Gly80Ser polymorphism of phospholipase A2-IID is associated with cytokine inducibility in A549 cells

BACKGROUND

The Gly80Ser polymorphism in phospholipase A2-IID (PLA2G2D, NCBI SNP reference: rs584367) is associated with a loss in body weight in patients with chronic obstructive pulmonary disease (COPD). The T allele missense mutation results in the 80th amino acid of the PLA2G2D protein changing from a glycine (Gly; C allele) to a serine (Ser; T allele). COPD patients carrying Ser lose a significant amount of weight compared with those carrying Gly. The mechanism for this weight loss following carriage of this Ser allele has not been clarified.

OBJECTIVES

We aimed to evaluate whether this allelic change alters PLA2 enzymatic activity and/or pro-inflammatory cytokine inducibility.

METHODS

A549 cells (a human pulmonary epithelial cell line) were transfected with PLA2G2D-Gly or PLA2G2D-Ser. We evaluated PLA2 activity and cytokine expressions in these cells.

RESULTS

The enzymatic activity of sPLA2 in A549-PLA2G2D-Ser cells did not differ from the A549-PLA2G2D-Gly cells. A549-PLA2G2D-Ser cells spontaneously produced higher levels of interleukin (IL)-6 and IL-8 than A549-PLA2G2D-Gly cells. Upon tumor necrosis factor-alpha stimulation, IL-6 and IL-8 mRNA and protein levels in A549-PLA2G2D-Ser cells were elevated compared with those of A549-PLA2G2D-Gly cells. Upon hydrogen peroxide stimulation, IL-8 mRNA and protein levels in A549-PLA2G2D-Ser cells were higher than those of A549-PLA2G2D-Gly cells.

CONCLUSIONS

PLA2G2D-Ser enhances the expression of IL-6 and IL-8 compared with PLA2G2D-Gly. This enhanced cytokine expression observed with the allelic change in PLA2G2D may be associated with the body weight loss seen in COPD patients.

The interaction of monocytes with rheumatoid synovial cells is a key step in LIGHT-mediated inflammatory bone destruction

Formation of osteoclasts and consequent joint destruction are hallmarks of rheumatoid arthritis (RA). Here we show that LIGHT, a member of the tumour necrosis factor (TNF) superfamily, induced the differentiation into tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells (MNCs) of CD14(+) monocytes cocultured with nurse-like cells isolated from RA synovium, but not of freshly isolated CD14(+) monocytes. Receptor activator of nuclear factor-kappaB ligand (RANKL) enhanced this LIGHT-induced generation of TRAP-positive MNCs. The MNCs showed the phenotypical and functional characteristics of osteoclasts; they showed the expression of osteoclast markers such as cathepsin K, actin-ring formation, and the ability to resorb bone. Moreover, the MNCs expressed both matrix metalloproteinase 9 (MMP-9) and MMP-12, but the latter was not expressed in osteoclasts induced from CD14(+) monocytes by RANKL. Immunohistochemical analysis showed that the MMP-12-producing MNCs were present in the erosive areas of joints in RA, but not in the affected joints of osteoarthritic patients. These findings suggested that LIGHT might be involved in the progression of inflammatory bone destruction in RA, and that osteoclast progenitors might become competent for LIGHT-mediated osteoclastogenesis via interactions with synoviocyte-like nurse-like cells.

Identification of the transporters involved in the hepatobiliary transport and intestinal efflux of methyl 1-(3,4-dimethoxyphenyl)-3-(3-ethylvaleryl)-4-hydroxy-6,7,8-trimethoxy-2-naphthoate (S-8921) glucuronide, a pharmacologically active metabolite of S-8921

