Correlation between killing activity towards the murine L929 cell line and expression of membrane-associated lymphotoxin-related molecule of human lymphokine-activated killer cells

Human lymphokine-activated killer (LAK) cells expressed a membrane-associated lymphotoxin-related molecule (mLT) which was detected by flow cytometric analysis with anti-lymphotoxin antibody. Upon removal of exogenous interleukin-2 from LAK cell culture medium and another 24 h cultivation, the expression of mLT was decreased. Corresponding to the decrease of mLT expression, the killing activity of LAK cells towards L929 cells was remarkably reduced and killing of MIA PaCa-2 and U937 cells was moderately reduced, whereas killing of Daudi and K562 cells was fully restored. The supernatant of mLT-expressing LAK cells had no cytotoxic activity towards L929 cells in the absence of actinomycin D. Moreover, not only the killing of L929 cells but also that of human tumor cell lines (MIA PaCa-2, U937) by mLT-expressing LAK cells was partially inhibited in the presence of anti-lymphotoxin antibody. These results suggest an involvement of mLT in the killing of some tumor target cells by LAK cells.

[Effect of indomethacin on delayed neuronal death of hippocampal CA1 sector in gerbil under different levels of controlled cranial temperatures]

Effect of indomethacin on post-ischemic changes of CA1 neurons was studied in the hippocampus of the Mongolian gerbil. The gerbil was employed because due to poor development of posterior communicating artery ischemia could be easily induced in the forebrain simply by occluding bilateral common carotid arteries. Indomethacin (5 mg/kg, i.p.) was administered 30 min before the occlusion. The occlusion lasted for 5 divided into four groups. In one group, the temperature was not controlled. In the remaining three groups, the temperature was kept at 35.5 degrees C, 37.5 degrees C, and 39.5 degrees C, respectively. Seven days after the occlusion neuronal density was assessed on histological sections stained with hematoxylin eosin. It was found that in all groups indomethacin was effective in preventing delayed neuronal death regardless of the difference in the cranial temperature. However, delayed neuronal death was the least in the lowest temperature group. The drug also prevented the post-ischemic hyperthermia observed in the temperature non-controlled group. These results indicate that indomethacin has its own pharmacological action to prevent delayed neuronal death.

Therapeutic potential of modulating potassium currents in the diseased myocardium

Myocardial disease states are characterized by multiple electrophysiologic abnormalities, including alterations in potassium channel activities. During acute myocardial ischemia, activation of ATP-regulated K+ current (IK(ATP)) results in shortening of action potential duration and elevation of extracellular K+ concentration. In hypertrophied myocardium, increases in inward rectifier K+ current (IK1) and decreases in delayed rectifier K+ current (IK) are observed. Alterations in K+ channel activity in myocardial disease states suggest the potential to therapeutically modify cardiac rhythm and function with K+ channel modulators. Class III anti-arrhythmic agents, which prolong myocardial refractoriness predominantly via a blockade of IK, have demonstrated efficacy in suppressing reentrant atrial and ventricular arrhythmias in animal models as well as promising efficacy in initial clinical studies. Potassium channel openers (PCOs), which activate cardiac IK(ATP), have demonstrated both antiarrhythmic and proarrhythmic activities in various experimental settings, and also are being investigated as potential cardioprotective agents. Sulfonylureas, which block cardiac IK(ATP), also have been investigated as potential antiarrhythmic agents with equivocal results, and have displayed a propensity to exacerbate ischemic myocardial dysfunction in experimental studies. A more comprehensive understanding of K+ channel activity in various myocardial disease states, including concomitant disorders such as myocardial ischemia and hypertrophy, will facilitate the development of more useful potassium channel modulators, as well as a clearer recognition of the undesirable effects of such agents.

Diurnal blood pressure variations and silent cerebrovascular damage in elderly patients with hypertension

OBJECTIVE

To examine the effect of diurnal blood pressure changes upon cerebrovascular damage in elderly patients with hypertension.

DESIGN

Fifty-four asymptomatic hypertensive and 34 normotensive elderly subjects underwent both 24-h non-invasive ambulatory blood pressure monitoring and brain magnetic resonance imaging. METHODS. Diurnal variation was defined as a difference of greater than or equal to 10 mmHg between mean awake and asleep systolic blood pressure. Hypertensives were thus classified as dippers or non-dippers. Low intense foci (lacunae) and advanced periventricular hyperintensity were identified as silent cerebrovascular damage.

