Familial IgA nephropathy: a study of HLA class II allogenotypes in a Chinese kindred

We have studied the restriction fragment length polymorphism (RFLP) of the major histocompatibility complex (MHC) class II DQ, DR pattern of a Chinese family with IgA nephropathy (IgAN). The three affected and one apparently unaffected sibling shared the same DR and DQ pattern. The subjects were homozygous for DRw12, DQw7, DQ alpha 1b. The DQw7 allele was further confirmed by polymerase chain reaction (PCR) and allele-specific oligonucleotide (ASO) probing. This study confirms that IgAN can run in a family and is consistent with the possible immunopathogenetic effects of MHC class II antigens on IgAN.

Fatal adult Henoch-Schönlein purpura due to small intestinal infarction

A 57-year-old woman presented with classical symptoms of Henoch-Schönlein purpura including arthralgia, abdominal pain, palpable purpuric rash and abnormalities of the urinary sediments. The clinical course was subsequently complicated by severe paralytic ileus leading to respiratory embarrassment. Laparotomy confirmed patchy areas of small bowel infarction due to necrotizing vasculitis. Skin biopsy revealed extensive leukocytoclastic vasculitis with granular deposits of IgA in the blood vessels. Anti-neutrophil cytoplasmic autoantibodies (ANCA) were not detectable. The patient continued to deteriorate despite bowel resection, intensive immunosuppressive therapy and plasma exchange, and eventually died. Gastrointestinal involvement in adult Henoch-Schönlein purpura has previously been reported to have a favourable clinical course. However, our case illustrates the rate but lethal complication of intestinal infarction in patients who fail to respond to conservative treatment.

Characteristics of covalent gossypol binding to microsomal proteins

Gossypol is a potent antifertility agent contained in seeds and other parts of cotton plants. The limit set in 1974 by the FDA for this C30H30O8 compound in consumer products is 450 ppm. The binding characteristics and the nature of the microsomal protein adducts of radiolabeled gossypol were studied using centrifugation, extraction, reverse phase HPLC and filter assay approaches. Results showed a significant amount of radiolabeled gossypol to be associated with the precipitated proteins after aqueous, ethanol, acetone and ether extractions. The nature of binding of these protein adducts involved covalent, covalent but reversible (e.g., Schiff bases), and tightly-bound and trapped noncovalent residues. Non-acid labile binding adducts constituted 40% of the precipitated microsomal proteins. Eight percent of the adducts were covalent, reversible and reducible by NaBH4. A gradient HPLC separation of the acetone extracts resulted in non-gossypolone hydrophilic protein adducts with a mean retention time of 2.3 minutes. Gossypol can bind tightly to hepatic microsomal proteins with a ratio of 80 nmoles/mg protein under physiological conditions. Significant portions of these bindings are not due to simple acid labile Schiff base formation. Purer membrane preparation provided results showing predominant binding of gossypol to endoplasmic reticulum (ER) and mitochondria, followed to a lesser extent by peroxisomes and plasma membranes. Difference spectra of the gossypol-bound rat hepatic microsomal preparations and controls demonstrated a 3 nm shift from 413 to 410 nm caused by gossypol covalent-binding. Results of this study indicate that gossypol binds covalently to microsomal proteins. Its binding to membrane proteins may affect metabolism of sterols, steroids, or fatty acids.

Effect of subcutaneous administration of recombinant human erythropoietin on plasma protein C, protein S, and antithrombin III levels in patients on continuous ambulatory peritoneal dialysis