The glucuronide conjugate of methyl 1-(3,4-dimethoxyphenyl)-3-(3-ethylvaleryl)-4-hydroxy-6,7,8-trimethoxy-2-naphthoate (S-8921; S-8921G) is a 6000-fold more potent inhibitor of an ileal apical sodium-dependent bile acid transporter (SLC10A2) than S-8921 and is responsible for the hypocholesterolemic effect of S-8921 in rats. Because S-8921G is formed in the intestine and liver, the present study investigated the transporters involved in the secretion of S-8921G that govern its exposure to the target site and thereby play an important role in its pharmacological action. Organic anion transporting polypeptide (OATP) 1B1- and OATP1B3-expressing cells exhibited saturable accumulation of S-8921G with K(m) values (micromolar) of 1.9. The uptake of [14C]S-8921G by human cryopreserved hepatocytes was saturable and sodium-independent. Comparison of protein expression between the cDNA transfectants and hepatocytes suggests that the contribution of OATP1B1, OATP1B3, and Na+-taurocholate cotransporting polypeptide to the hepatic uptake of S-8921G is 63, 35, and 2.6%, respectively. The basal-to-apical transport of S-8921G was enhanced in Madin-Darby canine kidney cells expressing both OATP1B1 and multidrug resistance-associated protein (MRP) 2. In Mrp2-deficient mutant rats [Eisai hyperbilirubinemic rats (EHBR)], the biliary excretion clearance based on the plasma concentration was 20% of the normal value, whereas the pharmacokinetic parameters did not show any significant change in Bcrp-/- mice. Furthermore, the secretion clearance of S-8921G to the mucosal side was also significantly lower in everted jejunum sacs from EHBR (9.18 and 20.8 microl/min/g tissue). These results suggest that MRP2 is responsible for the secretion of S-8921G to the intestinal lumen and bile and that OATP1B1 and OATP1B3 account for the hepatic uptake. These transporters deliver S-8921G to the target site of its pharmacological action.

Characterization of novel non-peptide thrombopoietin mimetics, their species specificity and the activation mechanism of the thrombopoietin receptor

A series of non-peptide small compounds discovered to be thrombopoietin receptor agonists showed species specificity to humans. Compound I could induce megakaryocyte lineage from human bone marrow cells, but not from mouse, guinea pig or cynomolgus monkey bone marrow cells. To elucidate the mechanism, we identified the pivotal amino acid residue for the receptor activation by compound I by taking advantage of its species specificity. The response of compound I to three human/mouse chimeric receptors indicated the importance of the transmembrane domain. Comparison of amino acid sequences of the transmembrane domain of the thrombopoietin receptor between human and three animal species led us to hypothesize that histidine 499 is necessary for the reactivity to the thrombopoietin mimetics. We verified the hypothesis using two mutant receptors: the human thrombopoietin receptor mutant His499Leu and the mouse thrombopoietin receptor mutant Leu490His. These results should be helpful for structure-activity relationship studies and conducting in vivo studies of thrombopoietin mimetics.

Toxicogenomics of Drug-Induced Hemolytic Anemia by Analyzing Gene Expression Profiles in the Spleen

Hemolytic anemia is a serious adverse effect of therapeutic drugs that is caused by increased destruction of drug-damaged erythrocytes by macrophages in the spleen and liver. We previously applied a toxicogenomic approach to the toxicity by analyzing microarray data of the liver of rats dosed with two hemolytic agents: phenylhydrazine and phenacetin. In the present study, we analyzed gene expression profiles in the spleen, the primary organ for destruction of damaged erythrocytes, of the same models in order to identify splenic gene expression alterations that could be used to predict the hematotoxicity. Microarray analyses revealed hundreds of genes commonly deregulated under all severe hemolytic conditions, which included genes related to splenic events characteristic of the hematotoxicity, such as proteolysis and iron metabolism. Eleven upregulated genes were selected as biomarker candidates, and their expression changes were validated by quantitative real-time PCR. The transcript levels of most of these genes showed strong correlation with the results of classical toxicological assays (e.g., histopathology and hematology). Furthermore, hierarchical clustering analysis suggested that altered expression patterns of the 11 genes sensitively reflected the erythrocyte damage even under a condition that caused no decrease in erythrocyte counts. Among the selected genes, heme oxygenase 1 was one of the most promising biomarker candidates, the upregulation of which on the protein level was confirmed by immunohistochemistry. These results indicate that altered splenic expression of a subset of genes may allow detection of drug-induced hemolytic anemia, with better sensitivity than that of erythrocyte counts in the blood.

