Biomedical subjects

L Bonaccorsi

Publications and source records attributed to L Bonaccorsi.

24 records · Page 2Linked to original sources

PubMed1995

Actions of progesterone on human sperm: a model of non-genomic effects of steroids.

Non-genomic actions of steroids have been extensively studied in the last few years. Among these actions, the non-genomic effect of progesterone (P) on human spermatozoa appears to be very promising, in view of the dramatic effect of this steroid on intracellular calcium, activation of tyrosine kinase, and induction of acrosome reaction. We have shown that the ability of spermatozoa to respond to P increases during the process of capacitation and is not counteracted by the P-receptor antagonist RU486 nor by the GABAA antagonists bicuculline and picrotoxin. We have also shown that P increases tyrosine phosphorylation of a sperm protein of about 97 kDa, suggesting activation of tyrosine kinase(s). In addition, we found that P induces a perturbation of sperm membrane phospholipid metabolism resulting in an increase of synthesis of platelet-activating factor and liberation of arachidonic acid. Results of these biochemical studies indicate that P is able to stimulate several signal transduction pathways in human sperm. We have also investigated responsiveness to P in sperm of oligozoospermic subjects as well as of men undergoing an in vitro fertilization (IVF) program. Our results show that the percentage increases of intracellular calcium and acrosome reaction in response to P is significantly reduced in oligozoospermic men as well as in subjects with reduced fertilization rate. Moreover, in the latter subjects response to P is highly significant correlated to fertilization rate of oocytes. These studies indicate that a biochemical alteration of sperm in their capacity to respond to P might be responsible for reduced fertilizing ability.

Acrosome↗

PubMed1995

Intracellular calcium increase and acrosome reaction in response to progesterone in human spermatozoa are correlated with in-vitro fertilization.

In this study we have investigated responsiveness to progesterone in spermatozoa from a group of unselected male partners of couples undergoing in-vitro fertilization (IVF). We evaluated progesterone-stimulated intracellular Ca2+ ([Ca2+]i) and percentage increase in acrosome reaction in the same sperm sample used for oocyte inseminations. [Ca2+]i was measured with a fluorimetric method, while the acrosome reaction was assessed using a fluorescent probe (fluorescein isothiocyanate-labelled peanut lectin). The average percentage [Ca2+]i as well as the rate of increase in the frequency of acrosome reaction following progesterone challenge were significantly lower (P < 0.005) in the group of patients with a fertilization rate < 50%. In addition, significant correlations between the fertilization rate and the progesterone-stimulated [Ca2+]i and acrosome reaction increases (r = 0.78 and r = 0.79 respectively) were observed. Furthermore, in cases of fertilization failure, no increase of [Ca2+]i or acrosome reaction was observed in response to progesterone with the exception of one case. Our results indicate that [Ca2+]i and acrosome reaction increases in response to progesterone can be of value in the prediction of sperm fertilizing ability. As the two parameters were significantly correlated to each other (r = 0.86), the two assays have similar IVF predictive value and might be used interchangeably as a diagnostic tool in the assignment of male patients to the different kinds of assisted fertilization techniques.

Acrosome↗

PubMed1994

Platelet-activating factor mediates an autocrine proliferative loop in the endometrial adenocarcinoma cell line HEC-1A.

We investigated the synthesis and biological effects of platelet-activating factor (PAF) in the human endometrial cancer cell line HEC-1A. We found that HEC-1A cells actively synthesize and release PAF, as demonstrated by both [3H]acetate incorporation into PAF and gas chromatography-mass spectrometry studies. HEC-1A cells not only synthesize but also respond to PAF. Indeed, in fura-2-loaded cells, PAF stimulates [Ca2+]i increase with a median effective concentration of 5.6 nM. Furthermore, PAF induces a time-dependent expression increase of the nuclear protooncogene c-fos with a median effective concentration of 130 nM and stimulates DNA synthesis (median effective concentration, 700 nM). All of these effects are inhibited by the PAF receptor antagonist L659,989. Radioligand binding studies indicated the presence of two populations of PAF receptors with affinity constants in the nanomolar and micromolar range. Since the PAF antagonist per se inhibits DNA synthesis and cell proliferation, we suggest that PAF supports an autocrine growth circuit in HEC-1A cells. On the contrary, in the uterine leiomyosarcoma cell line SK-UT-1, which does not express specific binding sites for PAF, neither this phospholipid nor its receptor antagonist affect DNA synthesis. Our results provide evidence for the existence of an autocrine proliferative loop involving PAF in the endometrial cancer cell line HEC-1A.

