Mechanistic insights into the inhibition of human placental glutathione S-transferase P1-1 by abscisic and gibberellic acids: An integrated experimental and computational study.

The interactions of the classic phytohormones gibberellic acid (gibberellin A3 , GA3 ) and abscisic acid (dormin, ABA), which antagonistically regulate several developmental processes and stress responses in higher plants, with human placental glutathione S-transferase P1-1 (hpGSTP1-1), an enzyme that plays a role in endo- or xenobiotic detoxification and regulation of cell survival and apoptosis, were investigated. The inhibitory potencies of ABA and GA3 against hpGSTP1, as well as the types of inhibition and the kinetic parameters, were determined by making use of both enzyme kinetic graphs and SPSS nonlinear regression models. The structural basis for the interaction between hpGSTP1-1 and phytohormones was predicted with the aid of molecular docking simulations. The IC50 values of ABA and GA3 were 5.3 and 5.0 mM, respectively. Both phytohormones inhibited hpGSTP1-1 in competitive manner with respect to the cosubstrates GSH and CDNB. When ABA was the inhibitor at [CDNB]f -[GSH]v and at [GSH]f -[CDNB]v , Vm , Km , and Ki values were statistically estimated to be 205 ± 16 µmol/min-mg protein, 1.32 ± 0.18 mM, 1.95 ± 0.25 mM and 175 ± 6 µmol/min-mg protein, 0.85 ± 0.06 mM, 1.85 ± 0.16 mM, respectively. On the other hand, the kinetic parameters Vm , Km , and Ki obtained with GA3 at [CDNB]f -[GSH]v and at [GSH]f -[CDNB]v were found to be 303 ± 14 µmol/min-mg protein, 1.77 ± 0.13 mM, 3.38 ± 0.26 mM and 249 ± 7 µmol/min-mg protein, 1.43 ± 0.07 mM, 2.89 ± 0.19 mM, respectively. Both phytohormones had the potential to engage in hydrogen-bonding and electrostatic interactions with the key residues that line the G- and H-sites of the enzyme's catalytic center. Inhibitory actions of ABA/GA3 on hpGSTP1-1 may guide medicinal chemists through the structure-based design of novel antineoplastic agents. It should be noted, however, that the same interactions may also render fetuses vulnerable to the potentially toxic effects of xenobiotics and noxious endobiotics.

Conversations in the Gut: The Role of Quorum Sensing in Normobiosis.

An imbalance in gut microbiota, termed dysbiosis, has been shown to affect host health. Several factors, including dietary changes, have been reported to cause dysbiosis with its associated pathologies that include inflammatory bowel disease, cancer, obesity, depression, and autism. We recently demonstrated the inhibitory effects of artificial sweeteners on bacterial quorum sensing (QS) and proposed that QS inhibition may be one mechanism behind such dysbiosis. QS is a complex network of cell-cell communication that is mediated by small diffusible molecules known as autoinducers (AIs). Using AIs, bacteria interact with one another and coordinate their gene expression based on their population density for the benefit of the whole community or one group over another. Bacteria that cannot synthesize their own AIs secretly "listen" to the signals produced by other bacteria, a phenomenon known as "eavesdropping". AIs impact gut microbiota equilibrium by mediating intra- and interspecies interactions as well as interkingdom communication. In this review, we discuss the role of QS in normobiosis (the normal balance of bacteria in the gut) and how interference in QS causes gut microbial imbalance. First, we present a review of QS discovery and then highlight the various QS signaling molecules used by bacteria in the gut. We also explore strategies that promote gut bacterial activity via QS activation and provide prospects for the future.

Gastric cancer diagnosis and staging in coronavirus disease 2019 (Covid-19) pandemic.

