The metabolic activation of pentachlorophenol to chloranil as a potent inhibitor of human and rat placental 3β-hydroxysteroid dehydrogenases

Pentachlorophenol (PCP) is a widely used pesticide. However, whether PCP and its metabolite chloranil have endocrine-disrupting effects by inhibiting placental 3β-hydroxysteroid dehydrogenase 1 (3β-HSD1) remains unclear. The study used in vitro assays with human and rat placental microsomes to measure 3β-HSD activity as well as human JAr cells to evaluate progesterone production. The results showed that PCP exhibited moderate inhibition of human 3β-HSD1, with an IC50 value of 29.83 μM and displayed mixed inhibition in terms of mode of action. Conversely, chloranil proved to be a potent inhibitor, demonstrating an IC50 value of 147 nM, and displaying a mixed mode of action. PCP significantly decreased progesterone production by JAr cells at 50 μM, while chloranil markedly reduced progesterone production at ≥1 μM. Interestingly, PCP and chloranil moderately inhibited rat placental homolog 3β-HSD4, with IC50 values of 27.94 and 23.42 μM, respectively. Dithiothreitol (DTT) alone significantly increased human 3β-HSD1 activity. Chloranil not PCP mediated inhibition of human 3β-HSD1 activity was completely reversed by DTT and that of rat 3β-HSD4 was partially reversed by DTT. Docking analysis revealed that both PCP and chloranil can bind to the catalytic domain of 3β-HSDs. The difference in the amino acid residue Cys83 in human 3β-HSD1 may explain why chloranil is a potent inhibitor through its interaction with the cysteine residue of human 3β-HSD1. In conclusion, PCP is metabolically activated to chloranil as a potent inhibitor of human 3β-HSD1.

Identification of an ex vivo inhibitor of the schizophrenia biomarker Ndel1 by high throughput screening

Ndel1 oligopeptidase activity shows promise as a potential biomarker for diagnosing schizophrenia (SCZ) and monitoring early-stage pharmacotherapy. Ndel1 plays a pivotal role in critical aspects of brain development, such as neurite outgrowth, neuronal migration, and embryonic brain formation, making it particularly relevant to neurodevelopmental disorders like SCZ. Currently, the most specific inhibitor for Ndel1 is the polyclonal anti-Ndel1 antibody (NOAb), known for its high specificity and efficient anti-catalytic activity. NOAb has been vital in measuring Ndel1 activity in humans and animal models, enabling the prediction of pharmacological responses to antipsychotics in studies with patients and animals. To advance our understanding of in vivo Ndel1 function and develop drugs for mental disorders, identifying small chemical compounds capable of specifically inhibiting Ndel1 oligopeptidase is crucial, including within living cells. Due to challenges in obtaining Ndel1's three-dimensional structure and its promiscuous substrate recognition, we conducted a high-throughput screening (HTS) of 2,400 small molecules. Nine compounds with IC50-values ranging from 7 to 56 μM were identified as potent Ndel1 inhibitors. Notably, one compound showed similar efficacy to NOAb and inhibited Ndel1 within living cells, although its in vivo use may pose toxicity concerns. Despite this, all identified compounds hold promise as candidates for further refinement through rational drug design, aiming to enhance their inhibitory efficacy, specificity, stability, and biodistribution. Our ultimate goal is to develop druggable Ndel1 inhibitors that can improve the treatment and support the diagnosis of psychiatric disorders like SCZ.

Charge-transfer chemistry of azithromycin, the antibiotic used worldwide to treat the coronavirus disease (COVID-19). Part II: Complexation with several π-acceptors (PA, CLA, CHL)

Finding a vaccine or cure for the coronavirus disease (COVID-19) responsible for the worldwide pandemic and its economic, medical, and psychological burdens is one of the most pressing issues presently facing the global community. One of the current treatment protocols involves the antibiotic azithromycin (AZM) alone or in combination with other compounds. Obtaining additional insight into the charge-transfer (CT) chemistry of this antibiotic could help researchers and clinicians to improve such treatment protocols. Toward this aim, we investigated the CT interactions between AZM and three π-acceptors: picric acid (PA), chloranilic acid (CLA), and chloranil (CHL) in MeOH solvent. AZM formed colored products at a 1:1 stoichiometry with the acceptors through intermolecular hydrogen bonding. An n → π* interaction was also proposed for the AZM-CHL CT product. The synthesized CT products had markedly different morphologies from the free reactants, exhibiting a semi-crystalline structure composed of spherical particles with diameters ranging from 50 to 90 nm.

Repetitive experiments of one or two-pulse sequences in NQR of spins I=3/2: Liouville space, steady-state, Ernst angle and optimum signal

In NMR, the repetition of pulse sequences with a recycle time that does not allow the spin system to completely relax back to equilibrium is a well known and often used method to increase the signal to noise ratio at given total measuring time. For isolated spins I=1/2, the steady-state of a train of strictly identical pulse sequences separated by free evolution periods of same duration is described by the well known Ernst-Anderson model, and the optimum pulse angle is given by the Ernst angle. We showed recently that equivalent formula, but with super-operators in the Liouville space, can be obtained for general spins I. In this article, this formalism is generalized to pure NQR of spins I=3/2, and applied to calculate the signal resulting from single and solid-echo sequences, in the limit when the recycle time T>5T_2q, where T_2q is the transverse (coherence) quadrupolar relaxation time. In particular, we show that powder samples have a behaviour that is very close to NMR of spins I=1/2. For instance, the generalized Ernst angle β_M that maximizes the signal amplitude for a single pulse train is well described by the simple formula cos(1.52β_M)≈exp(-T/T_1q), whatever the quadrupolar asymmetry parameter η, T_1q being the longitudinal (population) quadrupolar relaxation time. Moreover, a simplified NMR-like formula that describes the overall behaviour of nutation curves is proposed, and it is shown that the signal to noise ratio (SNR) at given experimental time is exactly the same as in NMR of spins I=1/2 as a function of recycle time, when properly normalized. Some theoretical predictions for the single pulse and solid-echo sequence were compared to experiments, and validated, by performing ³⁵Cl pure NQR experiment on chloranil (C₆Cl₄O₂ tetrachloro-1,4-benzoquinone) powder.