Pneumolysin potentiates oxidative inactivation of alpha-1-proteinase inhibitor by activated human neutrophils

This study was designed to investigate the effects of the Streptococcus pneumoniae-derived, pro-inflammatory toxin, pneumolysin (8.37 and 41.75 ng/ml), on the oxidative inactivation of alpha-1-protease inhibitor (API) by chemoattractant-activated human neutrophils in vitro. The elastase inhibitory capacity (EIC) of API in supernatants from unstimulated neutrophils, neutrophils treated with pneumolysin only, or with the chemoattractant FMLP (1 microM) only, or the combination of the toxin with FMLP was measured by a colorimetric procedure based on the activity of added porcine elastase. The EIC of API was unaffected by exposure to pneumolysin only, unstimulated neutrophils, or neutrophils treated with pneumolysin only. However, exposure to FMLP-activated neutrophils resulted in a reduction of the EIC of API, which was significantly (P<0.05) augmented by pneumolysin (mean reductions of 16%, 43% and 83% for FMLP only and in combination with 8.37 and 41.75 ng/ml pneumolysin, respectively), and was attenuated by wortmannin (1 microM), an inhibitor of NADPH oxidase, the oxidant-scavenger methionine (100 microM), and depletion of Ca2+ from the cell-suspending medium. These pro-proteolytic interactions of pneumolysin with chemoattractant-activated neutrophils may contribute to the invasiveness of the pneumococcus.     

In vitro protection by erdosteine against oxidative inactivation of alpha-1-antitrypsin by cigarette smoke

Direct exposure in vitro of the protein alpha 1-antitrypsin (alpha 1-AT; human neutrophil elastase inhibitor, alpha 1-proteinase inhibitor) to gas phase cigarette smoke causes a loss of elastase-inhibitory capacity (EIC). This effect appears to be related to the formation of reactive oxygen species in the smoke that inactivate alpha 1-AT by oxidizing the methionine terminal amino acid. Reducing agents such as glutathione and ascorbic acid prevent this inactivation. In the present investigation erdosteine, a novel thiol derivative, which contains two blocked SH groups with potential reducing properties, was tested in vitro for its capacity to protect human alpha 1-AT. For the purpose, the compound, previously hydrolyzed with bicarbonate-carbonate buffer or with microsomal enzymes was put in contact with alpha 1-AT and exposed to gas phase cigarette smoke. The EIC of alpha 1-AT was then measured by incubating the samples with leukocyte elastase and, subsequently, by titrating the residual elastolytic activity against a synthetic substrate. Under these conditions erdosteine effectively protected alpha 1-AT against the smoke injury and, after alkaline hydrolysis, it appeared to be as active as glutathione and ascorbic acid (EC50 being respectively 6.4, 7.2 and 6.2 mM). This evidence suggests that the erdosteine SH groups, which can become free, may have an important role in the mechanism of action, by blocking highly reactive oxygen-free radicals. Erdosteine may have a therapeutic application in preventing oxidative lung damage induced by cigarette smoke.     

The anti-inflammatory drug nimesulide rescues alpha-1-proteinase inhibitor from oxidative inactivation by phagocytosing neutrophils.

When neutrophils are recruited to tissue sites and exposed to phagocytosable targets, they release oxidants which may be responsible for the local inactivation of alpha-1-proteinase inhibitor (A1PI). Consequently, A1PI becomes incapable of inhibiting the proteolytic activity of elastase, released at the same time by neutrophils as a result of leakage from phagocytic vacuoles. In the present paper we show that phagocytosing neutrophils inactivate A1PI via a process inhibitable by chemical agents known to interfere with the hypochlorous acid (HOCl)-generating myeloperoxidase pathway. The anti-inflammatory drug nimesulide (NMS), which is able to efficiently limit the extracellular availability of HOCl in the neutrophil surroundings, was found to prevent the inactivation of A1PI by neutrophils. The results provide evidence for a possible way to control neutrophil elastase activity by rescuing its natural inhibitor (A1PI) at inflamed tissue sites during infectious and noninfectious processes.     