AIM: The aim of the study was to analyze whether COVID-19 cause a delay in the diagnosis of gastric cancer patients particularly in the TNM staging of the tumor, or not. MATERIAL AND METHODS: This retrospective single-center study included the patients diagnosed with gastric cancer from March, 2019 to December 2020. The patients were divided into two groups: baseline and the pandemic groups. The following parameters were compared between the groups; demographic data, numbers of newly diagnosed patients, type of the surgery, location of the tumor, frequency of neoadjuvant treatment, ASA score, length of hospital stay, clinical staging and pathologic TNM staging. RESULTS: The mean monthly number of newly diagnosed gastric cancer patients showed a significant decline from 7.5 to 5.6 (p< .001). There were no statistically significant differences between the groups with regard to the demographic factors, except CA 19-9 levels. Patients in the pandemic group had higher both clinical and pathological T-stages (p < 0.05). CONCLUSIONS: Our study showed a decline in the number of the newly diagnosed patients with gastric cancer during the pandemic and also more patients presented with advanced stage during the pandemic period. This study showed that the pandemic causes a potential delay in the diagnosis of gastric cancer patients. KEY WORDS: Cancer surgery, COVID-19, Gastric cancer, Gastric surgery SARS-COV-2, Pandemic.

The Role of Ca 19-9, Ca 72-4, Cea and Cholesterol Levels in Predicting Malignancy in Gallbladder Polyps.

OBJECTIVE: To determine the association of malignancy potential of gallbladder polyps with tumor markers and cholesterol levels, and at which value the presence of malignancy should be suspected. STUDY DESIGN: Observational study. PLACE AND DURATION OF STUDY: University of Health Sciences, Adana City training and research Hospital from December 2017 to November 2020. METHODOLOGY: Ninety patients diagnosed with gallbladder polyp by abdominal ultrasonography, were included in the study. Patients were divided into subgroups of true pseudopolyp, cholesterol-non-cholesterolpolyp, malignant-non-malignant polyp. The groups were compared in terms of age, gender, polyp size, number of polyps, preoperative total cholesterol, HDL (high-density lipoprotein), LDL (low-density lipoprotein), triglyceride, Ca 19-9 (carbohydrate antigen 19-9), Ca 72-4 (carbohydrate antigen 72-4), Cea (carcinoembryonic antigen) levels. RESULTS: In the true polyp group, polyp size, Ca 19-9, Ca 72-4 and Cea median values were significantly higher (p=0.001, p=0.029, p=0.003, and p=0.007, respectively); whereas, triglyceride levels were significantly lower compared to the pseudopolyp group (p=0.002). Polyp size was significantly lower in cholesterol polyp group compared to non-cholesterol polyp group (p= 0.032), and LDL and triglyceride medians were significantly higher (p=0.031, and p<0.001) in cholesterol group. Among the true polyps, polyp size, Ca 19-9, Ca 72-4 and Cea levels were significantly higher in adenocarcinoma group than non-malignant polyp groups (p<0.05). Cut-off values were determined as >11 mm AUC: 0.906 for size, >24.1 U/mL. AUC: 1.00 for Ca 19-9, >9.6 U/mL AUC: 1.00 for Ca 72-4, and >40 ng/mL AUC: 0.984 for CEA, respectively. CONCLUSION: Polyps larger than 11mm with high levels of CEA, Ca 72-4, Ca 19-9, evaluated together, may act as a guide for the clinician in predicting malignancy. The availability of economical and accessible parameters may allow a new algorithm to be developed in the treatment and follow-up approach of gallbladder polyps. Key Words: Gallbladder polpys, Ca 19-9 antigen, Ca 72-4 antigen, Tumor marker, Gallbladder cancer.

Littoral Cell Angioma of the Spleen presenting with Thrombocytosis and Splenic Infarct.

Littoral cell angioma is a non-hematologic vascular neoplasm originating from littoral cells lining the splenic red pulp. The diagnosis is usually made incidentally in splenectomy materials. It is often associated with anemia and thrombocytopenia, indicative of hypersplenism. We, herein present a case of symptomatic littoral cell angioma in a 32-year female, presumed to be accompanied by a hematologic malignancy manifesting with splenic infarct and thrombocytosis. Key Words: Littoral cell angioma, Splenic infarct, Thrombocytosis.

