Unusual clinical manifestation and challenging serological interpretation of syphilis: insights from a case report.

BACKGROUND: The clinical manifestations of recent syphilis can be variable, with typical and atypical patterns. Several conditions may cause atypical clinical aspects, including human immunodeficiency virus (HIV) co-infection. Besides the clinical features, co-infections may completely alter syphilis serological tests, causing interpretative difficulties and diagnostic delays. Aim of the work is to describe the difficulties encountered during the diagnostic evaluation of atypical skin manifestations and of the serology for syphilis of an HIV-infected patient who had contracted it several times. CASE PRESENTATION: In 2020, a 52-year old HIV-positive bisexual male patient was admitted to our department with a 4-month history of moderately itchy cutaneous lesions localized at his neck, trunk and arms. In 2013, the patient presented with a classic syphilitic roseola of the trunk and a secondary syphilis was diagnosed, with increased levels of rapid plasma reagin (RPR), Treponema pallidum hemagglutination assay (TPHA), anti-Treponema pallidum IgM and IgG Index. A second episode occurred in 2018, as a primary syphilis with multiple ulcerative lesions of the penis, and increased levels of RPR, IgG and IgM. In 2019, a further episode of secondary syphilis was treated with Doxycycline. In 2020, erythematous and papular lesions with vesicular components and urticarial erythema multiforme (EM)-like lesions were present at the neck, trunk and arms. Serological tests and Nucleic Acid Amplification Test (NAAT) for Treponema Pallidum were performed, as well as a cutaneous biopsy with histological and immunohistochemical evaluation of one lesion. NAAT was negative for T. pallidum. Serological test results were discordant with a new syphilis infection, showing only increased levels of RPR and anti-Treponema IgG. The cutaneous biopsy revealed a non specific histological pattern, while the immunohistochemical evaluation with anti-spirochetal antibodies was mandatory for the diagnosis of recent syphilis, showing clusters of rod-shaped elements, some of which with spiral form, focally present at the epidermis and adnexal structures. CONCLUSIONS: Nowadays, syphilis may present with atypical clinical and serological features. Physicians should be aware of these possible alterations and consider syphilis even in case of uncommon clinical aspect and unclear serological tests. Cutaneous biopsy and immunohistochemical exam may be mandatory for the diagnosis.

Cytomegalovirus infection in hematologic malignancy settings other than the allogeneic transplant.

Cytomegalovirus (CMV) infection in clinical settings other than the allogeneic transplant represents a poorly explored issue. Thus, we performed a comprehensive review of the medical literature about CMV infection in patients undergoing autologous hematopoietic stem cell transplant and in other nontransplant-related hematologic patients. In autologous hematopoietic stem cell transplant, a CMV reactivation is reported to occur in up to 41% of CMV seropositive patients, when a prospective monitoring of antigenemia and/or viremia by polymerase chain reaction was adopted. However, more contained frequencies, up to 12%, have been reported when the monitoring criteria were based on a clinically driven diagnostic strategy. The most relevant risk factors appear to be CD34 + selected autografts, total body irradiation, and prior treatment with Alemtuzumab, Fludarabine, or Bortezomib, respectively. Other possible risk factors (ie, prior treatment with Rituximab, T-cell lymphomas, and pretransplant HBcIgG seropositivity) are still debated. In nontransplant settings, the data are very heterogeneous; thus, CMV infection incidence and risk factors are more difficult to establish. Overall, the rate of CMV infection/reactivation ranges between 2 and 67%. High-dose steroids, advanced disease, poor performance status, and treatment with Alemtuzumab, Fludarabine, Bortezomib, and Rituximab appear as the most relevant, though putative, risk factors. Intravenous Ganciclovir represents the gold standard for first-line treatment of CMV infection in these patients. Oral Valganciclovir and Foscarnet are other possible options. Extensive prophylaxis and preemptive therapy are not generally recommended, with the exception of high-risk patients.

Evaluation of risk of symptomatic cytomegalovirus reactivation in myeloma patients treated with tandem autologous stem cell transplantation and novel agents: a single-institution study.

