Discovery of varlaxins, new aeruginosin-type inhibitors of human trypsins

Low-molecular weight natural products display vast structural diversity and have played a key role in the development of novel therapeutics. Here we report the discovery of novel members of the aeruginosin family of natural products, which we named varlaxins. The chemical structures of varlaxins 1046A and 1022A were determined using a combination of mass spectrometry, analysis of one- and two-dimensional NMR spectra, and HPLC analysis of Marfey's derivatives. These analyses revealed that varlaxins 1046A and 1022A are composed of the following moieties: 2-O-methylglyceric acid 3-O-sulfate, isoleucine, 2-carboxy-6-hydroxyoctahydroindole (Choi), and a terminal arginine derivative. Varlaxins 1046A and 1022A differ in the cyclization of this arginine moiety. Interestingly, an unusual α-D-glucopyranose moiety derivatized with two 4-hydroxyphenylacetic acid residues was bound to Choi, a structure not previously reported for other members of the aeruginosin family. We sequenced the complete genome of Nostoc sp. UHCC 0870 and identified the putative 36 kb varlaxin biosynthetic gene cluster. Bioinformatics analysis confirmed that varlaxins belong to the aeruginosin family of natural products. Varlaxins 1046A and 1022A strongly inhibited the three human trypsin isoenzymes with IC₅₀ of 0.62-3.6 nM and 97-230 nM, respectively, including a prometastatic trypsin-3, which is a therapeutically relevant target in several types of cancer. These results substantially broaden the genetic and chemical diversity of the aeruginosin family and provide evidence that the aeruginosin family is a source of strong inhibitors of human serine proteases.

Nexin-1 inhibits the activity of human brain trypsin

Trypsin and other trypsin-like serine proteases have been shown to play important roles in neural development, plasticity and neurodegeneration. Their activity is modulated by serine protease inhibitors, serpins. However, for human brain trypsin, trypsin-4, no brain-derived inhibitors have been described. Here, we report that nexin-1 inhibits trypsin-4, and forms stable complexes only with this trypsin-isoenzyme. This result suggests that nexin-1 could modulate trypsin activity in brain where both nexin-1 and trypsin-4 are expressed.

Glycodelin in reproductive endocrinology and hormone-related cancer

Glycodelin is an endocrine-regulated glycoprotein that has significant effects on immune cells, apoptosis, reproduction, cell adhesion, differentiation and cancer. In reproduction, glycodelin contributes to capacitation and immunoprotection of spermatozoa, and it modulates sperm-oocyte binding, acrosome reaction and implantation. In endocrine-related cancer, the differentiation inducing effects of glycodelin are accompanied by growth restriction of malignant cells, decreased expression of oncogenes, increased expression of tumour suppressor genes and morphological reversion of the malignant phenotype. This review features these properties and clinical connections, highlighting the role of glycosylation in biological actions.

Glycosylation related actions of glycodelin: gamete, cumulus cell, immune cell and clinical associations

Glycodelin is an example of a glycoprotein whose complex-type glycans mediate biological actions in human reproduction and immune reactions. Being attached to an identical protein backbone, glycodelin oligosaccharides vary significantly from one reproductive tissue to another and have an effect on its own secretion and role in cell communication. For instance, uterine glycodelin-A inhibits sperm-oocyte interaction by binding on the sperm head. This is a glycosylation-dependent phenomenon, in which fucosyltransferase-5 plays a key role. Glycodelin-S from seminal plasma binds evenly around the sperm head and maintains an uncapacitated state in the spermatozoa, until the isoform is detached during sperm passage through the cervix. Glycodelin-F from follicular fluid and Fallopian tube binds to the acrosomal region of the sperm head, thereby inhibiting both the sperm-oocyte binding and premature progesterone-induced acrosome reaction. The cumulus cells surrounding the oocyte can capture glycodelin-A and -F from the surrounding environment and convert these isoforms to a cumulus cell isoform, glycodelin-C. It differs by glycosylation from the other isoforms, and it too attaches on the sperm head, with the highest density in the equatorial region. Glycodelin-C is capable of detaching the sperm-bound inhibitory isoforms so that the sperm-oocyte binding is enhanced. Glycodelin-A also has immunosuppressive actions directed to cellular, humoral and innate immunity. Although these actions depend mainly on the protein backbone, glycosylation also plays a part. Glycosylated glycodelin may be involved in the protection of spermatozoa against maternal immune reactions, and glycodelin also has apoptogenic activity. Some glycosylation patterns of glycodelin may mask its apoptogenic domain. This review updates the recent research and clinical associations of glycodelin, highlighting the role of glycosylation.

The Contribution of d-Mannose, l-Fucose, N-Acetylglucosamine, and Selectin Residues on the Binding of Glycodelin Isoforms to Human Spermatozoa1

Previous data showed that glycodelin-A from amniotic fluid and glycodelin-F from follicular fluid inhibited sperm-zona pellucida binding. Solubilized zona pellucida reduced the binding of glycodelin-F to sperm extract dose dependently. This study demonstrated that the zona pellucida proteins also reduced the binding of glycodelin-A to sperm extract. Ionophore-induced acrosome reaction reduced the binding of iodinated glycodelin-A and -F to sperm, indicating that the glycodelin-binding sites are on the outer acrosomal membrane or on the sperm plasma membrane overlying the acrosome. While the binding of glycodelin-A to sperm was suppressed by mannose and fucose neoglycoproteins, that of glycodelin-F was also reduced by acetylglucosamine neoglycoprotein. Pretreatment of sperm with inhibitors of mannosidase and acetylglucosaminidase reduced the binding of glycodelin-F to sperm. On the other hand, inhibitor of mannosidase but not of acetylglucosaminidase inhibited the binding of glycodelin-A. In a competition binding assay, mannosidase reduced both glycodelin-A and -F binding whereas acetylglucosaminidase reduced only glycodelin-F binding. While fucosidase reduced the binding of both glycodelins, fucosidase inhibitor was marginally active in suppressing the binding of glycodelins to human sperm. Among the selectins tested, only E-selectin had a slight inhibitory effect on the binding of glycodelin-A to sperm. The binding of glycodelin-F was unaffected by selectins and their antibodies. In conclusion, the binding of glycodelin-A to sperm involves mannose, fucose, and possibly E- selectin residues, while that of glycodelin-F involves mannose, fucose, and N-acetylglucosamine but not the selectin residue.

