Joel Neugarten

The impact of gender on the progression of chronic renal disease

Observations in experimental animals and in humans have shown that the rate of progression of renal disease is influenced by gender. Deterioration of renal function in patients with chronic renal disease is more rapid in men than in women, independent of differences in blood pressure or serum cholesterol levels. In addition to genetically determined differences between the sexes in renal structure and function, sex hormones may directly influence many of the processes implicated in the pathogenesis of renal disease progression. Potential mechanisms include receptor-mediated effects of sex hormones on glomerular hemodynamics and mesangial cell proliferation and matrix accumulation as well as effects on the synthesis and release of cytokines, vasoactive agents, and growth factors. In addition, estrogens may exert potent antioxidant actions in the mesangial microenvironment, which may contribute to the protective effect of female gender.

Glomerulosclerosis in aging humans is not influenced by gender

Aging male rats develop progressive glomerulosclerosis, proteinuria, and loss of renal function, whereas females are remarkably resistant to the development of these abnormalities. Although sex hormones appear to contribute to gender-related differences in the development of glomerulosclerosis in aging rats, it is not clear that sexual dimorphism characterizes glomerular obsolescence in aging humans. To study this question further, the glomerular histology of males and females ranging in age from infancy to 90 years was compared in 250 autopsy specimens. We found no differences between the sexes in the development of glomerulosclerosis in aging humans. These data disprove the hypothesis that testosterone is an important factor contributing to progressive glomerulosclerosis in aging men. Conversely, any renoprotective effects of estrogen would be limited by the onset of menopause because significant glomerulosclerosis did not develop until after the age of 50 years.

Gender and the Progression of Renal Disease

The protective effect of female gender on the progression of chronic renal disease has only recently become an area of active investigation ([1][1]–[4][2]). Interestingly, the attention comes at a time of enormous controversy in light of unexpected adverse effects of combined estrogen/progestin

Estradiol suppresses mesangial cell type I collagen synthesis via activation of the MAP kinase cascade

We have previously shown that estradiol suppresses the synthesis of type I collagen by murine mesangial cells grown in the presence of serum via activation of the transcription factor activator protein-1 (AP-1). We hypothesized that estradiol upregulates AP-1 via activation of the mitogen-activated protein (MAP) kinase cascade, a signal transduction pathway that regulates AP-1 activity. Estradiol (10-10 to 10-7 M) upregulated the MAP kinase pathway in murine mesangial cells grown in the presence of serum in a dose-dependent manner. Activation was evident by 1 min, peaked at 10 min, and was completely dissipated by 2 h. In contrast, estradiol had no significant effect on total (phosphorylated + unphosphorylated) p44 extracellular signal-related protein kinase (ERK) or p42 ERK. Nuclear extracts isolated from mesangial cells treated with estradiol showed increased binding to a consensus sequence AP-1 binding oligonucleotide in gel shift assays. In contrast, nuclear extracts from cells exposed to PD-98059, a highly selective inhibitor of MAP kinase-ERK kinase 1 (MEK1) and MEK2, showed reduced binding. In addition, PD-98059 antagonizes the enhanced binding induced by estradiol. Estradiol (10-9M) suppressed mesangial cell type I collagen synthesis (37.8 ± 2.4%, expressed as a percentage of control values, P < 0.001 vs. control). In contrast, PD-98059 increased type I collagen synthesis (344.6 ± 98.8, P < 0.01) and reversed the suppression of type I collagen synthesis induced by estradiol. The effects of estradiol, PD-98059, and PD-98059 plus estradiol on type I collagen protein synthesis were closely paralleled by their effects on steady-state levels of mRNA for the α1 chain of type I collagen. These data suggest that estradiol suppresses type I collagen synthesis via upregulation of the MAP kinase cascade, leading to stimulation of AP-1 activity.We have previously shown that estradiol suppresses the synthesis of type I collagen by murine mesangial cells grown in the presence of serum via activation of the transcription factor activator protein-1 (AP-1). We hypothesized that estradiol upregulates AP-1 via activation of the mitogen-activated protein (MAP) kinase cascade, a signal transduction pathway that regulates AP-1 activity. Estradiol (10(-10) to 10(-7) M) upregulated the MAP kinase pathway in murine mesangial cells grown in the presence of serum in a dose-dependent manner. Activation was evident by 1 min, peaked at 10 min, and was completely dissipated by 2 h. In contrast, estradiol had no significant effect on total (phosphorylated + unphosphorylated) p44 extracellular signal-related protein kinase (ERK) or p42 ERK. Nuclear extracts isolated from mesangial cells treated with estradiol showed increased binding to a consensus sequence AP-1 binding oligonucleotide in gel shift assays. In contrast, nuclear extracts from cells exposed to PD-98059, a highly selective inhibitor of MAP kinase-ERK kinase 1 (MEK1) and MEK2, showed reduced binding. In addition, PD-98059 antagonizes the enhanced binding induced by estradiol. Estradiol (10(-9) M) suppressed mesangial cell type I collagen synthesis (37.8 +/- 2.4%, expressed as a percentage of control values, P < 0.001 vs. control). In contrast, PD-98059 increased type I collagen synthesis (344.6 +/- 98.8, P < 0.01) and reversed the suppression of type I collagen synthesis induced by estradiol. The effects of estradiol, PD-98059, and PD-98059 plus estradiol on type I collagen protein synthesis were closely paralleled by their effects on steady-state levels of mRNA for the alpha(1) chain of type I collagen. These data suggest that estradiol suppresses type I collagen synthesis via upregulation of the MAP kinase cascade, leading to stimulation of AP-1 activity.