A Toxicogenomic Approach Revealed Hepatic Gene Expression Changes Mechanistically Linked to Drug-Induced Hemolytic Anemia

A variety of pharmaceutical compounds causes hemolytic anemia as a significant adverse effect and this toxicity restricts the clinical utility of these drugs. In this study, we applied microarray technology to investigate hepatic gene expression changes associated with drug-induced hemolytic anemia and to identify potential biomarker genes for this hematotoxicity. We treated female Sprague-Dawley rats with two hemolytic anemia-inducing compounds: phenylhydrazine and phenacetin. Hepatic gene expression profiles were obtained using a whole-genome oligonucleotide microarray with pooled RNA samples from individual rats within each dose group and analyzed in comparison with hepatic histopathology, hematology, and blood chemistry data. We identified a small subset of genes that were commonly deregulated in all the severe hemolytic conditions, some of which were considered to be involved in hepatic events characteristic of hemolytic anemia, such as hemoglobin biosynthesis, heme metabolism, and phagocytosis. Among them, we selected six upregulated genes as putative biomarkers, and their expression changes from microarray measurements were confirmed by quantitative real-time PCR using RNAs from individual animals. They were Alas2, beta-glo, Eraf, Hmox1, Lgals3, and Rhced. Expression patterns of all these genes showed high negative and positive correlation against erythrocyte counts and total bilirubin levels in circulation, respectively, suggesting that these genes may be the potential biomarkers for hemolytic anemia. These findings indicate that drug-induced hemolytic anemia may be detected based on hepatic changes in the expression of a subset of genes that are mechanistically linked to the hematotoxicity.

Presence of the M-type sPLA(2) receptor on neutrophils and its role in elastase release and adhesion

Secretory phospholipase A(2) (sPLA(2)) produces lipids that stimulate polymorphonuclear neutrophils (PMNs). With the discovery of sPLA(2) receptors (sPLA(2)-R), we hypothesize that sPLA(2) stimulates PMNs through a receptor. Scatchard analysis was used to determine the presence of a sPLA(2) ligand. Lysates were probed with an antibody to the M-type sPLA(2)-R, and the immunoreactivity was localized. PMNs were treated with active and inactive (+EGTA) sPLA(2) (1-100 units of enzyme activity/ml, types IA, IB, and IIA), and elastase release and PMN adhesion were measured. PMNs incubated with inactive, FITC-linked sPLA(2)-IB, but not sPLA(2)-IA, demonstrated the presence of a sPLA(2)-R with saturation at 2.77 fM and a K(d) of 167 pM. sPLA(2)-R immunoreactivity was present at 185 kDa and localized to the membrane. Inactive sPLA(2)-IB activated p38 MAPK, and p38 MAPK inhibition attenuated elastase release. Active sPLA(2)-IA caused elastase release, but inactive type IA did not. sPLA(2)-IB stimulated elastase release independent of activity; inactive sPLA(2)-IIA partially stimulated PMNs. sPLA(2)-IB and sPLA(2)-IIA caused PMN adhesion. We conclude that PMNs contain a membrane M-type sPLA(2)-R that activates p38 MAPK.

