Past, current, and potential treatments for cryptosporidiosis in humans and farm animals: A comprehensive review.

The intracellular protozoan parasite of the genus Cryptosporidium is among the leading causes of waterborne diarrheal disease outbreaks throughout the world. The parasite is transmitted by ingestion of infective oocysts that are highly stable in the environment and resistant to almost all conventional disinfection methods and water treatments. Control of the parasite infection is exceedingly difficult due to the excretion of large numbers of oocysts in the feces of infected individuals that contaminate the environment and serve as a source of infection for susceptible hosts including humans and animals. Drug development against the parasite is challenging owing to its limited genetic tractability, absence of conventional drug targets, unique intracellular location within the host, and the paucity of robust cell culture platforms for continuous parasite propagation. Despite the high prevalence of the parasite, the only US Food and Drug Administration (FDA)-approved treatment of Cryptosporidium infections is nitazoxanide, which has shown moderate efficacy in immunocompetent patients. More importantly, no effective therapeutic drugs are available for treating severe, potentially life-threatening cryptosporidiosis in immunodeficient patients, young children, and neonatal livestock. Thus, safe, inexpensive, and efficacious drugs are urgently required to reduce the ever-increasing global cryptosporidiosis burden especially in low-resource countries. Several compounds have been tested for both in vitro and in vivo efficacy against the disease. However, to date, only a few experimental compounds have been subjected to clinical trials in natural hosts, and among those none have proven efficacious. This review provides an overview of the past and present anti-Cryptosporidium pharmacotherapy in humans and agricultural animals. Herein, we also highlight the progress made in the field over the last few years and discuss the different strategies employed for discovery and development of effective prospective treatments for cryptosporidiosis.

Molecular identification of genus Pipistrellus (Mammalia: Chiroptera) from Fata region, Pakistan / Identificação molecular do gênero Pipistrellus (Mammalia: Chiroptera) da região de Fáta, Paquistão

Abstract A total of 10 specimens were captured from selected sites of Bajaur Agency FATA, Pakistan using mist nets. The captured specimens were morphologically identified and various morphometric measurements were taken. The head and Body length (HB) of Pipistrellus coromondra and Pipistrellus kuhlii lepidus (n=10) was 43±0.11 mm and 45±1.1 respectively. Morphologically identified Pipistrellus kuhlii confirmed as Pipistrellus kuhlii lepidus based on 16S rRNA sequences. The DNA sequences were submitted to GenBank and accession numbers were obtained (MN 719478 and MT430902). The available 16S rRNA gene sequences of Pipistrellus coromondra and Pipistrellus kuhlii lepidus were retrieved from NCBI and incorporated in N-J tree analysis. Overall, the interspecific genetic variations among Pipistrellus coromondra and Pipistrellus kuhlii lepidus were 8% and 1% respectively. In our recommendation, a comprehensive molecular identification of bats is need of hour to report more cryptic and new species from Pakistan.

Resumo Um total de 10 espécimes foi capturado em locais selecionados da Bajaur Agency FATA, Paquistão, usando redes de neblina. Os espécimes capturados foram identificados morfologicamente e várias medidas morfométricas foram realizadas. O comprimento da cabeça e do corpo (HB) de Pipistrellus coromondra e Pipistrellus kuhlii lepidus (n = 10) foi de 43 ± 0,11 mm e 45 ± 1,1, respectivamente. Pipistrellus kuhlii identificado morfologicamente e confirmado como Pipistrellus kuhlii lepidus com base em sequências de rRNA 16S. As sequências de DNA foram submetidas ao GenBank e os números de acesso foram obtidos (MN 719478 e MT430902). As sequências do gene 16S rRNA disponíveis de Pipistrellus coromondra e Pipistrellus kuhlii lepidus foram recuperadas do NCBI e incorporadas na análise da árvore N-J. No geral, as variações genéticas interespecíficas entre Pipistrellus coromondra e Pipistrellus kuhlii lepidus foram de 8% e 1%, respectivamente. Em nossa recomendação, uma identificação molecular abrangente de morcegos precisa de uma hora para relatar mais espécies crípticas e novas do Paquistão.

