was unlikely, but may rather have been a secondary phenomenon. As most glomerulonephritis subgroups were seen and as some of the hydrocarbons produced more than one subgroup, the microscopic findings in a patient cannot be used as a clue to the causation of his disease. By the same reason, the lack of a specific histological pattern in patients with glomerulonephritis assumed to have been caused by hydrocarbon exposure is not contradictive.

Disruption of glomerular cell-cell and cell-matrix interactions in hydrocarbon nephropathy

Environmental chemicals play an etiological role in greater than 50% of idiopathic glomerular diseases. The present studies were conducted to define mechanisms of renal cell-specific hydrocarbon injury. Female rats were given 10 mg/kg benzo(a)pyrene (BaP) once a week for 16 wk. Progressive elevations in total urinary protein, protein/creatinine ratios, and microalbuminuria were observed in rats treated with BaP for up to 16 wk. The nephropathic response involved early reductions in mesangial cell numbers and fibronectin levels by 8 wk, coupled to transient increases in podocyte cellularity. Changes in podocyte numbers subsided by 16 wk and correlated with rebound increases in mesangial cell numbers and fibronectin levels, along with increased α-smooth muscle actin and Cu/Zn superoxide dismutase and fusion of podocyte foot processes. In culture, mesangial cells were more sensitive than podocytes to hydrocarbon injury and expressed higher levels of inducible aryl hydrocarbon hydroxylase activity. Naïve mesangial cells exerted a strong inhibitory influence on podocyte proliferation under both direct and indirect coculture conditions, and this response involved a mesangial cell-derived matrix that selectively inhibited podocyte proliferation. These findings indicate that hydrocarbon nephropathy in rats involves disruption of glomerular cell-cell and cell-matrix interactions mediated by deposition of a mesangial cell-derived growth-inhibitory matrix that regulates podocyte proliferation.

Nephrotoxicity of organic solvents: biomarkers for early detection

OBJECTIVES

Evidence for a relationship between chronic kidney diseases or progression of already existing diseases (glomerulonephritides) and occupational solvent exposure has been found in case reports, in case-control studies and also in cross-sectional studies. An analysis of the available literature was performed with respect to markers measured in cross-sectional studies that might be useful for an early detection of solvent-induced effects on the kidney.

METHODS

The relevant cross-sectional studies were evaluated and the following markers were analyzed with respect to their suitability as biomarker for renal damage: total protein, albumin, transferrin, IgG, beta(2)-microglobulin, retinol-binding protein, N-acetyl-beta-D: -glucosaminidase, alanine aminopeptidase, beta-galactosidase, beta-glucuronidase, leucin aminopeptidase, alkaline phosphatase, lysozyme, Tamm-Horsfall protein and laminin fragments in urine as well as E-selectin, laminin and anti-laminin antibodies and anti-glomerular basement membrane antibodies in serum.

RESULTS

An increased albumin excretion was observed more frequently in groups of workers exposed to various solvents (like toluene, styrene, aliphatic/aromatic hydrocarbon mixtures, tetrachloroethene, mixtures of chlorinated hydrocarbons) than in controls. No clear pattern emerged for the other markers.

CONCLUSIONS

The determination of albumin excretion in the urine appears to be a useful parameter for monitoring solvent-exposed workers.

Inducible cytochrome P450 activities in renal glomerular mesangial cells: biochemical basis for antagonistic interactions among nephrocarcinogenic polycyclic aromatic hydrocarbons

Background

Benzo(a)pyrene (BaP), anthracene (ANTH) and chrysene (CHRY) are polynuclear aromatic hydrocarbons (PAHs) implicated in renal toxicity and carcinogenesis. These PAHs elicit cell type-specific effects that help predict toxicity outcomes in vitro and in vivo. While BaP and ANTH selectively injure glomerular mesangial cells, and CHRY targets cortico-tubular epithelial cells, binary or ternary mixtures of these hydrocarbons markedly reduce the overall cytotoxic potential of individual hydrocarbons.

Methods

To study the biochemical basis of these antagonistic interactions, renal glomerular mesangial cells were challenged with BaP alone (0.03 – 30 μM) or in the presence of ANTH (3 μM) or CHRY (3 μM) for 24 hr. Total RNA and protein will be harvested for Northern analysis and measurements of aryl hydrocarbon hydroxylase (AHH) and ethoxyresorufin-O-deethylase (EROD) activity, respectively, to evaluate cytochrome P450 mRNA and protein inducibility. Cellular hydrocarbon uptake and metabolic profiles of PAHs were analyzed by high performance liquid chromatography (HPLC).

Results

Combined hydrocarbon treatments did not influence the cellular uptake of individual hydrocarbons. ANTH or CHRY strongly repressed BaP-inducible cytochrome P450 mRNA and protein expression, and markedly inhibited oxidative BaP metabolism.