Correlation of Breast Cancer Subgroups and Axillary Metastases with 18F-FDG PET/CT and the Contribution of 18F-FDG PET/CT in the Management of the Axilla.

OBJECTIVE: To investigate whether breast and axilla maximum standard uptake (SUVmax) values contribute to the treatment approach in breast cancer subgroups. STUDY DESIGN: A descriptive study. PLACE AND DURATION OF STUDY: University of Health Sciences/Adana City Training and Research Hospital, Turkey, from April 2017 to September 2019. METHODOLOGY: Ninety patients, operated for early breast cancer, were examined histopathologically and demographically. Those patients were divided into subgroups, according to the St. Gallen consensus. Breast and axillary SUVmax uptakes of these subgroups were determined using (Fluorine18 fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT). These values were compared with postoperative pathology results Results: The triple negative group had the highest values and the Luminal B pos (+) group had the lowest values, when the mean values of breast and axilla SUVmax were compared. Axilla SUVmax value in those with metastatic lymph node was 1.939 times higher than those without it. The cut-off value of SUVmax value of the axillary lymph nodes was found to be 1.1 in distinguishing metastatic from non-metastatic. CONCLUSION: As the biological aggressiveness of tumor increased, SUVmax values increased in parallel. As a result, SUVmax values guided in determining the presence of axillary metastasis and treatment strategy. Key Words: Breast cancer, 18F-FDG PET/ CT, SUVmax values, Tumor subgroups, Axilla.

Evaluating the feasibility of performing elective gastrointestinal cancer surgery during the COVID-19 pandemic: An observational study with 60 days follow-up results of a tertiary referral pandemic hospital.

BACKGROUND: The coronavirus disease 2019 (COVID-19) pandemic has interfered with the treatment algorithm for patients with gastrointestinal (GIS) cancer, resulting in deferral of surgery. We presented the outcomes of our patients to evaluate whether surgery could be safely performed and followed-up without delaying any stage of GIS cancer during the pandemic. METHODS: This was an observational study of 177 consecutive patients who underwent elective GIS cancer surgery between March 11 and November 1, 2020. They were assessed regarding their perioperative and 60 days follow-up results for either surgical or COVID-19 status. Morbidity was determined according to the Clavien-Dindo classification (CDC). Continuous and categorical data were presented as median ± SD and number with percentage (%), respectively. RESULTS: The study included 44 gastric, 33 pancreatic, 40 colon, and 59 rectal cancer patients. All patients underwent surgery and received neo/adjuvant treatments without delay. The overall morbidity (CDC grade II-IV) and mortality rates were 10.1% and 3.9%, respectively. None of the patients or medical staff were infected with COVID-19 during the study period. CONCLUSION: GIS cancer surgery can be safely performed even within a pandemic hospital if proper isolation measures can be achieved for both patients and health workers. Regardless of the tumor stage, surgery should not be deferred, depending on unstandardized algorithms.

Comparison of hemostatic efficacy of topical Ankaferd Blood Stopper on heparinized and nonheparinized rats in bleeding related to liver injury