Acetyl-CoA C-Acetyltransferase↗

PubMed1994

Platelet-activating factor in human endometrium.

Platelet-activating factor (PAF) is a phospholipid actively produced by human endometrium and deeply involved in the processes of ovoimplantation and labor. We recently found that PAF represents a new autocrine growth factor for a human adenocarcinoma cell line, HEC-1A. Indeed, biologically active PAF is synthesized by HEC-1A cells, under progesterone control. In HEC-1A cells, PAF regulates intracellular calcium concentration ([Ca2+]), DNA synthesis and expression of early oncogenes. All these effects are blocked by the receptor antagonist L659,989. However, while nanomolar concentrations of PAF mobilize [Ca2+], only micromolar concentrations affect cell growth, suggesting heterogeneity of PAF receptors or signaling. Two distinct populations of PAF receptors are present in HEC-1A cells, which bind PAF in nanomolar and micromolar concentrations, respectively. Since HEC-1A cells are producing elevated concentrations of PAF and micromolar concentrations of the PAF antagonist L659,989 inhibit cell proliferation, an autocrine role for PAF is suggested in HEC-1A cells.

Adenocarcinoma↗

PubMedDate not supplied

Nongenomic progesterone receptor on human spermatozoa: biochemical aspects and clinical implications.

Progesterone (P) is a physiological stimulus of human sperm functions. It is present in high levels at the site of fertilization (cumulus oophorus) and has been described to affect several sperm functions, including motility, capacitation, acrosome reaction, and the ability to bind and to respond to zona proteins. The effects of the steroid are mediated essentially by an increase of intracellular calcium concentrations, stimulation of activity of phospholipases, phosphorylation of proteins, efflux of chloride. These effects are due to activation of a rapid, nongenomic pathway. Whether the effects of progesterone are mediated or not by specific interactions with sperm membrane proteins is questioned. By using an antibody directed against the C-terminal region (P-binding region) of the genomic receptor, we have recently identified two sperm proteins with molecular weights distinct from the classic genomic receptors. In addition, ligand blot analysis with peroxidase-conjugated P demonstrated that P specifically binds these two proteins. Classical ligand binding experiments demonstrated the presence of two specific binding sites with affinity in the nanomolar and in the micromolar range, respectively. The involvement of progesterone in the physiological process leading to fertilization of the oocyte is suggested by several studies. In particular, the demonstration that sperm responsiveness to progesterone is impaired in subfertile patients and that is strictly correlated to the ability of fertilizing the oocyte represents a further indication of the participation of the steroid in this process. In addition, the determination of sperm responsiveness may be predictive of fertilizing ability with a positive predictive value of 90% and can be clinically useful for the preliminary assessment of the male partner to select the appropriate assisted reproductive technique.

Humans↗

PubMedDate not supplied

Endothelin-1 and its receptors in human testis.

We have previously found the presence of endothelin (ET) receptor and ET-like immunoreactivity in rat testis. We now extend our studies from rat to human testis. We found expression of a specific transcript for ET-1 and ET-1-like immunoreactivity in human testis. Positive staining was confined to the Sertoli cells of the tubular compartment, although few peritubular and interstitial cells were also stained. We also identified specific ETA and ETB receptor transcripts in human testis; ETA expression was more abundant than the ETB expression. Mathematical analysis of multiple self- and cross-competition studies among [125I]ET-1, [125I]ET-3, and analogues confirmed the presence of the ETA and ETB isoreceptors. In testicular homogenates, the ETA receptor was sevenfold more concentrated than the ETB receptor. In order to localize the receptors, we performed [125I]ET-1 autoradiography. Binding sites were mostly concentrated into the seminiferous tubules, although interstitial and peritubular myoid cells were also positive. Within the seminiferous tubules, [125I]ET-1 binding sites were confined to primary and secondary spermatocytes and early spermatids, whereas Sertoli cells were negative. We were unable to demonstrate the presence of functional ET receptors in ejaculated spermatozoa. Because ET-like immunoreactivity was present in Sertoli cells, we next asked whether authentic ET-1 is present in human seminal fluid and represents a good index for Sertoli cell function. Reverse-phase high-performance liquid chromatography analysis of ET-like immunoreactivity in seminal fluid indicated that most of the detected peptides correspond to the ET-1 precursor, big-ET-1. The seminal concentration of ET-like immunoreactivity was similar in normospermic, oligospermic, azoospermic, and vasectomized men, indicating that ETs are produced in different parts of the male genital tract and that they do not represent an useful tool for the diagnosis of male reproductive diseases. In conclusion, this study demonstrated, for the first time, the presence of ET-1 and its receptors in human testis.

Adult↗