Potential Mechanism For Inhibition Research Articles

A machine learning-based QSAR model reveals important molecular features for understanding the potential inhibition mechanism of ionic liquids to acetylcholinesterase

The broad application of ionic liquids (ILs) has been hindered by uncertainties surrounding their ecotoxicity. In this work, a Quantitative Structure-Activity Relationship (QSAR) model was devised to predict the inhibition of ILs towards the activity of AChE, employing both Random Forest (RF) and eXtreme Gradient Boosting (XGBoost) machine learning approaches. Fourteen kings of essential molecular feature descriptors were screened from an initial roster of 244 descriptors through the application of a feature importance index and they showed a significant impact on the activity of AChE activity. The two models based solely on the 14 most critical molecular descriptors could maintain model's robustness and reliability. The correlation analysis between these 14 descriptors and the inhibition of AChE activity revealed the potential impact of the molecular characteristics on ILs toxicity. The results underscored the main influence of cations in ILs on the inhibitory activity towards the AChE enzyme. Specifically, cations exhibiting hydrophobicity properties were found to exert more potent inhibitory effects on the AChE enzyme. In addition, some other properties of the cations, such as the degree of branching, atomic weight and partial charge also modulated their inhibition potential. This study enhances the comprehension of the structure-activity relationship between ILs and AChE inhibition, providing a reference for designing safer and greener ILs.

Fabrication of multinuclear copper cluster-based coordination polymers as urease inhibitors.

This study focused on the design and synthesis of two Cu-based coordination polymers, [Cu2(4-dpye)(5-HSIP)(μ3-O)(H2O)2]·3H2O (Cu-CP-1) and [Cu(4-dpye)0.5(BCA)2] (Cu-CP-2), where 4-dpye = N,N'-bis(4-pyridinecarboxamide)-1,2-ethane, 5-H3SIP = 5-sulfoisophthalic acid, and HBCA = benzoic acid, by using a hydrothermal method. Single-crystal X-ray diffraction (SCXRD) study revealed that by adding various auxiliary ligands, the architectures of the Cu-CPs could be altered, yielding two distinct multinuclear Cu clusters. Moreover, the Cu-CPs can be used as urease inhibitors (UIs). In vitro experiments showed that the Cu-CPs had good urease inhibition effects with IC50 values of 0.53 ± 0.01 μM for Cu-CP-1 and 1.44 ± 0.01 μM for Cu-CP-2 and 98.48% (Cu-CP-1) and 96.27% (Cu-CP-2) inhibition of urease was achieved at a concentration of 100 μM, respectively. Furthermore, the inhibition effect of the tetranuclear Cu-CP was better than that of the binuclear Cu-CP. To better understand the potential mechanism of inhibition of the two copper complexes, we performed kinetic analysis using Lineweaver-Burk (L-B) plots in the presence of different concentrations of urea and different concentrations of inhibitors, and both Cu-CP-1 and Cu-CP-2 showed a non-competitive mode of inhibition. In addition, molecular docking analysis showed that the Cu-CPs were able to enter well into the urease binding pocket, thus interacting with key amino acid residues of urease to different degrees. Both kinetic and molecular docking studies theoretically explain and demonstrate the inhibition effect of both Cu-CPs on urease activity in vitro, which is expected to provide reasonable guidance and effective strategies for the development of novel, efficient, stable and safe CP-based UIs.

Structural mechanism of TRPV5 inhibition by econazole

The calcium-selective TRPV5 channel activated by phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] is involved in calcium homeostasis. Recently, cryoelectron microscopy (cryo-EM) provided molecular details of TRPV5 modulation by exogenous and endogenous molecules. However, the details of TRPV5 inhibition by the antifungal agent econazole (ECN) remain elusive due to the low resolution of the currently available structure. In this study, we employ cryo-EM to comprehensively examine how the ECN inhibits TRPV5. By combining our structural findings with site-directed mutagenesis, calcium measurements, electrophysiology, and molecular dynamics simulations, we determined that residues F472 and L475 on the S4 helix, along with residue W495 on the S5 helix, collectively constitute the ECN-binding site. Additionally, the structure of TRPV5 in the presence of ECN and PI(4,5)P2, which does not show the bound activator, reveals a potential inhibition mechanism in which ECN competes with PI(4,5)P2, preventing the latter from binding, and ultimately pore closure.