ABSTRACT Purpose: In this study, hemostatic efficacy of Ankaferd Blood Stopper (ABS), a new generation hemostatic agent, was compared in the presence of heparin effect. Methods: Forty-eight Wistar albino rats were divided into two main groups as heparinized and nonheparinized, and these two main groupswere divided into six subgroups as control, Surgicel and ABS (n = 8). Grade 2 liver injury was performed on rats as standard. All groups were compared in terms of weight, laceration surface area, prothrombin time (PT), activated partial thromboplastin time (aPTT), international normalized ratio (INR), bleeding time, bleeding amount, hemoglobin (Hb) levels, macroscopic and microscopic reactions to the agent used. Results: Whereas there was no statistically significant difference between weight, laceration surface area, PT, INR and preoperative Hb values in the heparinized and nonheparinized groups, postoperative Hb, bleeding time, bleeding amount and aPTT values were statistically different (p < 0.05). In the heparin-hemostat interaction, the ABS group had the lowest bleeding in the heparinized group in terms of the amount of bleeding compared to the control and Surgicel groups (F = 0.764; p = 0.047). In macroscopic and microscopic comparison, there was no difference between the groups in terms of cell necrosis andfresh bleeding (p > 0.05), it was found that the Surgicel group had statistical significantly higher reaction scores (p < 0.05) than the other groups in terms of other parameters. Conclusions: Ankaferd Blood Stopper can be safely and effectively used in surgical practice and in patients with additional diseases requiring heparinization, since it causes minimal reaction in the liver and decreases the amount of bleeding especially in the heparinized group.

The effect of activated protein C in the experimental disseminated intravascular coagulation model formed by lipopolysaccharide infusion

Abstract Purpose: In this experimental study, activated protein C (APC), which has anticoagulant, antithrombotic, profibrinolytic, anti-inflammatory and antiapoptotic properties, was used to prevent coagulopathy in a disseminated intravascular coagulation (DIC) model formatted with lipopolysaccharide (LPS) infusion. Methods: Twenty-five Wistar albino rats weighting 280 - 320 g each were used. They were randomly divided into three groups: sham, control and study groups. To sham group (n = 5), only normal saline was infused. To control (n = 10) and study groups (n = 10), 30 mg/kg LPS was infused for 4 h from femoral vein. After LPS infusion, 100 µg/kg recombinant APC was given during 4 h in study group. Eight hours later, blood samples were taken from abdominal aorta and the animals sacrificed. From these samples, platelet, prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen and D-dimer levels were studied. Results: Platelet counts and fibrinogen levels were significantly lower in control and study groups than sham group (p < 0.05). The PT, aPTT and D-dimer levels were significantly higher in control and study groups than in sham group (p < 0.05). When comparing control and study groups, platelet counts were not statistically different (p = 0.36). However, the difference of the fibrinogen levels was significant between these groups (p = 0.0001). While PT and aPTT were longer in the study group compared to the control group (p < 0.05), D-dimer levels were lower in the study group than in control (p = 0.0001). Conclusion: Use of APC can prevent hypercoagulation and consumption coagulopathy in the DIC as a result of correcting hematological parameters other than prolongation of coagulation time.

Gallstone ileus with evident forchet sign:case report.

INTRODUCTION: Gallstone ileus (GSI) is a rare complication of cholelithiasis (gallbladderstone), which may lead to obstruction of the small intestine. Particularly, computerized tomographic (CT) imaging method and special findings in these images help diagnosing of gallstone ileus. Treatment of this disease is surgery, surgery involves cholecystectomy + fistula repair + enterolitotomy, but it is controversial to perform cholecystectomy with enterolitotomy and fistula repair in the same session. PRESENTATION OF CASE: A 75-year-old male patient consulted to the emergency department with the complaints of nausea and vomiting. In the examinations of the patient, bilienteric fistula and gallstones that impacted in the jejunum leading to obstruction were observed in abdominal CT images of the patient who has ileus. The patient was evaluated as gallstone ileus. In addition, on tomographic images significant Forchet sign and Rigler's triad images were viewed which were pathognomonic for gallstone ileus and did not have images as clear as in our case in the literature search. Laparotomy was performed on the patient due to the fact that he was elderly and the duration of anesthesia was wanted to be kept short and stone was extracted by enterolitotomy. Cholecystectomy and fistula repair were left for another session because of gallbladder and surrounding tissues were edematous. The patient was discharged with full recovery on the 6th post-operative day. DISCUSSION-CONCLUSION: As well as this disease is a rare cause of mechanical bowel obstruction, it is mostly seen in elderly patients. The most sensitive and specific imaging method in diagnosis is contrast-enhanced abdominal computerized tomography. In the tomographic images, especially the Rigler's triad, Forchet sign and Petren sign are pathognomonic for gallstone ileus.