Influence of lipophilicity and lysosomal accumulation on tissue distribution kinetics of basic drugs: a physiologically based pharmacokinetic model

This paper examines the role of lipophilicity in the tissue distribution kinetics of basic drugs. Basic drugs have a large distribution volume and are distributed widely in various tissues in the following order: lung, fat, heart, kidney, brain, gut, muscle and bone. The fat volume in the whole body influences the disposition kinetics. There is a good correlation in various tissues between the tissue-plasma concentration ratio and the octanol-water partition coefficient among various drugs. We constructed a physiologically-based pharmacokinetic model on the basis of drug lipophilicity and found that drug distribution decreased when NH4Cl was administered concomitantly. In regards to subcellular distribution, the relative specific contents of chlorpromazine, imipramine and biperiden with respect to the protein in lysosomes were 7.3, 9.6 and 4.2, respectively, while those in other subcellular organella, including mitochondria, were only 0.4-1.7, indicating preferential accumulation of these drugs in lysosomes. The uptake of basic drugs into lysosomes depended on both intralysosomal pH and drug lipophilicity. As the lipophilicity of the basic drugs increased, they accumulated more than would have been predicted from the pH-partition theory and raised the intralysosomal pH more potently, probably owing to their binding with lysosomal membranes, with or without intralysosomal aggregation. We conclude that the distribution kinetics of basic drugs is driven by drug lipophilicity and uptake into lysosomes, and these phenomena provide a possible basis for drug interaction in clinical treatments.

Five-year retrospective changes in hippocampal atrophy and cognitive screening test performances in very mild Alzheimer's disease: the Tajiri Project

The medial temporal lobe, especially the hippocampus, is important for normal cognitive function. especially for memory, and is the region with the earliest and most extensive pathological changes in Alzheimer's disease (AD). We investigated the atrophic changes of the hippocampus over a 5-year period and its relation to cognitive screening test performances in normal elderly subjects, those with very mild AD, and patients with AD. Fifty-seven elderly subjects without a moderate or greater degree of cerebrovascular disease as shown by MRI were randomly selected from the town of Tajiri. Thirty-three subjects with a clinical dementia rating (CDR) of 0 (normal), 18 CDR-0.5 (very mild AD) subjects, and six CDR-1&2 (AD) subjects underwent MRI and the Mini Mental State Examination (MMSE) twice during the period. Retrospective changes in the hippocampal width and the MMSE scores were evaluated. There were significant CDR group effects for the changes in the mean bilateral hippocampal widths and the MMSE scores. Normal subjects did not show cognitive decline, although there was a slight tendency for hippocampal atrophy. A significant and meaningful Spearman's correlation was noted between left hippocampal atrophy and the MMSE scores over the 5-year period for the CDR-0.5 group. These CDR-0.5 subjects met the MCI (mild cognitive impairment) criteria as proposed by the consensus paper. Findings suggested that normal elderly subjects maintain a high level of cognitive functions for at least 5 years, although hippocampal atrophy might occur. Atrophic change of the left hippocampus might be a good marker of the very early stage of AD.

Cognitive function and frontal lobe atrophy in normal elderly adults: Implications for dementia not as aging-related disorders and the reserve hypothesis

We examined the relations between cognitive function and age and education in the normal elderly population. As per the community-based stroke, dementia, and bed confinement prevention in the town of Tajiri, neuropsychological assessments, including the Cognitive Ability Screening Instrument (CASI), were performed for 99 randomly selected normal elderly subjects. We assessed the frontal function (working memory, word fluency, Trail-Making Tests, CASI subitems of list-generating fluency, attention, and concentration/mental manipulation), language function (proverbs, CASI subitem language), non-language function (the digit symbol test of the Wechsler Adult Intelligence Scale-Revised (WAIS-R), CASI subitem visual construction), memory (Alzheimer's Disease Assessment Scale recall/recognition, story recall, CASI subitems short and long-term memory, the Rey-Osterrieth Complex Figure Test), and the global function (CASI subitems orientation and abstraction and judgment). We found that the only test affected by age was the digit symbol test of the WAIS-R. The effects of education were distributed among various tests. There was a significant correlation between age and the frontal lobe atrophy in the lower educated group. The present findings suggest that cognitive function is spared by the aging process itself and dementia should be considered as age-related, not aging-related disorders, and that education might have a protective effect on cognitive change, supporting the reserve hypothesis.

