Overexpression of monkey oviductal protein: purification and characterization of recombinant protein and its antibodies

The secretory cells lining the lumen of the mammalian oviduct synthesize and secrete high molecular weight glycoprotein (OGP). Molecular cDNA cloning of most of the mammalian OGP has been accomplished. The nucleotide and deduced amino acid sequences show a remarkable homology across species and also to chitinase protein. Even though OGP has been shown to interact with gametes and the early embryo, the protein's direct function has not yet been established. A prerequisite for such studies is the availability of well-characterized protein in bulk. We used recombinant DNA technology to obtain OGP (rOGP). An authentic partial cDNA clone encoding bonnet monkey (Macaca radiata) OGP (accession number AF132 215) was recloned into expression vector pET20b. Overexpression of the protein could be demonstrated after induction with isopropylthio-beta-galactopyranoside. Recombinant protein was purified by gel filtration of Escherichia coli lysate through Sephadex G75. The protein migrated with a molecular weight of approximately 14 kDa on SDS-PAGE. The molecular weight as assessed by matrix-assisted laser adsorption time-of-flight was 14 439 daltons. With Western blot procedures the protein could be immunostained with antibodies to human OGP, baboon OGP, and antipeptide antibodies generated against a well-conserved region of mammalian OGP. The monospecificity of rabbit antibodies generated against rOGP was established by its ability to immunostain human OGP (100-110 kDa) isolated from hydrosalpinx by Western blot analysis, and the antibody immunostained epithelial cells that secrete OGP in human fallopian tubes. OGP binding sites on the head and tail region of monkey sperm could be demonstrated by using antibody against rOGP.

Spermicidal activity of seed oil of Pongamia glabra

The medicinal properties of seed oil of Pongamia glabra are well known in traditional Indian medicine. It has antimicrobial activity against several organisms. It is used in the treatment of herpes and scabies and, systemically, it is also used in the treatment of dyspepsia with sluggish liver. The present study demonstrates that in vitro, Pongamia oil has strong spermicidal activity.

Partial amino acid sequencing of 80-kDa human sperm antigen (80-kDa HSA)

An 80-kDa human sperm antigen (80-kDa HSA) has been identified as a sperm protein responsible for inducing immunoinfertility. Immunization with the purified protein induced infertility in male and female rats. Immunohistochemical and immunofluorescent studies have demonstrated that the antigen is specific to spermatozoa. The present study describes the partial amino acid sequencing of 80-kDa HSA. The homogeneous protein was electrophoretically transferred onto a PVDF membrane and the excised band of 80-kDa HSA was used to determine the partial N-terminal amino acid sequence. The protein was then subjected to enzymatic digestion with endoproteinase Lys-C and endoproteinase Glu-C. The partial amino acid sequence of the major peptides thus obtained was determined. The digestion with endoproteinase Lys-C generated 4 major peptides, two of which showed partial sequence homology with lactoferrin. Endoproteinase Glu-C digestion produced 3 major peptides. The sequences of the 2 peptides were determined for which no matches were found in the databank. These results confirmed earlier observations that 80-kDa HSA is a sperm-specific protein that is chemically distinct from any other protein involved in normal physiological process. Earlier studies have demonstrated that it is antigenic, efficacious, conserved, and could be a promising candidate for the development of an antifertility vaccine.

Characterization of 80 kDa human sperm antigen responsible for immunoinfertility

PROBLEM

An 80 kDa human sperm antigen (80 kDa HSA) has been identified by western blot technique using serum of an immunoinfertile woman as a probe. The 80 kDa HSA has been subsequently purified from sperm extract and investigated for antifertility effects.

METHOD OF STUDY

The purified 80 kDa HSA was used to immunize adult male and female rats. Rabbit anti 80 kDa HSA antibodies were used for immunofluorescent and immunohistochemical staining to demonstrate the presence of 80 kDa HSA on the sperm and to investigate its tissue distribution. The N-terminal sequence of native 80 kDa HSA and the peptides obtained by its endoproteinase Lys-C was determined.

RESULTS

Active immunization of male and female rats with 80 kDa HSA caused infertility in all the immunized animals. Immunofluorescent staining showed its localization on the head region of the human and rat spermatozoa. While immunohistochemical studies showed its localization in the testes and epididymis but not in other somatic tissues. Partial amino-acid sequence analysis showed no sequence homology with any of the known protein in the database.