RESULTS

In the hypertensive group, lacunae were correlated more closely with mean asleep systolic blood pressure than with mean awake systolic blood pressure. Age, awake blood pressure, predicted whole blood viscosity, lipid profiles or quantity of sleep did not differ between the hypertensive dippers or non-dippers. The non-dippers, however, showed significantly higher grades of cerebrovascular damage as well as cardiac hypertrophy by electrocardiography than the dippers, whose results were similar to those of normotensives in this regard.

CONCLUSIONS

An absent or lower nocturnal blood pressure fall in elderly hypertensives is associated with silent cerebrovascular damage. In contrast, the presence of a nocturnal fall could prevent the development of hypertensive vascular damage.

The natural history of acute disseminated leukoencephalitis. A serial magnetic resonance imaging study

The natural history of acute disseminated (leuko)encephalitis (ADE) in a 3-year-old girl who did not receive steroid therapy is reported. Serial MR studies disclosed: 1) white matter lesions resolved spontaneously, though very slowly, 2) active disease persisted for around three months and coincided with the onset of new subcortical lesions. These subcortical lesions were associated with hyperactivity, suggesting a possible etiologic correlation.

Clinical application of the polymerase chain reaction for a rapid diagnosis of Mycobacterium tuberculosis infection

A gene amplification method of Mycobacterium tuberculosis DNA by the polymerase chain reaction (PCR) has been devised. A primer pair used in this study is 5'GTTGCCGTGGCGG TATCGG3' and 5'GCGACATTACGGGGCAGGTGG3', which brackets a 152-base region encoding the 65KD antigen, and a specific probe is 5'TTTGGGGTCATCTTTGGAGCG3'. The procedure could be completed within 2 days. The specificity and the sensitivity of the PCR for M. tuberculosis complex in identifying M. tuberculosis complex did not conflict with the conventional methods at all. Using this method, we could diagnose three cases of the disease, which had been very difficult to diagnose by the conventional methods, by detecting the DNA from the blood, liver biopsy specimen, lung aspirate, and pleural effusion.

Erythema annulare centrifugum associated with gold sodium thiomalate therapy

Two women with rheumatoid arthritis developed erythema annulare centrifugum while receiving gold thiomalate therapy. Both patients had similar clinical and histologic findings. Results of a lymphocyte stimulation test were positive in one patient but not in the other.

Verapamil diminishes action potential changes during metabolic inhibition by blocking ATP-regulated potassium currents

Verapamil has beneficial effects on ischemic myocardium, including reduction in electrophysiological derangements, prevention of intracellular K+ loss, and preservation of high-energy phosphates, but the mechanisms underlying these actions are not clear. Recent studies have demonstrated a role of ATP-regulated K+ (KATP) current in action potential shortening and K+ loss during ischemia and metabolic inhibition. Therefore, we studied the effects of verapamil on KATP current in feline ventricular myocytes to test the hypothesis that the drug prevents ischemic electrophysiological disturbances by affecting the KATP channel. Membrane potentials and currents were recorded using standard patch-clamp techniques. During 15-minute superfusion with 1 mM CN-, action potential duration measured at 90% repolarization was reduced from 259 +/- 12 to 98 +/- 15 msec (62% reduction) in the absence of verapamil and from 266 +/- 11 to 183 +/- 16 msec (31% reduction) in the presence of 2 microM verapamil (p less than 0.01). In inside-out membrane patches, the KATP current, activated in the absence of ATP, was significantly suppressed by intracellular application of 2 microM verapamil, but the single-channel conductance was not changed. Verapamil did not change the mean open and closed times of the channel within bursts (e.g., the mean open time was 1.92 +/- 0.18 and 1.82 +/- 0.21 msec in the absence and presence of 2 microM verapamil, respectively), but it shortened the mean lifetime of bursts from 41.1 +/- 3.5 to 24.9 +/- 2.8 msec (p less than 0.01) and prolonged the closed time between bursts from 39.4 +/- 4.6 to 78.5 +/- 5.1 msec (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

[Silent lacunes in the elderly Parkinson's disease correlated with ambulatory blood pressure]