Activity of (1-benzyl-4-triazolyl)-indole-2-carboxamides against Toxoplasma gondii and Cryptosporidium parvum.

Parasitic diseases such as toxoplasmosis and cryptosporidiosis remain serious global health challenges, not only to humans but also to domestic animals and wildlife. With only limited treatment options available, Toxoplasma gondii and Cryptosporidium parvum (the causative agents of toxoplasmosis and cryptosporidiosis, respectively) constitute a substantial health threat especially to young children and immunocompromised individuals. Herein, we report the synthesis and biological evaluation of a series of novel (1-benzyl-4-triazolyl)-indole-2-carboxamides and related compounds that show efficacy against T. gondii and C. parvum. Closely related analogs 7c (JS-2-30) and 7e (JS-2-44) showed low micromolar activity with IC50 indices ranging between 2.95 µM and 7.63 µM against both T. gondii and C. parvum, whereas the compound representing (1-adamantyl)-4-phenyl-triazole, 11b (JS-2-41), showed very good activity with an IC50 of 1.94 µM, and good selectivity against T. gondii in vitro. Importantly, compounds JS-2-41 and JS-2-44 showed appreciable in vivo efficacy in decreasing the number of T. gondii cysts in the brains of Brown Norway rats. Together, these results indicate that (1-benzyl-4-triazolyl)-indole-2-carboxamides and (1-adamantyl)-4-phenyl-triazoles are potential hits for medicinal chemistry explorations in search for novel antiparasitic agents for effective treatment of cryptosporidiosis and toxoplasmosis.

Morphometrics of the indian false vampire bat (Megaderma lyra) from district Jhelum, Pakistan / Morfometria do falso morcego vampiro indiano (Megadermalyra) do distrito de Jhelum, Paquistão

Abstract During the present study thirteen Megaderma lyra bats were observed roosting in dark, domed shaped room of Rohtas Fort, district Jhelum. Out of these, six specimens were captured from the roosting site, using hand net. All captured specimens were male. These bats were identified through their unique facial features, an erect and elongated nose-leaf, large oval ears that joined above the forehead and no tail. Mean head and body length of captured specimens was 80 mm, forearm length was 67 mm while average lengths of 3rd, 4th and 5th metacarpals were 51.73 mm, 55.17 mm and 60.42 mm, respectively. Mean skull length was 29.84 mm, breadth of braincase was 12.77 mm. Average Penis length of two specimens was 6.6 mm and total bacular length was 3.08 mm respectively. This is the first record of Megaderma lyra from district Jhelum.

Resumo Durante o presente estudo, 13 morcegos Megadermalyra foram observados empoleirados em uma sala escura em forma de cúpula no Forte Rohtas, distrito de Jhelum, dos quais 6 espécimes foram capturados no local usando rede manual. Todos os espécimes capturados eram machos. Esses morcegos foram identificados por suas características faciais únicas, uma folha nasal ereta e alongada, grandes orelhas ovais que se juntam acima da testa e sem cauda. O comprimento médio da cabeça e do corpo dos espécimes capturados foi de 80 mm, o comprimento do antebraço foi de 67 mm, enquanto os comprimentos médios do 3º, 4º e 5º metacarpos foram de 51,73 mm, 55,17 mm e 60,42 mm, respectivamente. O comprimento médio do crânio foi de 29,84 mm, e a largura da caixa craniana, de 12,77 mm. O comprimento médio do pênis de duas amostras foi de 6,6 mm, e o comprimento total do báculo foi de 3,08 mm. Este é o primeiro registro de Megadermalyra no distrito de Jhelum.