CONCLUSIONS

80 kDa HSA is a promising candidate antigen for immunocontraception as it is characterized and found to cause infertility upon active immunization. specific to spermatozoa and is conserved.

Effect of immunization with synthetic peptide corresponding to region 1-17 of human seminal plasma inhibin on fertility of male rats

Immunization of adult male rats with a synthetic peptide corresponding to the region 1-17 of human seminal plasma inhibin (hSPI) resulted in agglutination of epididymal sperm, severely affecting the fertility of the animals (75% reduction in fertility as compared to control). This effect was found to be dependent on the antibody titer to hSPI. There was a significant rise in circulating follicle-stimulating hormone levels, with luteinizing hormone and testosterone levels remaining unaffected. The histology of the testes and other reproductive organs revealed that these organs remained unaltered. The N-terminal 1-17 amino acid peptide of hSPI may hold promise as an immunogen for male immunocontraception.

Seminal inhibin--prospects for immunocontraception

Passive immunization of adult rats, hamsters and marmosets with rabbit anti-seminal inhibin resulted in complete or partial block of fertility. The antiserum treatment presumably neutralized endogenous inhibin resulting in an unopposed rise in circulating FSH. This probably led to a refractoriness of the testes to FSH resulting in complete spermatogenic arrest. Nevertheless, there was no change in the mating behaviour of the animals. The antibodies also affected the epididymal spermatozoa by causing large scale agglutination.

Antifertility effects in rats actively immunized with 80 kDa human semen glycoprotein

A 80 kDa human sperm antigen has been identified using the serum of an infertile woman having circulating antisperm antibodies. The antigen was then purified to homogeneity by gel permeation chromatography using HPLC (protein PAK-125 column) system and on FPLC (superose-12 column) system. The antigen was found to be a glycoprotein. The antigen was mainly localized in the postacrosomal region of the human sperm, while it was localized in the head region of the rat sperm as demonstrated by immunofluorescent staining. The presence of this antigen was also demonstrated in the human prostate and endometrium and in the rat testis; epididymis and the prostate by immunocytochemical staining. The purified protein upon active immunization in female rats caused infertility in 100 percent animals. While in male rats it caused infertility in 90 percent animals. On morphometric analysis of testicular tissue it was observed that there was no significant change in spermatogonia and spermatocytes, but significant decrease in spermatids and sperm number as well as daily sperm production in the immunized male rats. The epididymal spermatozoa were markedly reduced in number and were largely found to be agglutinated. The results suggest that 80 kDa human sperm antigen appears to be a suitable candidate for immunocontraception both in male and female.

Inhibin: unity in diversity

Historically, inhibin was thought to be a testicular hormone involved in the regulation of pituitary FSH by a negative feedback control. The ability of inhibin to preferentially suppress FSH without affecting LH triggered extensive research for its possible use as a male contraceptive, suggesting a plurality of molecular forms and a multiplicity of biological actions of this putative hormone. It also became evident that inhibin is not unique to the testis, as presumed earlier, and can even be obtained from the ovary. This has necessitated a fundamental revision of the original concept of inhibin. Unfortunately, not many perceive inhibin as a loose conglomerate of structurally dissimilar, FSH-suppressing proteins and insist on singling out a 32-kDa protein derived from ovarian follicular fluid to be designated as inhibin. This article highlights features common to two distinctly different types of inhibin: seminal inhibin and ovarian inhibin. Evidence is also provided to indicate that the term inhibin need not be specific to the ovarian protein, but encompasses proteins hitherto dismissed as inhibin-like or inhibin-related proteins.

Localization and detection of ovarian follicular fluid protein in follicles of human ovaries

Human ovarian follicular fluid protein has been partially purified and the active fraction designated as hGF2. Using specific polyclonal antiserum to hGF2, it was observed to be localized immunohistochemically in the granulosa cells of medium but not large follicles of human ovary. The hGF2 levels were estimated by ELISA in serum and follicular fluid of 10 gonadotropin-stimulated women recruited for IVF-ET programme. The results revealed a 3-fold increase in the concentration of hGF2 in follicular fluid compared to that in serum of these patients. These data indicate that the protein is secreted by granulosa cells and plays an important role in the regulation of follicular maturation and ovulation.