Inhibitory effects of selected cannabinoids against dipeptidyl peptidase IV, an enzyme linked to type 2 diabetes

Ethnopharmacological relevanceIn recent times the decriminalisation of cannabis globally has increased its use as an alternative medication. Where it has been used in modern medicinal practises since the 1800s, there is limited scientific investigation to understand the biological activities of this plant. Aim of the studyDipeptidyl peptidase IV (DPP-IV) plays a key role in regulating glucose homeostasis, and inhibition of this enzyme has been used as a therapeutic approach to treat type 2 diabetes. However, some of the synthetic inhibitors for this enzyme available on the market may cause undesirable side effects. Therefore, it is important to identify new inhibitors of DPP-IV and to understand their interaction with this enzyme. MethodsIn this study, four cannabinoids (cannabidiol, cannabigerol, cannabinol and Δ9-tetrahydrocannabinol) were evaluated for their inhibitory effects against recombinant human DPP-IV and their potential inhibition mechanism was explored using both in vitro and in silico approaches. ResultsAll four cannabinoids resulted in a dose-dependent response with IC50 values of between 4.0 and 6.9 μg/mL. Kinetic analysis revealed a mixed mode of inhibition. CD spectra indicated that binding of cannabinoids results in structural and conformational changes in the secondary structure of the enzyme. These findings were supported by molecular docking studies which revealed best docking scores at both active and allosteric sites for all tested inhibitors. Furthermore, molecular dynamics simulations showed that cannabinoids formed a stable complex with DPP-IV protein via hydrogen bonds at an allosteric site, suggesting that cannabinoids act by either inducing conformational changes or blocking the active site of the enzyme. ConclusionThese results demonstrated that cannabinoids may modulate DPP-IV activity and thereby potentially assist in improving glycaemic regulation in type 2 diabetes.

Metformin-Induced Vitamin B12 Deficiency in Patients With Type-2 Diabetes Mellitus.

Diabetes mellitus (DM) is the most common metabolic disease worldwide. Hence, the prevalence of the disease continues to increase across the globe. Metformin is used as a first-line oral hypoglycemic drug to keep control of type-2 DM (T2DM) in adults. Diabetic patients on metformin have been largely seen to be suffering from a deficiency of vitamin B12. It is a water-soluble vitamin mainly obtained from animal food like meat. At the basic cell level, it acts as a cofactor for enzymes essential for DNA synthesis and neuroprotection. As a result, vitamin B12 deficiency can show clinical effects such as progressive demyelination, peripheral neuropathy and haematological abnormalities (such as macrocytic anaemia and neutrophil hypersegmentation). Various studies also show a relation between vitamin B12 insufficiency and metformin-treated T2DM patients as decreased absorption of vitamin B12. There could be a severe complication of vitamin B12 deficiency in T2DM patients. The use of proton pump inhibitors, gastric bypass surgery, older patients and patients with a higher red blood cell turnover are factors that hasten the depletion of vitamin B12 reserves in the liver. Methylmalonic acid and homocysteine levels can be measured to identify vitamin B12 insufficiency at its early stage if blood vitamin B12 levels are borderline. The action of metformin on vitamin B12 absorption and its potential mechanisms of inhibition will be the main topics of discussion in this review. The review will also discuss how vitamin B12 deficiencies in T2DM patients using metformin affect their clinical results.

Supply Chain Finance and Industrial Efficiency: Evidence From ICT Industry

This study explores the impact of supply chain finance on industrial efficiency and the internal mechanism. The super-efficiency model and quantitative analysis method were used based on the time series data of the ICT industry in Shenzhen from 2005 to 2020. In order to better investigate the impact of supply chain finance on industrial efficiency, this study categorized industrial efficiency into operational efficiency and innovation efficiency to reflect the durability and virtuousness of the industry development. Results indicate that supply chain finance has an inverted U-shaped nonlinear effect on industrial efficiency. Even though the long-term effect on operational efficiency is positive, the effect on innovation efficiency reveals an inverted U-shape, mainly due to the mediating effect of industrial concentration. Theoretically, this study sheds light on the intricate effects of supply chain finance at the industrial level, and also provides valuable insights into the potential inhibition mechanism, which enriches and deepens the related research on the supply chain finance from the nonlinear perspective, make the research findings more consistent with the fact of industrial development and avoid the linear stereotypes of the existing theory consensus. Practically, it is conductive to an objective understanding for managers and policymakers, so that supply chain finance can facilitate both operational and innovation efficiencies and realize the effective integration of supply chain finance and industrial development.