Lacunes on brain MRI, causal blood pressure, 24-hour ambulatory blood pressure and common carotid blood flow measured by the doppler method were studied in 31 elderly patients with Parkinson's disease (mean age 67.5 +/- 7.3 years). Nineteen patients with Parkinson's disease (61%) had at least one lacune. Patients with lacunes (P(+)) were significantly higher in age than patients without lacune (P(-)). The difference of casual blood pressure between patients in the two groups was not significant. On the other hand, the average of ambulatory blood pressure measurements during a 24-hour period was significantly higher in the P(+) group than in the P(-) group. The average of carotid blood flow was also significantly lower in the P(+) group than in the P(-) group, however, after adjustment for age, the difference between them became insignificant. In conclusion, the incidence of silent lacunes on brain MRI was fairly common in elderly patients with Parkinson's disease. A high average 24-hour ambulatory blood pressure was suggested to be one of the risk factors of lacunar stroke in elderly cases of Parkinson's disease. The concept of "combine type" in Parkinsonism was supposed to be suitable as well as in senile dementia of Alzheimer type.

[Amino acids as a modulator of hormone secretion]

Amino acids stimulate or inhibit the releases of some pituitary, pancreatic and gastrointestinal hormones by oral or intravenous administration. These effects are clinically used as amino acid loading tests to examine the reserve of hormones, including growth hormone, insulin, glucagon, somatostatin, etc., and of use for the diagnosis of endocrine and gastrointestinal diseases. The mechanism of pituitary hormone release, induced by amino acids, has been explained by their actions on peptidergic and monoaminergic systems in the brain but it is still not known as for pancreatic and gastrointestinal hormones.

A randomized trial of reduced doses of azidothymidine in Japanese patients with human immunodeficiency virus type 1 infection

Adverse reactions to the standard dose (1,200 mg/day-1,500 mg/day) of azidothymidine (AZT) are serious. An in vitro pharmacokinetic study of intracellular AZT-5'-triphosphate suggested the feasibility of a clinical trial with reduced doses of AZT. A randomized trial with reduced doses of AZT (group A; 400 mg/day, n = 15, group B; 800 mg/day, n = 13), was conducted enrolling 28 patients with human immunodeficiency virus infection. The effective rate of AZT on CD4+ lymphocyte counts was similar for both groups, but the duration of the effect of AZT was significantly longer in group A (p less than 0.05). In group B, adverse reactions were more frequently observed (p less than 0.01), and AZT was withdrawn or the dose was reduced more frequently (p less than 0.05). These results suggest that AZT at a dose of 400 mg/day is less toxic, and is more beneficial for long-term treatment.

Wide distribution of the skin type I collagen alpha 3 chain in bony fish

1. Skin Type I collagens were isolated from the five species of non-teleostean fish and examined with respect to their subunit chains. 2. In addition to alpha 1(I) and alpha 2(I) chains, a fish-specific chain, alpha 3(I), was previously found only in teleostean fish. The present study, however, has revealed the occurrence of alpha 3(I) in a chondrostean fish, white sturgeon. 3. The alpha 3(I) gene appears to have arisen from a duplication of the alpha 1(I) gene near the time of the adaptive radiation of bony fish.

Localization and elasticity of connectin (titin) filaments in skinned frog muscle fibres subjected to partial depolymerization of thick filaments

The localization and elasticity of connectin (titin) filaments in skinned fibres of frog skeletal muscle were examined for changes in the localization of connectin and in resting tension during partial depolymerization of thick filaments with a relaxing solution containing increased KCl concentrations. Immunoelectron microscopic studies revealed that deposites of antibodies against connectin at a sarcomere length of 3.0 microns remained at about 0.8 microns from the M-line, until the thick filament was depolymerized to the length of approximately 0.4 microns. On further depolymerization, the bound antibodies were found to move towards the Z-line and, on complete depolymerization, were observed to be within 0.3 microns of the Z-line; a marked decrease in resting tension accompanied this further depolymerization. These results suggest that connectin filament starts from the Z-line, extends to the M-line, and contributes to resting tension. After partial depolymerization of thick filaments, the distances between the anti-connectin deposits and the Z-line and between anti-connectin deposits and the M-line increased with sarcomere length, suggesting that connectin filaments are elastic along their entire length.