Comparative studies on the regulation of insulin-like growth factor-binding protein-1 (IGFBP-1) and sex hormone-binding globulin (SHBG) production by insulin and insulin-like growth factors in human hepatoma cells

Production of insulin-like growth factor-binding protein-1 (IGFBP-1) by the liver is efficiently inhibited by insulin both in vivo and in vitro. Consequently, serum IGFBP-1 concentration reflects insulin bioactivity in portal vein. Sex hormone-binding globulin (SHBG) is another insulin-regulated liver-derived protein that has appeared promising in detecting individuals with portal hyperinsulinemia. We compared the regulation of IGFBP-1 and SHBG production by insulin and insulin-like growth factors (IGF-I and IGF-II) in human hepatoma cell cultures. Insulin equipotently inhibited IGFBP-1 and SHBG production, with maximal decrease in culture medium concentrations being about 35% for both proteins during 48 h of culture in serum-free medium. IGF-I and IGF-II also inhibited the IGFBP-1 and SHBG levels. We conclude that IGFBP-1 and SHBG are equally sensitive to ambient insulin concentrations in human hepatoma cell cultures, and the production of both proteins is also attenuated by the IGFs.

Zona-binding inhibitory factor-1 from human follicular fluid is an isoform of glycodelin

Zona-binding inhibitory factor-1 (ZIF-1), a glycoprotein in human follicular fluid, reduces the binding of spermatozoa to the zona pellucida. ZIF-1 has a number of properties similar to those of glycodelin-A from human follicular fluid. The objective of this study was to compare the biochemical characteristics of these two glycoproteins. N-terminal sequencing and protease-digested peptide mapping showed that ZIF-1 and glycodelin-A have the same protein core. However, these glycoproteins differ in their oligosaccharide chains, as demonstrated by fluorophore-assisted carbohydrate electrophoresis, lectin-binding ability, and isoelectric focusing. ZIF-1 inhibited spermatozoa-zona pellucida binding slightly more than did glycodelin-A and significantly suppressed progesterone-induced acrosome reaction of human spermatozoa. Indirect immunofluorescence staining revealed specific binding of glycodelin-A and ZIF-1 to the acrosome region of human spermatozoa, where ZIF-1 produced a stronger signal than did glycodelin-A at the same protein concentration. These data suggest that ZIF-1 is a differentially glycosylated isoform of glycodelin that potently inhibits human sperm-egg interaction. Future study on the function role of ZIF-1 would provide a better understanding of the regulation of fertilization in humans.

The synthesis and fate of glycodelin in human ovary during folliculogenesis

The ontogeny of glycodelin in human ovarian follicles during folliculogenesis was studied. Glycodelin immunoreactivity began to be detected in the granulosa cells and thecal cells of late secondary follicles. Immunoreactivity was also found in both the luteinized granulosa cells and cumulus cells obtained from women undergoing the assisted reproduction treatment. However, only the luteinized granulosa cells, and not the cumulus cells, expressed glycodelin mRNA. Results also showed that the cumulus cells took up radiolabelled glycodelin and partially deglycosylated some of it. Glycodelin (and a partially deglycolsylated form of glycoldelin) appeared to complex with two cytoplasmic or membrane components of the cumulus cells. The data also demonstrated that ZIF-1, a glycoprotein isolated from human follicular fluid, was immunologically similar to glycodelin. In conclusion, we suggest that glycodelin is synthesized in the granulosa cells of ovarian follicles at late secondary follicle stage. It then may be released into the follicular fluid from where it is taken up and partially modified by the cumulus cells.

Endometrial expression of glycodelin in women with levonorgestrel-releasing subdermal implants

OBJECTIVE

To determine whether subdermal levonorgestrel implants induce endometrial expression of glycodelin.

DESIGN

Cross-sectional, blinded study.

SETTING

University clinic.

PATIENT(S)

One hundred and eight women with subdermal implants and 19 postmenopausal women.

INTERVENTION(S)

Endometrial biopsies, curettages, and hysterectomies.

MAIN OUTCOME MEASURE(S)

Endometrial glycodelin expression was examined through immunohistochemistry, in situ hybridization, and morphologic endometrial dating.

RESULT(S)

Overall, 80% of the endometrial specimens obtained from women with subdermal levonorgestrel implants stained positive for glycodelin. Endometrial morphology of these women showed proliferative (71%), inactive/weakly proliferative (19%), menstrual or regenerating (6.5%), and other patterns (2.8%). Of these, 79%, 71%, 100%, and 100% were glycodelin positive, respectively. Nineteen specimens were obtained during the midcycle when glycodelin is not normally expressed: of these, 89% stained positive for glycodelin. Implant-related amenorrhea was associated with endometrial glycodelin expression in 58% of the women, whereas the endometrium specimens obtained from women with postmenopausal hypoestrogenic amenorrhea contained no detectable glycodelin.

CONCLUSION(S)

Subdermal levonorgestrel implant use is often associated with endometrial expression of glycodelin. Because glycodelin has been shown to inhibit sperm-egg binding, the induction of glycodelin may contribute to the contraceptive activity of the implant.