The Relevance of Glutathione Reductase Inhibition by Fluoxetine to Human Health and Disease: Insights Derived from a Combined Kinetic and Docking Study.

Glutathione reductase (GR) is a homodimeric enzyme playing an important role in the regeneration of the central antioxidant molecule reduced glutathione (GSH) from oxidized glutathione (GSSG) at the expense of a molecule of NADPH. GSH scavenges and eliminates superoxide and hydroxyl radicals non-enzymatically or serves as an electron donor for several enzymes. Fluoxetine (FLU), a selective serotonin reuptake inhibitor, is widely prescribed in the treatment of major depressive disorder. Here, using enzyme kinetic studies and molecular docking simulations, we aimed at disclosing the mechanistic and structural aspects of the interaction between GR and FLU. Affecting enzyme activity in a dose-dependent manner, FLU was shown to be a moderately potent (IC50 = 0.88 mM) inhibitor of GR. When the variable substrate was GSSG, the type of inhibition was linear mixed-type competitive (Ki = 279 ± 32 µM; α = 5.48 ± 1.29). When the variable substrate was NADPH, however, the type of inhibition was non-competitive (Ki = 879 ± 82 µM). The observed difference in inhibition types was attributed to the binding of FLU in the large intermonomer cavity of GR, where it hampered catalysis and interfered with substrate binding. Overall, although it is anticipated that long-term use of FLU leads to acquired GR deficiency, the inhibitory action of FLU on GR may be therapeutically exploited in anti-cancer research.

Assessment of the inhibitory activity of the pyrethroid pesticide deltamethrin against human placental glutathione transferase P1-1: A combined kinetic and docking study.

Deltamethrin (DEL), which is a synthetic pyrethroid insecticide, has been used successfully all over the world to treat mosquito nets for the control of malaria. Glutathione S-transferases (GSTs; EC 2.5.1.18) catalyze the conjugation of reduced glutathione (GSH) to a variety of xenobiotics and are normally recognized as detoxification enzymes. Here, we used a colorimetric assay based on the human placental GSTP1-1 (hpGSTP1-1)-catalyzed reaction between GSH and the model substrate 1-chloro-2,4-dinitrobenzene (CDNB) as well as molecular docking to investigate the mechanistic and structural aspects of hpGSTP1-1 inhibition by DEL. We show that DEL is a potent, noncompetitive inhibitor of hpGSTP1-1 with an IC50 value of 6.1 µM and Ki values of 5.61 ±â€¯0.32 µM and 7.96 ±â€¯0.97 µM at fixed [CDNB]-varied [GSH] and fixed [GSH]-varied [CDNB], respectively. DEL appears to be accommodated well in an eccentric cavity located at the interface of the hpGSTP1-1 homodimer, presumably causing conformational changes to the enzyme's substrate-binding sites such that the enzyme is no longer able to transform GSH and CDNB effectively. Correspondingly, considerable maternal exposure to and subsequent accumulation of DEL may interfere with the proper development of the vulnerable fetus, possibly increasing the risk of developing congenital defects.

Mechanistic and structural insights into the in vitro inhibitory action of hypericin on glutathione reductase purified from baker's yeast.

This work aims at studying the interaction between glutathione reductase (GR) and hypericin. The type of inhibition was determined by measuring changes in GR activity at increasing concentrations of hypericin as well as at varying concentrations of glutathione disulfide (GSSG) and nicotinamide adenine dinucleotide phosphate (NADPH), and the binding pose of hypericin was predicted by molecular docking. Accordingly, hypericin emerges as an effective inhibitor of GR. When the variable substrate is GSSG, the type of inhibition is competitive. When the variable substrate is NADPH, however, the type of inhibition appears to be linear mixed-type competitive. Our computational analyses suggest that hypericin binds in the large intermonomer cavity of GR, and that it may interfere with the normal positioning/functioning of the redox-active disulfide center at the enzyme's active site. Overall, besides its contributory role in promoting oxidative stress via the formation of reactive oxygen species in photodynamic therapy, hypericin can also weaken cancer cells through inhibiting GR.