Flow cytometric evaluation of phagocytosis by peripheral blood polymorphonuclear leucocytes in human periodontal diseases

The complement-dependent phagocytic functions of polymorphonuclear leucocytes (PMNL) in peripheral blood from 15 patients with localized juvenile periodontitis (LJP), 13 with generalized juvenile periodontitis (GJP) and 52 with adult periodontitis (AP), and from 30 normal subjects as controls were measured by flow cytometry. Heparinized blood was collected and incubated with fluorescent microspheres, and erythrocytes were removed. By means of single-cell analysis the percentage of phagocytosing cells (% phagocytosis) and the mean number of microspheres phagocytosed by one PMNL (degree of phagocytosis; d-phagocytosis) were measured. Some but not all patients with LJP (53%) and GJP (46%) showed consistently low % phagocytosis and d-phagocytosis. On the other hand, only 6% of AP patients and no healthy subjects showed a reduction of PMNL phagocytosis. Phagocytosis was unchanged after initial periodontal treatment in all subjects, suggesting the depression of PMNL phagocytosis may not be a transient phenomenon associated with periodontal status. Furthermore, PMNLs from the LJP patients that showed depressed phagocytic function exhibited depressed phagocytic responses with either autologous or normal plasma, while control PMNLs with either normal or the patients' plasma showed normal responses. These results suggested that the depressed phagocytic responses in LJP patients could be due to cell-associated defect(s) on the PMNL.

Effect of cavity-modulating mutations on the stability of Escherichia coli ribonuclease HI

The size of the cavity around Ser68 of Escherichia coli ribonuclease HI was modulated by amino acid substitutions to examine the effects on the stability of the enzyme. Five mutant proteins, Ser68----Gly, Ser68----Ala, Ser68----Thr, Ser68----Val and Ser68----Leu, were constructed. Each of the mutant proteins exhibited at least 40% of the enzyme activity of the wild-type protein. The stabilities of the mutant proteins were determined from urea-denaturation and thermal-denaturation curves. Among the five mutations, only the Ser----Val mutation resulted in an increase in the stability of the enzyme. The melting temperature, tm, at pH 3.0 of the mutant protein Ser68----Val was increased by 1.9 degrees C. Its free-energy change of unfolding in the absence of urea, delta G(H2O), and the midpoint of the denaturation curve, [D]1/2, were also increased by 5.4 kJ/mol and 0.18 M, respectively. The increase in the stability of the enzyme is probably due to the filling of the cavity space around Ser68 by valine. However, the mutation of Ser68 to glycine or leucine residues resulted in a considerable decrease in stability. In these cases, some conformational changes occur, as suggested by the CD and 1H-NMR spectra of these mutant proteins.

Early afterdepolarizations and triggered activity induced by cocaine. A possible mechanism of cocaine arrhythmogenesis

BACKGROUND

Cocaine may produce life-threatening cardiac arrhythmias, but it is not clear whether this is an indirect effect of coronary vasoconstriction and ischemia or a direct myocardial effect of the substance. Except for its effects on the Na+ current as a local anesthetic, little is known about the direct electrophysiological actions on cardiac cells. Therefore, we studied the effects of cocaine on action potentials and membrane currents in isolated feline ventricular myocytes to test the hypothesis that cocaine-induced arrhythmogenesis may be based on cellular and ionic mechanisms.

METHODS AND RESULTS

Action potentials and membrane currents were recorded using the patch clamp technique. Single cells were isolated from feline left ventricles by enzymatic digestion. Exposure to cocaine (10 or 50 microM) depressed the plateau phase of the action potential and prolonged action potential duration. Action potential duration measured at 90% repolarization (APD90) was increased from 280 +/- 12 msec to 325 +/- 17 msec (p less than 0.01) by 5-minute exposure to 10 mumol cocaine, when the cells were stimulated at 1 Hz. During exposure to 50 mumol cocaine, APD90 was markedly increased from 298 +/- 13 msec to 437 +/- 35 msec (p less than 0.01) in seven of 16 cells, and early afterdepolarizations (EADs) developed in these cells. The take-off potential and the amplitude of EADs were -28.3 +/- 2.3 mV and 16.8 +/- 1.2 mV, respectively. Triggered activity arising from EADs was induced in four of the seven cells. Addition of 1 nmol isoproterenol augmented EADs and induced sustained triggered activity, whereas they were suppressed by exposure to 2 microM verapamil. Whole-cell voltage clamp experiments revealed that cocaine (50 microM) reduced the peak L-type Ca2+ current from 1.03 +/- 0.13 nA to 0.79 +/- 0.11 nA (23% reduction, p less than 0.05). Cocaine also reduced the peak delayed rectifier K+ current from 362 +/- 51 pA to 113 +/- 32 pA (69% reduction, p less than 0.01). However, cocaine did not affect activation and inactivation kinetics of these channels. Cocaine had no effect on the inward rectifier K+ current.