Factors regulating insulin-like growth factor binding protein-3 secretion from human hepatoma (HepG2) cells

Insulin-like growth factor (IGF) binding protein-3 (IGFBP-3) is a growth hormone (GH) dependent carrier of the IGFs in human serum. Apart from GH regulation the hormonal control of IGFBP-3 production is not well established and although the liver is considered to be the main source of circulating IGFBP-3, there are no in vitro studies of the effect of both insulin and IGFs on the IGFBP-3 produced in human hepatoma cells. The effect of sex hormones as well as cortisol has not been studied. To elucidate this we performed cell culture studies on HepG2 cells in the presence of various effectors. Insulin, IGF-I and IGF-II brought about a 1.5-2-fold enhancement of IGFBP-3 release at 7.5-30 nM concentrations. In contrast, cortisol decreased IGFBP-3 secretion by 30-40% whereas estradiol, tamoxifen and testosterone had no effect at physiological concentrations. We conclude that, in addition to GH, also insulin, IGF-I and IGF-II and glucocorticoids can modulate IGFBP-3 secretion by human hepatoma cells.

Glycodelins

Glycodelin is a major glycoprotein that is synthesized in the endometrium in response to progesterone and relaxin exposure. Endometrium-derived glycodelin-A has contraceptive and immunosuppressive properties. Glycodelin is absent from the endometrium during the fertile periovulatory phase, but is synthesized in this tissue during the peri-implantation phase and is abundant during the last week of the luteal phase. Changes in local and/or circulating glycodelin concentrations have been observed in women with reproductive disorders. The chemical modification of glycodelins has resulted in compounds with antiviral activity.

Insulin reduction with metformin increases luteal phase serum glycodelin and insulin-like growth factor-binding protein 1 concentrations and enhances uterine vascularity and blood flow in the polycystic ovary syndrome

We hypothesized that hyperinsulinemia contributes to early pregnancy loss in the polycystic ovary syndrome by adversely affecting endometrial function and environment. Serum glycodelin, a putative biomarker of endometrial function, is decreased in women with early pregnancy loss. Insulin-like growth factor-binding protein-1 may also play an important role in pregnancy by facilitating adhesion processes at the feto-maternal interface. We studied 48 women with polycystic ovary syndrome before and after 4 weeks of administration of 500 mg metformin (n = 26) or placebo (n = 22) 3 times daily. Oral glucose tolerance tests were performed, and serum glycodelin and insulin-like growth factor-binding protein-1 were measured during the follicular and clomiphene-induced luteal phases of menses. In the metformin group, the mean (+/-SE) area under the serum insulin curve after glucose administration decreased from 62 +/- 6 to 19 +/- 2 nmol/L.min (P < 0.001). Follicular phase serum glycodelin concentrations increased 20-fold from 150 +/- 46 to 2813 +/- 1192 pmol/L (P < 0.001), and serum insulin-like-growth factor-binding protein-1 concentrations increased from 936 +/- 152 to 2396 +/- 300 pmol/L (P < 0.001). Similarly, luteal phase serum glycodelin concentrations increased 3-fold from 3434 +/- 1299 to 10624 +/- 1803 pmol/L (P < 0.001), and serum insulin-like growth factor-binding protein-1 concentrations increased from 1220 +/- 136 to 4916 +/- 596 pmol/L (P < 0.001). Uterine vascular penetration also increased in the metformin group, as did blood flow of spiral arteries, as demonstrated by a 20% decrease in the resistance index from 0.71 +/- 0.02 to 0.57 +/- 0.03 (P < 0.001). These variables did not change in the placebo group. We conclude that insulin reduction with metformin increases follicular and luteal phase serum glycodelin and insulin-like growth factor-binding protein-1 concentrations and enhances luteal phase uterine vascularity and blood flow in the polycystic ovary syndrome. These changes may reflect an improved endometrial milieu for the establishment and maintenance of pregnancy.

Glycodelin: a reproduction-related lipocalin

Glycodelin, a human lipocalin, is a major endometrial protein with at least two differentially glycosylated isoforms. Glycodelin-A (GdA) is purified from human mid-trimester amniotic fluid, where it is secreted from the decidualized endometrium. Glycodelin-S (GdS) is synthesized in the male reproductive tract, mainly in the seminal vesicles, and secreted into seminal plasma. These two glycodelin isoforms, glycosylated in a completely different manner, serve as a good model for studying the effects of glycosylation on protein function and physicochemical properties. We have reviewed here the structure, expression and biological functions of glycodelin.

Seminal plasma glycodelin and fertilization in vitro

Endometrium-derived glycodelin-A inhibits sperm-egg binding, whereas differentially glycosylated seminal plasma glycodelin-S does not. The difference has been ascribed to the specific type of glycosylation of glycodelin-A. We studied whether the total glycodelin concentration or the relative glycodelin-A concentration in seminal plasma are related to the in vitro fertilization rate of oocytes. We found that total glycodelin levels were significantly higher in a quartile of men with the lowest in vitro fertilization rate compared with the remaining 3 quartiles combined (P = .01). However, for predicting low fertilization capacity of sperm, combining the glycodelin and sperm concentrations by logistic regression analysis did not significantly increase the information obtained from sperm concentration alone. We used specific lectin-immunoassays to determine whether increased glycodelin-A-type glycosylation in seminal plasma would be related to failure to fertilize. No difference was found between the groups with high fertilization and no fertilization in vitro. It is concluded that, although high seminal plasma total glycodelin level has a tendency of being associated with a lower fertilization rate, the difference has limited value to predict fertilization in vitro.