Evaluation of silybum marinaum efficacy on University of Wisconsin and histidine-tryptophan-ketoglutarate solutions latter the damage of the perfused liver.

PURPOSE:: To investigate the hepatoprotective and antioxidant effeicacies of Silybum marianum's (silymarin, S) on University of Wisconsin (UW) and histidinetryptophan-ketoglutarate (HTK) preservation solutions. METHODS:: Thirty two Wistar albino adult male rats were used. Group 1: UW group, Group 2: UW + Silymarin group(S), Group 3: HTK group, Group 4: HTK + silymarin group (S), respectively. Silymarin was enforced intraperitoneally before the surgery. Biopsies were enforced in 0, 6 and 12.hours to investigate. RESULTS:: Biochemical parameters examined in alanine aminotransferase (ALT), furthermore superoxide dismutase (SOD), catalase (CAT), and malondialdehyde (MDA) in rats were also evaluated. Detected histopathological changings were substantially declining in the groups that received silymarin, cellular damage was decreased significantly in HTK + Silymarin group, according to other groups. It has been identified as the most effective group was HTK + silymarin group in evaluation of ALT, electron microscopic results, also decreased MDA and elevated in SOD, and CAT activity. Caspase 3 analysis showed a substantial lower apoptosis ratio in the silymarin groups than in the non-performed groups (p<0.05). CONCLUSION:: Histidinetryptophan-ketoglutarate+silymarin group provides better hepatoprotection than other groups, by decreasing the hepatic pathologic damage, delayed changes that arise under cold ischemic terms.

Evaluation of silybum marinaum efficacy on University of Wisconsin and histidine-tryptophan-ketoglutarate solutions latter the damage of the perfused liver

Abstract Purpose: To investigate the hepatoprotective and antioxidant effeicacies of Silybum marianum's (silymarin, S) on University of Wisconsin (UW) and histidinetryptophan-ketoglutarate (HTK) preservation solutions. Methods: Thirty two Wistar albino adult male rats were used. Group 1: UW group, Group 2: UW + Silymarin group(S), Group 3: HTK group, Group 4: HTK + silymarin group (S), respectively. Silymarin was enforced intraperitoneally before the surgery. Biopsies were enforced in 0, 6 and 12.hours to investigate. Results: Biochemical parameters examined in alanine aminotransferase (ALT), furthermore superoxide dismutase (SOD), catalase (CAT), and malondialdehyde (MDA) in rats were also evaluated. Detected histopathological changings were substantially declining in the groups that received silymarin, cellular damage was decreased significantly in HTK + Silymarin group, according to other groups. It has been identified as the most effective group was HTK + silymarin group in evaluation of ALT, electron microscopic results, also decreased MDA and elevated in SOD, and CAT activity. Caspase 3 analysis showed a substantial lower apoptosis ratio in the silymarin groups than in the non-performed groups (p<0.05). Conclusion: Histidinetryptophan-ketoglutarate+silymarin group provides better hepatoprotection than other groups, by decreasing the hepatic pathologic damage, delayed changes that arise under cold ischemic terms.

Purification of Glutathione S-Transferase pi from Erythrocytes and Evaluation of the Inhibitory Effect of Hypericin.

