Novel human ocular glutathione S-transferases with high activity toward 4-hydroxynonenal

PURPOSE

To study the distribution and expression of glutathione S-transferase isozymes involved in detoxification of endogenously generated toxic products of lipid peroxidation, namely, 4-hydroxynonenal (4-HNE) in human lens, retina, cornea, iris, ciliary body and to study their kinetic and structural properties.

METHODS

The authors have previously cloned and sequenced cDNA of mouse mGSTA4-4, which shows high activity towards 4-HNE. They have expressed it in Escherichia coli and have raised antibodies against the recombinant mGSTA4-4. In the present study, these antibodies were used in Western blot analysis and immunoaffinity chromatography to study the expression and to purify the human ortholog(s) of mGSTA4-4 from ocular tissues.

RESULTS

Western blot analyses of human ocular tissues indicated that a glutathione S-transferases (GST) isozyme immunologically similar to mGSTA4-4 was expressed in cornea, retina, and iris and ciliary body, but not in lens. This isozyme designated as hGST 5.8 was purified to homogeneity from human retina, cornea, and iris and ciliary body by immunoabsorption on immobilized antibodies against mGSTA4-4. The human ortholog of mGSTA4-4, designated as hGST 5.8 purified from all these tissues and pI value of 5.8, subunit Mr value of 25 k and blocked N-terminal. Amino acid sequences of CNBr fragments of hGST 5.8 isozymes of human ocular tissues showed a high degree of primary structure homologies with the corresponding regions of mGSTA4-4. There were noticeable differences in the amino acid sequences of hGST 5.8 of cornea, retina, and iris and ciliary body, suggesting the presence of several closely related hGST 5.8 subunits in the ocular tissues. This heterogeneity was due to tissue-specific expression rather than simple allelic polymorphism. The hGST 5.8 had about sixfold to eightfold higher activity toward 4-hydroxynonenal than 1-chloro-2,4-dinitrobenzene, or CDNB. The catalytic efficiency (Kcat/Km) of ocular hGST 5.8 for 4-HNE was about 100-fold higher than those for the alpha, mu, or pi classes of GST. In addition, hGST 5.8 expressed glutathione peroxidase activity toward phospholipid hydroperoxides and GSH-conjugating activity toward 9,10-epoxy stearic acid.

CONCLUSIONS

The results indicate that hGST 5.8 isozyme(s) distinct from the alpha, mu, and pi classes of GSTs, are differentially expressed in human ocular tissues and may play an important role in protective mechanisms against endogenous toxicants generated during lipid peroxidation.

Organic anion-transporting ATPase of rat liver. I. Purification, photoaffinity labeling, and regulation by phosphorylation

An ATP-dependent transport system specific for non-bile acid organic anions such as S-(2,4-dinitrophenyl)-glutathione is present in the canalicular plasma membrane of hepatocytes. It has been shown recently that transport of these anions by isolated hepatocytes is modulated by the activity of cellular protein kinase C (Roelofsen, H., Ottenhoff, R., Oude Elferink, R. P., and Jansen, P.L. (1991) Biochem. J. 278, 637-641, 1991). Using a series of affinity chromatography steps, we have purified to apparent homogeneity a 90-kDa glycoprotein which has S-(2,4-dinitrophenyl)glutathione-dependent ATPase activity. As shown by binding to immobilized S-(2,4-dinitrophenyl)glutathione and by photoaffinity labeling with 8-azido-ATP, the binding sites for organic anions and for ATP of the 90-kDa protein are interdependent, a behavior that is consistent with an ATP-dependent transport function. The ATP binding site has been further characterized using a fluorescent ATP analog. The 90-kDa protein was phosphorylated by protein kinase C, and the Vmax (but not the Km) of the S-(2,4-dinitrophenyl)glutathione-dependent ATPase activity increased at least 2-fold upon phosphorylation. On the basis of its enzymatic properties, we propose that the 90-kDa protein is identical with the multispecific organic anion transporter (MOAT) of the hepatic canalicular plasma membrane. The size and oligosaccharide content of the 90-kDa protein indicate that it does not belong to the family of mammalian plasma membrane P-glycoproteins.

Organic anion-transporting ATPase of rat liver. II. Functional reconstitution of active transport and regulation by phosphorylation

We have previously purified to homogeneity from rat liver plasma membranes a 90-kDa glycoprotein with S-(2,4-dinitrophenyl)glutathione-stimulated ATPase activity and other properties which identify it as the multispecific organic anion transporter (MOAT) specific for the transport into bile of non-bile acid organic anions (Pikula, S., Hayden, J. B., Awasthi, S., Awasthi, Y. C., and Zimniak, P. (1994) J. Biol. Chem. 269, 27566-27573). In the present communication, we report the functional reconstitution of this protein into artificial proteoliposomes. The reconstituted protein catalyzed time- and concentration-dependent uptake of S-(2,4-dinitrophenyl)glutathione into the vesicles. The transport required the presence of ATP. Phosphorylation of the 90-kDa protein by protein kinase C prior to reconstitution more than tripled the Vmax of transport but did not change the Km for S-(2,4-dinitrophenyl)glutathione. The protein created and, at steady state, maintained a more than 200-fold and 500-fold S-(2,4-dinitrophenyl)glutathione gradient across the membrane for the unphosphorylated and phosphorylated form, respectively. The transport activity of the 90-kDa protein is sufficient to account for the hepatic secretory maximum of non-bile acid organic anions in the rat.