Recombinant glycodelin carrying the same type of glycan structures as contraceptive glycodelin-A can be produced in human kidney 293 cells but not in chinese hamster ovary cells

We have produced human recombinant glycodelin in human kidney 293 cells and in Chinese hamster ovary (CHO) cells. Structural analyses by lectin immunoassays and fast atom bombardment mass spectrometry showed that recombinant human glycodelin produced in CHO cells contains only typical CHO-type glycans and is devoid of any of the N, N'-diacetyllactosediamine (lacdiNAc)-based chains previously identified in glycodelin-A (GdA). By contrast, human kidney 293 cells produced recombinant glycodelin with the same type of carbohydrate structures as GdA. The presence of a beta1-->4-N-acetylgalactosaminyltransferase functioning in the synthesis of lacdiNAc-based glycans in human kidney 293 cells is concluded to be the cause of the occurrence of lacdiNAc-based glycans on glycodelin produced in these cells. Furthermore, human kidney 293 cells were found to be particularly suited for the production of recombinant glycodelin when they were cultured in high glucose media. Lowering the glucose concentration and the addition of glucosamine resulted in higher relative amounts of oligomannosidic-type glycans and complex glycans with truncated antennae. Human glycodelin is an attractive candidate for the development of a contraceptive agent, and this study gives valuable information for selecting the proper expression system and cell culture conditions for the production of a correctly glycosylated recombinant form.

Insulin-like growth factor I is not a useful marker of prostate cancer in men with elevated levels of prostate-specific antigen

High serum levels of insulin-like growth factor I (IGF-I) and low levels of IGF-binding protein-3 (IGFBP-3) have been shown to correlate with increased prostate cancer risk. To evaluate this, IGF-I, IGFBP-3, and prostate-specific antigen (PSA) were measured in serum from 665 consecutive men (179 with prostate cancer), aged 55-67 yr, with elevated serum prostate-specific antigen (PSA; > or = 4 microg/L) in a screening trial. Men in the highest quartile of IGF-I levels had an odds ratio (OR) for prostate cancer of 0.50 [95% confidence interval (CI) 0.26-0.97] when adjusting for serum IGFBP-3. IGFBP-3 itself was not significantly associated with prostate cancer risk (OR, 1.24; 95% CI, 0.68-2.24). Prostate volume was larger in men without than in those with prostate cancer (P < 0.001), and after adjustment for prostate volume, the negative association between serum IGF-I and prostate cancer risk was no longer significant (OR, 0.57; 95% CI, 0.28-1.16). In screen-positive men with elevated serum PSA, serum IGF-I is not a useful diagnostic test for prostate cancer, but it may be associated with benign prostatic hyperplasia and enlargement.

Leptin during and after preeclamptic or normal pregnancy: its relation to serum insulin and insulin sensitivity

Hyperleptinemia may be part of the insulin resistance syndrome. We studied serum leptin in preeclampsia, which is an insulin-resistant state, and sought associations between leptin and insulin or insulin sensitivity during and after pregnancy. Twenty-two proteinuric preeclamptic women and 16 normotensive controls were studied during the third trimester. Leptin was higher in preeclampsia (mean +/- SE, 34.6 +/- 3.9 v 20.0 +/- 3.3 microg/L, P = .002) and correlated directly with the level of proteinuria (r = .47, P = .03) and normal pregnancy (r = .52, P = .04), whereas insulin sensitivity as assessed by an intravenous glucose tolerance test showed no relationship to leptin. Leptin was 19.0 +/- 3.6 microg/L in 14 preeclamptic women and 10.1 +/- 2.0 microg/L (P = .11) in 11 controls 3 months after delivery. Leptin correlated directly with insulin both in preeclamptic puerperal women (r = .63, P = .02) and in controls (r = .81, P = .003). Leptin and insulin sensitivity correlated only in preeclamptic puerperal women (r = -.59, P = .02). In conclusion, (1) serum leptin is elevated in preeclampsia, (2) insulin is an important determinant of serum leptin in preeclamptic and normotensive women both during pregnancy and in the puerperium, and (3) hyperleptinemia may be part of the insulin resistance syndrome also in women with prior preeclampsia.

Estradiol increases the production of sex hormone-binding globulin but not insulin-like growth factor binding protein-1 in cultured human hepatoma cells

OBJECTIVE

To study the effects of E2 on insulin-like growth factor binding protein-1 (IGFBP-1) and sex hormone-binding globulin (SHBG) production with cultured human HepG2 hepatoma cells.

DESIGN

Experimental cell culture.

SETTING

Academic medical center.

PATIENT(S)

None.

INTERVENTION(S)

Addition of E2 to cell culture medium.

MAIN OUTCOME MEASURE(S)

Intracellular and released concentrations of IGFBP-1 and SHBG.

RESULT(S)

Estradiol did not affect the intracellular or extracellular IGFBP-1 concentration, whereas the intracellular SHBG concentration increased significantly in response to 0.5-2.5 microM of E2.

CONCLUSION(S)

Whereas the two binding proteins share a number of regulatory factors, their regulation by E2 is dissimilar in human hepatoma cells. Estradiol does not affect the intracellular or secreted IGFBP-1 concentration, but it does increase the production of SHBG.

Glycodelin and beta-lactoglobulin, lipocalins with a high structural similarity, differ in ligand binding properties

Human glycodelin, a lipocalin with a high amino acid similarity to beta-lactoglobulins, appears as various glycoforms with different biological activities in endometrium (glycodelin-A) and seminal plasma (glycodelin-S). We found that the structures of these glycodelins and beta-lactoglobulin are similar. Despite this structural similarity, unlike beta-lactoglobulin, glycodelin-A binds neither retinoic acid nor retinol. It was impossible to detect any endogenous retinoids or steroids in any of the two purified glycodelins. Both their glycoforms share similar thermodynamic parameters of reversible denaturation suggesting that native folding of glycodelin-A and glycodelin-S is not influenced by the differences in glycosylation or by ligand binding.