Imidazo[1,2-c]quinazolines as a novel and potent scaffold of α-glucosidase inhibitors: design, synthesis, biological evaluations, and in silico studies

α-Glucosidase inhibition is an approved treatment for type 2 diabetes mellitus (T2DM). In an attempt to develop novel anti-α-glucosidase agents, two series of substituted imidazo[1,2-c]quinazolines, namely 6a–c and 11a–o, were synthesized using a simple, straightforward synthetic routes. These compounds were thoroughly characterized by IR, 1H and 13C NMR spectroscopy, as well as mass spectrometry and elemental analysis. Subsequently, the inhibitory activities of these compounds were evaluated against Saccharomyces cerevisiae α-glucosidase. In present study, acarbose was utilized as a positive control. These imidazoquinazolines exhibited excellent to great inhibitory potencies with IC50 values ranging from 12.44 ± 0.38 μM to 308.33 ± 0.06 μM, which were several times more potent than standard drug with IC50 value of 750.0 ± 1.5 μM. Representatively, compound 11j showed remarkable anti-α-glucosidase potency with IC50 = 12.44 ± 0.38 μM, which was 60.3 times more potent than positive control acarbose. To explore the potential inhibition mechanism, further evaluations including kinetic analysis, circular dichroism, fluorescence spectroscopy, and thermodynamic profile were carried out for the most potent compound 11j. Moreover, molecular docking studies and in silico ADME prediction for all imidazoquinazolines 6a–c and 11a–o were performed to reveal their important binding interactions, as well as their physicochemical and drug-likeness properties, respectively.

Limosilactobacillus fermentum NCU003089 and Lactiplantibacillus plantarum NCU001261, two probiotics with inhibition of Escherichia coli and Cronobacter sakazakii translocation in vitro

The subject of this study was to screen lactic acid bacteria (LAB) with pathogen translocation inhibition and investigate the potential inhibition mechanism of it. Pathogens colonized in the intestine could cross the intestinal barrier to access blood circulation, causing severe complications. This study aimed to screen LAB with favorable inhibitory effects on the translocation of enterinvasive Escherichia coli CMCC44305 (E. coli) and Cronobacter sakazakii CMCC45401 (C. sakazakii), which were two common intestinal opportunistic pathogens. After an elaborate screening procedure including adhesion, antibacterial, and translocation assay, Limosilactobacillus fermentum NCU003089 (L. fermentum NCU3089) and Lactiplantibacillus plantarum NCU0011261 (L. plantarum NCU1261) were found to inhibit 58.38% and 66.85% of pathogen translocation, respectively. Subsequently, LAB pre-treatment suppressed the decline in TEER of Caco-2 monolayers caused by pathogens. Meanwhile, L. fermentum NCU3089 significantly inhibited claudin-1, ZO-1, and JAM-1 degradation caused by E. coli, and L. plantarum NCU1261 markedly reduced claudin-1 degradation caused by C. sakazakii. Also, the two LAB strains significantly decreased TNF-α level. In addition, L. fermentum NCU3089 but not L. plantarum NCU1261 tolerated well in the gastrointestinal fluids, and they were both sensitive or intermediate to nine common clinical antibiotics without hemolytic activity. In short, the two LAB strains could inhibit pathogen translocation by competing for adhesion sites, secreting antibacterial substances, reducing inflammatory cytokines levels, and maintaining intestinal barrier integrity. This study provided a feasible solution to prevent pathogen infection and translocation, and the two LAB strains were safe and had potential in food and pharmaceutical applications.

