Enzymology of human cytosolic sulfotransferases

Conjugation of many xenobiotics, drugs, and endogenous compounds with a sulfonate moiety is an important reaction in their biotransformation. Sulfation of these compounds generally results in a decrease in biological activity and an increase in their urinary excretion. However, in certain instances, sulfation results in bioactivation to reactive electrophilic or therapeutically active forms. At least four cytosolic sulfotransferases (STs) have been identified and characterized from human tissues. These enzymes are two forms of phenol ST (PST), the phenol-sulfating and the monoamine-sulfating forms of PST (P-PST and M-PST, respectively), an estrogen sulfotransferase (EST), and a hydroxysteroid ST, dehydroepiandrosterone ST (DHEA-ST). Although four cytosolic STs have been well characterized in human tissues, evidence is accumulating for the presence of allelic forms or additional distinct forms of the STs in human tissues. The STs possess distinct but overlapping substrate specificities, and all of the STs are capable of conjugating both xenobiotic and endogenous compounds. The individual forms of ST may display distinct patterns of tissue specific expression and different mechanisms of regulation. Although the role of sulfation in drug metabolism is well recognized, an increased understanding of the biochemistry and molecular biology of the STs should also provide additional information as to their functions in many normal physiologic processes.     

Phenol sulfotransferases: candidate genes for Batten disease

Batten disease (juvenile-onset neuronal ceroid lipofuscinosis; JNCL) is an autosomal recessive neurodegenerative disorder, characterized by the cytosomal accumulation of autofluorescent proteolipopigments in neurons and other cell types. The Batten disease gene (CLN3) has not yet been identified, but has been mapped to a small region of human chromosome area 16p12.1-p11.2. We recently reported the fortuitous discovery that the cytosolic phenol sulfotransferase gene (STP) is located within this same interval of chromosome 16p. Since phenol sulfotransferase is expressed in neurons, can sulfate lipophilic phenolic compounds, and is mapped near CLN3, STP is considered as a candidate gene for Batten disease. YAC and cosmid cloning results have further substantiated the close proximity of STP and a highly related sulfotransferase (STM), encoding the catecholamine-preferring enzyme, to the CLN3 region of chromosome 16p. In this report, we summarize some of the recent progress in the identification of two phenol sulfotransferase genes (STP and STM) as positional candidate genes for Batten disease.     

Interstitial cells of Cajal: mediators of communication between circular and longitudinal muscle layers of canine colon

Autopsy studies of patients with AIDS dementia have shown neuronal loss consistent with a neurotoxic component of this disease. In vitro studies suggest that viral products or cytokines from HIV-infected macrophages (Mphi) may modulate or directly mediate excitotoxic cell death of neurons. Mphi differentiated from peripheral mononuclear blood cultures were infected with HIV, and conditioned media (CM) were harvested from these cultures. Exposure of SK-N-MC (neuroblastoma) cells to CM from HIV-infected Mphi for 4, 24 or > or = 48 h resulted in a mean suppression of 12-34% of the glutamate transport Vmax with no appreciable change in transport Km. An astrocytoma tumor cell, U373MG, showed similar CM-mediated glutamate uptake suppression. Changes were evident in total and Na+-dependent glutamate uptake, with significantly more suppression of Na+-dependent uptake. Similar effects were seen with the nonmetabolizable transporter agonist D-aspartate, indicating that the effect was on transport and not metabolism. No suppression was seen with CM from uninfected Mphi or Mphi infected with heat-inactivated HIV. The magnitude of uptake suppression was not correlated with CM p24 values, and removal of CM virions by ultracentrifugation and immunoprecipitation did not alter the uptake-suppressive properties of infected Mphi CM. Uptake suppression was seen when Mphi were infected with Mphi-tropic strains HIV(SF162), HIV(JR-CSF), HIV(NFN-SX) and a Mphi-tropic patient isolate, but not the lymphotropic strain HIV(LAI). HIV-infected Mphi may produce substances which suppress neuronal and glial glutamate neurotransmitter uptake, resulting in higher extracellular glutamate levels and leading possibly to deficits in cell signaling and neurotoxicity.     