Relaxin stimulates glycodelin mRNA and protein concentrations in human endometrial glandular epithelial cells

Human endometrium is the major organ that produces glycodelin A (GdA). The production of endometrial GdA causes a fluctuation of the peripheral glycodelin concentrations in women during the menstrual cycle and pregnancy. It has recently been reported that the rise of plasma concentrations of glycodelin is correlated with relaxin during the late luteal phase and early pregnancy. In addition, administration of relaxin increases glycodelin plasma concentrations, suggesting that relaxin induces GdA production in endometrium. To investigate whether relaxin regulates the GdA synthesis, human endometrial glandular epithelial cells were isolated and cultured with or without relaxin for up to 4 days. Western blot showed that GdA synthesized and secreted from epithelial glands had a major molecular weight of 28 kDa, i.e. the same as the GdA isolated from amniotic fluid. Cells incubated with relaxin consistently increased in GdA production rate (2-6-fold). The GdA mRNA concentrations increased 2-11-fold in cells incubated with relaxin for 2-4 days, as determined by solution hybridization/ribonuclease protection assay. The increase of the mRNA concentration indicates that relaxin activates GdA transcription.

Growth hormone induced increase in serum IGFBP-3 level is reversed by anabolic steroids in substance abusing power athletes

OBJECTIVE

Body builders may use growth hormone (GH) and anabolic steroids to increase fitness and muscle mass. GH increases serum concentrations of IGF-I and IGFBP-3. The combined effects of GH and anabolic androgenic steroids on IGFBP-3 and IGF-I levels are not known under authentic substance-abusing conditions. The aim of this study was to investigate this in substance-abusing power athletes.

DESIGN AND PATIENTS

Nine healthy, non-obese and non-competing male power athletes, all aggressive substance abusers, used GH and/or anabolic steroids independently of this study. Blood samples were taken both during and between the drug intake. Sixteen substance non-abusing wrestlers served as controls.

MEASUREMENTS

Serum IGF-I concentration was measured by radioimmunoassay and the IGFBP-3 concentration was measured by two immunofluorometric assays, one detecting proteolytic fragments of IGFBP-3. The capacity of serum to proteolytically cleave IGFBP-3 was studied by the proteolysis assay.

RESULTS

While growth hormone increased the IGFBP-3 and IGF-I concentrations, anabolic steroids decreased the same. Concomitant use of growth hormone and anabolic steroids decreased the IGFBP-3 concentration in five out of six abuse periods in spite of the fact that the IGF-I concentration remained elevated in four of them. However, in two men who were on low calorie diet both the IGF-I and IGFBP-3 concentrations decreased during combined GH/anabolic steroid abuse. No proteolytic fragmentation of IGFBP-3 was observed.

CONCLUSION

Massive abuse of anabolic steroids decreases both the basal and GH-stimulated IGFBP-3 concentrations, whereas its effects on serum IGF-I concentration are variable and affected by low calorie diet. This study demonstrates that detection of GH doping by measuring the IGF-I and/or IGFBP-3 levels has notable confounding factors.

Glycodelins: role in regulation of reproduction, potential for contraceptive development and diagnosis of male infertility

Glycodelins are glycoproteins synthesized in various glands, with sequence homology to beta-lactoglobulins, and named according to their unique oligosaccharide structures. We purified, cloned and sequenced endometrium- and seminal plasma-derived glycodelins (GdA and GdS respectively) and found that they are involved in various types of cell-cell communications. These include interactions between the spermatozoon and the egg, and between immune cells and their targets. Endometrial GdA inhibits sperm-egg binding, whereas the differently glycosylated GdS in seminal plasma does not. These observation are of interest for reproductive physiology, detection of causes of infertility, and they also may have potential for contraceptive development.

Levonorgestrel-releasing intrauterine device-wearing women express contraceptive glycodelin A in endometrium during midcycle: another contraceptive mechanism?

Intrauterine devices (IUDs) exert contraceptive action by interfering with sperm transport, ovum development, fertilization and implantation. Glycodelin A (GdA) is a uterine glycoprotein that has local contraceptive activity by inhibiting sperm-egg binding. GdA is normally absent from endometrium during the fertile midcycle and it is not expressed until the fifth postovulatory day. The phase of menstrual cycle addressed in this study covers the phase when conception is most likely to follow an unprotected intercourse and when GdA is normally absent. We present here evidence that levonorgestrel-releasing IUD (LNg-IUD) is accompanied by 'inappropriate' expression of GdA in endometrium between days 7 and 16 of the menstrual cycle (six out of six cases). The same was also found in copper-releasing IUD (Cu-IUD)-wearing women, but less frequently (four out of 11 cases, P < 0.0345, Fisher's exact test). In-situ hybridization localized GdA mRNA into endometrial glands in the midcycle endometrium, confirming the cellular site of synthesis. Based on the potent inhibitory activity of GdA on sperm-egg binding, the presence of GdA in uterine glands of IUD wearers may lead to prior exposure of sperm to contraceptive GdA, thus contributing to the contraceptive activity of the IUD.

Glycodelins GdA and GdS modified by 3-hydroxyphthalic anhydride inhibit gp120-CD4 binding and HIV-1 infection in vitro

Bovine beta-lactoglobulin chemically modified with 3-hydroxyphthalic anhydride (3HP) was recently shown, at nanomolar concentrations, to block the binding site on CD4 for the HIV surface glycoprotein (gp120), potentially inhibiting HIV transmission. Human glycodelin has sequence homology with bovine beta-lactoglobulin and appears as different glycoforms in endometrium (GdA) and seminal plasma (GdS). We studied the anti-HIV effects of chemically modified GdA and GdS on both the infection of MT-2 cells by HIV-1IIIB, and the infection of peripheral blood mononuclear cells by the primary HIV isolate THA/93/051 belonging to subtype E. Whereas the native proteins were inactive when tested at physiologic concentrations, nanomolar concentrations of either 3HP-GdA or 3HP-GdS inhibited the production of HIV nucleocapsid p24, cytopathic effects of HIV-1IIIB, and infection of peripheral blood mononuclear cells by the primary HIV isolate THA/93/051. Moreover, both modified proteins inhibited gp120-CD4 binding, 3HP-GdS being more potent than 3HP-GdA (p = 0.0042). Because GdA and GdS have the same major protein core, the observed difference in gp120-CD4 binding must depend on the specific glycoform. In view of the previously reported contraceptive activity of GdA, the observed anti-HIV activity induced by its chemical modification should be of special interest in the development of antiviral strategies that may also have contraceptive effects.