Cryo-EM structures of ClC-2 chloride channel reveal the blocking mechanism of its specific inhibitor AK-42

ClC-2 transports chloride ions across plasma membranes and plays critical roles in cellular homeostasis. Its dysfunction is involved in diseases including leukodystrophy and primary aldosteronism. AK-42 was recently reported as a specific inhibitor of ClC-2. However, experimental structures are still missing to decipher its inhibition mechanism. Here, we present cryo-EM structures of apo ClC-2 and its complex with AK-42, both at 3.5 Å resolution. Residues S162, E205 and Y553 are involved in chloride binding and contribute to the ion selectivity. The side-chain of the gating glutamate E205 occupies the putative central chloride-binding site, indicating that our structure represents a closed state. Structural analysis, molecular dynamics and electrophysiological recordings identify key residues to interact with AK-42. Several AK-42 interacting residues are present in ClC-2 but not in other ClCs, providing a possible explanation for AK-42 specificity. Taken together, our results experimentally reveal the potential inhibition mechanism of ClC-2 inhibitor AK-42.

Total flavonoids of Chrysanthemum indicum L inhibit acute pancreatitis through suppressing apoptosis and inflammation

Acute pancreatitis (AP) is one of the most common acute abdomen. Inflammation and apoptosis are closely linked with AP development. Total flavonoids of Chrysanthemum indicum L (TFC) has been proved to inhibit inflammation and apoptosis. If TFC could suppress AP remains unclear. AP animal and cell models were established with Cerulein. The pancreatic tissue injury was measured with HE staining. Inflammatory factors were detected with ELISA method. The protein expression was evaluated with Western blotting. Inhibition of AP in vivo was achieved by TFC by inhibiting serum amylase, myeloperoxidase (MPO), and water content of pancreatic tissue. The increased inflammatory response and activation of NF-κB signaling pathway in AP rats were inhibited after TFC treatment. The activation of NF-κB signaling pathway, increase of cell apoptosis and inflammatory factors in AR42J cells were suppressed by TFC. We demonstrated that TFC could significantly inhibit AP through restraining serum amylase, MPO, water content of pancreatic tissue, inflammation levels, apoptosis, and NF-κB signaling pathway activation. This study might clarify the potential inhibition mechanism of TFC in AP development.

Natamycin as a safe food additive to control postharvest green mould and sour rot in citrus.

The purpose of this study was to explore the potential inhibitory mechanism and assess the feasibility of natamycin as an antifungal agent in the utilization of citrus storage. In this study, the mycelial growth, spore germination as well as germ tube elongations of Geotrichum citri-aurantii and Penicillium digitatum were significantly inhibited by natamycin treatment. The relative conductivities of G. citri-aurantii and P. digitatum mycelia were increased as time went by and the damages of plasma membranes were up to 17.43% and 28.61%. The mitochondria abnormalities and vacuolation were also observed in the TEM. Moreover, the sour rot and green mould decay incidences were reduced to 18.33% and 10% post incubation with G. citri-aurantii and P. digitatum under 300 mg L-1 natamycin application, respectively. For the citrus storage experiment, there was no significant difference in edible rate, juice yield, total soluble solid (TSS) content, titratable acid (TA) and decay incidences of the 'Newhall' navel orange fruit treated with 300 mg L-1 natamycin stored for 90 d. Natamycin could decrease the expansions of green mould and sour rot and maintain quality and improve storability on citrus fruit. This work explores the potential inhibition mechanism of natamycin G. citri-aurantii and P. digitatum and assesses the feasibility of natamycin as an antifungal agent in the utilization of citrus storage.

Redox-responsive hyaluronan-conjugated polypyrrole nanoparticles targeting chemo-photothermal therapy for breast cancer.

The combination of chemo-photothermal therapy has a wide application prospect in the intensive treatment of cancer. In this study, we developed a complex nanoparticle consist of polypyrrole, cystine dihydrochloride and hyaluronan. The polypyrrole nanoparticles loaded with paclitaxel exhibited good photothermal effects, and the drug release can be triggered by combined response of temperature and redox. In vitro biological studies indicated the nanoparticles could effectively induced apoptosis of MDA-MB-231 breast cancer cells involved in the potential mechanism of inhibition of biological expression of heat shock proteins and JAK-STAT signaling pathway. In addition, the nanoparticles have a significant inhibitory effect on cancer growth in breast tumor-bearing mice model, indicating that they have great potential for synergistic chemo-photothermal therapy.