Conclusion

These findings indicate that antagonistic interactions among nephrocarcinogenic PAHs involve altered expression of cytochrome P450s that modulate bioactivation profiles and nephrotoxic/ nephrocarcinogenic potential.

Characterization of glomerular cell phenotypes following repeated cycles of benzo[a]pyrene injury in vitro

Exposure of cultured glomeruli to benzo[a]pyrene (BaP), a carcinogenic hydrocarbon, modulates mesangial and visceral epithelial cell proliferation in vivo and in vitro. The present studies were conducted to characterize mitogenic signaling profiles of cultured glomeruli following repeated cycles of BaP challenge. Enhanced rates of DNA synthesis were observed by the third passage in randomly cycling cultures after single or repeated carcinogen exposure. This response was characterized by upregulation of mitogenic sensitivity during early cell cycle transit, and increased cell numbers under restrictive growth conditions. The mitogenic response to platelet-derived growth factor (0.5 to 25 ng/mL), acidic fibroblast growth factor (2.5 to 10 ng/mL), basic fibroblast growth factor (0.05 to 5 ng/mL), epidermal growth factor (0.5 to 5 ng/mL), or conditioned medium was not enhanced by hydrocarbon challenge. BaP-treated cultures exhibited anchorage-independent growth and increased expression of hepatocyte growth factor mRNA and E-cadherin protein. Binding of activator protein-1 to DNA was enhanced in BaP-treated cells, but this change did not involve truncation or mutation of the c-jun delta region. Collectively, the data demonstrate that repeated cycles of BaP injury alter mitogenic signaling profiles in cultured glomerular cells. These alterations may contribute to deregulation of proliferative control following carcinogen exposure in vivo.

Hydrocarbons may worsen renal function in glomerulonephritis: a meta-analysis of the case-control studies

BACKGROUND

Previous case-control studies of hydrocarbon exposure in glomerulonephritis may have given inconsistent results because the stage of disease has not been considered.

METHODS

The association between stage of disease and degree of previous exposure was studied by a meta-analysis of all published case-control studies and by reviewing all follow-up studies.

RESULTS

Odds ratios (OR) for exposure could be calculated for 16 patient groups from 14 case-control studies. After exclusion of four patient groups with 5-17% drop-outs due to death, the mean weighted OR for patient groups with acute or early glomerulonephritis, chronic renal failure, and end-stage renal failure were 0.95, 3.1, and 5.9, respectively. At follow-up, reported in four studies, renal failure was mainly seen in patients with extensive exposure, and improvement was seen only in patients who had discontinued the exposure.

CONCLUSIONS

Hydrocarbon exposure in glomerulonephritis is associated with the advancement of the disease and inversely associated with renal function. Early elimination of the exposure may, therefore, prevent the progress of renal failure in many patients.

Phenotypic profiles of cultured glomerular cells following repeated cycles of hydrocarbon injury

BACKGROUND

The glomerulus has been implicated as a target of hydrocarbon injury in vitro and in vivo. In the present studies, the phenotypic profiles of cultured rat glomerular cells (GCs) following repeated cycles of hydrocarbon injury were evaluated. Cultured GCs were incubated for 24 hours with benzo[a]pyrene (BaP; 3 micromol/L), a prototypical polycyclic aromatic hydrocarbon, and were allowed to recover overnight before two additional cycles of chemical challenge during serial propagation in vitro. At the end of this regimen, control cultures were characterized by predominance of fusiform cells that grew in "hills and valleys," while GCs subjected to hydrocarbon injury displayed an epithelial morphology characterized by a rounded, polygonal shape clearly distinct from that normally exhibited by glomerular mesangial cells (GMCs) in culture.

METHODS

Indirect immunofluorescent detection of cell markers was conducted to identify cells of mesenchymal or epithelial origin. Measurements of DNA synthesis and cell number were performed to determine proliferative capacities of the different cell types in response to hydrocarbon challenge.

RESULTS

Immunofluorescence studies revealed that control GC cultures contained mostly alpha-smooth muscle (SM) actin-positive cells, with a few (5.1% +/- 2.6) E-cadherin-positive cells occasionally identified. In contrast, BaP-treated cultures exhibited a mixed cell population in which E-cadherin-positive cells were predominant (66.6% +/- 4.1). Single-cell cloning of naive cultures of GCs yielded four clones, three of which exhibited a fusiform morphology and were alpha-SM actin positive (SCC 1 through SCC 3) and one (SCC 4E) that exhibited epithelial characteristics similar to those found in hydrocarbon-treated cultures. Immunofluorescence studies showed that epithelial cells in hydrocarbon-treated cultures, as well as SCC 4E-derived clones, were vimentin positive and cytokeratin negative, characteristics similar to glomerular visceral epithelial cells (GVECs). DNA synthesis and cell proliferation in clone SCC 1 were decreased following acute BaP challenge, while growth rates in SCC 4E-derived clones were unaffected by hydrocarbon injury. Repeated cycles of hydrocarbon challenge in clonal populations yielded different profiles of DNA synthesis, with significant decreases in SCC 1 and no changes in SCC 4E.