Global intellectual deterioration in Alzheimer's disease and a reverse model of intellectual development: an applicability of the Binet scale

Since intellectual deterioration in Alzheimer's disease (AD) might be considered to demonstrate a reverse of the intellectual development of children, we herein investigated the applicability of the Tanaka-Binet Intelligence scale (TB scale). This scale can assess the mental age (MA) and the lower-limit age (LLAge) values, and was reported to be correlated with the tasks determining Piaget's developmental stages of intelligence. Thirty AD patients and 30 age-matched normal control subjects were examined with the scale. We found that the mean MA values of the AD patients and controls were 97.4 and 150.3 months, respectively. In the control group, there were significant correlations between the MA and chronological age, and between the MA and years of education. In the AD patients, there was a significant correlation between the MA and the MMSE score. Regarding the LLAge for the AD patients, similar to the theory of Piaget, there was a tendency that they could be classified into three LLAge groups. We consider that the TB scale is useful in assessing the intellectual function in AD patients.

Kinetic phenotypic diagnosis of N-acetylation polymorphism in patients based on ratio of urinary metabolites of salicylazosulfapyridine

We found that N-acetylation polymorphism can be evaluated from the disposition kinetics of sulfapyridine (SP) and 5-aminosalicylic acid (5-ASA) and their acetylated metabolites generated by N-acetyltransferase (NAT2) after oral administration of salicylazosulfapyridine (SASP). In 126 Japanese subjects, the homozygote of NAT2*4 was the most frequent (40%), followed by heterozygotes of NAT2*4 and mutant genes (28% NAT2*4/*6A, 15% NAT2*4/*7B, and 2% NAT2*4/*5B). Combinations of mutant genes accounted for 16%. When the relationship between the molar ratio of N-acetyl-SP (Ac-SP)/SP or N-acetyl-5-ASA(Ac-5-ASA)/5-ASA in serum and five genotypes of polymorphic NAT2* was examined in patients who received multiple doses of SASP, the molar ratios of Ac-SP/SP, rather than Ac-5-ASA/5-ASA tended to decrease according to the classification of genotype. We calculated the pharmacokinetic parameters in healthy subjects with various genotypes of polymorphic NAT2* after a single p.o. administration of SASP, according to a model of the SP metabolic pathways. The molar ratios of Ac-SP/SP in serum and urine were simulated using these parameters, and the molar ratio of Ac-SP/SP in urine at 4 days after the first administration could be categorized into ranges that were specific to various NAT2* genotypes. Thus, we were able to predict the N-acetylation polymorphic genotypes of patients by measuring the molar ratio of Ac-SP/SP in urine, after administration of SASP.

A 5-year retrospective examination of cognitive screening test stages in normal older adults and patients with Alzheimer's disease: the Tajiri project

One conception of aging and cognitive deterioration is that cognitive decline becomes common with age, and dementia may be regarded as one extreme of the continuum. An alternative conception is that the cognitive process is spared by the aging process itself and that cognitive functioning of normal older adults and those with slight cognitive impairment, a CDR (Clinical Dementia Rating) score of 0.5 (suspected dementia), should be different. We examined changes in the screening test performances of 170 older adults over a 5-year period and found the following: (a) The CDR 0 (normal) participants did not show remarkable changes even in the older groups and (b) the subitems of orientation, memory, and so forth were useful for distinguishing normal older adults from early Alzheimer's disease patients. The results support the idea that dementia is better conceptualized as an age-related than as an "aging-related" disorder and that a CDR score of 0.5 should be considered very mild Alzheimer's disease.

Effect of meropenem on disposition kinetics of valproate and its metabolites in rabbits

PURPOSE

We investigated the effect of meropenem (MEPM) on the disposition kinetics of valproate (VPA) and its metabolites in rabbits.

METHODS

Rabbits were given 75 mg/kg VPA intravenously with or without 300 mg/kg MEPM.