Parasitic prevalence in bat fauna captured from selected sites in northwestern Pakistan / Prevalência parasitária na fauna de morcegos capturados em locais selecionados no noroeste do Paquistão

Abstract Present study was conducted to record ecotoparasitic prevalence in bat fauna of the northwestern parts of Pakistan. A total of 204 bat specimens representing 14 species were captured during a two year survey, extending from June 2015 through May 2016. A species of soft ticks Argas vespertilionis was identified from 23 bat specimens. Similarly, members of the family Dermanyssoidae (dermanyssoid mites) were isolated from 10 bat specimens, that of Spinturnicidae (spinturnicid mites) from 3 and Streblidae (bat flies) from 2 bat specimens. These parasites were collected using entomological tweezers and were identified on morphological basis. Further studies on parasitic prevalence, molecular characterization of bat parasites and their control measures are recommended.

Resumo O presente estudo foi realizado para registrar a prevalência de ectoparasitas na fauna de morcegos em partes do noroeste do Paquistão. Um total de 204 espécimes de morcegos, representando 14 espécies, foi capturado durante uma pesquisa de dois anos, de junho de 2015 a maio de 2016. A espécie de carrapato Argas vespertilionis foi identificada em 23 espécimes de morcegos. Da mesma forma, os membros da família Dermanyssidae (ácaros dermanyssoid) foram isolados de 10 espécimes de morcego, os da Spinturnicidae (ácaros spinturnicid), de 3, e os da Streblidae (mosca de morcego), de 2 espécimes de morcego. Esses parasitas foram coletados com pinça entomológica e identificados com base morfológica. Estudos adicionais sobre prevalência parasitária, caracterização molecular de parasitas de morcego e suas medidas de controle devem ser realizados.

Molecular identification of genus Pipistrellus (Mammalia: Chiroptera) from Fata region, Pakistan.

A total of 10 specimens were captured from selected sites of Bajaur Agency FATA, Pakistan using mist nets. The captured specimens were morphologically identified and various morphometric measurements were taken. The head and Body length (HB) of Pipistrellus coromondra and Pipistrellus kuhlii lepidus (n=10) was 43±0.11 mm and 45±1.1 respectively. Morphologically identified Pipistrellus kuhlii confirmed as Pipistrellus kuhlii lepidus based on 16S rRNA sequences. The DNA sequences were submitted to GenBank and accession numbers were obtained (MN 719478 and MT430902). The available 16S rRNA gene sequences of Pipistrellus coromondra and Pipistrellus kuhlii lepidus were retrieved from NCBI and incorporated in N-J tree analysis. Overall, the interspecific genetic variations among Pipistrellus coromondra and Pipistrellus kuhlii lepidus were 8% and 1% respectively. In our recommendation, a comprehensive molecular identification of bats is need of hour to report more cryptic and new species from Pakistan.

Cryptosporidium parvum Pyruvate Kinase Inhibitors With in vivo Anti-cryptosporidial Efficacy.

Cryptosporidium parvum is a highly prevalent protozoan parasite that causes a diarrheal disease in humans and animals worldwide. Thus far, the moderately effective nitazoxanide is the only drug approved by the United States Food and Drug Administration for treating cryptosporidiosis in immunocompetent humans. However, no effective drug exists for the severe disease seen in young children, immunocompromised individuals and neonatal livestock. C. parvum lacks the Krebs cycle and the oxidative phosphorylation steps, making it dependent solely on glycolysis for metabolic energy production. Within its glycolytic pathway, C. parvum possesses two unique enzymes, the bacterial-type lactate dehydrogenase (CpLDH) and the plant-like pyruvate kinase (CpPyK), that catalyze two sequential steps for generation of essential metabolic energy. We have previously reported that inhibitors of CpLDH are effective against C. parvum, both in vitro and in vivo. Herein, we developed an in vitro assay for the enzymatic activity of recombinant CpPyK protein and used it to screen a chemical compound library for inhibitors of CpPyK's activity. The identified inhibitors were tested (at non-toxic concentrations) for efficacy against C. parvum using in vitro assays, and an in vivo mouse infection model. We identified six CpPyK inhibitors that blocked in vitro growth and proliferation of C. parvum at low micromolar concentrations (EC50 values ranging from 10.29 to 86.01 µM) that were non-toxic to host cells. Among those six compounds, two (NSC252172 and NSC234945) were found to be highly efficacious against cryptosporidiosis in immunocompromised mice at a dose of 10 mg/kg body weight, with very significant reduction in parasite load and amelioration of intestinal pathologies. Together, these findings have unveiled inhibitors for an essential molecular target in C. parvum and demonstrated their efficacy against the parasite in vitro and in vivo. These inhibitors are, therefore, potential lead-compounds for developing efficacious treatments for cryptosporidiosis.