Sulfation of minoxidil by multiple human cytosolic sulfotransferases

Minoxidil is an antihypertensive agent and hair growth promoter that is metabolized by sulfation to the active compound, minoxidil sulfate. Thermostable phenol sulfotransferase (TS PST or P-PST) was initially thought to catalyze the reaction, and the enzyme was designated minoxidil sulfotransferase (MNX-ST). Information about human ST activities toward minoxidil would be useful in developing the capacity to predict individual responses to minoxidil based on tissue levels of STs. Therefore, human STs were studied from platelet homogenates, partially purified platelets, scalp skin high speed supernatants and COS-1 cell cDNA expressed preparations using a radiochemical enzymatic assay with minoxidil as the substrate. Studies showed the presence of TS PST, TL (thermolabile) PST and MNX-ST activities in human scalp skin. Biochemical properties and correlation studies suggested that in addition to TS PST, the TL PST activity, another ST activity or both were involved in the reaction. Partially purified human platelet TL PST tested with minoxidil and dopamine showed identical thermal stabilities and similar responses to the inhibitors 2,6-dichloro-4-nitrophenol (DCNP) and NaCl. To characterize the activity of TL PST toward minoxidil, several biochemical properties of the enzyme expressed from a human liver cDNA clone were investigated. When assayed with minoxidil and dopamine, thermal stabilities of the expressed enzyme were identical and IC50 values for the inhibitors DCNP and NaCl were similar. It was also demonstrated that cDNA encoded human liver dehydroepiandrosterone sulfotransferase and estrogen sulfotransferase contributed to the sulfation of minoxidil. The results confirm that at least four human STs contribute to minoxidil sulfation. MNX-ST activity represents a combination of ST activities. The data indicate that multiple ST activities should be taken into account in attempts to predict the regulation of minoxidil sulfation and individual responses to minoxidil.     

P-glycoproteins: mediators of multidrug resistance

Multidrug resistance represents a major obstacle to successful chemotherapy of metastatic disease. Elevated levels in cancer cells of the product of the multidrug resistance gene, P-glycoprotein or the multidrug transporter, have been associated with the development of simultaneous resistance to a great variety of amphiphilic cytotoxic drugs. P-glycoprotein is an integral plasma membrane protein which contains 12 putative transmembrane regions and two ATP binding sites. It confers multidrug resistance by functioning as an energy-dependent drug efflux pump. Here we describe recent studies on the biosynthesis, structure, function, and mechanism of action of P-glycoprotein which have provided insights into the complexity of this multifunctional transport system and revealed an additional chloride channel activity. The physiological role of P-glycoprotein, however, still remains to be elucidated.     

Caspases: key mediators of apoptosis

Recent studies have established that members of the caspase protease family are essential components of a conserved cell death program. Insights into their biological roles, structure and mechanism are enabling investigators to begin to explore the therapeutic potential of caspase inhibition.     

Sulfation of parabens and tyrosylpeptides by bacterial arylsulfate sulfotransferases

Arylsulfate sulfotransferase purified from Eubacterium A-44 has higher specific activity than the enzymes from Klebsiella K-36 and Haemophilus K-12. Propylparaben and butylparaben were good substrates among several parabens. The antibacterial activity of parabens was reduced by the sulfation of the phenolic hydroxy group. Tyrosine-containing peptides, kyotorphin, enkephalin and cholecystokinin non-sulfate, were effective as acceptor substrates by A-44, K-36 and K-12 sulfotransferases.     

Carbohydrate chromatography: towards yoctomole sensitivity

Ward atmosphere was assessed with the help of the Ward Atmosphere Scale (WAS) by patients, nurses and physicians on 8 admission units before and after the introduction of the partial open door system. On average, on 45% of the days on which the units could have been potentially open, they were indeed at least temporarily open. Several significant changes in the WAS scores, mostly in desirable direction, were registered. However, close relationship with the partial opening of the units could be substantiated only with regard to the scale "praxis orientation"; still a positive result. No unequivocal relationships could be demonstrated between the introduction of the partial open door system and the changes in the frequency of "special events".     

The cardiac endothelium: cardioactive mediators

Endothelial cells within the heart release a number of substances that modulate myocardial contractile function. These agents include nitric oxide, endothelin, prostanoids, adenylpurines, and other substances that have so far been characterized only in bioassay studies. A notable feature of many of these agents is that they influence contractile behavior predominantly by modifying cardiac myofilament properties rather than altering cytosolic Ca2+ transients. A consequence of this subcellular action is often a disproportionate effect on myocardial relaxation and diastolic tone. The paracrine modulation of cardiac myocyte function by endothelial cell factors is likely to be an important mechanism contributing to the overall regulation of cardiac contractile function, both physiologically and in pathological states.     