The introduction of proteasome inhibitors and/or immunomodulators in the treatment of myeloma has led to an increase in viral infections, particularly in the Herpesviridae family. Previous studies about the risk of cytomegalovirus (CMV) reactivation after autologous stem cell transplantation (ASCT) have examined the clinical outcome after the first ASCT; however, only 1 study to date has investigated the risk of CMV reactivation after a second transplantation. To address this issue, we performed a retrospective chart review on 78 consecutive myeloma patients (median age 56 years) who underwent a tandem non-CD34(+) selected ASCT after induction treatment with either conventional chemotherapy (n = 42) or with novel agents (n = 36), respectively. All subjects had been mobilized and conditioned with cyclophosphamide plus granulocyte colony-stimulating factor and melphalan alone, respectively. CMV DNA load in the blood has been determined by polymerase chain reaction in the case of a clinical suspicion of CMV reactivation; therefore, routine monitoring was not performed. Considering the outcome of both the first and the second transplantations, we observed a total of 13 episodes of symptomatic CMV reactivation (13/156, 8%), in 12 subjects (12/78, 15%), all successfully treated. Eight subjects experienced a CMV reactivation after the first ASCT (8/78, 10%); however, only 1 of them (1/8, 12%) experienced a CMV reactivation after the second transplantation. Conversely, 4 CMV reactivations (6%) were observed after the second transplantation in the group of 70 patients who did not experience a CMV reactivation after the first ASCT. No statistically significant difference was observed between first and second ASCT (8/78, 10% vs. 5/78, 6%; P = 0.767). Univariate analysis showed that a pre-transplant treatment with novel agents was the only baseline factor significantly associated with the occurrence of post-ASCT CMV symptomatic reactivation after the first transplant (odds ratio [OR]: 9.897; 95% confidence interval [CI]: 1.154-84.840; P = 0.021) but not after the second transplant (OR: 5.125; 95% CI: 0.546-48.119; P = 0.115). No end-organ disease or primary infection was documented. Our data suggest that second transplantation does not increase the risk of CMV reactivation in our patient population, when compared with the first one, and confirm the role of a pre-transplant treatment with novel agents as a risk factor for CMV symptomatic reactivation.

Pemphigus vulgaris in a patient with arthritis and uveitis: successful treatment with immunosuppressive therapy and acyclovir.

A case of pemphigus vulgaris in a 41-year-old man with undifferentiated arthritis and uveitis is described. Histology of labial mucosa showed acantholytic, necrotic, and multinucleated giant keratinocytes having some nuclear inclusions suggestive of a virus infection. Specific serological tests revealed IgG positivity for HSV-1, CMV, and EBV, while real-time polymerase chain reaction assay from a biopsy of the mucosal lesion showed the presence of HSV-1/2 DNA. Treatment with prednisone, methotrexate, and acyclovir induced the complete remission of mucosal and joint symptoms, which then relapsed after interruption of antiviral therapy or immunosuppressive therapy. Therefore, a combined treatment with low doses of prednisone, methotrexate, and acyclovir was restarted and during 18 months of follow-up no recurrence was registered. Correlations between pemphigus and the herpes virus infection and also between autoimmune arthritis and herpetic agents have been well documented, but the exact role of the herpes virus in these disorders still needs further discussion. Our case strongly suggests that when autoimmune disorders do not respond to immunosuppressive agents, a viral infection should be suspected, researched, and treated.

Continuous increase in HIV-1 incidence after the year 2000 among men who have sex with men in Rome: insights from a 25-year retrospective cohort study.

To assess trends in HIV-1 incidence and risk factors for seroconversion among men who have sex with men (MSM) resident in Rome, Italy, a retrospective longitudinal cohort study was conducted over 25 years. Incidence rates and trends were modelled using Poisson regression and risk factors were assessed by multivariate Cox models. Of 1,862 HIV-1-negative individuals, 347 seroconverted during follow-up. HIV-1 incidence rates increased from 5.2/100 persons/year (p/y) in 1986 (95% confidence interval (CI): 2.3­11.5) to 9.2/00 p/y in 1992 (95% CI: 6.4­13.0), decreased to 1.3/100 p/y in 2001 and increased until 2009 (11.7/100 p/y; 95% CI: 7.4­18.6). The risk of HIV-1 seroconversion increased during the study period in younger MSM (incidence rate ratio (IRR) = 17.18; 95% CI: 9.74­30.32 in 16­32 year-olds and IRR = 5.09; 95% CI: 2.92­8.87 in 33­41 year-olds) and in those who acquired syphilis (IRR = 7.71; 95% CI: 5.00­11.88). In contrast, the risk of seroconversion decreased among highly educated MSM (IRR = 0.54; 95% CI: 0.35­0.82) and those without Italian citizenship (IRR = 0.45; 95% CI: 0.28­0.71). The HIV epidemic in MSM living in Rome continues to expand. Targeted prevention programmes against sexually transmitted infections to enhance knowledge transfer and behavioural skills are urgently required.