CONCLUSIONS

We conclude that cocaine can prolong action potential duration and induce EADs and triggered activity by blocking the delayed rectifier K+ current, and that cocaine-induced abnormalities of repolarization, modulated by its inhibitory effects on catecholamine reuptake, may play a role in the potential of cocaine for induction of acute fatal arrhythmias.

Studies of autonomic properties after healing of experimental myocardial infarction

The link between healed myocardial infarction, sympathetic activation, and sudden death has led to a series of studies in a specifically designed animal model. Transmural and non-transmural infarcts were produced in cat hearts and the studies were performed few months later. Using direct stimulation of cardiac sympathetic nerves and measuring local refractory periods it was found that there was an exaggerated response in the border zone. Competitive binding studies revealed that there was a modest reduction in the number of beta-adrenergic receptors in tissue adjacent to the scar. In similar preparations the norepinephrine content, in hearts with healed transmural infarcts, was significantly reduced in areas adjacent to scars. In contrast, in hearts with non-transmural infarcts, the norepinephrine content was not different from normal controls. Phenylephrine and isoproterenol induced afterdepolarizations, blocked respectively by phentolamine and propranolol, in 34% of Purkinje fibers of the preparations with a healed infarct. Thus, afterdepolarizations and triggered activity may be mediated by both alpha- and beta-adrenergic activity in hearts with healed myocardial infarction. These data suggest the persistence, after healing of myocardial infarction, of regional abnormalities in autonomic function at a myocardial level. These regional disparities are likely to influence propensity to arrhythmias.

[Anesthetic experience of two patients with holoprosencephaly]

We experienced anesthetic management of two 6-month-old female patients with holoprosencephaly (HP). HP is characterized by hypoplasia of prosencephalon, facial anomalies (hypotelorism, flat nose, and/or small prolabium), abnormality of autonomic nervous system functions (hypernatremia and/or poikilothermia), and clonic convulsion. First case was a lobar type and the second case was an alobar type according to DeMyer's classification. In both cases repair of bilateral cleft lip was performed. Anesthesia was slowly induced with N2O-O2-halothane and maintained with fentanyl in N2O-O2. Body temperature (BT) was adjusted with a warming blanket while monitoring rectal temperature. In the first case clonic convulsion and bradycardias occurred during the postoperative period, which were treated with IV diazepam and isoproterenol. In the second case BT rose to 39 degrees C during postoperative period; 2 episodes of convulsions were observed; and airway obstruction occurred. They were treated accordingly. The most important points which should be kept in mind in the management of HP patients are the prevention of convulsion, adjustment of BT, maintenance of normal pulse rate and keeping a patient airway.

Studies of membrane-associated and soluble (secreted) lymphotoxin in human lymphokine-activated T-killer cells in vitro

The expression, release, and cytolytic activity of membrane-associated lymphotoxin was examined in cultures of phytohemagglutinin-P (PHA-P) and interleukin 2 (IL-2)-stimulated human T-lymphokine-activated killer (T-LAK) cells in vitro. Lymphotoxin (LT/TNF-beta) was identified on the membrane of T-LAK cells using flow cytometry. The membrane form of LT (mLT) is detected not only on T-LAK cells but also on LT-secreting human B-cell lymphoid cell lines, RPMI 1788 and Raji, but not on U937 or K562 cells. Maximum expression of mLT on T-LAK cells and the secretion of LT into the supernatant depended on the concentration of IL-2. Expression of mLT on T-LAK cells was reduced by stimulation with PHA-P; however, supernatant LT levels greatly increased. Both expression of mLT and release of soluble LT was reduced after incubation of T-LAK cells with actinomycin D (ActD) or cycloheximide (CHx). Paraformaldehyde-fixed T-LAK cells caused cytolysis of WEHI 164 cells in vitro, which was blocked by anti-LT but not anti-TNF antibody. These data support the concept that mLT may be an intermediate form to secreted LT, and that the mLT form is cytolytically active.

[Pneumonia caused by Moraxella subgenus Moraxella sp]

Moraxella subgenus Moraxella sp. was isolated in pure culture from the sputum of a 43-year-old male with pneumonia and congestive heart failure due to idiopathic dilated cardiomyopathy. In this case, we concluded that the patient's bacterial pneumonia was caused by M. (M.) sp. based on a Gram stain of the sputum smear and bacterial findings, increased WBC count, and elevated CRP. A chest X-ray revealed right middle, and left upper and middle lobe infiltrates. This Moraxella strain produced a BRO-type beta-lactamase, a carbenicillinase-type enzyme.