Hydrate phase equilibria in natural sediments: Inhibition mechanism and NMR-based prediction method

The hydrate phase equilibrium condition in natural sediments is an important prerequisite for gas hydrate exploitation and subsea sequestration of CO2. However, its rapid and accurate prediction remains a challenge. In this work, we proposed a novel method to predict the hydrate phase equilibria in various natural sediments using low-field NMR technology. Also, its potential inhibition mechanism was clarified from the perspective of different types of pore water. The results indicated the peaks of T2 spectra for all types of pore water shifted to lower transverse relaxation times during the hydrate formation, meaning that the formed hydrates act as solid matrices in sediments and thus reduce pore size. Furthermore, it was observed that hydrate formation from bound water was much more difficult than capillary water, even at the same pore size. More importantly, not all bound water participated in hydrate formation. During the hydrate dissociation, montmorillonite exhibited the greatest dissociation temperature depression, followed by SA sediments, while illite and kaolin showed a relatively low inhibition on hydrate phase equilibria. This difference in dissociation temperature depression is attributed to water adsorption on the mineral surface and interlayer cation hydration, in addition to the capillary effect. Among them, the capillary-induced phase equilibrium inhibition is the lowest, followed by interlayer cation hydration, and mineral surface adsorption shows the most strong inhibition. Finally, the feasibility and validity of the NMR-based method in predicting the hydrate phase equilibrium condition in natural sediments were verified. These findings not only add further insights into the hydrate phase behavior in clayey-silty sediments but also provide an effective tool for rapid and accurate predictions of hydrate phase equilibria.

Alleviating Oxidative Damage-Induced Telomere Attrition: a Potential Mechanism for Inhibition by Folic Acid of Apoptosis in Neural Stem Cells.

DNA oxidative damage can cause telomere attrition or dysfunction that triggers cell senescence and apoptosis. The hypothesis of this study is that folic acid decreases apoptosis in neural stem cells (NSCs) by preventing oxidative stress-induced telomere attrition. Primary cultures of NSCs were incubated for 9days with various concentrations of folic acid (0-40µM) and then incubated for 24h with a combination of folic acid and an oxidant (100-µM hydrogen peroxide, H2O2), antioxidant (10-mM N-acetyl-L-cysteine, NAC), or vehicle. Intracellular folate concentration, apoptosis rate, cell proliferative capacity, telomere length, telomeric DNA oxidative damage, telomerase activity, intracellular reactive oxygen species (ROS) levels, cellular oxidative damage, and intracellular antioxidant enzyme activities were determined. The results showed that folic acid deficiency in NSCs decreased intracellular folate concentration, cell proliferation, telomere length, and telomerase activity but increased apoptosis, telomeric DNA oxidative damage, and intracellular ROS levels. In contrast, folic acid supplementation dose-dependently increased intracellular folate concentration, cell proliferative capacity, telomere length, and telomerase activity but decreased apoptosis, telomeric DNA oxidative damage, and intracellular ROS levels. Exposure to H2O2 aggravated telomere attrition and oxidative damage, whereas NAC alleviated the latter. High doses of folic acid prevented telomere attrition and telomeric DNA oxidative damage by H2O2. In conclusion, inhibition of telomeric DNA oxidative damage and telomere attrition in NSCs may be potential mechanisms of inhibiting NSC apoptosis by folic acid.

An invasive grass and litter impact tree encroachment into a native grassland

AbstractQuestionsWoody plant encroachment and invasive plants are two critical factors that negatively impact grass‐dominated ecosystems. While studies have extensively investigated these factors individually, research on how invasive species impact the susceptibility of grasslands to encroachment is less common. Using the aspen parkland, an endangered savannah‐type ecosystem, we asked how the presence of a widespread invasive grass in North America, smooth brome (Bromus inermis), impacted the growth and survival of one‐year old trembling aspen (Populus tremuloides) seedlings. We also asked if plant litter was a potential mechanism of inhibition (as has been proposed for brome litter) or coexistence (as has been hypothesized for aspen litter) in this system.LocationAlberta, Canada.MethodsWe used a manipulative experimental approach to determine if the survival and subsequent growth of planted aspen seedlings was impacted by the presence of smooth brome and manipulation of litter amount and type.ResultsWe found that the presence of smooth brome reduced aspen survival by 57% compared to uninvaded habitats, likely mediated by reduced soil moisture, while litter manipulation had no effect on survival. For surviving seedlings, local context had complex impacts on growth; the addition of aspen litter to brome‐invaded communities increased seedling growth while aspen litter additions to native communities resulted in decreased growth.ConclusionThese results suggest that invasion by smooth brome will alter the dynamics of aspen establishment in this system, potentially leading to significant changes to this already endangered landscape. Though smooth brome may serve as a barrier to aspen establishment, accumulation of aspen litter from nearby stands to brome patches could lead to faster growth of seedlings in invaded areas at the edge of existing aspen stands. Our results also suggest more generally that the impact of invasive plants on the establishment of native woody plants can be dependent on litter inputs.