Multiple forms of messenger ribonucleic acid encoding glycodelin in male genital tract

Glycodelin-A is a human endometrium-derived glycoprotein with contraceptive and immunosuppressive activities. Recently, we found that seminal plasma contains immunoreactive glycodelin (GdS) that is differentially glycosylated and has no contraceptive activity. We now report localization and variant forms of GdS in the male genital tract. Northern blot and reverse transcription-PCR analyses showed that GdS mRNA is expressed in the seminal vesicles and ampulla of the vas deferens. Immunohistochemical staining localized GdS to the epithelial cells and lumen of glands in the seminal vesicles and ampullary part of the vas deferens. The same tissues and cells contained glycodelin mRNA as localized by in situ hybridization. Whereas the major reverse transcription-PCR products were identical to the glycodelin-A cDNA from decidual expression library, there were also several splicing variants of GdS mRNA. Seminal plasma also contained smaller immunoreactive forms of the GdS protein. Some of them were posttranslational cleavage products of GdS, because incubation of 125I-labeled GdS in seminal plasma resulted in smaller molecular weight cleavage products. Based on these results, we concluded that multiple forms of glycodelin mRNA are expressed in the male genital tract, including those lacking the coding sequences for the glycosylation sites, and that seminal plasma has proteolytic activity that cleaves GdS.

Collagen formation and degradation increase during growth hormone therapy in children

A comprehensive set of serum markers of collagen turnover and growth was investigated in a longitudinal study of short children during growth induced by growth hormone (hGH) treatment. The study comprised 18 prepubertal children with short stature who had no other current illness or continuous medication. The growth rates and endogenous GH secretions covered a continuum from subnormal to normal. Before treatment, the concentrations of carboxyterminal propeptide of type I procollagen (PICP), reflecting type I collagen formation, of carboxyterminal telopeptide of type I collagen (ICTP), a degradation product of type I collagen, of amino-terminal propeptide of type III procollagen (PIIINP), a marker for type III collagen formation, of alkaline phosphatase (AP), and of insulin-like growth factor binding protein-3 (IGFBP-3) were within the lower limits of normal. The median IGF-I concentration was lower than the reference. One week after the start of treatment, the serum concentrations of ICTP, PIIINP, and osteocalcin (OC), and the increments in ICTP, PIIINP, and IGF binding protein-3 (IGFBP-3) correlated with the subsequent height velocity. During the 12-month treatment, all markers were higher than those of age-matched references, but only the three collagen markers paralleled the changes in height velocity. In molar concentrations, ICTP increased less than PICP. Throughout the study period, the serum level of ICTP correlated with that of PIIINP, but not with that of PICP. The findings suggest that during hGH treatment, linear body growth is closely associated with collagen formation and degradation.

Gender-specific glycosylation of human glycodelin affects its contraceptive activity

We have recently demonstrated that a human amniotic fluid-derived glycoprotein, glycodelin-A (GdA; previously known as PP14 or PAEP), potently inhibits gamete binding in an established sperm-egg binding system and expresses immunosuppressive activities directed against a variety of different immune cell types. GdA has high mannose-, hybrid-, and complex-type biantennary oligosaccharides including structures with fucosylated or sialylated N, N'-diacetyllactosediamine (GalNAcbeta1-4GlcNAc) sequences, which are rare in other human glycoproteins. We now report the characterization of glycodelin-S (GdS). This is a human seminal plasma glycoprotein that is immunologically indistinguishable from GdA, but unlike the latter, does not inhibit human sperm-zona pellucida binding under hemizona assay conditions. Analysis of the N-glycans of GdS by mass spectrometry revealed that all glycoforms of GdS are different from those of GdA. GdS glycans are unusually fucose-rich, and the major complex-type structures are biantennary glycans with Lewisx (Galbeta1-4(Fucalpha1-3)GlcNAc) and Lewisy (Fucalpha1-2Galbeta1-4(Fucalpha1-3)GlcNAc) antennae. It is probable that these highly fucosylated epitopes contribute to the immunosuppressive activity of human seminal plasma and to the low immunogenicity of sperm. This study provides the first evidence for gender-specific glycosylation that may serve to regulate key processes involved in human reproduction.

Genetic and environmental components of interindividual variation in circulating levels of IGF-I, IGF-II, IGFBP-1, and IGFBP-3

We assessed the magnitude of the genetic component in the variation of circulating levels of insulin-like growth factors I and II (IGF-I and IGF-II), and their binding proteins IGFBP-1 and IGFBP-3 by measuring their serum concentrations in 32 monozygotic and 47 dizygotic adult twin pairs of the same sex. The intrapair correlation for the IGF-I levels was r = 0.41 (P < 0.009) for monozygotic twins and r = 0.12 (P < 0.22) for dizygotic twins. For the IGF-II concentration the intrapair correlations were r = 0.66 (P < 0.0001) for the monozygotic and r = 0.34 (P < 0.01) for the dizygotic twins. No significant intrapair correlation was found for IGFBP-1 levels in either group. The correlations for IGFBP-3 concentration were r = 0.65 (P < 0.0001) and r = 0.23 (P < 0.06) for monozygotic and dizygotic twins, respectively. Women had higher IGF-II levels than men (635+/-175 vs. 522+/-144 microg/liter; P < 0.0001) and IGFBP-3 levels were also higher in women compared with men (5441+/-1018 vs. 4496+/-1084 microg/liter; P < 0.001). The proportion of variance attributable to genetic effects was 38% for the IGF-I concentration, 66% for the IGF-II concentration, and 60% for the IGFBP-3 concentration. No significant heritability was found for the IGFBP-1 concentrations. Our results show that, in adults, there is a substantial genetic contribution responsible for interindividual variation of the circulating levels of IGF-I, IGF-II, and IGFBP-3, but not for the IGFBP-1 levels.