RESULTS

The plamsa total clearance of VPA was significantly increased to about 1.5 times the control (6.09 mL/min/kg vs. 4.28 mL/min/kg) by MEPM (P < 0.05). The values of the area under the plasma concentration-time curve (AUC) of 2-en-VPA, a product of beta-oxidation, and VPA-glucuronide (VPA-G) were significantly decreased to about 55% and 78% of the control, respectively (P < 0.05). The cumulative urinary excretions of VPA in the control and MEPM-treated groups were 0.54% and 0.62% of the dose, respectively, whereas those of VPA-G were 45.6% and 62.5%, respectively. The urinary excretion of VPA-G was significantly increased by MEPM (P < 0.05). Further, in the case of 33.8 mg/kg VPA-G administered intravenously the AUC value of VPA-G was unchanged by MEPM, whereas that of the generated VPA was significantly decreased to about half of the control.

CONCLUSIONS

The increase of the total clearance of VPA caused by MEPM appears to be a consequence of increased renal clearance of VPA-G, as well as suppression of VPA-G hydrolysis in the liver.

Elderly Japanese emigrants to Brazil before World War II: I. Clinical profiles based on specific historical background

OBJECTIVE

To research the demographic and clinical profiles of elderly Japanese emigrants, who arrived in Brazil before World War II, in order to give them appropriate psychogeriatric care.

DESIGN

Elderly Japanese immigrants aged 65 years and over, belonging to the Miyagi Association in the São Paulo Metropolitan Area, were targeted. They emigrated from Miyagi Prefecture to Brazil and are now living in the area. We were able to interview 166 respondents. All data were gathered using standardized interview methods covering (a) free interview about the immigration history, (b) demographics, and (c) physical status.

RESULTS

Through the free interview, we found their immigration histories, which affected their clinical profiles. The mean age and educational level were 77.5 years and 6.3 years, respectively. Sixty per cent of them immigrated when they were younger than 14. Ninety-four per cent of them still keep Japanese nationality. Fifty-seven per cent of them usually use Japanese, while 10% of them use Portuguese. Although their emigration histories were hard, 76% of them perceived their health as being excellent or relatively good. The percentages of subjects with histories of disease were hypertension, 52.5%; cardiac disease, 20.8%; diabetes mellitus, 24.2%; and hyperlipidemia, 25.0%, which were affected by the Brazilian environment.

CONCLUSION

The elderly Japanese who emigrated to Brazil before World War II have a unique historical and demographic background. Their clinical profiles cannot be fully understood without knowing their histories. They definitely need high quality international psychogeriatric care.

Elderly Japanese emigrants to Brazil before World War II: II. Prevalence of senile dementia

BACKGROUND

We previously showed the prevalence of dementia in the town of Tajiri (Miyagi Prefecture, Japan), and found it to be 8.0%. The first population-based study on dementia in Brazil (Catanduva) disclosed the prevalence as being 7.1%. To evaluate the effects of environment on development of dementia, elderly Japanese immigrants living in Brazil were examined. Brazil is the country with the largest number of Japanese immigrants.

METHODS

All immigrants aged 65 years and over from Miyagi Prefecture, living in the four cities of the São Paulo Metropolitan area were targeted (n = 192). We were able to examine 166 subjects (86.5%). The diagnosis of dementia was based on the DSM-IV with the severity assessed by the CDR (clinical dementia rating) scales. The cognitive ability screening instrument (CASI) was used for neuropsychological assessment.

RESULTS

Thirteen subjects were diagnosed with dementia, CDR 1-3, the prevalence being 7.8%. Older subjects suffered more from dementia, and, paradoxically, the more highly educated subjects also suffered more. All the CASI items, except for long-term memory and visual construction, significantly deteriorated in the CDR 0.5 group compared with the CDR 0 group.

COMMENTS

The prevalence of dementia was not thought to be affected by environmental factors. A paradoxically higher rate of dementia in the more educated subjects was probably due to the historical problems of the immigrants. Intact CASI item long-term memory in the CDR 0.5 group indicated that suspected dementia patients could maintain this function. This is the first epidemiological study on dementia in elderly Japanese immigrants in Brazil.