Estradiol reverses TGF-β1-stimulated type IV collagen gene transcription in murine mesangial cells

We have previously shown that estradiol suppresses types I and IV collagen synthesis by mesangial cells grown in the presence of serum. In the present study, we examined the interaction between estradiol and transforming growth factor-β (TGF-β) on collagen IV synthesis. In a luciferase reporter gene construct containing the type IV collagen promoter and α1-chain regulatory sequences, we found that TGF-β1 (2 ng/ml) stimulated α1-collagen IV gene transcription in serum-free media (140.5 ± 6.2 relative luciferase units, expressed as a percent of control untreated cells, P < 0.001). Estradiol reversed the stimulatory effects of TGF-β1 on reporter gene transcription in a dose-dependent manner [for 2.5 × 10-9 M, 114.2 ± 0.2, P < 0.002 vs. TGF-β1; for 10-7 M, 89.5 ± 4.0, P < 0.001 vs. TGF-β1 and P = not significant (NS) vs. control]. Using immunoprecipitation techniques, we found that estradiol (10-7 M) reversed TGF-β1-stimulated type IV collagen synthesis (175.3 ± 14.7 vs. 111.6 ± 7.1, expressed as a percent of control untreated cells, P < 0.001) but did not affect TGF-β1-stimulated type I collagen synthesis (166.9 ± 18.8 vs. 162.2 ± 16.2, P = NS). These results were confirmed with Western blotting. Nuclear extracts from mesangial cells treated with TGF-β1 showed increased binding to a Sp1 consensus binding sequence oligonucleotide and to an Sp1 binding site in the collagen IV promoter. Estradiol reversed this enhanced binding. These data suggest that estradiol antagonizes TGF-β1-stimulated type IV collagen synthesis at a transcriptional level and that this effect may be mediated by interactions with the transcription factor Sp1.

Glomerulonephritis in bacterial endocarditis

The introduction of antibiotic therapy and changing epidemiologic patterns have altered the nature of glomerulonephritis as it occurs during the course of bacterial endocarditis. Observations made predominantly in the pre-antibiotic era suggested that infections with less virulent organisms, by virtue of their indolent subacute course, favored an antibody response predisposing to immune complex glomerulonephritis. Although antibiotic prophylaxis and therapy have reduced the incidence of both Streptococcus viridans bacterial endocarditis and concomitant glomerulonephritis, Staphylococcus aureus has become a major cause of acute bacterial endocarditis with a high incidence of glomerulonephritis. Parenteral drug abuse itself, which has emerged as a major factor predisposing to endocarditis, may also favor the development of glomerulonephritis. The course of glomerulonephritis has been altered in association with these changes in etiology and epidemiology. This review summarizes the clinical and morphologic features of glomerulonephritis as it currently occurs during the course of bacterial endocarditis.

Effects of Sex on Renal Structure

Aims: There are few data examining differences in renal structure between the sexes. Elucidation of the mechanisms responsible for the observed effects of sex on the progression of chronic renal disease requires knowledge of the effects of sex on renal structure. Results: Although we found that male kidneys weigh more than female kidneys, sex is not an independent determinant of kidney weight. The increased kidney weight seen in men is solely dependent on their greater body surface area. We found no difference in glomerular number between men and women. Although men had larger glomeruli than women, sex is not an independent determinant of glomerular volume. The occurrence of larger glomeruli in men is solely dependent on their greater body surface area. Similarly, the greater total glomerular volume seen in men as compared to women reflects increased kidney weight in men. Sex is not an independent determinant of total glomerular volume. Conclusions: These findings do not support the hypothesis that renal structural differences contribute to sex-related differences in the rate of progression of chronic renal disease.