Identification and characterization of cytosolic sulfotransferases in normal human endometrium

Understanding the factors which alter estrogen metabolism and activity in endometrial tissue is important because unopposed estrogen stimulation is an important risk factor in the development of endometrial carcinoma. The cyclic progression of the endometrium through proliferative and secretory phases is normally under the control of the ovarian hormones beta-estradiol (E2) and progesterone. One mechanism by which progesterone inhibits the activity of E2 in secretory endometrium is by elevating the degree of E2 sulfation, thereby reducing its ability to bind to the estrogen receptor and elicit a cellular response. Our laboratories have investigated the cytosolic sulfotransferases (STs) found in biopsies of both proliferative and secretory endometrium obtained from five normal pre-menopausal women who were not taking any drugs or steroids. Two of the human cytosolic STs were detected in human endometrial tissues. The phenol-sulfating form of phenol ST (P-PST) was found at varying levels in cytosol from both proliferative and secretory endometrium in all of the women studied but with no consistent correlation to the phase of the menstrual cycle. In contrast, estrogen ST (EST) was not detected in the proliferative endometrial cytosol of any of the women studied but was consistently found in all of the secretory endometrial cytosols. The presence and levels of these STs was confirmed by ST activity studies, immunoblot analysis and Northern blot analysis. These results indicate that the expression of EST in human endometrial tissues varies with the phase of the menstrual cycle and is most likely regulated by progesterone secreted from the ovaries.     

On the nature of rat hepatic and mouse olfactory sulfotransferases

Seasonal differences in the particle size fractions and mass loadings of household dust deposited on indoor surfaces were examined in four New Jersey homes. Housedust was collected during a 30-day period on non-electrostatic polyethylene sample plates on which a glass slide had been placed. In each home two samples were collected at a height of 1.5 m and two were collected at a height of 0.3 m above the floor. Dust samples were obtained from each home during a summer and winter collection period. Particle size measurement was completed using an adaptation of a Meridian ACAS 570 Interactive Laser Cytometer. Results indicated that the dust mass deposited on household surfaces during the summer was greater than during the winter. The arithmetic mean mass deposition rate for all houses was 0.37 +/- 0.13 microgram/cm2/day during the summer and 0.22 +/- 0.13 microgram/cm2/day during the winter. The total number of particles deposited, however, was greater during the winter than during the summer. The increase in winter time particle number was caused by greater numbers of particles with an equivalent spherical diameter < 2.5 microns. The most probable source of these particles was winter time combustion emissions within the residences and the subsequent particle deposition on household surfaces. The greater mass loadings measured on the low sampling plates during the summer were associated with a greater number of particles with an equivalent spherical diameter > 5 microns. In the winter, however, the particle mass and number loadings were similar at both heights. These results suggested that ventilation of the house during the summer allowed resuspended particles to enter which led to the higher levels of settled dust. Measurement of contaminant levels in housedust for exposure estimation therefore, should account for the seasonal and height differences in dust mass, and collect representative fractions of housedust that are available for human contact. Furthermore, since over 99% of the particles on indoor surfaces were < 50 microns any indirect sampling technique for dermal exposure estimation should have collection efficiencies similar to the hand of particles < 50 microns.     

Molecular cloning, expression, and functional characterization of novel mouse sulfotransferases

STUDY OBJECTIVE: The present study was performed to determine the influence of a perioperative myocardial infarction on long-term mortality in patients who have undergone elective vascular surgery. STUDY DESIGN: This was a 4-year follow-up of patients who had undergone elective vascular procedures at a Veterans Affairs Medical Center. Between January 1989 and December 1990, 115 consecutive patients underwent surgery for either an expanding abdominal aortic aneurysm (AAA) (38%) or for pain in the lower extremities (62%). RESULTS: Vital status at 4 years postsurgery was determined for all patients. Thirty-day postoperative mortality was 3%, while estimates at 1, 2, 3, and 4 years were 19%, 26%, 35%, and 39%, respectively. Of the 45 patients who died within 4 years following surgery, the major causes of death were cardiac (40%), cancer (18%), cerebrovascular (13%), and peripheral vascular disease (11%). Univariate predictors of 1-year mortality on preoperative evaluation were an abnormal ECG, moderate or greater sized exercise thallium defect and left ventricular ejection fraction < or =40%, and a perioperative myocardial infarction. Univariate predictors of 4-year mortality were non-AAA surgery and diabetes mellitus. Perioperative myocardial infarction was a marginally significant independent predictor of 1-year mortality (p=0.06), while the need for non-AAA surgery was a strong independent predictor at 4 years. CONCLUSIONS: Cardiac mortality is the major cause of late death among patients undergoing elective vascular surgery. Although preoperative indicators of symptomatic coronary artery disease and nonfatal perioperative myocardial infarction identified those individuals at increased mortality in the first postoperative year, the extent of vascular disease at presentation may be a more important determinant of long-term survival. A randomized trial in such patients is needed to assess the best strategy for treating patients with coexistent coronary artery and vascular diseases.     