Inactivation of human alpha 1-proteinase inhibitor by cigarette smoke: effect of smoke phase and buffer

In order to resolve a discrepancy in the literature, we have examined the in vitro inactivation of human alpha 1-proteinase inhibitor by direct exposures either to whole cigarette smoke or to filtered (i.e., gas-phase) smoke. Wyss and coworkers (2) reported that whole smoke does not inactivate the protein, whereas we reported that gas-phase smoke does. We now find that direct exposure to gas-phase cigarette smoke causes a slightly greater inactivation of the protein than does direct exposure to whole cigarette smoke, confirming our earlier suggestion that whole smoke is less oxidizing than is gas-phase smoke. This difference, however, does not explain the dramatic difference between our previous findings and those of Wyss and coworkers (2). The explanation for the discrepancy lies in the nature of the buffers used. Wyss and coworkers used Tris buffer and the use of Tris quenches the inactivation process almost completely. Our experiments used phosphate buffer. We suggest that Tris is an unsuitable buffer for use in experiments that probe the effects of cigarette smoke.     

Inhalation of nitrogen dioxide fails to reduce the activity of human lung alpha-1-proteinase inhibitor

Healthy, nonsmoking human volunteers were exposed to environmentally relevant concentrations of NO2 followed by bronchoalveolar lavage (BAL) to study whether NO2 exposure decreases the functional activity of alpha-1-proteinase inhibitor (alpha 1-PI) in the lung. Two 3-h exposure protocols with intermittent exercise were employed and BAL was performed 3.5 h after exposure. The first exposure protocol with nine subjects involved three 2-ppm "peaks" with a 0.05 ppm background, whereas the second protocol with 15 subjects was a continuous exposure to 1.5 ppm NO2. All subjects were randomly exposed to either air or NO2, with at least a 2-wk interval between treatments, and the BAL fluids obtained after air exposure served as the controls. The BAL fluids were analyzed for alpha 1-PI elastase inhibitory activity, the immunologic concentration of alpha 1-PI, total protein, and albumin. The ratio of alpha 1-PI activity to its immunologic concentration was taken as the functional activity of alpha 1-PI, and possible changes in the amount of alpha 1-PI in the lung were assessed by examining the ratio of the immunologic concentration of alpha 1-PI to total protein. Neither of the NO2 exposure protocols resulted in a decrease in the functional activity of alpha 1-PI, nor were there alterations in the immunologic levels of alpha 1-PI. These data suggest that short-term exposures to low levels of NO2 do not result in a lung-localized deficiency of active alpha 1-PI, which has been hypothesized to be a contributing factor in the pathogenesis of emphysema.     

Enhanced release of elastase and oxidative inactivation of alpha-1-protease inhibitor by stimulated human neutrophils exposed to Pseudomonas aeruginosa pigment 1-hydroxyphenazine.

The in vitro effects of the Pseudomonas aeruginosa-derived phenazine pigments pyocyanin and 1-hydroxyphenazine (1-hp) on neutrophil elastase release and myeloperoxidase-induced inactivation of alpha-1-protease inhibitor (alpha 1-PI) were investigated. 1-hp (6-25 microM), but not pyocyanin, caused a dose-dependent enhancement of elastase release by FMLP:cytochalasin B (CB)-activated human neutrophils. 1-hp (0.78-6.25 microM) also increased the oxidative inactivation of the elastase inhibitory capacity of alpha 1-PI exposed to FMLP:CB-activated neutrophils. Methionine, a scavenger of hypochlorous acid, completely protected alpha 1-PI from inactivation by stimulated neutrophils in the presence or absence of 1-hp. Similar protective effects were observed with sodium azide, an inhibitor of myeloperoxidase. P. aeruginosa-derived 1-hp may promote an elastase-antielastase imbalance in vivo by increasing the release of neutrophil elastase and by enhancing the oxidative inactivation of alpha 1-PI, thereby contributing to the development of tissue destruction in P. aeruginosa-infected patients.     