The effect of subcutaneous administration of recombinant human erythropoietin (rHuEPO) on plasma natural coagulation inhibitors (protein C, protein S, and antithrombin III) was evaluated in 10 uremic patients on continuous ambulatory peritoneal dialysis (CAPD). These patients were commenced on a 16 week-course of twice weekly rHuEPO by the subcutaneous route. The hemoglobin increased significantly from 6.9 +/- 1.3 g/dl to 9.6 +/- 1.9 g/dl after subcutaneous rHuEPO treatment (p less than 0.01) at an average dose of 84 +/- 9 U/kg body wt/week. With rHuEPO therapy, a significant increase in platelet counts was observed, albeit within the normal range. A significant increase in the prothrombin time was demonstrated at 6 weeks after treatment and increased activated partial thromboplastin time was observed at 6 weeks and 16 weeks after rHuEPO administration although these measurements still remained in normal range. CAPD patients have comparable or even higher plasma levels of natural coagulation inhibitors compared with healthy controls supporting our previous findings that patients on CAPD have normal plasma levels due to an effective compensatory production despite peritoneal losses of these proteins with CAPD. No change in either the immunological or the functional activity of these natural coagulation inhibitors was demonstrated with rHuEPO therapy and clinical thrombosis was not observed during and after rHuEPO therapy. We conclude that there is no laboratory evidence of increased risk of thrombogenesis due to reduction of natural coagulation inhibitors with rHuEPO therapy.

Crescentic glomerulonephritis related to hepatitis B virus

Crescentic glomerulonephritis was diagnosed in two chronic hepatitis B surface antigen carriers. In all three biopsies performed, hepatitis B e antigen was found in glomerular capillary tufts. The first patient presented with nephrotic syndrome and acute renal failure. The glomerular pathology revealed crescentic glomerulonephritis with endocapillary proliferation, and she recovered spontaneously with normal renal function over the following 6 mo despite a persistent hepatitis B surface antigenemia. The other patient presented with nephrotic syndrome and normal renal function. Hepatitis B virus-related membranous nephropathy was diagnosed on the first biopsy, and he did well on symptomatic treatment for 20 mo. The nephrotic syndrome recurred and subsequently he developed acute renal failure a month following interferon treatment. The repeated biopsy revealed a crescentic glomerulonephritis that was associated with mixed membranous and membranoproliferative glomerulopathies. This patient responded to immunosuppression and plasma exchange with residual impairment of renal function. He has been stable after 18 mo follow-up.

Use of recombinant erythropoietin in thalassemic patients on dialysis

We studied the therapeutic benefit of recombinant human erythropoietin (rHuEPO) in dialysis patients with thalassemia minor. Four of the 40 randomly selected patients (22 on hemodialysis [HD], 18 on continuous ambulatory peritoneal dialysis [CAPD]) were identified to be thalassemic prior to a trial of rHuEPO (alpha-thalassemia trait in three and beta-thalassemia minor in one). All patients were initially treated with rHuEPO at a dose of 100 +/- 25 U/kg/wk subcutaneously depending on the hemoglobin level. EPO injections were continued for 16 weeks with further adjustments of the doses according to the hemoglobin level increases attained. All nonthalassemic patients reached a target hemoglobin of 10 g/dL at week 16, with an average maintenance dose of 120 +/- 7.8 U/kg/wk, but the hemoglobin was increased by only 1 g/dL in the thalassemic patients receiving 175 U/kg/wk. Following cessation of rHuEPO therapy for 6 weeks, all four thalassemic patients and 18 randomly selected nonthalassemic patients received a fixed dose of rHuEPO 4,000 U/wk (equivalent to 80 U/kg/wk) for 16 weeks. The hemoglobin remained unchanged in the thalassemic patients, but a progressive and significant increase of hemoglobin was observed in the nonthalassemic patients. At the last phase of the study, the thalassemic patients received rHuEPO at a dose of 100 or 125 U/kg/wk with 4-weekly increments of 25 U/kg/wk until their hemoglobin reached 10 g/dL. One patient developed uncontrolled hypertension with a dose of 150 U/kg/wk, and one reached the target hemoglobin at a dose of 200 U/kg/wk.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute renal failure in hepatitis B virus-related membranous nephropathy with mesangiocapillary transition and crescentic transformation

We report the first case of hepatitis B virus (HBV)-related membranous nephropathy (MN) that progressed to crescentic transformation superimposed on a mixed membranous and mesangiocapillary glomerulonephritis. The patient developed acute renal failure, which partially responded to pulse methylprednisolone therapy, and subsequently recovered after plasma exchange.

Glomerulonephritis associated with Robertsonian translocation t(13;14)

We report the first case of glomerulonephritis associated with Robertsonian translocation t(13;14) in a 18-year-old female. The renal biopsy revealed mesangial proliferative glomerulonephritis with mesangial IgG and C3 deposits. The patient also has congenital absence of ovaries and an underdeveloped uterus. Our report suggests that renal abnormalities may be found in patients with Robertsonian translocation.