Naturally occurring human glutathione S-transferase GSTP1-1 isoforms with isoleucine and valine in position 104 differ in enzymic properties

Glutathione S-transferase P1-1 isoforms, differing in a single amino acid residue (Ile104 or Val104), have been previously identified in human placenta [Ahmad, H., Wilson, D. E., Fritz, R. R., Singh, S. V., Medh, R. D., Nagle, G. T., Awasthi, Y. C. & Kurosky, A. (1990) Arch. Biochem. Biophys. 278, 398-408]. In the present report, the enzymic properties of these two proteins are compared. [I104]glutathione S-transferase P1-1 has been expressed from its cDNA in Escherichia coli and purified to homogeneity by affinity chromatography; the cDNA has been mutated to replace Ile104 by Val104, and [V104]glutathione S-transferase P1-1 was expressed and isolated as described for [I104]glutathione S-transferase P1-1. The two enzymes differed in their specific activity and affinity for electrophilic substrates (KM values for 1-chloro-2,4-dinitrobenzene were 0.8 mM and 3.0 mM for [I-104]glutathione S-transferase P1-1 and [V-104]glutathione S-transferase P1-1, respectively), but were identical in their affinity for glutathione. In addition, the two enzymes were distinguishable by their heat stability, with half-lives at 45 degrees C of 19 min and 51 min, respectively. The resistance to heat denaturation was differentially modulated by the presence of substrates. These data, in conjunction with molecular modeling, indicate that the residue in position 104 helps to define the geometry of the hydrophobic substrate-binding site, and may also influence activity by interacting with residues directly involved in substrate binding.

Modulation of cisplatin cytotoxicity by sulphasalazine

The efficacy of cisplatin [cis-diamminedichloroplatinum (II); DDP] is hampered by acquired or de novo resistance of malignant cells to its cytotoxic effects. We have previously reported that cisplatin resistance parallels glutathione S-transferase (GST) activity in several human small-cell lung cancer cell lines. In the presently described studies, we used sulphasalazine, an inhibitor of GSTs, to evaluate the relative role of GSTs in mediating cisplatin resistance in two human small-cell lung cancer cell lines, NCI H-69 and H-2496. The H-69 cell line, which contained relatively higher GST activity than the H-2496 cell line (317 +/- 7 vs 9 +/- 1 mU mg-1 protein respectively), also displayed a greater degree of cisplatin resistance (IC50 values of 25.0 +/- 3.9 vs 4.5 +/- 1.0 microM respectively). Western blot and Northern blot analyses of purified GSTs revealed the expression of only the pi-class GST in both cell lines. Sulphasalazine inhibited the purified GSTs (IC50 of 10 microM for H-69 and 12 microM for H-2496) from both lines in a competitive manner with similar Ki values (6.5 and 7.9 microM for the H-69 and H-2496 cell lines respectively). Cytotoxicity studies revealed that sulphasalazine increased the cytotoxicity of cisplatin towards both cell lines. Isobologram analysis showed that sulphasalazine synergistically enhanced the cytotoxicity of cisplatin towards both cell lines, the magnitude of synergy being remarkably higher in H-69 cells than in H-2496 cells. Our studies indicate that clinically achievable concentrations of sulphasalazine may be useful in modulating cisplatin resistance in malignancies with increased GST-pi content.

Gender-related differences in expression of murine glutathione S-transferases and their induction by butylated hydroxyanisole

The basal levels of mu and pi class glutathione S-transferases RNA were 18-fold higher in the male mouse liver as compared with the female. When 0.75% (w/w) BHA was included in the diet it altered the RNA levels of alpha, mu, pi GST classes and mGSTA4-4 in a tissue and sex specific manner. The most marked induction of RNA was seen for the mu class GSTs of female liver, lung and kidney (52, 10 and 8-fold, respectively), and of male liver and kidney (25 and 3.5-fold, respectively), the pi class GSTs of female liver, lung, and kidney (11, 10, and 5-fold, respectively), and mGSTA4-4 of female liver (4-fold). The effect of BHA on the induction of the mu and pi class GST RNA was 2-9 fold greater in female as compared with male tissues. The degree of induction of GST RNA did not correlate directly with changes in GST protein indicating that post-transcriptional events regulating GST expression may be affected by BHA particularly for GST mu and mGSTA4-4.

Several closely related glutathione S-transferase isozymes catalyzing conjugation of 4-hydroxynonenal are differentially expressed in human tissues

A human acidic glutathione S-transferase, hGST 5.8, was isolated from heart, pancreas, and brain by a procedure involving immunoadsorption chromatography on immobilized antibodies raised against mouse mGSTA4-4. The human hGST 5.8 enzymes isolated from these tissues had similar pI (5.8) and subunit M(r) (24.5 kDa) values, showed about 17- to 20-fold higher specific activities for 4-hydroxynon-2-enal than that for 1-chloro-2,4-dinitrobenzene, and expressed glutathione peroxidase activity toward phospholipid hydroperoxides. In this respect, the enzymes belong together with rat GST 8-8 and mouse mGSTA4-4 to a subgroup of GSTs involved in the detoxification of lipid peroxidation products. Partial sequencing of CNBr-peptide fragments of hGST 5.8 proteins isolated from various human tissues revealed significant similarity to mGSTA4-4 and the existence of several distinct isoforms differing in their primary structures. These isoforms had similar but nevertheless clearly distinguishable catalytic properties. These results indicate the existence of multiple hGST 5.8-related genes in the humans, which is consistent with our previous studies showing the presence of several closely related genes for the mouse ortholog mGSTA4-4 (Zimniak et al., J. Biol. Chem., 1994, 269, 992-1000).