Conscientiousness and longevity: An examination of possible mediators.

Objective: Conscientious individuals tend to experience a number of health benefits, not the least of which being greater longevity. However, it remains an open question as to why this link with longevity occurs. The current study tested two possible mediators (physical health and cognitive functioning) of the link between conscientiousness and longevity. Method: We tested these mediators using a 10-year longitudinal sample (N = 512), a subset of the long-running Health and Retirement Study of aging adults. Measures included an adjective-rating measure of conscientiousness, self-reported health conditions, and three measures of cognitive functioning (word recall, delayed recall, and vocabulary) included in the 1996 wave of the HRS study. Results: Our results found that conscientiousness significantly predicted greater longevity, even in a model including the two proposed mediator variables, gender, age, and years of education. Moreover, cognitive functioning appears to partially mediate this relationship. Conclusions: This study replicates previous research showing that conscientious individuals tend to lead longer lives, and provides further insight into why this effect occurs. In addition, it underscores the importance of measurement considerations. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Referential communication: Some factors influencing communication efficiency.

Examined differences in message variables and listener response measures as a function of pleasant vs unpleasant content in a referential communication task. The 5 basic components of the referential communication model are speaker, listener, task, message, and listener response. 192 female undergraduates formed 96 pairs (86 pairs were already acquainted), and Ss participated in written and communication sessions. The "speaker" described pleasant or unpleasant pictures that the "listener" identified from among 5 similar alternatives. Measures of message style, listener responses, and speaker and listener traits yielded 40 variables whose factor analysis supported the model. Pleasant content was associated with greater diversity, shorter words, less verbal output, and longer pauses. For pleasant tasks, listener accuracy was related to a message style that included high productivity, more precise words, numerous speech errors, and few pauses; unpleasant task accuracy was related to few errors and pauses. The association of listener traits with message indices suggests that speakers adapt their message to a particular listener. (French abstract) (38 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Self-efficacy and perceived control: Cognitive mediators of pain tolerance.

The cold-pressor task was used with 102 female undergraduates in 2 experiments to determine (a) whether self-efficacy has validity as a true causal determinant of behavior change or is a correlate of change that has already occurred and (b) how perceptions of control and self-efficacy interact to determine choice behavior, persistence, and the impact of an aversive stimulus. Results of Experiment 1 indicate that self-efficacy expectations affected performance beyond what would have been expected from past performance alone. Changes in self-efficacy expectations predicted changes in cold-pressor tolerance. These findings suggest that self-efficacy expectations can be causal determinants of behavior in an aversive situation. Results of Experiment 2 indicate that self-efficacy was separable from control and that performance was best if both high levels of perceived control and self-efficacy were present. These findings support the notion that self-efficacy expectations can mediate the desirability of providing control, in that those who benefit most from control are those who are most confident they can exercise it. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Enhanced Dissolution of Trichloroethene: Effect of Carbohydrate Addition and Fermentation Processes

Remediation of source areas is challenging because lingering contaminants are often present as nonaqueous phase liquid (NAPL) and sorbed mass, and therefore difficult to remove via biodegradation or other commonly used remedial methods. Experimental results indicate that enhanced dissolution of a model NAPL, trichloroethene (TCE), can occur through the addition and/or subsequent fermentation of a dilute molasses solution. Enhanced mass transfer occurs by two mechanisms, depending upon whether the molasses solution is fresh or has fermented. The addition of fresh molasses worked to increase TCE solubility (>200%), thereby increasing mass transfer from the NAPL phase. Mixing TCE NAPL with a fermented molasses solution, however, increased TCE mass flux via the formation of a NAPL/aqueous phase emulsion. In addition, fermented liquid may have also decreased the soil partitioning coefficient (Kd) of TCE, indicating that enhanced transfer of sorbed mass to the aqueous phase could also occur in the presence of fermented molasses. These results provide guidance on how remedial systems may be optimized to increase NAPL and sorbed-mass dissolution and are therefore important, particularly when bioremediation is used to polish residual source zones.