Parasitic prevalence in bat fauna captured from selected sites in northwestern Pakistan.

Present study was conducted to record ecotoparasitic prevalence in bat fauna of the northwestern parts of Pakistan. A total of 204 bat specimens representing 14 species were captured during a two year survey, extending from June 2015 through May 2016. A species of soft ticks Argas vespertilionis was identified from 23 bat specimens. Similarly, members of the family Dermanyssoidae (dermanyssoid mites) were isolated from 10 bat specimens, that of Spinturnicidae (spinturnicid mites) from 3 and Streblidae (bat flies) from 2 bat specimens. These parasites were collected using entomological tweezers and were identified on morphological basis. Further studies on parasitic prevalence, molecular characterization of bat parasites and their control measures are recommended.

Morphometrics of the indian false vampire bat (Megaderma lyra) from district Jhelum, Pakistan.

During the present study thirteen Megaderma lyra bats were observed roosting in dark, domed shaped room of Rohtas Fort, district Jhelum. Out of these, six specimens were captured from the roosting site, using hand net. All captured specimens were male. These bats were identified through their unique facial features, an erect and elongated nose-leaf, large oval ears that joined above the forehead and no tail. Mean head and body length of captured specimens was 80 mm, forearm length was 67 mm while average lengths of 3rd, 4th and 5th metacarpals were 51.73 mm, 55.17 mm and 60.42 mm, respectively. Mean skull length was 29.84 mm, breadth of braincase was 12.77 mm. Average Penis length of two specimens was 6.6 mm and total bacular length was 3.08 mm respectively. This is the first record of Megaderma lyra from district Jhelum.

Novel acyl carbamates and acyl / diacyl ureas show in vitro efficacy against Toxoplasma gondii and Cryptosporidium parvum.

Toxoplasma gondii and Cryptosporidium parvum are protozoan parasites that are highly prevalent and opportunistically infect humans worldwide, but for which completely effective and safe medications are lacking. Herein, we synthesized a series of novel small molecules bearing the diacyl urea scaffold and related structures, and screened them for in vitro cytotoxicity and antiparasitic activity against T. gondii and C. parvum. We identified one compound (GMG-1-09), and four compounds (JS-1-09, JS-2-20, JS-2-35 and JS-2-49) with efficacy against C. parvum and T. gondii, respectively, at low micromolar concentrations and showed appreciable selectivity in human host cells. Among the four compounds with efficacy against T. gondii, JS-1-09 representing the diacyl urea scaffold was the most effective, with an anti-Toxoplasma IC50 concentration (1.21 µM) that was nearly 53-fold lower than its cytotoxicity IC50 concentration, indicating that this compound has a good selectivity index. The other three compounds (JS-2-20, JS-2-35 and JS-2-49) were structurally more divergent from JS-1-09 as they represent the acyl urea and acyl carbamate scaffold. This appeared to correlate with their anti-Toxoplasma activity, suggesting that these compounds' potency can likely be enhanced by selective structural modifications. One compound, GMG-1-09 representing acyl carbamate scaffold, depicted in vitro efficacy against C. parvum with an IC50 concentration (32.24 µM) that was 14-fold lower than its cytotoxicity IC50 concentration in a human intestinal cell line. Together, our studies unveil a series of novel synthetic acyl/diacyl urea and acyl carbamate scaffold-based small molecule compounds with micromolar activity against T. gondii and C. parvum that can be explored further for the development of the much-needed novel anti-protozoal drugs.