分泌型白细胞蛋白酶抑制剂对香烟烟雾提取物诱导人支气管上皮细胞炎症介质表达的影响

目的 检测分泌型白细胞蛋白酶抑制剂(SLPI)对香烟烟雾提取物(CSE)诱导体外培育的正常人支气管上皮细胞(NHBE)炎症介质表达水平的影响,探讨SLPI对慢性气道炎症局部保护作用的机制.方法 实验设对照组、CSE组、SLPI组和SLPI+CSE组,均采用免疫细胞化学方法检测NHBE细胞中基质金属蛋白酶-9(MMP-9)蛋白的表达,采用酶联免疫吸附试验检测各组培养上清液中白细胞介素8(IL-8)的表达.应用SPSS 11.5软件进行统计学处理,多样本均数比较采用单因素方差分析和SNK检验,若方差不齐进行校正,P<0.05为差异有统计学意义.结果 对照组能少量表达MMP-9(积分值为3.1±0.5)和IL-8[(4.9±0.6)ng/L];用CSE干预NHBE细胞能诱导MMP-9和IL-8的表达,且在一定范围内与CSE干预时间呈依赖性,24 h达峰值,MMP-9积分值和IL-8浓度分别为6.6±0.4和(17.7±1.9)ng/L,随后呈明显下降趋势;用SLPI干预NHBE细胞能明显抑制MMP-9(积分值为0.8±0.5)和IL-8[(0.7±0.6)ng/L]的表达.结论 SLPI能抑制CSE诱导的NHBE细胞的MMP-9和IL-8表达.     

Salmonella paratyphi A is more genetically homogeneous than Salmonella typhi, as indicated by pulsed-field gel electrophoresis

We analyzed 18 Salmonella Paratyphi A and 12 Salmonella Typhi isolates from domestic and imported cases in Aichi, Japan, using pulsed-field gel electrophoresis. Paratyphoid fever cases have increased and outbreaks of Salmonella Paratyphi A occasionally occur in Japan, but S. Paratyphi A has not been extensively analyzed. Our study suggests significant genetic homogeneity among Salmonella Paratyphi A belonging to different phage types, which is in contrast to the genetic heterogeneity of Salmonella Typhi. These results suggest that a limited number of clones are responsible for paratyphoid fever.     

Investigation of the protective effects of the antioxidants ascorbate, cysteine, and dapsone on the phagocyte-mediated oxidative inactivation of human alpha-1-protease inhibitor in vitro

Oxidants derived from the atmosphere or from activated pulmonary phagocytes mediate functional inactivation of alpha-1-protease inhibitor (alpha-1-PI). Chronic exposure to these oxidants may cause emphysema. In this study we have investigated the effects of the antioxidants ascorbate, cysteine (10(-4) M to 10(-1) M), and dapsone (10(-6) M to 10(-3) M) on the oxidative inactivation of human alpha-1-PI by leukoattractant-activated polymorphonuclear leukocytes (PMNL) in vitro. During exposure of alpha-1-PI to stimulated PMNL in the presence of ascorbate and cysteine at concentrations of greater than 10(-4) M and dapsone at greater than 10(-6) M, the elastase inhibitory activity of alpha-1-PI was preserved. However, exposure of the alpha-1-PI to the antioxidants subsequent to PMNL-mediated oxidative inactivation was not associated with reactivation of elastase inhibitory capacity. Ascorbate, cysteine, and dapsone at concentrations that caused 50% protection of alpha-1-PI did not affect degranulation or the binding of radiolabeled leukoattractant to PMNL. It is suggested that the protective effects of the antioxidants are related to their ability to scavenge superoxide and oxidants generated by the PMNL-myeloperoxidase/H2O2/halide system. Because the effects of ascorbate and especially those of dapsone were observed at concentrations of these agents that are attainable in vivo, our results may have clinical significance.     

The drug 5-aminosalicylic acid rescues alpha 1-proteinase inhibitor from the neutrophil oxidative inactivation. A possible contribution to its therapeutic action in ulcerative colitis.

The glycoprotein alpha 1-proteinase inhibitor is the specific inhibitor of neutrophil elastase, a major tissue-damaging protease. When incubated with activated neutrophils, alpha 1-proteinase inhibitor lost its pancreatic porcine elastase inhibitory capacity and became incapable of forming a sodium dodecyl sulphate-stable complex with pancreatic porcine elastase. Inhibitors and scavengers of neutrophil-derived reactive oxygen species outlined the crucial role of hypochlorous acid in the alpha 1-proteinase inhibitor inactivation. Moreover, the drug 5-aminosalicylic acid prevented the inactivation of alpha 1-proteinase inhibitor by neutrophils in a dose-dependent manner. Finally, when the capacity of 5-aminosalicylic acid to rescue alpha 1-proteinase inhibitor from the neutrophil-derived attack was plotted as a function of the 5-aminosalicylic acid ability to scavenge neutrophil-derived hypochlorous acid, a positive linear relationship was found. Thus, our results provide a direct evidence that 5-aminosalicylic acid is able to prevent the oxidative inactivation of alpha 1-proteinase inhibitor by neutrophils. Therefore, we suggest that the drug has the potential to limit the elastase-mediated damage of colonic connective tissue by creating a microenvironment of active alpha 1-proteinase inhibitor around the neutrophils.     