Hypericin is a photosensitizer compound used in the photodynamic therapy (PDT). PDT is an alternative cancer treatment strategy whose function is dependent on the photosensitizers accumulating selectively in tumor cells and following visible or infra-red light induced activation lead to the apoptosis/necrosis of the tumor cells via the formation of reactive oxygen species. Thus, the cellular redox balance is essential for the efficacy of PDT. Among the protective enzyme systems glutathione S-transferases (GST, E.C.2.5.1.18) function in detoxification, protection against oxidative stress and intracellular transport of molecules. It is known that isoenzymes of GST and especially GST-pi is increased in cancer cells and it plays very important functions in the development of resistance to anticancer drugs. Since photosensitizers are used intravenously, it is important to elucidate the effects of photosensitizers on the erythrocyte enzymes. The aim of the present study was to investigate the impact of hypericin on human erythrocyte GST-pi (heGST-pi). Purification yield of 71% and purification fold of 2550 were achieved by using conventional chromatographic methods. The specific activity of the enzyme is found as 51 U/mg protein. Hypericin inhibited heGST-pi in a dose dependent manner and inhibition was biphasic. Noncompetitive type of inhibition was observed with both substrates, GSH and CDNB. The inhibitory constant (K i ) values obtained from Lineweaver-Burk, Dixon, secondary plots; slope and y-intercept versus 1/S (substrate) and from non-linear regression analysis were in good correlation: K i (GSH) was calculated as 0.19 ± 0.01 µM and K i (CDNB) as 0.26 ± 0.03 µM.

Amitriptyline may have a supportive role in cancer treatment by inhibiting glutathione S-transferase pi (GST-π) and alpha (GST-α).

A tricyclic anti-depressant, amitriptyline, is a highly prescribed drug for cancer patients for mood elevation but there are limited studies about the interaction of amitriptyline with glutathione S-transferases pi (GST-π) and glutathione S-transferases alpha (GST-α). GST isozymes have been implicated in chemotherapeutic drug resistance. We demonstrated that the concentration dependent inhibition of GST-π and GST-α by amitriptyline followed inverse hyperbolic inhibition curves with IC(50) values of 5.54 and 8.32 mM, respectively. When the varied substrate was GSH, amitriptyline inhibited both isozymes competitively and similar K(i) values were found for GST-π (K(i) = 1.61 ± 0.17 mM) and GST-α (K(i) = 1.45 ± 0.20 mM). On the other hand, when the varied substrate was CDNB, the inhibition types were non-competitive for GST-π (K(i) = 1.98 ± 0.31 mM) and competitive for GST-α (K(i) = 1.57 ± 0.16 mM). Amitriptyline, in addition to its antidepressant effect, might also have a minor supportive role on the effectiveness of the anticancer drugs by decreasing their elimination through inhibiting GST-π and GST-α.

Evaluation of the in vitro inhibitory impact of hypericin on placental glutathione S-transferase pi.

St John's Wort (SJW) extracts are herbal products which are available without prescription in most countries and widely used in the treatment of mild to moderate depression. Since it is a herbal product and available without prescription, use of SJW is common among pregnant and/or lactating woman. The principal of the study was to clarify the effects of hypericin, one of the components of SJW, on glutathione S-transferase-pi (GST-pi) purified from human placenta. The K (m) values of GST-pi were 0.21 ± 0.03 mM for glutathione (GSH) and 2.29 ± 0.54 mM for 1-chloro-2,4-dinitrobenzene (CDNB). At fixed [GSH], the V (m) value calculated was about 3 times higher than the conditions in which [CDNB] was fixed; 201 ± 30 U/mg protein versus 74 ± 3 U/mg protein. At constant substrate concentrations (1 mM), an average IC (50) value of 0.70 ± 0.02 µM was obtained. Hypericin inhibited GST-pi competitively with respect to both substrates. When GSH was the varied substrate a K (i) value of 0.31 ± 0.05 µM was found; when CDNB was the varied substrate, a K (i) value of 0.85 ± 0.02 µM was obtained. On the basis of these data considering transplacental transfer of hypericin and immature hepatic clearance of the baby, using this herbal product may cause abnormalites due to the inhibition of one of the most important placental detoxification enzymes, GST-pi.