Treatment of pharmaceutical industrial wastewater by nano-catalyzed ozonation in a semi-batch reactor for improved biodegradability.

The study reports the biodegradability enhancement of pharmaceutical wastewater along with COD (Chemical Oxygen Demand) color and toxicity removal via O3, O3/Fe2+, O3/nZVI (nano zero valent iron) processes. Nano catalytic ozonation process (O3/nZVI) showed the highest biodegradability (BI = BOD5/COD) enhancement of pharmaceutical wastewater up to 0.63 from 0.18 of control with a COD, color and toxicity removal of 62.3%, 93% and 82% respectively. The disappearance of the corresponding Fourier transform infrared (FTIR) and gas chromatography-mass spectrometry (GC-MS) peaks after pretreatment indicated the degradation or transformation of the refractory organic compounds to more biodegradable organic compounds. The subsequent aerobic degradation study of pretreated pharmaceutical wastewater resulted in biodegradation rate enhancement of 5.31, 2.97, and 1.22 times for O3/nZVI O3/Fe2+ and O3 processes respectively. Seed germination test using spinach (Spinacia oleracea) seeds established the toxicity removal of pretreated pharmaceutical wastewater.

Nano catalytic ozonation of biomethanated distillery wastewater for biodegradability enhancement, color and toxicity reduction with biofuel production.

The effectiveness of O3, O3/Fe2+, and O3/nZVI processes on biomethanated distillery wastewater (BMDWW) was evaluated in terms of biodegradability index (BI) enhancement, biofuel production, COD, color & toxicity reduction. A significant increase in biodegradability, COD, color and toxicity reduction was observed in O3/nZVI compared with O3, O3/Fe2+ due to more hydroxyl radical production. The O3/nZVI pretreated wastewater with enhanced BI (up to 0.71) showed 60% COD removal with additional biogas generation (64% methane content). From the Gas Chromatography Mass Spectrometry (GC-MS) analysis, 18 foremost organic compounds were predominantly detected in the raw distillery wastewater. The disappearance of the corresponding FTIR (Fourier Transform Infrared Spectroscopy) & GC-MS spectra during pretreatment processes signified the degradation or transformation of the recalcitrant present in the distillery wastewater. Subsequent (AnO + AO, AO) of pretreated BMDWW resulted in biodegradation rate enhancement by (1.83, 1.67), (3.5, 2.4) and (4.7, 2.9) times for O3, O3/Fe2+ and O3/nZVI processes respectively.

Synergistic effect on co-pyrolysis of rice husk and sewage sludge by thermal behavior, kinetics, thermodynamic parameters and artificial neural network.

This study investigates the thermal decomposition, thermodynamic and kinetic behavior of rice-husk (R), sewage sludge (S) and their blends during co-pyrolysis using thermogravimetric analysis at a constant heating rate of 20 °C/min. Coats-Redfern integral method is applied to mass loss data by employing seventeen models of five major reaction mechanisms to calculate the kinetics and thermodynamic parameters. Two temperature regions: I (200-400 °C) and II (400-600 °C) are identified and best fitted with different models. Among all models, diffusion models show high activation energy with higher R2(0.99) of rice husk (66.27-82.77 kJ/mol), sewage sludge (52.01-68.01 kJ/mol) and subsequent blends (45.10-65.81 kJ/mol) for region I and for rice husk (7.31-25.84 kJ/mol), sewage sludge (1.85-16.23 kJ/mol) and blends (4.95-16.32 kJ/mol) for region II, respectively. Thermodynamic parameters are calculated using kinetics data to assess the co-pyrolysis process enthalpy, Gibbs-free energy, and change in entropy. Artificial neural network (ANN) models are developed and employed on co-pyrolysis thermal decomposition data to study the reaction mechanism by calculating Mean Absolute Error (MAE), Root Mean Square Error (RMSE) and coefficient of determination (R2). The co-pyrolysis results from a thermal behavior and kinetics perspective are promising and the process is viable to recover organic materials more efficiently.

