Dendritic cells phenotype fitting under hypoxia or lipopolysaccharide; adenosine 5'-triphosphate-binding cassette transporters far beyond an efflux pump

This study examines adenosine 5'-triphosphate-binding cassette (ABC) transporters as a potential therapeutic target in dendritic cell (DC) modulation under hypoxia and lipopolysaccharide (LPS). Functional capacity of dendritic cells (DCs) (mixed lymphocyte reaction: MLR) and maturation of iDCs were evaluated in the presence or absence of specific ABC-transporter inhibitors. Monocyte-derived DCs were cultured in the presence of interleukin (IL)-4/granulocyte-macrophage colony-stimulating factor (GM-CSF). Their maturation under hypoxia or LPS conditions was evaluated by assessing the expression of maturation phenotypes using flow cytometry. The effect of ABC transporters on DC maturation was determined using specific inhibitors for multi-drug resistance (MDR1) and multi-drug resistance proteins (MRPs). Depending on their maturation status to elicit T cell alloresponses, the functional capacity of DCs was studied by MLR. Mature DCs showed higher P-glycoprotein (Pgp) expression with confocal microscopy. Up-regulation of maturation markers was observed in hypoxia and LPS-DC, defining two different DC subpopulation profiles, plasmacytoid versus conventional-like, respectively, and different cytokine release T helper type 2 (Th2) versus Th1, depending on the stimuli. Furthermore, hypoxia-DCs induced more B lymphocyte proliferation than control-iDC (56% versus 9%), while LPS-DCs induced more CD8-lymphocyte proliferation (67% versus 16%). ABC transporter-inhibitors strongly abrogated DC maturation [half maximal inhibitory concentration (IC50 ): P-glycoprotein inhibition using valspodar (PSC833) 5 μM, CAS 115104-28-4 (MK571) 50 μM and probenecid 2·5 μM], induced significantly less lymphocyte proliferation and reduced cytokine release compared with stimulated-DCs without inhibitors. We conclude that diverse stimuli, hypoxia or LPS induce different profiles in the maturation and functionality of DC. Pgp appears to play a role in these DC events. Thus, ABC-transporters emerge as potential targets in immunosuppressive therapies interfering with DCs maturation, thereby abrogating innate immune response when it is activated after ischaemia.

In vivo therapeutic efficacy of intra-renal CD40 silencing in a model of humoral acute rejection

The humoral branch of the immune response has an important role in acute and chronic allograft dysfunction. The CD40/CD40L costimulatory pathway is crucial in B- and T- alloresponse. Our group has developed a new small interfering RNA (siRNA) molecule against CD40 that effectively inhibits its expression. The aim of the present study was to prevent rejection in an acute vascular rejection model of kidney transplant by intra-graft gene silencing with anti-CD40 siRNA (siCD40), associated or not with sub-therapeutic rapamycin. Four groups were designed: unspecific siRNA as control; sub-therapeutic rapamycin; siCD40; and combination therapy. Long-surviving rats were found only in both siCD40-treated groups. The CD40 mRNA was overexpressed in control grafts but treatment with siCD40 decreased its expression. Recipient spleen CD40+ B-lymphocytes were reduced in both siCD40-treated groups. Moreover, CD40 silencing reduced donor-specific antibodies, graft complement deposition and immune-inflammatory mediators. The characteristic histological features of humoral rejection were not found in siCD40-treated grafts, which showed a more cellular histological pattern. Therefore, the intra-renal effective blockade of the CD40/CD40L signal reduces the graft inflammation as well as the incidence of humoral vascular acute rejection, finally changing the type of rejection from humoral to cellular.

Facilitation of sympathetic neurotransmission contributes to angiotensin regulation of body weight

Previous studies demonstrated that angiotensin II (AnglI) decreases body weight. The purpose of this study was to determine if AngII-reductions in body weight result from stimulation of sympathetic neurotransmission to interscapular brown adipose tissue (ISBAT). Following 7 days of chronic AngII infusion (350ng/kg/min), body weight decreased compared to controls. Using superfused ISBAT tissue slices preloaded with [3H]norepinephrine (NE), evoked [3H]overflow was greater in ISBAT slices from AngII-infused rats compared to controls. When AngII was included in the buffer, evoked [3H]overflow increased in a concentration-dependent manner in ISBAT slices from AngII-infused and control rats. The EC50 for the presynaptic effect of AngII was shifted to the left in ISBAT slices from AnglI-infused rats compared to controls; however, the maximal response to AngII was decreased. These results demonstrate that chronic AngII infusion enhances evoked release of NE from ISBAT sympathetic nerve terminals. Moreover, responsiveness to the presynaptic effect of AngII was altered following chronic AngII infusion. Increased sympathetic neurotransmission to ISBAT may contribute to AnglI-regulation of body weight.