Depressive symptoms and associated factors in a cognitively normal elderly population: the Tajiri Project

BACKGROUND AND OBJECTIVE

Since depression is one of the main problems of elderly subjects, it is important to examine the prevalence of this condition and to identify associated factors.

METHODS

A total of 1525 cognitively normal subjects aged 65 years and over in the town of Tajiri, a typical agricultural town in Japan, were analysed. Their MMSE (mini-mental state examination) scores were 24 or over. Depressive state was assessed by Zung's SDS (self-rating depression scale) with a comprehensive interview to examine ADL, demographics and symptoms associated with illness, etc. The prevalence of depression was calculated. To determine the factors associated with depression, the t-test and the Chi-square test were used. To examine the relative strength of each factor, logistic regression analysis was performed.

RESULTS

The ratio of the depressive subjects was 6.4%, lower than those of previous reports, probably due to the effect of excluding dementia subjects. The ratio for older females aged 80 years and over was 14.3%, which was significantly higher than that of the males. Among socio-demographic factors, sex, age, number of children and perception of economic status, were significantly related. For health status and ADL, such factors as perception of health and medical history of heart disease and rheumatism were related. For familial and social status, factors such as daily activity and several conversation abilities were related. The logistic regression analysis indicated that perception of health and daily activity were associated.

CONCLUSIONS

In this study, we isolated some factors related to depression in a cognitively normal population. Knowledge of such factors is important for appropriate mental care of aged subjects.

[Studies on the mechanism of subcellular distribution of basic drugs based on their lipophilicity]

This paper described the studies on the mechanism of subcellular distribution of lipophilic weak bases. Although the tissue distribution of basic drugs appeared to decrease with time simply in parallel with their plasma concentration, their subcellular distribution in various tissues exhibited a variety of patterns. Basic drugs were distributed widely in various tissues, but were concentrated in lung granule fraction, where their accumulation was dependent on their lipophilicity and lysosomal uptake. As the plasma concentration of drugs decreased after maximum level, the contribution of lysosomes to their subcellular distribution increased. The uptake of the basic drugs into lysosomes depended both on their intralysosomal pH and on the drug lipophilicity. As the lipophilicity of the basic drugs increased, they accumulated more than the values predicted from the pH-partition theory and raised the intralysosomal pH more potently, probably owing to their binding with lysosomal membranes with or without additional intralysosomal aggregation. These phenomena should be considered as a basis of drug interaction in clinical treatments.

Mouse group X secretory phospholipase A2 induces a potent release of arachidonic acid from spleen cells and acts as a ligand for the phospholipase A2 receptor

Group X secretory phospholipase A2 (sPLA2-X) has recently been shown to possess a powerful potency for releasing arachidonic acid from cell membrane phospholipids. Here, we report the purification of mouse pro- and mature forms of sPLA2-X, as well as its expression and biological functions. Purified pro-sPLA2-X was found to possess a propeptide of 11 amino acid residues attached at the NH2-terminals of the mature protein, and showed as little as 8% of the PLA2 activity of the mature form. Limited proteolysis of pro-sPLA2-X with trypsin resulted in the appearance of the mature form with a concomitant increase in PLA2 activity, suggesting a requirement of proteolytic removal of the propeptide for the optimal activity. The expression of sPLA2-X mRNA was detected in various tissues including the lung, thymus, and spleen, and immunohistochemical analysis revealed its expression in splenic macrophages. In the spleen cells, mature sPLA2-X elicited a prompt release of arachidonic acid with significant production of prostaglandin E2 more efficiently than group IB and IIA sPLA2s. In addition, sPLA2-X was identified as a high-affinity ligand for both native and recombinant form of mouse PLA2 receptor (PLA2R). However, there was no significant difference in the sPLA2-X-induced arachidonic acid release responses in the spleen cells between wild-type and PLA2R-deficient mice. These findings strongly suggest that sPLA2-X possesses two distinct biological functions in mice: it elicits a marked release of arachidonic acid from membrane phospholipids leading to the production of lipid mediators based on its enzymatic potency, and it acts as a natural ligand for the PLA2R that has been shown to play a critical role in the production of inflammatory cytokines during endotoxic shock.