Dickkopf-1, an inhibitor of Wnt signaling, is regulated by progesterone in human endometrial stromal cells

CONTEXT: Some members of the Wnt family, including ligands, receptors, inhibitors, and signaling components, are expressed in human endometrium. Dickkopf-1 (Dkk-1), a potent inhibitor of the Wnt signaling pathway, was recently found to be up-regulated in decidualizing endometrial stromal cells during the secretory phase of the menstrual cycle, suggesting regulation by progesterone. OBJECTIVES: To test the hypothesis that progesterone regulates Dkk-1 expression in human endometrial stromal cells, we investigated the following effects on stromal cell expression of Dkk-1 mRNA and protein: decidualizing stimuli (progesterone or cAMP), RU486 (an inhibitor of progesterone action), and withdrawal of progesterone. RESULTS: Short-term treatment (up to 72 h, which corresponds to the full decidualized phenotype in response to cAMP and an early response to progesterone) did not reveal regulation of Dkk-1 mRNA or protein by cAMP but did show induction of Dkk-1 expression when the cells were treated with progesterone, an effect that was blocked by RU486. In long-term cultures (from 14 to 23 d, which corresponds to the full decidualized phenotype in response to progesterone), a significant increase in Dkk-1 mRNA and protein production was observed. Addition of RU486 or withdrawal of progesterone after long-term decidualization resulted in a decrease of Dkk-1 mRNA and protein to control levels. Estradiol alone had no effect on stromal Dkk-1 expression. CONCLUSIONS: These data strongly support regulation by progesterone of Dkk-1 mRNA synthesis and protein expression in human endometrial stromal cells and that the response is specific for progesterone and independent of cAMP and estradiol.     

The superficial layer of human articular cartilage is more susceptible to interleukin-1–induced damage than the deeper layers

Objective. To compare the responses of chondrocytes from superficial and deep layers of normal human articular cartilage to interleukin-1 (IL-1) and IL-1 receptor antagonist protein (IRAP), and to evaluate the binding sites for IL-1 on these cells. Methods. Cartilage and chondrocytes from superficial and deeper layers of human femoral condyles were cultured with and without IL-1 in the presence and absence of IRAP. The effect of these agents on ³⁵S-proteoglycan synthesis and catabolism and production of stromelysin and tissue inhibitor of metalloproteinases 1 (TIMP-1) were measured by biochemical and immunologic assays. Receptor binding was evaluated using ¹²⁵I-labeled IL-1. Results. IL-1 induced more severe inhibition of proteoglycan synthesis and a lower ratio of secreted TIMP-1:stromelysin in chondrocytes from superficial cartilage than those from deeper cartilage. IRAP blocked responses to IL-1 more effectively in chondrocytes from deep cartilage than those from superficial cartilage. Chondrocytes from the articular surface showed approximately twice the number of high-affinity binding sites for IL-1 as did cells from deep cartilage. Conclusion. Chondrocytes from the surface of articular cartilage show a greater vulnerability to the harmful effects of IL-1 and are less responsive to the potential therapeutic effects of IRAP than cells in the deeper layers of the tissue.     

High normal serum levels of C3 and C1 inhibitor,two acute-phase proteins belonging to the complement system,occur more frequently in patients with Crohn's disease than ulcerative colitis

Few data are available on measurements of serum concentrations of complement proteins in inflammatory bowel disease (IBD). Therefore we measured serum levels of C3, C4, and C1-esterase inhibitor (C1-INH) as well as C-reactive protein (CRP) in 167 patients with Crohn's disease (CD) and 111 patients with ulcerative colitis (UC). Median serum concentrations of C3 and C1-INH were significantly higher in CD than in UC. According to multiple logistic regression analysis adjusted to age, sex, activity of disease, and presence of extraintestinal manifestations, IBD patients with high-normal (128%, 75th percentile ) C1-INH concentrations had significantly (0.0275) higher odds ratio to have a diagnosis of CD than UC. Patients with high-normal C3 (1.40 g/liter) and high (20 mg/liter) CRP concentrations had an even higher odds ratio of a CD diagnosis (P = 0.0132). Our findings indicate that measurement of C3, C1-INH, and CRP can be used as an additional marker to pANCA/ASCA for distinguishing patients with CD and UC.     