Interaction of rat lecithin-cholesterol acyltransferase with rat apolipoprotein A-I and with lecithin-cholesterol vesicles

The interaction of rat plasma lecithin-cholesterol acyltransferase with lecithin-cholesterol vesicles and with rat apo-A-I was studied in comparison with that of human plasma lecithin-cholesterol acyltransferase to clarify the reaction mechanism of rat plasma lecithin-cholesterol acyltransferase. The interaction of both human and rat lecithin-cholesterol acyltransferase with lecithin-cholesterol vesicles was investigated by gel permeation chromatography on Superose 12. Both enzymes had almost the same affinity to the vesicles. The affinity of rat enzyme to rat apo-A-I was stronger than that of human enzyme to human apo-A-I when estimated on the apo-A-I-Sepharose 4B column. When human apo-A-I was added to the human enzyme/vesicle mixture which contained the enzyme-vesicle complex, the enzyme was effectively dissociated from the complex. But when rat apo-A-I was added to the rat enzyme/vesicle mixture, apo-A-I-enzyme-vesicle complex was still recognized by its elution pattern on gel permeation chromatography. This suggests that the mixture of rat enzyme, rat apo-A-I, and vesicles, which are the major components in the rat lecithin-cholesterol acyltransferase reaction, forms a stronger complex than do the components of the human reaction.

N-Methyl-N′-nitro-N-nitrosoguanidine-induced light emission in Chinese hamster cell cultures: correlation with enhancement of chromosomal aberrations

N-Methyl-N'-nitro-N-nitrosoguanidine (MNNG) was found to induce an ultraweak photon emission in cultures of Chinese hamster fibroblasts (CHL). Measurements suggest that the light emission is due to a reaction between MNNG and cellular metabolites. The light emission depended on the concentration of MNNG and was oxygen-dependent, disappearing in a nitrogen atmosphere. Superoxide dismutase (SOD) or sodium azide decreased the emission intensity. The production of chromosomal aberrations in CHL by MNNG was correlated with the light emission intensity and was inhibited in the presence of SOD.

High blood pressure in transgenic mice carrying the rat angiotensinogen gene

Transgenic mice were generated by injecting the entire rat angiotensinogen gene into the germline of NMRI mice. The resulting transgenic animals were characterized with respect to hemodynamics, parameters of the renin angiotension system, and expression of the transgene. The transgenic line TGM(rAOGEN)123 developed hypertension with a mean arterial blood pressure of 158 mmHg in males and 132 mmHg in females. In contrast, the transgenic line TGM(rAOGEN)92 was not hypertensive. Rat angiotensinogen was detectable only in plasma of animals of line 123. Total plasma angiotensinogen and plasma angiotensin II concentrations were about three times as high as those of negative control mice. In TGM(rAOGEN)123 the transgene was highly expressed in liver and brain. Transcripts were also detected in heart, kidney and testis. In TGM(rAOGEN)92 the brain was the main expressing organ. In situ hybridization revealed an mRNA distribution in the brain of TGM(rAOGEN)123 similar to the one in rat. In TGM(rAOGEN)92 the expression pattern in the brain was aberrant. These data indicate that overexpression of the angiotensinogen gene in liver and brain leads to the development of hypertension in transgenic mice. The TGM(rAOGEN)123 constitutes a high angiotensin II type of hypertension and may provide a new experimental animal model to study the kinetics and function of the renin angiotensin system.

Baculovirus-mediated expression and functional characterization of human NADPH-P450 oxidoreductase

Human NADPH-P450 oxidoreductase (OR) is an intrinsically membrane-bound flavoprotein that serves to transfer electrons from NADPH to cytochrome P450. OR is also involved in the metabolic activation of chemotherapeutic alkylating agents. The human OR cDNA was engineered into baculovirus and the recombinant virus was used to infect Spodoptera frugiperda (Sf9) cells. Approximately 3.3% of total protein of infected cells was human OR. The enzyme was purified by ion exchange and affinity chromatography to a specific activity of 20 units/mg protein. Baculovirus-expressed OR displayed an absolute spectrum typical of the protein purified from tissue sources. The purified enzyme was able to support P450 activity in a reconstituted lipid vesicle system where maximal P450 activity was achieved at an OR/P450 ratio of 2. When recombinant OR and P450 DNA-containing baculoviruses were used to coinfect Sf9 cells, the OR/P450 ratio needed to achieve half maximal P450 catalytic activity was less than 0.5. These studies demonstrate the utility of baculovirus to analyze the functional and structural relationship of OR and P450.