Chronic angiotensin II infusion promotes atherogenesis in low density lipoprotein receptor -/- mice

The purpose of this study was to determine the effect of chronic angiotensin II (AngII) infusion on the severity of the atherogenic process in low density lipoprotein (LDL) receptor -/- mice with established lesions. LDL receptor -/- mice receiving a diet enriched in cholesterol, saturated fat, and cholate, were infused with saline or AngII (500 ng/kg/min) for 28 days. Systolic blood pressure increased in LDL receptor -/- mice following 7 days of AngII infusion, followed by a decline to baseline levels at 28 days, despite continued AngII infusion. Serum cholesterol was not influenced by AngII infusion in LDL receptor -/- mice; however, serum triglyceride concentrations were reduced significantly in LDL receptor -/- mice receiving AngII. The percent of intimal surface area covered by lesion was not increased in LDL receptor -/- mice receiving AngII; however, the content of cholesterol (esterified and unesterified) in lesions of the arch, thoracic, and abdominal aorta was significantly increased in those mice infused with AngII. Of note, in 20% of the LDL receptor -/- mice receiving AngII, large aneurysms were found in the abdominal aorta. Aneurysms appeared as breaks in the media and surrounding tissue of the vessel wall, encompassing amorphous and acellular masses with patches of thrombotic material. These results demonstrate that chronic infusion of AngII promotes the atherogenic processes in LDL receptor -/- mice, manifest as increases in lesion cholesterol content. Effects of AngII to promote atherogenesis were apparent at doses which did not markedly elevate systolic pressure. Importantly, infusion of AngII in LDL receptor -/- mice resulted in the development of aortic aneurysms.

Cold exposure regulates the renin-angiotensin system

The effect of cold exposure on the systemic renin-angiotensin system and on regulation of the angiotensin II (Ang II) receptor was examined in target organs for Ang II with cardiovascular relevance (left ventricle, kidney, lung) and metabolic relevance [interscapular brown adipose tissue (ISBAT), liver] to the functional consequences of cold exposure. In time course studies, the effects were examined of 4 hr or 1, 3 and 7 days of exposure to cold (4 degrees C) on plasma Ang II concentration and Ang II receptor binding characteristics in rat liver. Plasma Ang II concentration increased 10-fold after 4 hr of cold exposure, returned to control levels at days 1 and 3 of cold exposure, and was again increased (2-fold) at 7 days of cold exposure. The affinity of [125I]Sar1, Ile8-Ang II binding in membranes prepared from rat liver was not altered in cold-exposed rats. The density (Bmax) of binding sites in liver from cold-exposed rats was increased by day 1 and remained elevated over time-matched controls. Alterations in Ang II receptor density did not parallel plasma Ang II concentration in their time course, suggesting that cold-induced regulation of the Ang II receptor was not substrate mediated. In rats from the 7-day time point of cold exposure, Ang II receptor binding characteristics were examined in ISBAT and lung. Increases in Ang II receptor density were evident in ISBAT but not lung. To determine whether cold-induced increases in food intake contributed to elevations in plasma Ang II concentration and/or Ang II receptor density, a group of cold-exposed rats (7 days) were pair-fed to food intake levels of control rats. Pair-feeding of cold-exposed rats eliminated increases in plasma Ang II and norepinephrine concentration but did not prevent increases in Ang II receptor density in liver, ISBAT, kidney and left ventricle. Moreover, increases in Ang II receptor density were augmented in kidney and left ventricle from cold-exposed rats that were pair-fed. Results from these studies demonstrate that cold exposure resulted in an increase in plasma Ang II concentration through mechanisms related to increased food intake. Elevations in food intake in cold-exposed rats contributed to tissue-specific increases in Ang II receptor density. Moreover, cold-induced increases in Ang II receptor density were not related to plasma Ang II concentration.

Lung angiotensin receptor binding characteristics during the development of monocrotaline-induced pulmonary hypertension

Alterations in lung angiotensin converting enzyme (ACE) activity in monocrotaline (MCT)-induced pulmonary hypertension in rats have suggested a pathophysiologic role for angiotensin II (AII) in pulmonary vascular remodeling. ACE inhibitors suppress MCT-induced pulmonary hypertension; however, losartan, an angiotensin type 1 (AT1) receptor antagonist, was without impact. The present study examined AII receptor binding characteristics by radioligand binding during the development of MCT-induced pulmonary hypertension. Saturation binding isotherms for [125I]AII binding to membrane preparations from rat lung were performed at 4, 10, and 21 days following a single injection of MCT (60 mg/kg) or saline vehicle. Right ventricular hypertrophy, an index of pulmonary hypertension, increased at 21 days post-MCT. Saturation binding isotherms revealed a single, high affinity site for [125I]AII binding in lung membranes from MCT-treated and control rats, with no change in receptor affinity or density during the development of pulmonary hypertension. Competition displacement binding demonstrated that the AT1 receptor predominates in lung membranes from control rats, with no alterations in AII receptor subtype distribution following MCT treatment. In summary, these results suggest that the AT1 receptor subtype predominates in rat lung and does not contribute to the development of MCT-induced pulmonary hypertension.