Once weekly versus twice weekly subcutaneous administration of recombinant human erythropoietin in haemodialysis patients

Optimal route and frequency of administration of recombinant human erythropoietin (rHuEPO) have not yet been determined. There is some evidence to suggest that subcutaneous administration of rHuEPO may be more effective than the intravenous route in reversing renal anemia. It is also unclear whether rHuEPO is more effective when given by a large intermittent dose or by more frequent multiple divided doses. We have compared the effect of twice weekly versus once weekly subcutaneous administration of rHuEPO in two groups of haemodialysis patients. At the end of 12 weeks of treatment with rHuEPO, the mean haemoglobin levels had risen from 6.9 +/- (SD) 0.7 to 8.9 +/- 1.3 g/dl in the once weekly group and from 7.2 +/- 1.0 to 9.3 +/- 1.6 g/dl in the twice weekly group. The average doses of rHuEPO used during the study were 127 +/- 6 and 115 +/- 18 U/kg body weight/week for the once weekly and twice weekly groups, respectively. Subcutaneous administration of low-dose rHuEPO is effective in reversing renal anaemia. Similar responses were obtained with once weekly and twice weekly regimens.

Acute renal failure (ARF) caused by rhabdomyolysis due to diabetic hyperosmolar nonketotic coma: a case report and literature review

We report a case of rhabdomyolysis secondary to diabetic hyperosmolar nonketotic coma leading to acute renal failure. The patient had no overt muscle pain or swelling. Urinary myoglobin was negative. The patient was managed with continuous veno-venous hemodiafiltration (CVVHD) and his renal function subsequently recovered. The clinical features of five other reported cases of rhabdomyolysis caused by diabetic hyperosmolar nonketotic coma in the literature are reviewed.

Aromatase inhibition by 7-substituted steroids in human choriocarcinoma cell culture

Androstenedione analogs containing 7 alpha-substituents have proven to be potent inhibitors of aromatase both in vitro and in vivo. Several of these agents have exhibited higher affinity for the enzyme complex than the substrate. In order to examine further the interaction(s) of 7-substituted steroids with aromatase, 7-substituted 4,6-androstadiene-3,17-diones were synthesized and demonstrated competitive inhibition of aromatase activity in human placental microsomes. 7-Substituted 1,4,6-androstatriene-3,17-diones demonstrated mechanism-based inhibition of placental aromatase activity. These agents were evaluated for inhibition of aromatase activity in the JAr human choriocarcinoma line. The 7-substituted 4,6-androstadiene-3,17-diones produced dose dependent inhibition of aromatase activity in the cell cultures, with IC50 values ranging from 490 nM to 4.5 microM. However, these agents are less effective when compared to other steroidal inhibitors, such as 7 alpha-thiosubstituted androstenediones. These results on the 7-substituted 4,6-androstadiene-3,17-diones are consistent with the data from biochemical enzyme inhibition studies using human placental aromatase. On the other hand, 7-phenethyl-1,4,6-androstatriene-3,17-dione exhibits greater inhibitory activity, with an IC50 value of 80 nM. Other mechanism-based inhibitors, 7 alpha-(4'-amino)phenylthio-1,4-androstadiene-3,17-dione and 4-hydroxyandrostenedione, also exhibited potent inhibition of aromatase activity in JAr cells. In summary, the most effective B-ring modified steroidal aromatase inhibitors are those derivatives that can project the 7-aryl substituent into the 7 alpha-position.