Glycodelin from seminal plasma is a differentially glycosylated form of contraceptive glycodelin-A

Glycodelin-A is a human amniotic fluid-derived glycoprotein with contraceptive and immunosuppressive activities. An immunoreactive form of glycodelin was detected in seminal plasma over a decade ago, but definitive characterization of this glycoprotein was not pursued. We considered it unlikely that the seminal plasma of fertile men would contain an appreciable amount of contraceptive glycodelin-A. To address this issue we purified seminal plasma glycodelin (glycodelin-S) and performed comparative studies with glycodelin-A. Glycodelin-S behaved differently when compared with glycodelin-A during sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and isoelectric focusing but identically after enzymatic deglycosylation. N-terminal sequencing of glycodelin-A and glycodelin-S gave identical results, and digestion with trypsin gave identical peptide fragments. The glycoproteins were also found to be indistinguishable from each other based upon immunological analyses. These results indicate that glycodelin-S and glycodelin-A have similar overall protein structure, suggesting the likelihood that these glycoproteins are differentially glycosylated forms of very similar proteins. This latter possibility is supported by lectin binding studies indicating that, unlike glycodelin-A, glycodelin-S does not manifest any affinity for lectins from Wisteria floribunda or Sambucus nigra. The results of sugar analysis and neuraminidase digestion also lead us to conclude that glycodelin-S and glycodelin-A are differentially glycosylated forms of similar proteins. Our evidence indicates that glycodelin-A mediated its biological activities via its unusual oligosaccharide sequences that are not associated with glycodelin-S. In lectin-immunoassay no appreciable amount of contraceptive glycodelin-A was found in the 22 seminal plasma samples studied.

A role for glycoconjugates in human development: the human feto-embryonic defence system hypothesis

The mechanisms underlying the protection of the human embryo/fetus from the maternal immune response are poorly understood. Substantial evidence indicates that carbohydrate recognition plays a primary role in the sequestration of leukocytes during inflammatory processes, lymphocyte homing, and initial gamete binding. Our previous studies suggest a possible convergence in the types of carbohydrate sequences recognized during initial human gamete binding and immune/inflammatory cell interactions. Our more recent findings indicate that oligosaccharides participating in such processes are also associated with soluble glycoconjugates found in the human placenta, amniotic fluid, and decidua. We theorize that such glycoconjugates may abrogate the maternal immune/inflammatory response by blocking the primary adhesive interactions required for the expression of such activities. Foreign embryonic cells may also be protected by surface expression of oligosaccharide sequences that suppress immune effector cell action in a manner not dependent upon classical major histocompatibility (MHC) recognition. Glycoconjugates expressing selectin ligands may also manifest a potent contraceptive effect that may also be beneficial for both the mother and the developing embryo/fetus. This hypothesis provides a preliminary framework for understanding how temporally and spatially restricted immunosuppressive effects could be expressed in utero that protect the human embryo/fetus during this period of human development.

Effect of marathon run on serum IGF-I and IGF-binding protein 1 and 3 levels

Acute physical exercise increases growth hormone (GH) secretion, and GH regulates the expression of insulin-like growth factor I (IGF-I) and IGF-binding protein (IGFBP) 3. IGFBP-1 is a local modulator of IGF activity with rapid dynamic regulation that is downregulated by insulin. The IGF system mediates the metabolic actions of GH, and possibly it regulates glucose metabolism. We hypothesize that strenuous exercise causes changes in the IGF system. We studied the effects of the marathon run on the circulating levels of IGF-I, IGFBP-1, IGFBP-3, and insulin in 23 participants. Immediately after the run, the most striking change was an 11.6-fold median increase in serum IGFBP-1 level (from 63.7 +/- 50.5 to 736 +/- 408 micrograms/l; P < 0.001). Because the insulin level remained unchanged, the elevation of serum IGFBP-1 level cannot be explained by changes in insulin. One day after the run, the IGFBP-1 level had returned to baseline. The physiological role of this increment could be the inhibition of hypoglycemic effects of IGF-I and/or regulation of glucose availability to the muscles. The changes in IGF-I and IGFBP-3 levels were less dramatic: the IGF-I and IGFBP-3 levels were lower 1 and 3 days after the run. This report provides an important basis for authentic effects of strenuous exercise on the IGF-system.

Hemoglobin level is linked to growth hormone-dependent proteins in short children

Erythropoiesis was investigated in 32 children wih short stature and in eight children with skeletal dysplasia by studying blood hemoglobin in relation to growth and to serum concentrations of insulin-like growth factor I (IGF-I), IGF binding protein-3 (IGFBP-3), and erythropoietin (EPO) before, during, and after 12 months of recombinant human growth hormone (GH) treatment. Blood hemoglobin concentration was positively correlated with relative body height and with serum IGF-I and IGFBP-3 levels (P = .001 to .02), but not with the concentrations of EPO. The normal age-dependency of hemoglobin was lacking. Hemoglobin levels and their responses to GH treatment were similar in the patients with GH deficiency and those with normal GH secretion. Treatment with GH accelerated growth and elevated the concentrations of hemoglobin, IGF-I, and IGFBP-3. In the eight patients with skeletal dysplasia, body mass increased similarly, but gain in height was less than in the other patients, and the increase in hemoglobin was markedly pronounced. In this group, the correlations between hemoglobin, IGF-I, and IGFBP-3 were extremely close (r = 0.80 to 0.85, P = .031 to .008). These findings are in accord with earlier observations from in vitro and animal studies, and suggest that the GH-IGF axis is involved in the physiologic elevation of hemoglobin levels during childhood.