Interference with ovulation and luteal function by human ovarian follicular fluid peptide in bonnet monkeys, Macaca radiata

Partially purified human ovarian follicular fluid peptide (hGF2) was administered during follicular phase in 5 bonnet monkeys. In control as well as hGF2-injected animals, ovulation was synchronized by treatment with FSH, Pergonal and hCG. All the 5 control bonnet monkeys showed plasma estradiol peak followed by increased progesterone levels. In 4 out of 5 hGF2-injected animals, plasma progesterone levels were drastically reduced. Plasma estradiol levels were decreased only in 3 animals in which amenorrhea was observed. These data reveal that hGF2 injection disrupted ovarian function in bonnet monkeys.

An enzyme-linked immunosorbent assay for the detection of human seminal plasma inhibin

A simple and sensitive enzyme-linked immunosorbent assay (ELISA) is described for the measurement of inhibin in urine and seminal plasma. Standards used cover a range from 50 ng to 0.05 ng/0.1 ml with a detection limit of 0.098 ng/0.1 ml. Coefficients of variation for intra-assay precision and for inter-assay precision were obtained and compared favourably with RIA. Given the ease of application, this technique is an useful alternative to existing radioimmuno-assays for this peptide.

Suppression of antral formation in the ovarian follicles of marmosets by human ovarian follicular fluid protein

Ovarian follicular fluid peptide (OFFP) has earlier been shown to inhibit maturation of large follicles and ovulation in mice. An active fraction hGF2, obtained following partial purification from human ovarian follicular fluid, was injected at a dose of 20 micrograms to 4-month-old immature marmosets, every alternate day for 2 months. The animal were autopsied at 4 and 6 months of age. Ovarian morphology indicated the appearance of large follicles at 6 months of age in the control group. In contrast, in hGF2 treated marmosets development up to preantral follicles could be seen at 6 months. Furthermore, only in 1 out of the 3 treated marmosets, presence of large preantral follicles was observed and in the remaining 4 animals only primary and secondary follicles were noted. These results reveal that OFFP suppresses follicular development and antrum formation in marmosets.

Shortening of luteal phase in common marmosets by sheep ovarian follicular fluid peptide

A low molecular weight peptide has been partially purified from sheep follicular fluid. It inhibited FSH binding to granulosa cells from ovarian follicles of common marmosets (Callithrix jacchus). When injected into cycling marmosets during the follicular phase, it reduced the area under the curve (AUC) of circulating progesterone. The peptide also shortened the luteal phase in all marmosets during the treatment cycle compared to the pretreatment control cycle. These results indicate that the ovarian follicular fluid peptide inhibited FSH binding to granulosa cells thereby probably resulting in decreased progesterone secretion (AUC) from these cells and subsequently inducing luteal insufficiency.

Luteal deficiency caused by human ovarian follicular fluid peptide in post-partum marmosets, Callithrix jacchus

A peptide purified from human ovarian follicular fluid (hOFFP) was administered during the follicular phase of post-partum marmosets. Four of the five animals treated with hOFFP, ovulated as evidenced by the presence of ovarian stigmata at the time of laparotomy. However, only 2 of these animals became pregnant, one had a normal delivery while the other aborted. A shortening of the luteal phase was observed in the other three animals and all animals conceived in subsequent cycles. The results indicated that treatment with the ovarian follicular fluid peptide resulted in impairment of fertility as a result of luteal insufficiency.

Localization of inhibin in testes of human, bonnet monkey, dog and rat by immunoperoxidase technique

Immunocytochemical study on the localization of inhibin in the testes of human, bonnet monkey, dog and rat was carried out using indirect immunoperoxidase technique, in order to investigate the cell types involved in inhibin production/storage. A positive reaction was observed in the testes of human, monkey and dog while it was negative in rat testis using specific antiserum to human testicular inhibin generated against homogeneous preparation of human testicular inhibin in our laboratory. Inhibin was found to be localized in Sertoli cells, spermatogonia and primary spermatocytes of human, monkey and dog testes. A weak positive reaction was observed in spermatids of human testis only. Interestingly, Leydig cells of human, monkey and dog testes showed positive reaction indicating presence of inhibin in these cells also.

Does inhibin have intrinsic prolactin suppressing activity?