Cytokine production by peripheral blood mononuclear cells in IgA nephropathy

The regulation of cytokine production and T cell proliferation by other cytokines is mandatory in mediating inflammatory responses but the full understanding is far from complete. We have previously reported increased production of IL-2 and IL-2 receptors (IL-2R) in IgA nephropathy. The present study was undertaken to examine other cytokine production during T cell activation in IgA nephropathy. Peripheral blood mononuclear cells (PBMC) from 17 IgA nephritic patients and 14 controls were cultured with phytohaemagglutinin and phorbol myristate acetate for 48 h for maximal cytokine production. IL-2Rs and IL-4 receptors (IL-4Rs) expressed on cultured PBMC were studied by a radioimmunoassay using monoclonal antibodies against these receptors. Although the total cellular IL-2R expression and percentages of T helper and T suppressor cells did not differ between the patients and controls, there was a significant increase in activated T helper cells expressing IL-2R in patients with IgA nephropathy. The total cellular IL-4R expression was elevated in IgA nephritic patients (P less than 0.005). IL-2 production by PBMC was raised in IgA nephritic patients compared with controls (P less than 0.05) but no difference in IL-4 or IL-6 production was observed. The interferon-gamma production by PBMC was significantly increased in patients with IgA nephropathy (P less than 0.025). No correlation was observed between individual cytokine levels. Our data suggest there are selective increases in cytokine production in IgA nephropathy.

Membranous nephropathy associated with spinal schwannoma

Clinical cure was effected in a patient with biopsy-proven membranous nephropathy associated with spinal schwannoma. The renal manifestation of nephrotic syndrome antedated the clinical presentation of the spinal tumor. The proteinuria and edema subsided 4 mths after the complete resection of the intradural component and partial removal of the extradural component of the schwannoma. Careful workup in patients with membranous nephropathy should include not only malignant but also benign tumors.

Gossypolone suppresses progesterone synthesis in bovine luteal cells

Gossypolone, a proposed major metabolite of gossypol, was synthesized and investigated for its effect on progesterone synthesis in cultured bovine luteal cells. Gossypolone inhibited human chorionic gonadotropin(hCG)-stimulated progesterone secretion, reduced substrate-enhanced conversions of 25-hydroxycholesterol to pregnenolone and of pregnenolone to progesterone in a dose-dependent fashion. These findings indicate that gossypolone inhibits not only 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) activity, as gossypol does, but also side-chain cleavage enzyme complex (cytochrome P450scc) activity. However, the two compounds appear to have a similar potency in inhibiting progesterone secretion. Both gossypolone and gossypol (8.5 microM) induced morphological changes in cellular organelles.

Membranous nephropathy related to hepatitis B virus in adults

BACKGROUND

The natural course of adult hepatitis B virus (HBV)-related membranous nephropathy in areas where HBV infection is endemic (characterized by vertical and horizontal transmission of HBV in early childhood) has not been fully defined.

METHODS

We evaluated the clinical features, pathological findings, serologic profiles, therapeutic responses, and prognoses of 21 patients with adult-onset HBV-related membranous nephropathy. The patients were followed for a mean of 60 months (range, 12 to 108). Only patients with evidence of glomerular capillary deposition of hepatitis B e antigen (HBeAg) in a renal-biopsy specimen were included.

RESULTS

The clinical features and serologic studies suggested that the patients had acquired chronic HBV infection in early childhood; moreover, other causes of membranous nephropathy had been excluded. All were seropositive for hepatitis B surface antigen and had high titers of antibody to hepatitis B core antigen at first clinical presentation. HBeAg was detected in the serum of 17 patients (81 percent), yet only 3 had even slightly increased plasma alanine aminotransferase levels. The clinical response to therapy with interferon alfa was disappointing; only one of the five patients treated had a complete remission with seroconversion to antibody to HBeAg. Contrary to reports of studies in children, spontaneous remission of the nephrotic syndrome or proteinuria was uncommon in the adults with HBV-related membranous nephropathy whom we studied. Proteinuria and HBV antigenemia persisted in untreated patients. During the follow-up period, 29 percent of the patients had progressive renal failure and 10 percent required maintenance dialysis therapy.

CONCLUSIONS

The course of HBV-related membranous nephropathy in adults in areas where HBV is endemic is not benign. Regardless of treatment, the disease has a slowly but relentlessly progressive clinical course in approximately one third of patients.