Uptake of imipramine in rat liver lysosomes in vitro and its inhibition by basic drugs

We investigated the uptake of imipramine (IMP) in highly purified lysosomes from rat liver and its inhibition by a variety of basic drugs in vitro. The uptake of [(3)H]IMP into lysosomes peaked in less than 20 s, showing little temperature dependency or countertransport phenomena. It was accelerated by increase of extralysosomal pH, stimulated by Mg(2+)-ATP in KCl buffer, and suppressed by acidic ionophores. However, the uptake of [(3)H]IMP in lysosomes was approximately 140-fold higher than the value expected from the pH-partition theory. IMP and other weak lipophilic bases like chlorpromazine and propranolol raised the intralysosomal pH, and their potency was stronger than that of NH(4)Cl, a typical pH-perturbing weak base. A variety of basic drugs inhibited the uptakes of [(3)H]IMP and [(14)C]methylamine into lysosomes, their 50% inhibitory concentrations (IC(50)) being almost the same for [(3)H]IMP and [(14)C]methylamine uptake (r = 0.842). A high correlation (r = 0.946) was observed between the IC(50) values (for the inhibition of [(3)H]IMP uptake) and the lipophilicity (P(oct) values). These results suggest that the accumulation of lipophilic basic drugs is driven primarily by the transmembrane pH difference (pH-partition theory) but with the involvement of some additional mechanism(s) related to drug lipophilicity, possibly binding (partition or adsorption) to lipophilic substance(s) and/or aggregation within lysosomes. Based on this idea, we have established a model that described and successfully simulated the weak base-induced pH increase, the accumulation of a lipophilic weak base (IMP), and the inhibition of accumulation of IMP by lipophilic basic drugs.

Structures, enzymatic properties, and expression of novel human and mouse secretory phospholipase A(2)s

Mammalian secretory phospholipase A(2)s (sPLA(2)s) form a family of structurally related enzymes that are involved in a variety of physiological and pathological processes via the release of arachidonic acid from membrane phospholipids or the binding to specific membrane receptors. Here, we report the cloning and characterization of a novel sPLA(2) that is the sixth isoform of the sPLA(2) family found in humans. The novel human mature sPLA(2) consists of 123 amino acids (M(r) = 14,000) and is most similar to group IIA sPLA(2) (sPLA(2)-IIA) with respect to the number and positions of cysteine residues as well as overall identity (51%). Therefore, this novel sPLA(2) should be categorized into group II and called group IIE (sPLA(2)-IIE) following the recently identified group IID sPLA(2) (sPLA(2)-IID). The enzymatic properties of recombinant human sPLA(2)-IIE were almost identical to those of sPLA(2)-IIA and IID in terms of Ca(2+) requirement, optimal pH, substrate specificity, as well as high susceptibility to the sPLA(2) inhibitor indoxam. Along with the biochemical properties of proteins, genetic and evolutional similarities were also observed among these three types of group II sPLA(2)s as to the chromosomal location of the human gene (1p36) and the exon/intron organization. The expression of sPLA(2)-IIE transcripts in humans was restricted to the brain, heart, lung, and placenta in contrast to broad expression profiles for sPLA(2)-IIA and -IID. In sPLA(2)-IIA-deficient mice, the expression of sPLA(2)-IIE was markedly enhanced in the lung and small intestine upon endotoxin challenge, which contrasted with the reduced expression of sPLA(2)-IID mRNA. In situ hybridization analysis revealed elevation of sPLA(2)-IIE mRNA at alveolar macrophage-like cells in the lung of endotoxin-treated mice. These findings suggest a distinct functional role of novel sPLA(2)-IIE in the progression of inflammatory processes.