Serum-stimulated α1 type IV collagen gene transcription is mediated by TGF-β and inhibited by estradiol

We examined the hypothesis that fetal calf serum (FCS) stimulates murine mesangial cell α1 type IV collagen ( COL4A1) gene transcription by increasing autocrine production of transforming growth factor-β (TGF-β) through a platelet-derived growth factor (PDGF)-dependent mechanism. PDGF-stimulated COL4A1 gene transcription was inhibited by neutralizing antibody to TGF-β (119.3 ± 3.6 vs. 106.0 ± 6.2 relative luciferase units, expressed as a percentage of control untreated cells, P < 0.003). FCS-stimulated gene transcription was inhibited by neutralizing antibody to PDGF (148.3 ± 4.1 vs. 136.7 ± 0.3 relative luciferase units, P < 0.002) and by neutralizing antibody to TGF-β (148.3 ± 4.1 vs. 127.1 ± 3.4 relative luciferase units, P < 0.036). The inhibitory effect of combined treatment with anti-PDGF and anti-TGF-β antibody on gene transcription was no greater than that of anti-TGF-β antibody alone [129.5 ± 0.53 vs. 127.1 ± 3.4 relative luciferase units, P = not significant (NS)]. FCS-stimulated gene transcription was also inhibited by estradiol (10-7 M) (148.4 ± 3.1 vs. 119.4 ± 8.1 relative luciferase units, P < 0.019). In the presence of estradiol, anti-TGF-β antibody failed to further reduce serum-stimulated gene transcription (119.4 ± 8.1 vs. 115.6 ± 9.8, P = NS), suggesting that estradiol reverses FCS-stimulated COL4A1 gene transcription by antagonizing the actions of TGF-β. Measurement of type IV collagen synthesis by Western blotting confirmed that the intact gene responded in a manner analogous to the promoter construct.

Effects of sex hormones on mesangial cells

Male gender is associated with a more rapid progression of chronic renal disease. In various experimental models of renal injury, manipulation of the hormonal milieu can replicate the effects of gender on the course of renal disease. These observations suggest that sex hormones per se may be important determinants of the greater susceptibility of the male kidney to progressive renal injury. Sex hormones may influence many of the processes implicated in the pathogenesis of renal disease progression, including cell proliferation and the synthesis and degradation of collagen and proteoglycans. In addition, sex hormones may indirectly influence these processes by modulating the synthesis and release of vasoactive agents, cytokines, and other growth factors, which in turn are capable of altering mesangial cell function. Finally, estrogens also exert potent antioxidant effects that may contribute to the protective effect of female gender on the course of renal disease.

Cocaine-induced rhabdomyolysis masquerading as myocardial ischemia

PURPOSE Cocaine abuse has recently emerged as a major problem among young adults, and is increasingly associated with a variety of medical complications. In view of recent reports demonstrating that illicit cocaine use may cause rhabdomyolysis, we reviewed the collective experience of a university-affiliated medical center to identify patients with cocaine-induced rhabdomyolysis. PATIENTS AND METHODS Among hospital admissions due to acute cocaine abuse during the period June 1987 through June 1988, we identified seven patients who exhibited biochemical evidence of skeletal muscle injury. Six of these patients presented within one hour of free-basing cocaine with complaints of thoracic skeletal muscle pain. Hospital admission was prompted by the suspicion of myocardial ischemia or infarction. The remaining patient was incidentally found to have an elevated serum level of creatine phosphokinase (CPK) after abusing cocaine and was hospitalized to exclude a cardiac origin. RESULTS Serum CPK levels in the seven patients rose to a mean peak value of 16.1 +/- 3.6 mu kat/L, and returned toward normal within 72 hours. A cardiac origin for the elevated CPK values was excluded by negative results of determinations of CPK-MB fractions. CONCLUSION Rhabdomyolysis must be added to the every-growing list of medical complications associated with the illicit use of cocaine. Skeletal muscle injury may be a more common complication of cocaine abuse than has previously been appreciated, escaping medical attention when the clinical manifestations are relatively mild. The importance of recognizing this clinical entity lies in the potential confusion with myocardial ischemia. This point is illustrated by the fact that each of our patients was hospitalized to exclude the possibility of cocaine-induced myocardial infarction. Cardiac ischemia could not be differentiated from skeletal muscle injury solely on the basis of clinical assessment.