Application of carboxylated cellulose nanocrystals as eco-friendly shale inhibitors in water-based drilling fluids

Shale hydration, swelling, and dispersion are the main reasons causing wellbore instability in oil and gas drilling operations. In this research, carboxylated cellulose nanocrystals(C-CNC) were prepared and developed as a shale inhibitor in water-based drilling fluids (WBDF). The inhibitive property of C-CNC was evaluated through immersion experiments, linear swelling measurements and a shale recovery test. The potential inhibition mechanism was studied by observing the external morphology through the scanning electron microscope (SEM), transmission electron microscopy (TEM), and measuring the zeta potential and particle size distribution, and evaluating the plugging performance through filtration test and BET test. The inhibition evaluation results showed that the expansion of 1%C-CNC was 1.41 mm, and the recovery rate of shale of 3%C-CNC can reach 78.8%. C-CNC has better inhibition properties than the widely used potassium chloride(KCl), polyester amine(PA) and polyether(PEA). The mechanism study revealed that these nanoparticles can form a core-shell structure with clay through electrostatic interaction, thereby suppressing the hydration of clay. Furthermore, the free water content of C-CNC suspension is low, and it is easy to form a gel. Through the action of drilling pressure and capillary pressure, C-CNC is squeezed into and filled in the pores and cracks of the shale, forming an adsorption layer and preventing water intrusion. In addition, C-CNC could considerably decrease the filtrate volume of the drilling fluid, while KCl and PEA had negative influences on the properties of the drilling fluid. C-CNC performed great potential to be an effective and biodegradable shale inhibitor in drilling fluids.

Bacterial cellulose/lignin nanoparticles composite films with retarded biodegradability

In practical applications, the full biodegradability of all-biomass-based bacterial cellulose (BC) composites enhances their environmentally friendliness but results in the poor durability especially at humid conditions. This work prepared BC/lignin nanoparticles (LNPs) composite films with retarded biodegradability, which could broaden their application area. Three LNPs were fabricated using technical lignins extracted by deep eutectic solvent (DES), ethanol organosolv, soda/anthraquinone from poplar. LNPs involvement during BC fermentation showed limited influence on its productivity but significantly retarded the biodegradation of composite films. The potential inhibition mechanism was physical barrier and non-productive binding of LNPs. The BC/Soda LNPs showed much higher retarded degradation property (~58 wt% degradation) compared to BC/Organosolv LNPs and BC/DES LNPs (~85 wt% and ~ 97 wt% degradation respectively) at high enzyme loadings of 5 mg g−1 BCE. While at low enzyme loadings of 1 mg g−1 BCE, all these three composite films showed comparable retarded degradation property of ~60 wt%.

Chlorogenic acid and Epicatechin: An efficient inhibitor of heterocyclic amines in charcoal roasted lamb meats

There are few studies on controlling the formation of heterocyclic amines (HAs) by adding polyphenols to roasted lamb. The aim of this study was to assess the inhibitory effect of 0.025, 0.125, and 0.625 mmol of chlorogenic acid, epicatechin, rutin, quercetin and quinic acid on the formation of HAs in charcoal roasted lamb, respectively, by UHPLC-MS/MS. The results indicated that Harman, Norharman, PhIP, IQx and 8-MeIQx were detected, but both chlorogenic acid and epicatechin greatly inhibited the formation of IQx, 8-MeIQx, Norharman, Harman and PhIP, and epicatechin had better inhibitory effect than chlorogenic acid. PLSR-VID analysis suggested the key precursors of HAs formation in roasted lamb were glucose, ribose, fructose, isoleucine, valine, and lysine. In addition, this work also implied that the potential mechanism of inhibition of HAs formation by chlorogenic acid and epicatechin in roasted lamb might attribute to competitive chemical reactions between polyphenols and key precursors of HAs.