The DQw7 allele at the HLA-DQB locus is associated with susceptibility to IgA nephropathy in Caucasians

The frequencies of the MHC class II HLA-DR and DQ alleles in 36 Caucasian patients with IgA nephropathy (IgAN) were analyzed by RFLP analysis and allele specific oligonucleotide (ASO) probing of specifically amplified genomic DNA. The class II alleles HLA-DR4 (52.7%) and DR5 (30.5%) were increased in the patient group compared to 1103 UK Caucasoid controls, but these increases were not statistically significant. However, there was a significant increase in the HLA-DQw7 allele frequency (71%) (c = 27.8%, chi 2 = 29.2, P less than 0.001, Relative Risk = 6.17). This can be explained by linkage disequilibrium between the DQw7 allele at the DQB1 locus and DRB1 genes of some DR4 and all DR5 haplotypes. The polymorphic portion of the DQ alpha chains from DR4, DQw7 and DR5, DQw7 haplotypes differ but they have identical DQ beta chains. DNA encoding DQw7 allele at the DQB1 locus was sequenced in two patients and was identical to that previously published. We conclude that the DQw7 allele at the DQB1 locus is strongly associated with susceptibility to IgAN in Caucasians.

Vasoactive hormones in uremic patients on continuous ambulatory peritoneal dialysis

Plasma levels of atrial natriuretic peptide (ANP), renin activity (PRA), and endothelin (ET) are often elevated in uremic patients on hemodialysis treatment. The profile of these vasoactive hormones and their relationships with hemodynamic indices in patients on continuous ambulatory peritoneal dialysis (CAPD), however, are not clear. We therefore measured plasma concentrations of ANP, PRA, ET, together with parathyroid hormone (PTH) in 17 patients (mean age 38.5 years) on maintenance CAPD over a period of 12 weeks. Baseline ANP, PRA, and ET levels were significantly higher than those of healthy subjects, and no significant changes in these indices were observed over the 12 week period. There was a significant positive correlation between levels of plasma ANP and PRA [rank correlation coefficient, R(s) = 0.496, p less than 0.05] as has been reported in cardiac failure. Despite the absence of clinically overt heart failure, a significant proportion (approximately 50%) of our patients demonstrated evidence of myocardial dysfunction on echocardiography. Furthermore, a significant positive correlation was demonstrated between plasma ANP and left atrial size [R(s) = 0.61, p less than 0.01] and an inverse correlation existed between plasma ANP and the left ventricular ejection fraction [R(s) = 0.51, p less than 0.05]. Twelve patients (71%) had biochemical evidence of hyperparathyroidism with raised levels of serum PTH. Our study demonstrates increased levels of plasma ANP, PRA, and ET in uremic patients on long-term CAPD. A positive correlation exists between plasma ANP and PRA suggesting their myocardial function may be compromised and this was confirmed on echocardiography. The possibility that high circulating PTH concentrations contribute to impaired cardiac function in such patients, deserves further study.

The effects of blockade of interleukin 2 receptors and interleukin 4 receptors on cytokine production

The understanding of the regulation of cytokine production and T-cell proliferation by other cytokines is far from complete. We have examined the supernatant concentration of different cytokines in cultured peripheral blood lymphocytes (PBL) incubated with monoclonal antibodies against the interleukin-2 receptor (IL-2R) or interleukin-4 receptor (IL-4R) complex in order to analyse the importance of these receptors in the production of other cytokines. The PBL cultures were stimulated with phytohaemagglutinin and phorbol myristate acetate. The addition of anti-Tac to PBL cultures resulted in increased free IL-2 due to blockade of IL-2R. MR6 (a monoclonal antibody against IL-4R) did not affect the supernatant concentration of IL-2 in cultured PBL. Blockade of IL-2R or IL-4R both resulted in increased IL-4 in supernatant. The increase in supernatant concentration of IL-4 in PBL cultured with MR6 was due to a direct interaction with the IL-4R complex but the increase in IL-4 with anti-Tac was due to the accumulation of free IL-4 as an effective blockade of IL-2R prevented the full expression of IL-4R. Neither anti-Tac nor MR6 affected the IL-6 production by activated PBL, suggesting the existence of an IL-2- and IL-4-independent pathway. Blockade of IL-2R or IL-4R both resulted in a reduction of interferon-gamma (IFN-gamma) production, indicating that both endogenously generated IL-2 and IL-4 are important mediators of IFN-gamma induction in PBL cultures stimulated with T-cell mitogens.