A report about the experience of COVID-19 active surveillance of homeless, undocumented people, and shelter staff in two cities of Lazio, Italy.

OBJECTIVE: This study aimed to investigate COVID-19 spread among people experiencing homelessness (PEH), undocumented migrants (UMs), and shelter staff of homeless service sites. Another aim has been to prevent an outbreak among these populations. A San Gallicano Institute's initiative to sustain the health system in helping hard-to-reach populations, very often with no community medical care coverage. SUBJECTS AND METHODS: The San Gallicano Dermatological Institute performed active surveillance for COVID-19 on PEH and UMs living in Rome and Latina, Italy. The screening was performed with two swabs: real-time polymerase chain reaction (RT-PCR) and antigen rapid tests. RESULTS: From June 2020 to January 2022, we performed 10,651 tests: 5,442 molecular swabs and 5,209 antigen rapid tests. A total of 3,503 individuals were screened. The prevalence of SARS-CoV-2 infection was 2.9% among the health and social workers and 5.7% among PEH and UMs. None of the people positive for COVID-19 had symptoms or signs of several illnesses. PEH and UMs who tested positive for COVID-19, asymptomatic or pauci-symptomatic, were transferred to a COVID Hotel or dedicated apartment for further clinical monitoring. CONCLUSIONS: People experiencing homelessness and undocumented migrants are often not registered in the National Health Service and, therefore, difficult to trace. These data could aid in estimating the spread of SARS-CoV-2 among people experiencing homelessness, undocumented migrants, and shelter staff in two Italian cities.

Hepatitis C virus infection prevalence and liver dysfunction in a cohort of B-cell non-Hodgkin's lymphoma patients treated with immunochemotherapy.

Several studies have reported a higher prevalence of hepatitis C virus (HCV) infection in patients with B-cell non-Hodgkin's lymphoma (NHL) than in the general population. Treatment for NHL includes the use of chemotherapeutic agents such as cytotoxic drugs, corticosteroids, and rituximab, which can be immunosuppressive and hepatotoxic. While reactivation of hepatitis B virus (HBV) when undergoing immunosuppressive therapy for haematological malignancies is a well-documented complication, data on HCV reactivation or liver function impairment after chemotherapy for NHL are controversial. From January 2006 to December 2009, 207 consecutive NHL patients treated with chemotherapy without rituximab (CHOP) or with rituximab (R-CHOP) were observed; screening for HCV infection and baseline liver function tests were performed in all patients. The prevalence of HCV infection was 9.2%. This prevalence is higher than that observed in the general population in Italy (3%). Among the HCV-infected subjects, the incidence of hepatitis flares was 26.3% vs 2.1% among the HCV-uninfected individuals. Although less frequent and less severe than in HBV-infected subjects, liver dysfunction can occur as a consequence of rituximab-containing regimens in HCV-infected patients with NHL. In the cases considered in this study, no patient treated with chemotherapy without rituximab developed hepatitis flares. The frequency and the severity of this complication vary in different reports. Therefore, we recommend the assessment of liver function and the screening of all patients with NHL for HCV infection before starting chemotherapy; we also recommend monitoring of liver function tests and HCV-RNA serum levels during treatment.

SARS-CoV-2 infection prevalence in people experiencing homelessness.

OBJECTIVE: People experiencing homelessness have peculiar characteristics that make them more vulnerable to Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) transmission and to more serious forms of Coronavirus Disease 19 (COVID-19). The aim of this study was to evaluate the prevalence of SARS-CoV-2 infection in the homeless population assisted by the primary care services of the Eleemosynaria Apostolica, Vatican City. PATIENTS AND METHODS: Persons experiencing homelessness and the volunteers assisting them were tested for COVID-19 through PCR and antigen rapid test between October 1st, 2020, and June 5th, 2021, in the clinical facilities of the Eleemosynaria Apostolica. RESULTS: A total of 1665 subjects from 96 different countries in five continents were included in the study; age range was 1-90 years. Overall, 2315 COVID-19 tests through nasopharyngeal swab were performed; 1052 Polymerase Chain Reaction (PCR) tests and 1263 antigen rapid tests. Nearly 40% of the subjects underwent both tests (n=650, 39.04%), 402 were tested with PCR test only (24.14%) and 613 with antigen test only (36.8%). PCR tests were negative in 966 cases and positive in 86 (8.17%), while antigen tests were negative in 1205 cases and positive in 58 (4.59%). The number of positive cases varied over time, with a drastic increase during the winter months of 2020 and a progressive decrease over 2021. Among positive cases, 24.41% were symptomatic; symptoms included fever, breathing difficulties, anosmia/hyposmia, cough, headache, and diarrhea. CONCLUSIONS: This study reported an overall prevalence of SARS-CoV-2 infection in our sample slightly above 8%. Additional data on viral genome through sequencing of SARS-CoV-2 in positive cases are of utmost importance to help identify variants and implement specific infection control measures.