Adenosine triphosphate-dependent transport of doxorubicin, daunomycin, and vinblastine in human tissues by a mechanism distinct from the P-glycoprotein

Previous studies have demonstrated that a human glutathione conjugate transporter, designated as dinitrophenyl-S-glutathione ATPase (DNP-SG ATPase), catalyzed ATP hydrolysis in the presence of several amphiphilic compounds other than glutathione conjugates (Singhal, S. S., R. Sharma, S. Gupta, H. Ahmad, P. Zimniak, A. Radominska, R. Lester, and Y. C. Awasthi. 1991. FEBS [Fed. Eur. Biochem. Soc.] Lett. 281:255-257). We now demonstrate that DNP-SG ATPase purified from human lung and erythrocyte membranes catalyzed the hydrolysis of ATP in the presence of doxorubicin and its metabolites. Doxorubicin-stimulated ATP hydrolysis by DNP-SG ATPase was saturable with respect to doxorubicin (Km 1.2 and 2.8 microM for the lung and erythrocyte enzymes, respectively). Antibodies against DNP-SG ATPase immunoprecipitated the ATP hydrolyzing activity stimulated by doxorubicin, its metabolites, and glutathione conjugates. Inside our vesicles prepared from erythrocyte membranes took up doxorubicin, daunomycin, and vinblastine in an ATP-dependent manner. The uptake was linear with respect to time and vesicle protein, was dependent on ATP and magnesium, was inhibited by heavy metal salts or by heating the vesicles, and was sensitive to both osmolarity and orientation of the vesicles. The transport had an activation energy of 13 kcal/mol, was saturable with respect to both doxorubicin and ATP (Km values of 1.8 microM and 1.9 mM, respectively), and was competitively inhibited by glutathione conjugates as well as by a number of amphiphiles such as daunomycin or vinblastine. Transport was diminished upon coating the vesicles with antibodies against DNP-SG ATPase. Incorporation of increasing amounts of purified DNP-SG ATPase into the vesicles resulted in a linear increase in transport of doxorubicin. These studies demonstrated for the first time that a membrane protein that catalyzed the transport of anionic amphiphilic molecules such as glutathione conjugates could also mediate the transport of weakly cationic antitumor antibiotic, doxorubicin. Notably, the Km of transport was in the range of doxorubicin concentration achievable in human serum after intravenous dosing of doxorubicin.

A novel glutathione S-transferase isozyme similar to GST 8-8 of rat and mGSTA4-4 (GST 5.7) of mouse is selectively expressed in human tissues

A mouse glutathione S-transferase (GST) isozyme designated as GST 5.7 or mGSTA4-4 belongs to a distinct subclass of the alpha-class isozymes of GST. It is characterized by kinetic properties intermediate between the alpha- and pi-classes of GSTs. We have recently cloned and expressed this isozyme (rec-mGSTA4-4) in E. coli and have reported its complete primary sequence (Zimniak, P., et al. (1992) FEBS Lett., 313, 173-176). Using antibodies raised against the homogenous rec-mGSTA4-4 expressed in E. coli, we now demonstrate that an ortholog of this isozyme was selectively expressed in various human tissues. The human ortholog of mGST A4-4 purified from liver had a pI value of 5.8 and constituted approx. 1.7% of total GST protein of human liver. Similar to other alpha-class GSTs, the N-terminus of this isozyme (GST 5.8) was also blocked. CNBr digestion of the enzyme yielded two major fragments with M(r) values of 12 kDa and 6 kDa. The sequences of these two fragments showed identities in 16 out of 20 residues and 17 out of 20 residues with the corresponding sequences of its mouse ortholog (mGSTA4-4), and showed significant homologies with the rat and chicken orthologs, GST 8-8 and GST CL3. Human liver GST 5.8 showed more than an order of magnitude higher activity towards t-4-hydroxy-2-nonenal as compared to 1-chloro-2,4-dinitrobenzene. This isozyme also expressed glutathione-peroxidase activity towards fatty acid, as well as phospholipid hydroperoxides suggesting its role in protection mechanisms against the toxicants generated during lipid peroxidation. Western blot analysis of human tissues revealed that this GST isozyme was selectively expressed in human liver, pancreas, heart, brain and bladder tissues, but absent in lung, skeletal muscle, spleen and colon.