Pharmacokinetics of parenteral imipenem/cilastatin in patients on continuous ambulatory peritoneal dialysis

We investigated the pharmacokinetics of two intravenous (iv) dose regimens of imipenem/cilastatin in Chinese patients on chronic ambulatory peritoneal dialysis (CAPD), who had an average creatinine clearance of 3.2 ml/min/1.73 m2. Doses of 0.5 and 1.0 g produced mean peak serum imipenem concentrations of 30 and 70 mg/l respectively, about 60% of cilastatin. Peritoneal dialysis fluid (PDF) imipenem concentrations reached 20-30% of the serum peak 4-5 h after iv injection, and the lowest maximum PDF concentrations were 2 mg/l after the 0.5 g dose and 14 mg/l after 1.0 g. Thus both regimes produced PDF imipenem concentrations above the MICs of susceptible pathogens. The half-life of imipenem was 6.4 h and the plasma clearance 66 ml/min; serum and PDF imipenem were in equilibration after about 5 h. Cilastatin had a prolonged half-life of 19 h and a plasma clearance of 10 ml/min, and accumulated in both serum and PDF. With a 0.5 g dose, the pharmacokinetics of imipenem/cilastatin suggest that the combination may prove an effective treatment for peritonitis associated with CAPD.

Effect of hemodialysis on protein C, protein S, and antithrombin III levels

We studied the effect of hemodialysis on natural coagulation inhibitors including protein C (PC), protein S (PS), and antithrombin III (AT III), as well as the correlations between the antigen level (immunological activity) and functional activity of individual coagulation inhibitor. Plasma AT III, PS, and PC were measured in 20 uremic patients on maintenance hemodialysis immediately before, during, and after dialysis treatment. These values were compared with those obtained from 20 matched healthy controls. Plasma PC and total PS antigen levels were measured by enzyme immunoassay. The plasma AT III antigen level was determined by Laurell rocket immunoelectrophoresis. Functional activities of PC and AT III were determined by the amidolytic method. Free PS antigen level was quantitated by measuring the free PS-related antigen after the sample was treated with polyethylene glycol to remove the C4b-binding protein. Uremic patients on maintenance hemodialysis had a higher total PS antigen level, but a lower free PS antigen level compared with the controls. Both the antigen level and functional activity of AT III in uremic patients were significantly lower than those of controls. Their predialysis plasma PC antigen level and functional activity were not different from those of normal controls. A significant correlation between the antigen level and functional activity of PC, PS, and AT III was demonstrated in healthy controls, but not in hemodialysis patients. No significant change in the level of AT III or PS was observed with hemodialysis, but a progressive increase of functional activity of PC was documented with hemodialysis. Furthermore, the coefficient of correlation between the antigen level and functional activity of PC improved significantly with dialysis treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Biochemical and pharmacological development of steroidal inhibitors of aromatase

Androstenedione analogs containing 7 alpha-substituents have proven to be potent inhibitors of aromatase both in vitro and in vivo. Several of these agents have exhibited higher affinity for the enzyme complex than the substrate. In order to examine further the interaction(s) of 7-substituted steroids with aromatase, biochemical and pharmacological studies were performed on 7 alpha-thiosubstituted androstenediones and 7-substituted 4,6-androstadiene-3,17-diones. Potent inhibition of aromatase activity in human placental microsomes has been observed with several new 7 alpha-thiosubstituted androstenediones. 7-Benzyl- and 7-phenethyl-4,6-androstadiene-3,17-diones effectively inhibited microsomal aromatase, with apparent Kis ranging from 61 to 174 nM. On the other hand, 7-phenyl-4,6-androstadiene-3,17-dione exhibited poor activity, with an apparent Ki of 1.42 microM. Similar inhibitory activity was observed with reconstituted, purified cytochrome P450Arom preparations. Additionally, these agents were evaluated for inhibition of aromatase activity in two human carcinoma cell lines, the MCF-7 human mammary cancer line and the JAr choriocarcinoma line. The 7 alpha-thiosubstituted androstenediones and 7-substituted 4,6-androstadiene-3,17-diones produced dose-dependent inhibitions of aromatase activity in the cell cultures. The most effective inhibitors were the 7 alpha-substituted androstenediones, with EC50 values ranging from 7.3 to 105 nM. Finally, the JAr cell culture system exhibited prolonged inhibition of aromatase activity following exposure to 7 alpha-APTADD, suggesting enzyme inactivation by this inhibitor. Thus, these agents are effective aromatase inhibitors, and the results encourage further development of this group of medicinal agents for the treatment of estrogen-dependent mammary carcinoma.