CD81 expression on CD19+ peripheral blood lymphocytes is associated with chronic HCV disease and increased risk for HCV infection: a putative role for inflammatory cytokines.

The level of CD81 cell surface expression, a cellular co-receptor for hepatitis C virus (HCV), is critical for productive HCV infection of host cells. In addition, the cross-linking of HCV-E2 protein to CD81 can alter the function of T and B lymphocytes as well as that of NK cells by interfering with the activation signalling pathway. The down-regulation of CD81 expression on peripheral blood lymphocytes (PBL) has been associated to effective therapy of HCV infection. The aim of the present study is to quantitatively assess the levels of CD81 expression in PBL from HCV-infected patients compared to subjects at high risk for HCV infection such as HIV-infected individuals or patients with Porphyria Cutanea Tarda (PCT). The expression of CD81 was quantified by flow-cytometry using Phycoerythrin-labelled standard beads. Determination of CD81 was performed on CD3+ and CD19+ lymphocytes from 34 healthy controls, 51 patients with HCV infection and different clinical outcomes [these included HCV-RNA-negative subjects (8), patients with chronic active hepatitis (16), recipients of liver transplantation under immunosuppressive therapy (12), a subgroup with concomitant HIV infection (9) or concomitant PCT (6)]. In addition, 60 HIV-infected subjects and 4 patients with PCT were studied. The putative role of inflammatory cytokines in modulating CD81 was explored in vitro by assessing the effect of IL-6 or IFN-gamma on cultured human hepatocytes. A significant increase of the CD81 expression was found on CD19+ lymphocytes in association with either HIV or HCV infection, as compared to the control group. Immunosuppressive therapy with FK506, subsequent to liver transplantation, restored CD81 expression at normal levels. Data gathered in vitro using the WRL 68 hepatocytic cell line confirmed that inflammatory cytokines can up-regulate CD81 expression in liver cell inclusion. Our data suggest that CD81 up-regulation can increase the risk of HCV infection, particularly in HIV-infected subjects. In addition, the results strongly suggest that the cytokines released by activated lymphocytes at sites of inflammation may play a part in up-regulating CD81 expression.

Polarization of caveolins and caveolae during migration of immortalized neurons.

During CNS development neurons undergo directional migration to achieve their adult localizations. To study neuronal migration, we used a model cell line of immortalized murine neurons (gonadotropin-releasing hormone expressing neurons; GN11), enriched with caveolins and caveolae invaginations that show in vitro chemotaxis upon serum exposure. Cholesterol depletion with methyl-beta-cyclodextrin induced the loss of caveolae and the inhibition of chemotaxis, thus suggesting that GN11 migration depends upon the structural integrity of caveolae. Polarization of proteins and organelles is a hallmark of cell migration. Accordingly, GN11 cells transmigrating through filter pores exhibited a polarized distribution of caveolin-1 isoform (cav-1) in the leading processes. In contrast, during two-dimensional migration cav-1 and caveolae polarized at the trailing edge. As caveolae are enriched with signaling molecules, we suggest that asymmetrical localization of caveolae may spatially orient GN11 neurons to incoming migratory signals thereby transducing them into directional migration.

Inflammatory cytokines and biofilm production sustain Staphylococcus aureus outgrowth and persistence: a pivotal interplay in the pathogenesis of Atopic Dermatitis.

Individuals with Atopic dermatitis (AD) are highly susceptible to Staphylococcus aureus colonization. However, the mechanisms driving this process as well as the impact of S. aureus in AD pathogenesis are still incompletely understood. In this study, we analysed the role of biofilm in sustaining S. aureus chronic persistence and its impact on AD severity. Further we explored whether key inflammatory cytokines overexpressed in AD might provide a selective advantage to S. aureus. Results show that the strength of biofilm production by S. aureus correlated with the severity of the skin lesion, being significantly higher (P < 0.01) in patients with a more severe form of the disease as compared to those individuals with mild AD. Additionally, interleukin (IL)-ß and interferon γ (IFN-γ), but not interleukin (IL)-6, induced a concentration-dependent increase of S. aureus growth. This effect was not observed with coagulase-negative staphylococci isolated from the skin of AD patients. These findings indicate that inflammatory cytokines such as IL1-ß and IFN-γ, can selectively promote S. aureus outgrowth, thus subverting the composition of the healthy skin microbiome. Moreover, biofilm production by S. aureus plays a relevant role in further supporting chronic colonization and disease severity, while providing an increased tolerance to antimicrobials.