Estimation of genomic complexity, heterologous expression, and enzymatic characterization of mouse glutathione S-transferase mGSTA4-4 (GST 5.7)

We have previously isolated a cDNA clone for a unique mouse lung glutathione S-transferase, mGSTA4-4 (GST 5.7) (Zimniak, P., Eckles, M. A., Saxena, M., and Awasthi, Y. C. (1992) FEBS Lett. 313, 173-176). By genomic Southern blotting and polymerase chain reaction single strand conformation polymorphism analysis we have now demonstrated the presence of at least two mGSTA4-related genes in the mouse. The heterogeneity of mGSTA4-4 was further examined by comparing the structural and kinetic properties of mGSTA4-4 isolated from mouse lung with those of recombinant rec-mGSTA4-4 expressed in Escherichia coli. Except for the isoelectric point, the physical properties of the two proteins were indistinguishable. Western blots using antibodies against rec-mGSTA4-4 have shown selective expression of the enzyme in mouse tissues. Even though the substrate specificity profiles of the tissue-isolated and recombinant enzymes, which point to a role of mGSTA4-4 in the detoxification of lipid peroxidation products, were generally similar, significant differences were observed with selected substrates. The existence of functionally distinct forms of mGSTA4-4 and the presence of more than one gene strongly suggest that the previously observed differences in properties of mGSTA4-4 isolated from various mouse tissues (Awasthi, S., Singhal, S. S., Srivastava, S. K., and Awasthi, Y. C. (1993) Arch. Biochem. Biophys. 301, 143-150) may be due to tissue-specific expression of mGSTA4-related genes.

Lipid peroxidation and oxidative stress during acute allylamine-induced cardiovascular toxicity

Allylamine is an aliphatic amine that causes vascular lesions in aorta and medium-sized arteries. This primary amine has been shown to be metabolized to acrolein both in vivo and in vitro. Acrolein may cause allylamine's toxic effects, since it acts as a strong peroxidizing agent itself; in addition, deamination of allylamine is accompanied by production of hydrogen peroxide. To investigate the relative roles of oxidative stress and lipid peroxidation in allylamine intoxication, we conducted an acute in vivo time-course study following administration of allylamine (150 mg/kg) to rats by gavage. Animals were sacrificed at 1, 3 and 5 h after allylamine treatment, and subcellular fractions of aorta, epicardium and endocardium were assayed for enzymes of the oxidant defense system and thiol (-SH) status, capacity for lipid peroxidation, and .OH radical generation. Results suggest that in vivo treatment with allylamine causes preferential damage to aortic mitochondria. A marked depletion of total and free -SH content was found in aorta, epicardium and endocardium, with a striking increase in the formation of thiobarbiturate-reactive substance by aortic mitochondria at all time points. A significant increase in the capacity to generate .OH was found in aorta (with lesser increases in epicardium and endocardium) after allylamine treatment. Levels of defense system enzymes were not consistently altered, however. In a totally in vitro experiment, liposomes incubated with acrolein (0.2-2 mM) showed a proportional increase in lipid peroxidation of liposomal membrane. A likely basis of allylamine's cardiovascular toxicity is acrolein-induced lipid peroxidation, especially in mitochondria.

Glutathione and glutathione linked enzymes in human small cell lung cancer cell lines

Glutathione levels and several glutathione-linked enzyme activities have been variably correlated with cisplatin chemosensitivity in cultured neoplastic cells. In order to determine the relative contribution of the glutathione-linked enzymes towards mediating inherent cisplatin resistance in cancer cells, we have measured the chemosensitivity to cisplatin, glutathione levels and activities of glutathione S-transferase, glutathione peroxidase, glutathione reductase and glucose-6-phosphate dehydrogenase in 8 cultured human small cell lung cancer (SCLC) cell lines with widely differing cisplatin sensitivities. Of these parameters, only glutathione S-transferase activity correlated with degree of cisplatin resistance in a linear fashion.

Interactions of glutathione S-transferase-pi with ethacrynic acid and its glutathione conjugate

Ethacrynic acid, a diuretic drug known to be an inhibitor of glutathione S-transferases (GSTs), has been shown to enhance the cytotoxicity of the alkylating agent class of chemotherapeutic drugs in cultured cancer cells resistant to alkylating agents. This action of ethacrynic acid is presumably mediated by inhibition of GSTs which are implicated in detoxification of alkylating agents. In addition to being an inhibitor of GSTs, ethacrynic acid also interacts with GSTs as a substrate for conjugation with GSH to yield an ethacrynic acid-GSH conjugate. This conjugate is formed both enzymatically and non-enzymatically and itself is a GST inhibitor. Since ethacrynic acid-GSH conjugate is itself likely to be able to mediate reversal of alkylating agents through GST inhibition, we have synthesized and purified the ethacrynic acid-GSH conjugate, studied the kinetics of inhibition of human lung pi-class GST by ethacrynic acid and the conjugate, and compared the kinetics of the enzymatic and non-enzymatic formation of the conjugate using an HPLC method. Results of our studies showed that the ethacrynic acid-GSH conjugate was a more potent inhibitor of human lung GST-pi than ethacrynic acid (Ki = 1.5 vs. 11.5 microM, respectively) and that their mechanisms for GST inhibition were distinct (competitive and non-competitive, respectively). Comparison of enzymatic and non-enzymatic rates of conjugate formation in vitro indicated that GST-pi catalyzed a rapid conjugation of ethacrynic acid with GSH at a concentration of ethacrynic acid an order of magnitude above that required to nearly completely inhibit GST catalyzed conjugation of 1-chloro-2,4-dinitrobenzene. However, because of the rapid non-enzymatic reaction, and the inhibition of GST-pi with the accumulation of the conjugate in the reaction mixture, the overall quantity of the conjugate formed after 150 min was nearly identical in the presence or absence of GST-pi. Results of these studies suggest that inhibition of GSTs by ethacrynic acid-GSH conjugate may be the main mechanism through which ethacrynic acid reverses alkylating agent resistance.