Anesthetic management of a case of Sanjad-Sakati syndrome.

Sanjad-Sakati syndrome is an autosomal recessive genetic disorder first described in Saudi Arabia. Anesthetic management of these patients is challenging due to airway difficulties, electrolyte imbalance, growth and mental retardation, and seizures. The anesthetic management of the syndrome is described in this case report.

Copper toxicity in Chinese cabbage is not influenced by plant sulphur status, but affects sulphur metabolism-related gene expression and the suggested regulatory metabolites.

The toxicity of high copper (Cu) concentrations in the root environment of Chinese cabbage (Brassica pekinensis) was little influenced by the sulphur nutritional status of the plant. However, Cu toxicity removed the correlation between sulphur metabolism-related gene expression and the suggested regulatory metabolites. At high tissue Cu levels, there was no relation between sulphur metabolite levels viz. total sulphur, sulphate and water-soluble non-protein thiols, and the expression and activity of sulphate transporters and expression of APS reductase under sulphate-sufficient or-deprived conditions, in the presence or absence of H2 S. This indicated that the regulatory signal transduction pathway of sulphate transporters was overruled or by-passed upon exposure to elevated Cu concentrations.

Validation of the femoral anteversion measurement method used in imageless navigation.

Total hip arthroplasty restores lost mobility to patients suffering from osteoarthritis and acute trauma. In recent years, navigated surgery has been used to control prosthetic component placement. Furthermore, there has been increasing research on what constitutes correct placement. This has resulted in the definition of a safe-zone for acetabular cup orientation. However, there is less definition with regard to femoral anteversion and how it should be measured. This study assesses the validity of the femoral anteversion measurement method used in imageless navigation, with particular attention to how the neutral rotation of the femur is defined. CT and gait analysis methodologies are used to validate the reference which defines this neutral rotation, i.e., the ankle epicondyle piriformis (AEP) plane. The findings of this study indicate that the posterior condylar axis is a reliable reference for defining the neutral rotation of the femur. In imageless navigation, when these landmarks are not accessible, the AEP plane provides a useful surrogate to the condylar axis, providing a reliable baseline for femoral anteversion measurement.

Inhibitory effect of Allium sativum and Zingiber officinale extracts on clinically important drug resistant pathogenic bacteria.

BACKGROUND: Herbs and spices are very important and useful as therapeutic agent against many pathological infections. Increasing multidrug resistance of pathogens forces to find alternative compounds for treatment of infectious diseases. METHODS: In the present study the antimicrobial potency of garlic and ginger has been investigated against eight local clinical bacterial isolates. Three types of extracts of each garlic and ginger including aqueous extract, methanol extract and ethanol extract had been assayed separately against drug resistant Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, Staphylococcus aureus, Klebsiella pneumoniae, Shigella sonnei, Staphylococcusepidermidis and Salmonella typhi. The antibacterial activity was determined by disc diffusion method. RESULTS: All tested bacterial strains were most susceptible to the garlic aqueous extract and showed poor susceptibility to the ginger aqueous extract. The (minimum inhibitory concentration) MIC of different bacterial species varied from 0.05 mg/ml to 1.0 mg/ml. CONCLUSION: In the light of several socioeconomic factors of Pakistan mainly poverty and poor hygienic condition, present study encourages the use of spices as alternative or supplementary medicine to reduce the burden of high cost, side effects and progressively increasing drug resistance of pathogens.

Treating pulmonary arterial hypertension: current treatments and future prospects.