Structural analysis of the oligosaccharides derived from glycodelin, a human glycoprotein with potent immunosuppressive and contraceptive activities

Glycodelin, also known as placental protein 14 (PP14) or progesterone-associated endometrial protein (PAEP), is a human glycoprotein with potent immunosuppressive and contraceptive activities. In this paper we report the first characterization of glycodelin-derived oligosaccharides. Using strategies based upon fast atom bombardment and electrospray mass spectrometry we have established that glycodelin is glycosylated at Asn-28 and Asn-63. The Asn-28 site carries high mannose, hybrid and complex-type structures, whereas the second site is exclusively occupied by complex-type glycans. The major non-reducing epitopes in the complex-type glycans are: Gal beta 1-4GlcNAc (lacNAc), GalNAc beta 1-4GlcNAc (lacdiNAc), NeuAc alpha 2-6Gal beta 1-4GlcNAc (sialylated lacNAc), NeuAc alpha 2-6Gal beta 1-4GlcNAc (sialylated lacdiNAc), Gal beta 1-4(Fuc alpha 1-3)GlcNAc (Lewisx), and GalNAc beta 1-4(Fuc alpha 1-3)GlcNAc (lacdiNAc analogue of Lewisx). It is possible that the oligosaccharides bearing sialylated lacNAc or lacdiNAc antennae may manifest immunosuppressive effects by specifically blocking adhesive and activation-related events mediated by CD22, the human B cell associated receptor. Oligosaccharides with fucosylated lacdiNAc antennae have previously been shown to potently block selectin-mediated adhesions and may perform the same function in glycodelin. The potent inhibitory effect of glycodelin on initial human sperm-zona pellucida binding is consistent with our previous suggestion that this cell adhesion event requires a selectin-like adhesion process. This result also raises the possibility that a convergence between immune and gamete recognition processes may have occurred in the types of carbohydrate ligands recognized in the human.

Insulin-like growth factor I and insulin-like growth factor binding protein 3 as determinants of blood hemoglobin concentration in healthy subjects

We studied the serum concentrations of IGF-I, IGF-binding protein 3 (IGFBP-3), and testosterone in relation to blood Hb in 60 healthy prepubertal or early pubertal boys twice, with a 9-mo interval. Serum IGF-I and testosterone levels were measured by RIA, and serum IGFBP-3 was measured by monoclonal immunofluorometric assay. Positive correlations were observed between the concentrations of blood Hb and serum IGF-I at the first examination (r = 0.36, p = 0.008) and Hb and IGFBP-3 at both examinations (r = 0.53, p < 0.001, and r = 0.39, p = 0.003). No association between Hb and testosterone concentrations was found. Our results show that blood Hb is positively correlated to serum IGF-I and IGFBP-3 levels, indicating indirectly the involvement of growth hormone in the regulation of physiologic Hb concentration. Because no association was found between Hb and testosterone concentrations, this may indicate that the role of androgens in erythropoiesis may be different at different stages of puberty. It is concluded that the IGF system may be involved in the rise of Hb level during early puberty.

Different forms of insulin-like growth factor-binding protein-3 detected in serum and seminal plasma by immunofluorometric assay with monoclonal antibodies

Monoclonal antibodies against recombinant insulin-like growth factor-binding protein-3 (IGFBP-3) were produced to study the various forms of IGFBP-3 and to develop a specific immunofluorometric assay. We tested seven antibodies that showed no cross-reactions with the other five human IGFBPs. By immunoblotting, the main bands in normal serum were seen at &gt; 90, 45, 41, 29, and 25 kDa. In pregnancy serum, the 29-kDa was stronger, and the double band at 41-45 kDa was weaker or totally absent. We characterized two immunofluorometric assays. IGF-I had no effect on either assay. Added IGF-II lowered the amount of recombinant IGFBP-3 measured by the 5C11/7F8 assay, but not by the 1B6/5C11 assay. In normal serum and follicular fluid, IGFBP-3 measurements were lower by the 5C11/7F8 assay, but in most pregnancy sera and amniotic fluids the assays gave similar results. The 5C11/7F8 assay also detected IGFBP-3 in seminal plasma, whereas the 1B6/5C11 assay did not. We conclude that the results of IGFBP-3 measurement depend on the antibodies used, and that different antibodies are suitable for the IGFBP-3 measurement in different body fluids.

Different forms of insulin-like growth factor-binding protein-3 detected in serum and seminal plasma by immunofluorometric assay with monoclonal antibodies

Monoclonal antibodies against recombinant insulin-like growth factor-binding protein-3 (IGFBP-3) were produced to study the various forms of IGFBP-3 and to develop a specific immunofluorometric assay. We tested seven antibodies that showed no cross-reactions with the other five human IGFBPs. By immunoblotting, the main bands in normal serum were seen at > 90, 45, 41, 29, and 25 kDa. In pregnancy serum, the 29-kDa was stronger, and the double band at 41-45 kDa was weaker or totally absent. We characterized two immunofluorometric assays. IGF-I had no effect on either assay. Added IGF-II lowered the amount of recombinant IGFBP-3 measured by the 5C11/7F8 assay, but not by the 1B6/5C11 assay. In normal serum and follicular fluid, IGFBP-3 measurements were lower by the 5C11/7F8 assay, but in most pregnancy sera and amniotic fluids the assays gave similar results. The 5C11/7F8 assay also detected IGFBP-3 in seminal plasma, whereas the 1B6/5C11 assay did not. We conclude that the results of IGFBP-3 measurement depend on the antibodies used, and that different antibodies are suitable for the IGFBP-3 measurement in different body fluids.