Primary lymphoma of the liver. Report of a case with diagnosis by fine needle aspiration

In a 69-year-old man with hepatomegaly, a diagnosis of primary non-Hodgkin's lymphoma (NHL) of the liver was made by fine needle aspiration (FNA). At the time of presentation there was no evidence of involvement of the lymph nodes, bone marrow or any other organ. Although hepatic involvement is common in advanced stages of Hodgkin's disease and NHL, primary lymphoma of the liver is rare. The purpose of this paper is to report a rare occurrence of primary lymphoma of the liver and to demonstrate the possibility of making this diagnosis by FNA.

Glutathione S-transferases of human skin: qualitative and quantitative differences in men and women

Glutathione S-transferase (GST) isozymes of male and female leg skin have been characterized. GST activities and protein have been quantified in a number of male and female skin samples and the results indicate that as compared to the male skin, female skin contains a higher amount of GST activity as well as protein. Both male and female leg skin contain three GST isozymes with pI values 9.9, 9.1 and 4.8. In accordance with previous findings the major isozyme, pI 4.8 belongs to the pi-class, whereas the two minor forms pI 9.1 and 9.9 belong to the alpha-class. Each of the three isozymes is more abundant in female skin. Surprisingly, the specific activities and Kcat values of the female skin GSTs, particularly of the pi-class isozyme were found to be significantly higher as compared to those of male skin isozyme. Studies into the kinetics of inhibition by hematin also indicated differences in male and female skin GSTs. Whereas we confirm the presence of an alpha-class GST, pI 9.9, in human skin with an apparently higher subunit M(r) value as compared to other human alpha-class GSTs, contrary to the previous report (Del Boccio et al. (1987) Biochem. J. 244, 21-25), the results of the present studies show that the N-terminus of this alpha-class GST is blocked.

Purification and characterization of glutathione S-transferase of murine ovary and testis

Recent studies have indicated that sex hormones may regulate expression of murine glutathione S-transferase (GST) isozymes. Therefore, we have purified and compared GST isozymes of murine ovary and testis, two tissues with markedly different hormonal milieu. Isoelectric profiles of the GST isozymes of both these tissues were found to be closely similar. Both expressed one alpha-class GST (pI9.8), one pi-class GST (pI8.9), and three mu-class GSTs (pI8.5, 7.9, and 6.7). In addition, an isozyme (pI5.8) corresponding to the rat GST 8-8 was also expressed in both these tissues. Total GST protein/g tissue was about 1.7-fold more abundant in testis. The specific activities of the cationic isozymes of testis were 1.2- to 2.4-fold higher as compared to those of ovaries. On the other hand, the specific activities of the anionic testicular isozymes were 6.4- to 10-fold higher compared to the corresponding ovarian isozymes. Structural properties including the N-terminal sequences of the testicular isozymes were indistinguishable from those of their ovarian counterparts. The N-terminal sequence of the pi-class GST of both tissues was similar to that of mouse liver GST pi. The three mu-class GSTs of testis and ovary arise from the dimeric combinations of two subunits whose N-terminal sequences determined up to 24 residues were similar to those of mouse liver GST subunits mu 1 and mu 2. Although testicular and ovarian isozymes were structurally similar, Kcat values of some of the testicular isozymes were up to 10-fold higher than those of the corresponding ovarian isozymes. The substrate specificities were also significantly different for the corresponding isozymes of testis and ovary.

Semicarbazide protection from in vivo oxidant injury of vascular tissue by allylamine

Allylamine is a specific cardiovascular toxin that causes vascular and myocardial lesions. Previous studies showed that allylamine-induced chronic lesions are markedly reduced by semicarbazide, an inhibitor of semicarbazide-sensitive amine oxidase (SSAO), and that allylamine is metabolized to the aldehyde, acrolein, by SSAO. We hypothesized that inhibitors of SSAO might reduce the acute cardiovascular toxicity of allylamine. To test our hypothesis, we fed 150 mg/kg allylamine to semicarbazide-pretreated (3 h; 98 mg/kg) rats. Animals were sacrificed 1 h after allylamine treatment. Aorta, epicardium, and endocardium were assayed for SSAO, glutathione peroxidase, catalase, thiol status and lipid peroxidation. SSAO activity was decreased significantly in aorta, epicardium and endocardium. Activity was 30-times higher in aorta than in epicardium and endocardium. A striking decrease in malonaldehyde level (lipid peroxidation) was found in aorta of pretreated rats as compared to allylamine-only treated rats. The reduction of free-SH content in aortic mitochondria was also attenuated in pretreated rats. Changes were not so marked in epicardium and endocardium. These results suggest that in vivo pretreatment with semicarbazide at least partially protects aortic mitochondria from allylamine toxicity. The mechanism can be explained on the basis of the fact that semicarbazide inhibits acrolein formation in allylamine-treated rats.