Pulmonary arterial hypertension (PAH) consists of a group of heterogeneous but distinct disorders characterized by complex proliferation of the pulmonary vascular endothelium and progressive pulmonary vascular remodeling that leads to right ventricular failure and death. Over the past two decades, significant advances in our understanding of the pathobiology of PAH have led to the development of several therapeutic targets in this disease. Besides conservative therapeutic strategies such as anticoagulation and diuretics, the current treatment paradigm for PAH targets the mediators of the three main biologic pathways that are critical for its pathogenesis and progression: endothelin receptor antagonists inhibit the upregulated endothelin pathway by blocking the biologic activity of endothelin-1; phosphodiesterase-5 inhibitors prevent breakdown and increase the endogenous availability of cyclic guanosine monophosphate, which signals the vasorelaxing effects of the downregulated mediator nitric oxide; and prostacyclin derivatives provide an exogenous supply of the deficient mediator prostacyclin. In addition to these established current therapeutic options, a large number of potential therapeutic targets are being investigated. These novel therapeutic targets include soluble guanylyl cyclase, phosphodiesterases, tetrahydrobiopterin, 5-hydroxytryptamine (serotonin) receptor 2B, vasoactive intestinal peptide, receptor tyrosine kinases, adrenomedullin, rho kinase, elastases, endogenous steroids, endothelial progenitor cells, immune cells, bone morphogenetic protein and its receptors, potassium channels, metabolic pathways, and nuclear factor of activated T cells. This review provides an overview of the current therapeutic options and potential therapeutic targets for PAH.

The human progesterone receptor A-form functions as a transcriptional modulator of mineralocorticoid receptor transcriptional activity.

The human progesterone receptor (hPR) exists as two distinct molecular forms in most cells, hPR-A and -B. These receptor isoforms display distinct biological functions and demonstrate a cell and promoter specific ability to regulate gene transcription. In cellular contexts where hPR-A is transcriptionally inactive it can function as a ligand dependent inhibitor of mineralocorticoid receptor (MR) transcriptional activity. Inhibition occurs by a non-competitive mechanism as direct binding to MR is not required. Interestingly, PR agonists differ in their ability to facilitate the inhibitory function of hPR-A, suggesting that a specific receptor conformation may be preferred for this activity. Those compounds derived from 19-nor-testosterone are the most effective. The antiprogestins RU486, ZK98299 and ZK112993 are effective MR antagonists in the presence of coexpressed hPR-A. The mechanism of hPR-A mediated inhibition of MR transcriptional activity is unknown. We propose that inhibition results from a competition of hPR-A with MR for a common transcription factor and that the association of hPR-A with this factor is not transcriptionally productive.

Human progesterone receptor A form is a cell- and promoter-specific repressor of human progesterone receptor B function.

Two distinct isoforms of the human progesterone receptor (hPR-A and hPR-B) have been identified previously. They differ only in that hPR-B contains an additional 164 amino acids at the amino terminus. Among various species these two forms arise as a result of either alternate initiation of translation from the same mRNA or by transcription from alternate promoters within the same gene. In order to understand the reason for their existence, we studied the transcriptional capacity of these individual receptors and observed that their activity was influenced strongly by cell and promoter context. More surprising was the observation that in promoter and cell contexts where hPR-A was inactive, it acted as a potent trans-dominant repressor of hPR-B-mediated transcription. This event occurred at substoichiometric concentrations of hPR-A and was hormone dependent. Human PR-A was not a general repressor of ligand-mediated transcription, as it had no effect on vitamin D receptor function. Interestingly, hPR-A but not hPR-B was capable of a similar inhibition of glucocorticoid, androgen, and mineralocorticoid receptor-mediated gene transcription. This suggests a specific role for the hPR-A isoform in this regulatory process. The trans-dominant effects of hPR-A were induced also by the antiprogestins ZK112993 and ZK98299 and a DNA binding defective hPR-A mutant, suggesting that the inhibitory function of hPR-A does not require DNA binding. The dual role of hPR-A as an activator or repressor of transcription defines a potential mechanism by which cells can generate dissimilar responses to a single hormone and provides a molecular explanation for the existence of two distinct forms of the hPR.