The inhibition characteristics of human placental glutathione S-transferase-π by tricyclic antidepressants: amitriptyline and clomipramine.

Tricyclic antidepressants (TCAs) are the non-selective amine re-uptake inhibitors, well absorbed from small intestine, cross the blood-brain barrier, distributed in the brain, and are bound to glutathione S-transferase-π (GST-π). TCAs can pass through placenta, accumulate in utero baby, and cause congenital malformations. Thus, the study of the interaction of GST-π with antidepressants is crucial. In this study, the interaction of GST-π with amitriptyline and clomipramine was investigated. The K (m) values for glutathione (GSH) and 1-chloro-2,4-dinitrobenzene (CDNB) were found to be 0.16 ± 0.04 and 3.60 ± 1.67 mM, respectively. The V (m) values were varying according to the fixed substrate; [CDNB] fixed, 53 ± 3 and [GSH] fixed 182 ± 63 U/mg protein. At variable [GSH] and variable [CDNB], the k (cat) values of 7.0 × 10(6) and 1.42 × 10(7) s(-1) and the k (cat)/K (m) values of 4.38 × 10(10) and 3.94 × 10(9 )M(-1 )s(-1) were obtained, respectively. At fixed [CDNB] and variable [GSH], amitriptyline (K (s) = 0.16 ± 0.03 mM; α = 2.08; and K (i) = 1.75 ± 0.37 mM) and clomipramine (K (s) = 0.24 ± 0.05 mM; α = 1.57; and K (i) = 3.90 ± 2.26 mM) showed linear mixed-type inhibition whereas when the varied substrate is CDNB, amitriptyline (K (i) = 4.90 ± 0.68 mM) and clomipramine (K (i) = 3.37 ± 0.39 mM) inhibition were noncompetitive. The inhibition of GST-π by TCAs means the destruction of its protective role against toxic electrophiles. The effect of antidepressants on fetus will be much severe, thus, the antidepressant therapy of pregnant women should be done with caution.

Inhibition characteristics of hypericin on rat small intestine glutathione-S-transferases.

Glutathione-S-transferases constitute a family of enzymes involving in the detoxification of xenobiotics, signalling cascades and serving as ligandins or/and catalyzing the conjugation of various chemicals and drugs. The widely expressed cytosolic GST-pi is a marker protein in various cancers and its increased concentration is linked to drug resistance. GST-pi is autoregulated by S-glutathionylation and it catalyzes the S-glutathionylation of other proteins in response to oxidative or nitrosative stress. S-glutathionylation of GST-pi results in multimer formation and the breakage of ligand binding interactions with c-Jun NH(2)-terminal kinase (JNK). Another widely expressed GST enzyme, GST-alpha is assumed as a marker in hepatocellular damage, is implicated in cancer, asthma, cardiovascular disease and response to chemotherapy. Although, it was shown that hypericin binds and inhibits GST-alpha and GST-pi, the inhibition characteristics have not been investigated in detail. The aim of this study was to investigate the effects of hypericin on major GSTs; GST-alpha and GST-pi purified from rat small intestine. When GSH used as varied substrate the inhibition pattern with hypericin was uncompetitive for GST-alpha (K(i)=0.16 + or - 0.02 microM) and noncompetitive for GST-pi (K(i) = 2.46 + or - 0.43 microM). While using CDNB (1-chloro-2,4-dinitrobenzene) as the varied substrate, the inhibition patterns were noncompetitive for GST-alpha and competitive for GST-pi; K(i) values for GST-alpha and GST-pi were 1.91 + or - 0.21 and 0.55 + or - 0.07 microM, respectively. Since hypericin accumulated in cancer cells and important in photodynamic therapy (PDT), inhibition of GST-alpha and GST-pi by hypericin might increase the effectivity of the treatment. Considering that GST-pi is responsible for the drug resistance its inhibition might increase the benefit obtained from chemotherapy.