Reversed-phase chromatographic method for specific determination of glutathione in cultured malignant cells

A chromatographic method for the specific determination of glutathione in malignant cell lines is described. The method is based on the ability of glutathione-S-transferase to specifically and quantitatively conjugate glutathione to 1-chloro-2,4-dinitrobenzene and chromatographic quantitation of the resultant conjugate, dinitrophenyl-S-glutathione, by reversed-phase liquid chromatography. The assay can be performed on 20,000 g supernatants of cell homogenates without acid extraction. 2-Mercaptoethanol, a sulfhydryl compound often used as a thiol-protective agent to preserve enzymatic activities of a number of enzymes, did not interfere with glutathione determination by this method. The dinitrophenyl-S-glutathione isolated from either standard glutathione samples or from cell homogenates was shown to be identical to authentic dinitrophenyl-S-glutathione using mass spectrometry. Recovery of glutathione in standard samples by the current method was identical to that determined using 5,5'-dithiobis(2-nitrobenzoic acid). Exogenous glutathione added to supernatants of cell homogenate in the presence or absence of 2-mercaptoethanol was also completely recovered.

Glutathione S-transferases of human lung: characterization and evaluation of the protective role of the alpha-class isozymes against lipid peroxidation

Glutathione S-transferase (GST) isozymes of human lung have been purified, characterized, quantitated, and, based on their structural and immunological profiles, identified with their respective classes. The tau-, mu-, and alpha-class GSTs represented 94, 3, and 3% activities of total human lung GSTs toward CDNB, respectively, and 60, 10, and 30% of total GST protein, respectively. Both the mu- and the alpha-class GSTs of human lung exhibited heterogeneity. The two mu-class GSTs of human lung had pI values of 6.5 and 6.25 and were differentially expressed in humans. Significant differences were seen between the kinetic properties of these two isozymes and also between the lung and liver mu-class GSTs. The alpha-class GST isozymes of lung resolved into three peaks during isoelectric focusing corresponding to pI values of 9.2, 8.95, and 8.8. All three alpha-class GSTs isozymes had blocked N-termini and were immunologically similar to human liver alpha-class GSTs. Peptide fingerprints generated by SV-8 protease digestion and CNBr cleavage indicated minor structural differences between the liver and the lung alpha-class GSTs. The three alpha-class GSTs of lung expressed glutathione peroxidase activities toward the hydroperoxides of phosphatidylcholine, phosphatidylethanolamine, and phosphatidylglycerol, with Km values in the range of 22 to 87 microM and Vmax values in the range of 67-120 mol/mol/min, indicating the involvement of the alpha-class GSTs in the protection mechanisms against peroxidation. All three classes of lung GSTs expressed activities toward leukotriene A4 methyl ester and epoxy stearic acid but the mu-class GSTs had relatively higher activities toward these substrates.

Gender related differences in the expression and characteristics of glutathione S-transferases of human colon

In the present study, the expression of glutathione S-transferase (GST) isozymes was compared in human male and female colon tissues. GST isozymes were purified and quantified in five male and five female colon tissue samples. Noticeable differences were observed in the isoelectric focusing profiles (IEF) of the GSTs, from male and female colon tissues. Both male and female colon tissues had three common GST peaks with pI values of 9.2, 6.7 and 4.8. An additional GST peak with a pI value of 6.2 found in all females was not found in males. Based on kinetic, immunological and structural properties, these isozymes were classified into alpha (pI 9.2), mu (pI 6.7 and 6.2) and pi (pI 4.8) classes. Activity of the alpha-class GST in male colon was approx. 2-fold higher than the corresponding isozyme in female colon. The pi-class GST 4.8 was the most predominant GST in both the sexes and its activity with CDNB as substrate was more abundant (about 1.6-fold) in female colon as compared to that in male colon. Significant differences were seen in substrate specificities between male and female colon GST 4.8. Sex related differences were also observed in the inhibition kinetics of GST pi from male and female colon in the presence of hematin. In addition, GST pi isolated from female colon was more thermostable as compared to the corresponding male isozyme. The thermostability of purified GST pi isozyme from males or females was not affected by incubation of the enzyme with either estrogen, testosterone or progesterone.

Dinitrophenyl S-glutathione ATPase purified from human muscle catalyzes ATP hydrolysis in the presence of leukotrienes

Dinitrophenyl S-glutathione (Dnp-SG) ATPase has been purified from human muscle to apparent homogeneity using Dnp-SG affinity chromatography and immunoaffinity chromatography using antibodies raised against human erythrocyte Dnp-SG ATPase. The enzyme purified from human muscle showed a subunit M(r) value of about 38 kDa in denaturing gels. The M(r) value of the native enzyme as determined by Sephadex G-200 gel filtration was found to be about 80 kDa, which indicates that it is a dimer. The N-terminus of the enzyme was blocked. Its immunological and kinetic properties were similar to Dnp-SG ATPase of human erythrocytes. Besides catalyzing the ATP hydrolysis in the presence of Dnp-SG, the muscle enzyme also catalyzed ATP hydrolysis in the presence of various leukotrienes, namely LTC4.LTD4, LTE4, and N-acetyl LTE4. The specific activity of the enzyme toward LTC4 was relatively higher than other GSH-xenobiotic conjugates. The muscle enzyme exhibits a low Km value for all leukotrienes as compared to Dnp-SG, indicating high affinity of the enzyme for leukotrienes as activators. The enzyme also catalyzed ATP hydrolysis in the presence of GSH conjugates of endogenously generated fatty acid epoxides. Our results might suggest that Dnp-SG ATPase is involved in the transport of GSH conjugates, leukotrienes, and other organic anions in muscle, erythrocytes, liver, and probably other tissues.