CONCLUSIONS

These observations suggest that hydrocarbon injury induces differential responses in cells of the glomerulus, resulting in inhibition of GMCs and selective growth advantage of GVECs. These alterations are reminiscent of critical events described in the pathogenesis of focal segmental glomerulosclerosis and raise important questions about the pathogenesis of hydrocarbon-induced nephropathies.

Risk factors for IgA nephropathy: a case-control study in Japan

To disclose the risk factors for immunoglobulin A nephropathy (IgAN), we conducted a case-control study in the Tokai area of central Japan. The subjects were 94 patients, aged 20 years or older at diagnosis, who had histologically confirmed IgAN. Two sex-, age-, and residence-matched controls were randomly selected for each case from the general population. Information on medical history and lifestyle was collected using a self-administered questionnaire. The strength of association between IgAN and a potential risk factor was assessed by calculating an odds ratio. A family history of chronic nephritis, susceptibility to the common cold, preference for salty foods, frequent consumption of raw eggs, and a high intake of carbohydrates, including rice, were significantly associated with an increased risk for IgAN. Alcohol consumption, use of antioxidant vitamin supplements, and a high intake of protein, fat, monounsaturated fatty acids, and all/n-3 polyunsaturated fatty acids were somewhat protective against IgAN. Episodes of tonsillitis and exposure to organic solvents were found not to be associated with the risk in the present study. Our findings may provide some clues to the cause of IgAN.

Assessment for Subclinical Kidney Damage in Workers Exposed to Low Concentrations of Hydrocarbons

It has been suggested the risk of hydrocarbon-induced chronic nephropathy is negligible at low exposure levels. The first purpose of the study was to test this hypothesis by selecting a population slightly exposed to hydrocarbons. Moreover, as hypertension might be associated with an increased excretion of nephrotoxic mercapturates, the association between blood pressure and urinary concentration of S-phenylmercapturic acid (S-PMA) was also examined. Lifetime exposure assessment, main tests of subclinical kidney damage, and statistical approach were taken from a previous study that had included primarily moderately or heavily exposed workers and had found hydrocarbon-induced nephrotoxic effects. No nephrotoxic effect of exposure could be ascertained in the present study. S-PMA concentration was not increased in hypertensive workers. Thus, the risk of hydrocarbon-induced chronic nephropathy might be extremely low in workers slightly exposed to hydrocarbons. The negative results of some studies might be due to the low lifetime hydrocarbon exposures of the study populations.

Atypical cytochrome P450 induction profiles in glomerular mesangial cells at the mRNA and enzyme level. Evidence for CYP1A1 and CYP1B1 expression and their involvement in benzo[a]pyrene metabolism

Recent studies in this laboratory have shown that benzo[a]pyrene (BaP) modulates growth factor-related gene expression and proliferation of renal glomerular mesangial cells (GMCs) in vitro. Because many of the toxic and biochemical effects of this polycyclic aromatic hydrocarbon are mediated through oxidative metabolism, the present studies were conducted to examine the patterns of cytochrome P450IA1 (CYP1A1) and P4501B1 (CYP1B1) inducibility in mesangial cells and the molecular consequences of this response. Exposure of cultured GMCs to BaP (30 microM) or 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, 10 nM) for 24 hr induced CYP1A1 mRNA levels, a response abolished by cotreatment with 10 microM cycloheximide. The pattern of hydrocarbon inducibility was atypical in that BaP was a more effective inducer of CYP1A1 gene expression than TCDD, and both hydrocarbons induced aryl hydrocarbon hydroxylase (AHH) activity, but not ethoxyresorufin-O-deethylase activity. Cotreatment with alpha-naphthoflavone (alpha NF, 1 microM) or ellipticine (ELLIP, 0.1 nM) only partially inhibited the induction of AHH activity by BaP (30 microM). BaP and TCDD also induced expression of the CYP1B1 protein and the pattern of induction was comparable to that observed for CYP1A1. Treatment of GMCs with 30 microM BaP was associated with the formation of eight DNA adducts, and their occurrence could be inhibited by pretreatment with alpha NF (1 microM), but not ELLIP (0.1 nM). These results demonstrate that CYP1A1 and CYP1B1-related activities are induced in GMCs by BaP and TCDD and this induction is associated with metabolism of BaP to reactive intermediates that bind covalently to DNA.