Resveratrol attenuates cigarette smoke extract induced cellular senescence in human airway epithelial cells by regulating the miR-34a/SIRT1/NF-κB pathway

Chronic obstructive pulmonary disease (COPD) is characterized by accelerated lung aging. Smoking is the critical risk factor for COPD. Cellular senescence of airway epithelial cells is the cytological basis of accelerated lung aging in COPD, and the regulation of microRNAs (miRNAs) is the central epigenetic mechanism of cellular senescence. Resveratrol (Res) is a polyphenol with anti-aging properties. This study investigated whether Res attenuates cigarette smoke extract (CSE)-induced cellular senescence in human airway epithelial cells (BEAS-2B) through the miR-34a/SIRT1/nuclear factor-kappaB (NF-κB) pathway. BEAS-2B cells were treated with Res, CSE and transfected with miR-34a-5p mimics. Cellular senescence was evaluated by senescence -related β-galactosidase (SA-β-gal) staining and expression of senescence-related genes (p16, p21, and p53). The expressions of miR-34a-5p, SIRT1, and NF-κB p65 were examined using quantitative real time polymerase chain reaction and western blotting. The senescence-associated secretory phenotype (SASP) cytokines (IL-1β, IL-6, IL-8, TNF-α) were assessed by enzyme-linked immunosorbent assay. The binding between miR-34a-5p and SIRT1 was confirmed by dual-luciferase reporter assay. The results showed that CSE dose-dependently decreased cell viability and elevated cellular senescence, characterized by increased SA-β-gal staining and senescence-related gene expressions (p16, p21, and p53). Further, CSE dose-dependently increased the expression of miR-34a-5p and SASP cytokines (IL-1β, IL-6, IL-8, TNF-α) in BEAS-2B cells. Pretreatment with Res inhibited CSE-induced cellular senescence and secretion of SASP cytokines (IL-1β, IL-6, IL-8, TNF-α) in a dose-dependent manner. Moreover, Res reversed the CSE-induced down-regulation of SIRT1 and up-regulation of miR-34a-5p and NF-κB p65. SIRT1 is a target of miR-34a-5p. Overexpression of miR-34a-5p via transfection with miR-34a-5p mimic in BEAS-2B cells attenuated the inhibitory effect of Res on cellular senescence, accompanied by reversing the expression of SIRT1 and NF-κB p65. In conclusion, Res attenuated CSE-induced cellular senescence in BEAS-2B cells by regulating the miR-34a/SIRT1/NF-κB pathway, which may provide a new approach for COPD treatment.     

Growth restriction of influenza A virus by M2 protein antibody is genetically linked to the M1 protein.

The M2 protein of influenza A virus is a 97-amino acid integral membrane protein expressed at the surface of infected cells. Recent studies have shown that a monoclonal antibody (14C2) recognizes the N terminus of M2 and restricts the replication of certain influenza A viruses. To investigate the mechanism of M2 antibody growth restriction, 14C2 antibody-resistant variants of strain A/Udorn/72 have been isolated. Most of the variant viruses are not conventional antigenic variants as their M2 protein is still recognized by the 14C2 antibody. A genetic analysis of reassortant influenza viruses prepared from the 14C2 antibody-resistant variants and an antibody-sensitive parent virus indicates that M2 antibody growth restriction is linked to RNA segment 7, which encodes both the membrane protein (M1) and the M2 integral membrane protein. Nucleotide sequence analysis of RNA segment 7 from the variant viruses predicts single amino acid substitutions in the cytoplasmic domain of M2 at positions 71 and 78 or at the N terminus of the M1 protein at residues 31 and 41. To further examine the genetic basis for sensitivity and resistance to the 14C2 antibody, the nucleotide sequences of RNA segment 7 of several natural isolates of influenza virus have been obtained. Differences in the M1 and M2 amino acid sequences for some of the naturally resistant strains correlate with those found for the M2 antibody variant viruses. The possible interaction of M1 and M2 in virion assembly is discussed.     