The relationship of doxorubicin binding to membrane lipids with drug resistance

Doxorubicin (DOX, Adriamycin) binds with high affinity to cellular membranes inflicting multiple lesions which are believed to be important in DOX-mediated neoplastic cell death. Using fluorescence and radioactive [14-14C-14]DOX assays for DOX, we have measured the partitioning of DOX between the cytosolic and membrane fractions of erythrocytes and of DOX-sensitive (V-79) and -resistant (LZ) Chinese hamster lung fibroblast cells. In both erythrocytes and fibroblasts, a significant fraction of DOX was associated with the membrane fraction. More significantly, the quantity of lipid-bound DOX in the fibroblasts correlated with the cell's susceptibility to DOX. The significance of these findings in the context of existing knowledge about DOX-membrane interactions is discussed.

Periampullary carcinoma in a young female with situs inversus

Periampullary carcinoma in a young female with situs inversus viscerum is reported. Endoscopy was difficult because of the altered anatomy.

Inhibition of liposomal lipid peroxidation by spermidine

Spermidine was found to inhibit the in vitro formation of thiobarbituric acid-reactive material from sonicated vesicles of rat brain and individual phospholipids, especially in the presence of externally added iron. With arachidonic acid incorporated liposomes spermidine inhibited lipid peroxidation in the presence or the absence of Fe2+, to similar extent. Thus spermidine inhibition of lipid peroxidation may not be entirely iron-dependent.

Agenesis of the gallbladder--a case report

Agenesis of the gallbladder, which is an extremely rare anomaly, may present with biliary symptoms but is virtually impossible to diagnose by such conventional investigations as oral cholecystogram or ultrasonography. We report herein a case of a young man presenting with episodic epigastric pain on whom an ultrasonographic diagnosis of gallstones was made. A gallbladder was not visualized on oral cholecystogram, however, he was subsequently found to have agenesis of the gallbladder, the diagnosis of which was confirmed by intra-operative cholangiography and a postoperative N-2,6-dimethylphenylcarbamoyle methyl iminodiacetic acid scan (HIDA scan). His symptoms responded to antiulcer treatment with upper gastrointestinal endoscopic findings suggestive of oesophagitis and duodenitis.

Increase in lysolecithin content of brain microsomes in phenobarbitone-administered rats and its relation to lipid peroxidation

Administration of phenobarbitone caused a marked increase in the capacity of rat brain microsomes to produce thiobarbituric acid-reactive substances in vitro. Enzymatic peroxidation of lipids was more affected than the nonenzymatic processes occurring in heat-inactivated preparations. Analysis of the phospholipid profile showed a drastic decrease in phosphatidylcholine and total phospholipid contents in the exposed animals, but about a fivefold increase in the lysophosphatidylcholine fraction. Data for in vivo incorporation of [14C]choline showed a similar pattern of high radioactivity in lysolecithin. The increase in lipid peroxidation could be related to the higher level of lysolecithin and the accompanying structural and functional changes in microsomes resulting from the neurotoxic effects of phenobarbitone.

Diverticular disease of colon; Indian variant

Diverticular disease of colon is a rare entity in our country; true incidence of which is not known. We present three cases of diverticular disease, two with lower gastro-intestinal (GI) hemorrhage and one with sigmoid colon perforation and peritonitis. All three patients underwent emergency surgical treatment. Two patients survived and one died. No further complications were noted on follow up.

Mortality patterns in breast versus artificially fed term babies in early infancy: a longitudinal study

The present study comprised 381 term babies weighing greater than 2.5 kg and 126 babies weighing less than or equal to 2.5 kg (low birth weight; LBW) at birth. A longitudinal follow up of 334 babies was done for 6 months. There were 273 'breast fed' babies and 234 'artificially fed' babies. Neonatal mortality rate per 1000 live births for term babies was 37.5, LBW had a rate of 31.5 while those weighing greater than 2.5 kg at birth a rate of 5.9; artificially fed had a mortality rate of 21.6 while breast fed had a low rate of 15.8. For 1-6 months period a mortality rate per 1000 live births of 53.8 was found for term babies, breast fed a rate of 23.9 while artificially fed a rate of 29.9; LBW had a rate of 44.9 while those weighing more than 2.5 kg at birth, a rate of 9. Low birth weight babies whether breast fed or artificially fed had significantly higher mortality than similarly fed babies weighing more than 2.5 kg at birth. Hence, mortality rate for term babies in early infancy can be reduced by simultaneous promotion of breastfeeding and prevention of low birth weight as it was dependent on both variables in this study.