Factors involved in the migration of neuroendocrine hypothalamic neurons.

Neuroendocrine control of physiological functions needs a complex developmental organisation of the hypothalamic parvicellular neurons, which synthesise and release hypophysiotropic hormones. Among the hypothalamic neuroendocrine cells, Gonadotropin-releasing hormone (GnRH) neurons represent a unique class; they are generated in the olfactory placode and, during embryonic life, migrate to the septo/hypothalamic region along terminal and vomeronasal nerves. At this level GnRH neurons undergo terminal differentiation and start to release GnRH to modulate the secretion of pituitary gonadotropins. All these steps are under the strict control of several developmental cues and their defect might represent a cause of clinical disorders. A number of factors have been proposed to be involved in the migration of GnRH neurons, but their role is still unclear. By using gene knockout techniques it has been found that mice carrying a targeted deletion of Ebf2 gene, a component of Olf/Ebf bHLH transcription factors, show a defective migration of GnRH neurons, providing the first evidence of a mouse model of such defect. Since the investigation of GnRH neurons is hindered by their peculiar anatomical distribution, other studies has been forwarded by the availability of immortalized GnRH-expressing neurons (GN11 cells) that retain a strong chemomigratory response "in vitro". Among the factors analysed, we found that hepatocyte growth factor/scatter factor (HGF/SF) and vascular endothelial growth factor (VEGF) induce specific chemotaxis of GN 11 neurons, suggesting that migratory signals can arise from nasal mesenchyme and from the concomitant vasculogenesis. Finally, anosmin-1 (the product of the gene responsible of the X-linked form of Kallmann's disease) was found to induce a significant chemotactic response of GN11 cells, confirming a permissive/instructive role of KAL1 gene product in the migratory behaviour of GnRH neurons. In conclusion, the migration of the GnRH neurons appears to be a complex process, which involves the interplay of multiple molecular cues. These studies may provide new insights on the etiopathogenesis of the large proportion of reproductive dysfunctions that affect humans and could provide novel insights on common biochemical events controlling neuronal development and migration.

Characterization of functional opioid delta receptors in a luteinizing hormone-releasing hormone-producing neuronal cell line.

Endogenous opioids participate in the regulation of gonadotropin secretion through an influence on the release of the hypothalamic LHRH. However, it is not clear whether opioids exert a direct effect on LHRH-producing neurons or interfere with other systems able to influence LHRH release. A neuronal LHRH-producing cell line (GT1) developed recently provides a good model to study the mechanisms controlling LHRH release. In the present study, the presence of opioid receptors on a subclone of GT1 cells (GT1-1) has been investigated. A specific and saturable binding of the 3H-labeled nonselective opioid ligand diprenorphine ([3H]DIP) was detected by a receptor binding assay on both intact GT1-1 cells and crude membrane preparations obtained from these cells. Analysis of saturation curves revealed that [3H]DIP apparently binds to a single class of sites with a Kd of 0.2 nM and a binding capacity of 125 fmol/mg protein, corresponding to approximately 20,000 sites/cell. Selective displacement of the binding of [3H]DIP to GT1-1 cells by [D-Ala2,N-Me-Phe4,Gly5-ol]enkephalin, [D-Pen2,D-Pen5]enkephalin (DPDPE), and U50488H, which are selective ligands, respectively, for mu-, delta-, and kappa-receptors, was also evaluated. Only the specific delta-ligand DPDPE produced a significant inhibition of the binding of [3H]DIP. [D-Ala2,N-Me-Phe4,Gly5-ol]Enkephalin and U50488H were totally ineffective. The inhibitory effect of the agonist DPDPE on the binding of [3H]DIP was decreased by the presence of sodium ions, a typical characteristic of the binding of agonists to opioid receptors. Finally, it has been observed that treatment with prostaglandins E1 and E2 produces a dramatic increase in cAMP accumulation in GT1-1 cells, and DPDPE is highly effective in suppressing this effect. On the basis of these results, it is possible to postulate the presence of functional delta-opioid receptors on GT1-1 cells. By extrapolation, one might suggest that endogenous opioids may affect LHRH neurons by two mechanisms: a direct one, acting via delta-receptors, and an indirect one, through the activation of neurons impinging on the LHRH system, which uses mu-receptors.