Molecular Insight of the Possible Inhibition Mechanism of Therapeutic Cephalosporin Derivatives against Human Glutathione Reductase Enzyme

Glutathione reductase is a key enzyme for glutathione metabolism. Inhibition of the enzyme activity related to various health problems. Therefore, determination of inhibitors of the enzyme and its possible inhibition mechanism are quite important. Some cephalosporins have exhibited potent inhibitory effect against human glutathione reductase (hGR). In order to understand the inhibition mechanism of the cephalosporins, we carried out molecular docking studies with Glide docking and Induced-fit Docking methods. Binding sites of hGR were predicted and the best suitable binding site of the drugs was identified with the Glide docking method. The binding affinity of the drugs was calculated with the induced-fit docking method. The best binding site of the drugs was detected as a part of the catalytic active site for Cefoperazone, Cefodizime, and Ceftazidime, dimerization site for Cefotaxime, Ceftriaxone, and Cefuroxime, and aromate binding site for Ceftizoxime. The Binding affinity of the Cefoperazone was calculated as -10.643 kcal/mol. The results have indicated that hGR enzyme would be inhibited with different mechanisms because of its several druggable sites. These findings would be helpful for designing new inhibitors for hGR enzyme and understanding of potential inhibition mechanism of its other known inhibitors.

CMT-308, a Nonantimicrobial Chemically-Modified Tetracycline, Exhibits Anti-Melanogenic Activity by Suppression of Melanosome Export

CMT-308 is a nonantimicrobial chemically-modified tetracycline (CMT), which we have previously shown exhibits antifungal activity and pleiotropic anti-inflammatory activities, including inhibition of the enzymatic activity of matrix metalloproteinases (MMPs). Based on its chemical structure, we hypothesized that CMT-308 could inhibit melanogenesis and might be a candidate for the treatment of skin hyperpigmentation disorders which occur due to unregulated melanin biosynthesis and/or transport. CMT-308 was first studied for any effects on activity of the enzyme tyrosinase in vitro using a purified preparation of mushroom tyrosinase; the mode of inhibition of the soluble fungal enzyme was evaluated by Lineweaver-Burk and Dixon plots as well as by non-linear least squares fitting. Next, the effects of CMT-308 were tested in mammalian cell cultures using B16F10 mouse melanoma cells and further validated in darkly-pigmented human melanocytes (HEMn-DP). Our results showed that micromolar concentrations of CMT-308 inhibited mushroom tyrosinase enzyme activity, using the first two substrates in the melanogenesis pathway (l-tyrosine and l-3,4-dihydroxyphenylalanine (l-DOPA)); CMT-308 inhibited mushroom tyrosinase primarily via a mixed mode of inhibition, with the major contribution from a competitive mode. In B16F10 cell cultures, CMT-308 (10 µM) significantly diminished total melanin levels with a selective reduction of extracellular melanin levels, under both basal and hormone-stimulated conditions without any cytotoxicity over a duration of 72 h. Studies of potential mechanisms of inhibition of melanogenesis in B16F10 cells showed that, in mammalian cells, CMT-308 did not inhibit intracellular tyrosinase activity or the activity of α-glucosidase, an enzyme that regulates maturation of tyrosinase. However, CMT-308 suppressed MITF protein expression in B16F10 cells and showed copper chelating activity and antioxidant activity in a cell-free system. The significantly lower extracellular melanin levels obtained at 10 µM indicate that CMT-308’s anti-melanogenic action may be attributed to a selective inhibition of melanosome export with the perinuclear aggregation of melanosomes, rather than a direct effect on the tyrosinase-catalyzed steps in melanin biosynthesis. These results were validated in HEMn-DP cells where CMT-308 suppressed dendricity in a fully reversible manner without affecting intracellular melanin synthesis. Furthermore, the capacity of CMT-308 to inhibit melanosome export was retained in cocultures of HEMn-DP and HaCaT. In summary, our results offer promise for therapeutic strategies to combat the effects of hyperpigmentation by use of CMT-308 at low micromolar concentrations.