Effect of anaesthetic ether on lipid peroxidation and superoxide dismutase isozymes of young and adult rat brain

Changes in lipid peroxidation and superoxide dismutase level in rat brain due to single exposure to diethyl ether (anaesthetic) were studied in 100 and 300 day old rats. Enhancement of superoxide dismutase activity was more pronounced in young rat brain, while the reverse was the case with lipid peroxidation. The neurotoxic effects of diethyl ether may involve active oxygen species and superoxide dismutase activity increases as a defensive adaptation.

Simple hematological tests for diagnosis of neonatal sepsis

Simple hematological tests, TLC, DLC, mESR, platelet count, were performed in 128 neonates of which 50 were controls and 78 were cases of suspected septicemia. Thirty three had positive blood cultures and were taken as 'proved' and remaining as 'probable' sepsis. A band cell neutrophil (B/N) ratio of greater than 0.2 was most sensitive index (92%) followed by raised mESR of greater than 8 mm for 1st hour, whereas leukopenia of greater than 5 x 10(3)/mm3 was most specific index (88%) for the diagnosis of sepsis. Thrombocytopenia of less than 1.5 x 10(5)/cu mm was also taken as positive test for sepsis. A combination of three positive tests had highest positive predictive accuracy (94%) for early diagnosis of sepsis, when compared to single test or two positive test combinations. The best combination of tests was B/N ratio, leukopenia and mESR which can be easily done in a side laboratory.

Is high protein milk beneficial for SGA-terms?

A three months longitudinal followup of SGA term babies was done for their response to feeding of high protein milk (3.1 g/100 ml) and they were compared with their breast fed counterparts. The formula fed infants had no advantage over the breast fed when weight was compared. However, blood urea and serum creatinine levels were higher in the formula fed infants, than the breast fed ones. The serum valine concentrations, indicative of protein nutritional status, increased with increasing postnatal age in all the infants. Formula fed had higher serum valine than breast fed ones. Serum phenylalanine and serum tyrosine levels, which may hamper CNS development, were higher in the formula fed infants than the breast fed ones.

Activation of human erythrocyte, brain, aorta, muscle, and ocular tissue aldose reductase

Based upon kinetic, structural, and immunologic properties, we have demonstrated that human tissues have three major forms of aldo-keto reductases: aldose reductase (AR), and aldehyde reductases I (AR I) and II (AR II). The proposed subunit compositions are AR, alpha; AR I, alpha-beta; and AR II, delta. Only AR can effectively reduce glucose to sorbitol. The beta subunits in AR I alter the substrate specificity of AR and prevent conformational changes required for the activation of alpha subunits. Partially purified AR (by DE-52) from human erythrocytes expresses biphasic kinetics with glucose and glyceraldehyde. The enzyme can be activated with glucose + glucose-6-P + NADPH and is strongly inhibited by sorbinil, alrestatin, and quercetrin, and by ADP, 2,3DPG, 1,3DPG, and 3PGA. The activated enzyme expresses monophasic kinetics with substrates (Km glucose less than 1 mmol/L) and is less susceptible to inhibition by synthetic AR inhibitors and phosphorylated intermediates. The enzyme from human brain, aorta, muscle, and ocular tissues was also activated under similar conditions. Erythrocyte enzyme was activated by incubation of blood with 30 to 50 mmol/L glucose. In diabetic subjects with blood sugar levels higher than 250 mg%, almost all the erythrocyte enzyme exists in the activated form. As demonstrated by enzyme-linked immunosorbent assay (ELISA), the increase in AR activity (in vivo and in vitro) was due to the activation of the enzyme and not to the de novo synthesis. In each case, the activation of the enzyme was confirmed by NADPH oxidation and the formation of proportionate amounts of sorbitol.

Interrelationships among human aldo-keto reductases: immunochemical, kinetic and structural properties

We have proposed earlier a three gene loci model to explain the expression of the aldo-keto reductases in human tissues. According to this model, aldose reductase is a monomer of alpha subunits, aldehyde reductase I is a dimer of alpha, beta subunits, and aldehyde reductase II is a monomer of delta subunits. Using immunoaffinity methods, we have isolated the subunits of aldehyde reductase I (alpha and beta) and characterized them by immunocompetition studies. It is observed that the two subunits of aldehyde reductase I are weakly held together in the holoenzyme and can be dissociated under high ionic conditions. Aldose reductase (alpha subunits) was generated from human placenta and liver aldehyde reductase I by ammonium sulfate (80% saturation). The kinetic, structural and immunological properties of the generated aldose reductase are similar to the aldose reductase obtained from the human erythrocytes and bovine lens. The main characteristic of the generated enzyme is the requirement of Li2SO4 (0.4 M) for the expression of maximum enzyme activity, and its Km for glucose is less than 50 mM, whereas the parent enzyme, aldehyde reductase I, is completely inhibited by 0.4 M Li2SO4 and its Km for glucose is more than 200 mM. The beta subunits of aldehyde reductase I did not have enzyme activity but cross-reacted with anti-aldehyde reductase I antiserum. The beta subunits hybridized with the alpha subunits of placenta aldehyde reductase I, and aldose reductase purified from human brain and bovine lens. The hybridized enzyme had the characteristic properties of placenta aldehyde reductase I.