7-substituted 1,4,6-androstatriene-3,17-diones as enzyme-activated irreversible inhibitors of aromatase

7-Phenyl-1,4,6-androstatriene-3,17-dione (4), 7-benzyl-1,4,6-androstatriene-3,17-dione (5) and 7-phenethyl-1,4,6-androstatriene-3,17-dione (6) were synthesized and evaluated in vitro in human placental microsomes as enzyme-activated irreversible inhibitors of aromatase. The compounds were synthesized from appropriate 7-substituted 4,6-androstadiene-3,17-diones by reaction with DDQ under neutral conditions. All the compounds produced a first order inactivation of aromatase in the presence of NADPH but not in the absence of NADPH. Substrate 4-androstene-3,17-dione protected the enzyme from inactivation by the inhibitors. Furthermore, cysteine failed to protect aromatase from inactivation by compounds 5 and 6. In contrast, cysteine partially protected aromatase from inactivation by compound 4. Irreversibility studies illustrated the covalent nature of the inactivation by 4, 5 and 6. The above experimental evidence demonstrated that compounds 5 and 6 are effective enzyme-activated irreversible inhibitors of aromatase.

7-substituted steroidal aromatase inhibitors: structure-activity relationships and molecular modeling

Androstenedione analogs containing 7 alpha-substituents have proven to be potent inhibitors of aromatase both in vitro and in vivo. Several of these agents have exhibited higher affinity for the enzyme complex than the substrate does. In order to examine further the interaction(s) of 7-substituted steroids with aromatase, biochemical and molecular modeling studies were performed on 7-substituted 4,6-androstadiene-3,17-diones. 7-Benzyl- and 7-phenethyl-4,6-androstadiene-3,17-diones effectively inhibited microsomal aromatase, with apparent Kis ranging from 61 to 174 nM. On the other hand, 7-phenyl-4,6-androstadiene-3,17-dione exhibited poor activity, with an apparent Ki of 1.42 microM. Energy minimization calculations and molecular modeling indicated that the 7-substituent is perpendicular to the steroid nucleus in the 7-phenyl analog and can only adopt a pseudo beta position. The 7-benzyl- and 7-phenethyl- groups of 4,6-androstadiene-3,17-diones orient themselves in the minimized structure in a way that the phenyl rings can protrude into the 7 alpha pocket. These orientations are similar to those observed in minimized structures for potent 7 alpha-substituted androstenediones.

Synthesis and biochemical studies of 7-substituted 4,6-androstadiene-3,17-diones as aromatase inhibitors

Inhibitors of aromatase, the cytochrome P-450 enzyme complex responsible for the biosynthesis of estrogens, may be useful as therapeutic agents for the treatment of estrogen-dependent disease states such as breast and endometrial cancer. Several 7 alpha-thio-substituted androstenediones have proven to be potent inhibitors of aromatase in vitro and in vivo. Recent research efforts have focused on designing aromatase inhibitors with both substitution at C-7 and extended linear conjugation in rings A and B of the steroid nucleus. The targeted compounds, 7-substituted 4,6-androstadiene-3,17-diones 4-10, were prepared by the addition of either Grignard or lithium reagents to 3,3:17,17-bis(ethylenedioxy)-5-androsten-7-one (3). Inhibitory activities of the compounds were evaluated in vitro by enzyme kinetic studies employing the microsomal fraction isolated from human term placenta. 7-Benzyl- and 7-phenethyl-4,6-androstadiene-3,17-dione analogues are effective inhibitors with apparent Ki's of 60.9-174 nM, while the 7-phenyl analogue exhibited an apparent Ki of 1.424 microM. Thus, several 7-substituted 4,6-androstadiene-3,17-diones were prepared and exhibited good competitive inhibition of aromatase in vitro in human placental microsomes.