Evidence to demonstrate suppressive effect of inhibin on prolactin has been presented. The inhibin preparations derived from human testicular tissue, human seminal plasma and porcine follicular fluid were tested and all the three preparations were found to exhibit prolactin suppressing activity.

Flow cytometric analysis of human spermatozoa treated with antiserum to human seminal inhibin

Inhibin from human seminal plasma is structurally identical to sperm coating antigen. Using the flow cytometric technique it has been demonstrated that there is a positive correlation between initial motility of sperm and the amount of inhibin coated on the spermatozoal surface.

Localization of inhibin in human testes by immunoperoxidase technique

Immunohistological studies on the localization of inhibin in human testes were carried out to investigate the cell types involved in inhibin synthesis/storage. The paraffin embedded testicular tissues were stained by an indirect immunoperoxidase technique. Specific antiserum to human testicular inhibin generated against the homogenous preparation of human testicular inhibin at our laboratory was used as the first antibody. Inhibin was found to be localized in Sertoli cells, spermatogonia, and primary spermatocytes. A weak positive reaction was also observed in spermatids. Interestingly, Leydig cells showed positive reaction indicating presence of inhibin in these cells too.

Inhibition of delta 5-3 beta hydroxysteroid dehydrogenase activity in pre-implantation mouse embryos and their implantation by sheep ovarian follicular fluid peptide

The activity of delta 5-3 beta hydroxysteroid dehydrogenase (delta 5-3 beta HSD) in pre-implantation mouse embryos was inhibited following their prior incubation with partially purified sheep ovarian follicular fluid peptide (OFFP). OFFP, 5 microliter, injected into the uterine lumen of day 4 pregnant mice impaired the ensuing implantation of embryos. Our observations suggest that OFFP may inhibit steroid metabolizing activity in pre-implantation embryos and thereby interfere with the process of implantation.

Effect of inhibin on testosterone metabolism by rat ventral prostate in vitro

Conversion of radiolabeled testosterone to 5 alpha-dihydrotestosterone (5 alpha-DHT) was determined in the rat ventral prostate in vitro, and the effect of inhibin on this conversion was demonstrated. The data revealed that the reduction of testosterone to 5 alpha-DHT was inhibited in a dose-related manner in the presence of inhibin as compared with the basal reduction. The percentage of testosterone reduced per 10-mg tissue also showed a similar trend. The ratio of radioactive counts for DHT and testosterone was also minimum at the highest dose of inhibin used. Inhibin can thus modulate the conversion of testosterone to 5 alpha-DHT in the rat ventral prostate, and therefore can autocrine-paracrine function can be attributed to the prostate.

Isolation and partial characterization of early pregnancy factor (EPF) from human pregnancy serum

The isolation and partial characterization of an immunosuppressive early pregnancy factor (EPF) present in the serum of pregnant women, between 3 and 8 weeks of gestation, is described. EPF was purified using ion-exchange chromatography, affinity chromatography and HPLC gel permeation techniques. A homogeneous, active fraction containing a single polypeptide of Mr 21,000 was obtained. This 21 kDa polypeptide appears to represent the major form of rosette-inhibiting active material present in maternal serum during early human gestation.

Superoxide dismutase in human testis preparations

A protein fraction from human testis was structurally investigated. The main component of the fraction reported to contain inhibin-like activity was purified and analyzed by tryptic digestion. The peptides obtained identified the protein as an enzyme, superoxide dismutase, previously known to be present in seminal plasma. The results show that superoxide dismutase is a major enzyme, also of testicular material. They further demonstrate the importance of using pure fractions, and controls such as checks with structural analysis or synthetic peptides, in the work of elucidating the nature of inhibin and other hormonal peptides.

Potential application of inhibin in male and female contraception

After a review of investigations into the possible use of inhibin in the regulation of male and female fertility, briefly described and summarized in this article, the authors conclude that, at least in experimental animals, inhibin causes a significant reduction in testicular and epididymal spermatozoa in the male and luteal phase defect in the female. The precise mechanism by which inhibin brings about these effects is not known at present, and its elucidation will greatly help in the more effective use of inhibin.