Inhibition of luteinizing hormone-releasing hormone secretion by delta-opioid agonists in GT1-1 neuronal cells.

The endogenous opioids play a major role in regulation of the secretion of hypothalamic LHRH. However, it is not clear whether opioids exert a direct effect on LHRH neurons or interfere with other neuronal systems impinging on the cells synthesizing LHRH. The neuronal LHRH-producing cell line GT1 provides a new model to evaluate which signals may directly modify LHRH release. In a previous paper it has been reported that opioid-binding sites of the delta-type are present in a clone of the GT1 cells (GT1-1). In the present study, the possible effects of opioids on the release of LHRH were studied in GT1-1 cells. The results obtained show that only the addition of opioid agonists that bind to delta-receptors brings about a significant inhibition of forskolin- or prostaglandin E2-stimulated LHRH release in GT1-1 cells. The effect of the delta-opioid agonist [D-Pen2,D-Pen5]enkephalin is dose dependent and is reversed by the universal opioid antagonist naltrexone and the delta-specific antagonist naltrindole. No effect of opioid agonists or antagonists was observed in unstimulated cells. These results suggest that opioids may control the release of LHRH also, acting directly on LHRH-producing neurons.

Immortalized luteinizing hormone-releasing hormone neurons show a different migratory activity in vitro.

The development of two cell lines (GT1 and GN) of immortalized LHRH neurons has allowed an accurate study of the mechanisms controlling the synthesis and the secretion of LHRH. These cell lines, obtained in mice by genetic targeted tumorigenesis, retain many of the phenotypic characteristics of LHRH neurons. Of interest, GT1 cells derive from an hypothalamic tumor, whereas GN cells were obtained from a tumor localized in the olfactory bulb. The different origin of these cell lines lead to hypothesize that they might represent hypothalamic postmigratory neurons (GT1 cells), or LHRH neurons blocked at an early stage of their migration (GN cells). Using different experimental procedures, we found that the two cell subclones GT1-7 and GN11 express a different morphology and migratory behavior in vitro. In particular, we found that GN11 cells, but not GT1-7 cells, show the morphological shape of migrating neurons. When analyzing the spontaneous motility we found that only GN11 cells express a high capacity of migrating in a matrix of collagen gel. Moreover, in a chemomigratory assay GN11 cells did show a significant response to the chemotactic stimulus represented by the FBS. On the contrary, GT1-7 cells show very low spontaneous motility and appear insensitive to the FBS stimulus. These results suggest that the simultaneous use of the GT1-7/GN11 cells may represent an experimental tool for screening the factors possibly involved in the control of the migratory processes of LHRH neurons in normal and in pathological conditions, such as those due to their impaired migration, like it happens in Kallmann's syndrome.

Expression of prostacyclin receptors in luteinizing hormone-releasing hormone immortalized neurons: role in the control of hormone secretion.

PGs of the E series are involved in the control of LHRH secretion. The present experiments were conducted to clarify whether PGI2 (prostacyclin) might be also involved in such a control, using multiple methodological approaches on immortalized LHRH-secreting neurons. A RT-PCR procedure to detect mouse PGI2 receptor (IP) messenger RNA was first applied, and the results obtained showed the presence of a specific transcript in two cell lines of immortalized LHRH neurons (GT1-1 and GN11 cell lines). Receptor binding assays on membrane preparations from GT1-1 cells showed the presence of a single specific and saturable class of binding sites (Kd = 4.6 nM; 10,000 sites/cell) for [3H]iloprost, a stable analog of PGI2. Competition experiments showed that the binding sites labeled by [3H]iloprost possess the pharmacological characteristics of IP receptors. In functional studies, PGI2 and its analogs, iloprost and cicaprost, were able to stimulate LHRH release from the GT1-1 cells with elevated potencies (EC50 = 0.6-4.3 nM); PGE1 was only slightly less active (EC50 = 28.5 nM), whereas PGE2, considered the major PG involved in LHRH secretion, was poorly effective (EC50 = 921 nM). The relative potencies (EC50) of these compounds in stimulating the intracellular accumulation of cAMP were in line with their LHRH-releasing activities. In conclusion, these results indicate that immortalized LHRH-secreting neurons express IP receptors through which PGI2 may exert relevant effects on LHRH release.