Genetic control of cobalamin binding in normal and mutant cells: Assignment of the gene for 5-methyltetrahydrofolate:L-homocysteine S-methyltransferase to human chromosome 1

When extracts prepared from cultured human or rodent fibroblasts grown in medium containing [(57)Co]cobalamin were analyzed by polyacrylamide gel electrophoresis, most of the intracellular radioactivity migrated with the activity of the cobalamin-dependent enzyme 5-methyltetrahydrofolate:L-homocysteine S-methyltransferase (EC 2.1.1.13). Because the rodent and human forms of this enzyme are electrophoretically different, we used the binding of [(57)Co]cobalamin to detect the presence of the human methyltransferase isozyme in rodent-human somatic cell hybrids. As expected, binding and methyltransferase activities were found to cosegregate, thus confirming genetically their electrophoretic identity. Accordingly, we examined the [(57)Co]cobalamin-binding patterns and human chromosome contents of a panel of 12 rodent-human hybrid clones, and concluded that the gene for the methyltransferase (designated Mtr) is located on human chromosome 1. Using this information, we probed the nature of the molecular defect exhibited by fibroblasts cultured from patients expressing the cbl C mutation. Although these cells are unable to associate newly taken up [(57)Co]cobalamin with the methyltransferase, hybrids of mouse L-cells and cbl C cells containing chromosome 1 show a "reappearance" of the human [(57)Co]cobalamin-methyltransferase. These results indicate that the cbl C mutation does not affect the methyltransferase apoprotein, but rather some metabolic step that must convert cobalamin to a chemical form capable of attaching to the enzyme.     

Differences in substrate and inhibitor kinetics of human type 1 and type 2 3beta-hydroxysteroid dehydrogenase are explained by the type 1 mutant,H156Y

Two distinct genes encode the human type 1 (placenta, mammary gland) and type 2 (adrenal, gonad) isoforms of 3beta-hydroxysteroid dehydrogenase/isomerase (3beta-HSD). We have produced the Y154F, H156Y, and K158Q mutant enzymes in the Y154-P-H156-S-K158 motif of the human type 1 3beta-HSD/isomerase. The H156Y mutant was created to produce a chimera of the type 2 enzyme motif (Y154-P-Y156-S-K158) in the type 1 enzyme. The wild-type (WT) 1 and 2 plus the mutant enzymes were expressed and purified. The Km for dehydroepiandrosterone and Ki for epostane measured with both the H156Y mutant and WT 2 are 13-fold to 17-fold greater than those values obtained with the WT 1 3beta-HSD. The Y154F and K158Q mutants exhibit no 3beta-HSD but have significant isomerase activity. Thus, H156 in WT 1 vs. Y156 in WT 2 accounts for the substantially higher affinity of WT 1 3beta-HSD activity for these substrate and inhibitor steroids relative to the WT 2 enzyme.     

Up-regulation of p27Kip1 by progestins is involved in the growth suppression of the normal and malignant human endometrial glandular cells

Progestins are known to suppress the growth of normal human endometrial glands and endometrial carcinomas possessing PRs. To elucidate the molecular mechanisms of progestin-induced growth inhibition, the expression and functional involvement of p27Kip1 (p27), a cyclin-dependent-kinase inhibitor, was investigated using cultured normal endometrial glandular cells and endometrial carcinoma cell lines (Ishikawa; PR-positive, KLE; PR-negative). Growth of the normal endometrial glandular cells and Ishikawa cells was suppressed by treatment with progesterone and medroxyprogesterone acetate, respectively, in association with an increase in p27 protein expression. Immunoprecipitation revealed that progestins accelerated the complex formation of p27 and cdk2 in both types of cells. However, treatment with progestins did not show any marked alterations in the mRNA expression of p27 in either normal glandular cells or Ishikawa cells. On the other hand, p27 protein degradation experiments indicated that treatment with progesterone and medroxyprogesterone acetate prolonged the degradation time of the normal endometrial glandular cells and Ishikawa cells, respectively. Forced expression of the p27 protein using a p27 expression plasmid reduced the growth activity of normal endometrial glandular cells. These findings suggest that p27 is functionally involved in progestin-induced growth suppression of normal and malignant endometrial epithelial cells and that up-regulation of the p27 protein by progestins possibly occurs via posttranslational mechanisms.