Stimulation of ornithine decarboxylase in the rat prostate by seminal plasma inhibin

The effect of seminal plasma inhibin on ornithine decarboxylase activity (ODC) in the rat prostate was studied. A single bolus injection of seminal plasma inhibin caused a 3- to 4-fold increase in ODC activity within 2 h whereas testicular ODC was unchanged. The ODC response to seminal plasma inhibin was neutralized by specific antibodies generated against the inhibin preparation. Another peptide, thyroid releasing hormone has no effect on prostatic ODC activity, but it blocked the increase in enzyme activity induced by treatment with seminal plasma inhibin.

Inhibition of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) activity in the granulosa cells of mouse ovarian follicles by follicular fluid peptide

A protein fraction (GF2) was purified from sheep ovarian follicular fluid. Its action on 3 beta-HSD activity in the mouse granulosa cells was measured in an in vitro system. The fraction (GF2) caused dose-dependent depletion of the 3 beta-HSD activity in granulosa cells and progesterone in the spent medium. A maximum inhibition of the activity was achieved after 30 min incubation of the granulosa cells with the GF2 fraction. Further purified HPLC fraction (Fr1) also inhibited 3 beta-HSD activity. In vivo administration of the GF2 fraction in normal cycling female mice also decreased the 3 beta-HSD activity in the granulosa cells of the ovarian follicles and plasma progesterone levels indicating the GF2 fraction to be a 3 beta-HSD inhibitor.

Autoradiographic analysis of FSH binding during follicular atresia

Binding of FSH to ovarian cells was studied in PMSG primed immature Swiss mice, 48 h after PMSG treatment, FSH-binding was higher in the periphery than in the cumulus cells of the antral follicles. Binding of FSH to granulosa cells of normal follicles was observed to be specific, 48 h after PMSG injection. No localization in the atretic follicles could be seen by autoradiography 72 h after priming.

Effect of inhibin on ovulation and implantation in mice

Injection of antiserum to ovine FSH on the day of proestrus could inhibit ovulation in the next cycle. Inhibin preparation purified from sheep ovaries failed to affect ovulation in mice. Suppression of FSH by this preparation of inhibin during early pregnancy reversed the mitotic index. Administration of inhibin during the peri-implantation period terminated pregnancy in mice. The inhibin preparation decreases FSH in circulation which in turn may possibly reduce ovarian estrogens, thereby inhibiting pregnancy.

Biological studies with low and high molecular weight inhibin preparations

The effects of both high and low molecular weight inhibin preparations on testicular and pituitary receptors were studied. Both these preparations were able to inhibit the binding of labelled hFSH to testicular receptor in a dose related manner, but were unable to affect the binding of labelled hCG to its receptor, suggesting that the observed inhibition of FSH binding was specific to inhibin. In addition, the binding of LHRH to pituitary receptors was affected by inhibin preparations. Interestingly, the antiserum raised against high molecular weight inhibin was able to neutralize, totally, the biological effect of high molecular weight inhibin, and only, partially, the biological effect of low molecular weight inhibin.

Measurement of inhibin

The bioassays developed so far, although good for detecting inhibin from different sources and for monitoring their purification, are not really practical for physiological studies. Moreover, they are influenced by steroidal hormones. In this regard radioimmunoassays, with their high capacity and greater sensitivity, are of immense value in studies involving the physiology of inhibin. More information on this aspect will probably lead to the development of more rational methods of assay. However, the need for an international reference preparation that will provide a common basis for comparing data from different laboratories cannot but be emphasized.

Modulation of FSH action by inhibin

Both testicular and ovarian inhibin preparations caused a dose-related inhibition of binding of 125I-hFSH to rat testicular receptors. Testicular inhibin also suppressed the FSH-induced production of cAMP by rats testis in vitro. These data demonstrate a direct action of inhibin at the testicular level by interfering with FSH action.

Isolation and characterization of ovine testicular and ovarian inhibin

Low-molecular-weight (< 1500 daltons) peptides with inhibin activity have been isolated from sheep testes and ovaries by simple gel filtration. These peptides were capable of inhibiting the ovarian weight increase in hCG-primed immature female mice and also of suppressing the post-castration rise of serum FSH levels in adult male rats, suggesting similarities in their biological properties. Both testicular and ovarian inhibin were typsin sensitive and heat stable at 100 degrees C for 30 min and were shown to act by interfering with the production of a hypothetical FSH-RH.