Characterization of renin activity in brown adipose tissue

Angiotensin (ANG) II plays a vital role in blood pressure regulation and body fluid homeostasis. Although many peripheral tissues synthesize components of the renin-ANG system, very few synthesize all of the major components involved in the generation ofANG II. This study used interscapular brown adipose tissue (ISBAT) as a model system to evaluate the mechanism of ANG II generation in an extrarenal tissue. Polymerase chain reaction analysis of DNA from ISBAT demonstrated angiotensinogen gene expression; however, renin gene expression was not detected. Renin activity that was not completely derived from the residual blood pool was detected in ISBAT homogenates. Kinetic parameters for renin activity were similar in ISBAT and adrenal gland. Renin activity was partially inhibited by anti-renin antibody and completely inhibited by a specific rat renin inhibitor. Bilateral nephrectomy did not decrease renin activity in ISBAT. Western blot analysis, employing two species-specific renin antibodies, indicated the presence of a variety of isoforms of renin in ISBAT. The presence of renin activity in isolated brown adipocytes demonstrated that the enzyme is localized to adipocytes. The release of immunoreactive ANG peptides from ISBAT slices over 3 h indicated de novo synthesis. These studies support the existence of a local renin-ANG system in ISBAT and suggest involvement of renin in the formation of ANG II.

Fetal expression of the angiotensinogen gene

To determine whether the angiotensinogen (Ao) gene is expressed in multiple organs of the fetal rat and the changes associated with maturation, fetal (15-20 days of gestation), newborn (1-10 days old), and adult (90 days old) rat tissues were subjected to Northern analysis and hybridization with a full length Ao complementary DNA (cDNA). Whereas Ao messenger RNA (mRNA) was undetectable in fetal livers, Ao sequences were readily detectable 1 h after birth and reached a peak at 24 h of birth. Levels remained elevated at 5 and 10 days after birth to decrease slightly at 90 days of postnatal life. Poly A+ enriched liver RNA was subjected to a similar analysis demonstrating that fetal liver Ao mRNA levels were 50-fold less than the corresponding adult levels. In contrast to the finding in the fetal liver, Ao mRNA was found in fetal brown fat, brains, and kidneys. We conclude that 1) Expression of the Ao gene is developmentally regulated in a tissue-specific manner; 2) Unlike the adult animal, the liver may not be the primary source of Ao in the fetus; 3) Alternate sources of Ao synthesis include fetal brown fat, brain, and kidneys.

The functional coupling of neuronal and extraneuronal transport with intracellular monoamine oxidase

"Metabolizing systems" are responsible for the quick inactivation of noradrenaline released from adrenergic nerve endings: a transport mechanism (uptake1 or uptake2) is arranged in series with the intracellular enzyme (monoamine oxidase, MAO; catechol-O-methyltransferase, COMT). In the perfused rat heart, kenzyme-values were determined, i.e., those rate constants which characterize the unsaturated intracellular enzymes. In the extraneuronal metabolizing system kcomt greater than kmao for noradrenaline and adrenaline, while rather similar rate constants were obtained for dopamine. However, for the neuronal deaminating system, kmao is considerably higher than kmao for the extraneuronal system. Second, in the rat vas deferens it is demonstrated that inhibition of neuronal MAO leads to very pronounced rises of the axoplasmic noradrenaline concentration--and this is again a reflection of the high activity of neuronal MAO. In a third series of experiments (with the rat vas deferens), the evidence indicates that the neuronal inward transport of substrates of MAO fails to saturate the enzyme. This is the functional consequence of the high activity of neuronal MAO. It is concluded that a) neuronal MAO activity is very high, and--as a consequence--b) axoplasmic noradrenaline levels are very low.

The effect of partial inhibition of monoamine oxidase on the steady-state rate of deamination of 3H-catecholamines in two metabolizing systems

Two different "deaminating systems" were compared (i.e., intact tissues in which an uptake process translocates the 3H-catecholamine from the extracellular space to the intracellular MAO): the adrenergic nerve endings of the rat vas deferens exposed to 10 nmol/l 3H-(-)-noradrenaline, and the extraneuronal deaminating system of the rat heart perfused with 50 nmol/l 3H-(-)-adrenaline. Vesicular uptake and COMT were inhibited. In both systems MAO was partially inhibited by pargyline, and the steady-state tissue content of the 3H-catecholamine was determined as well as the steady-state rate of deamination. Rat vas deferens (preincubated with 10-40 nmol/l pargyline for 30 min). Inhibition of neuronal MAO caused not more than a moderate decrease of the steady-state rate of deamination of 3H-(-)-noradrenaline, but the steady-state tissue content was greatly increased. Determinations of the activity of MAO in homogenates of vasa deferentia showed that preincubation with 10 and 20 nmol/l pargyline inhibited the enzyme by 80 to 95%. Rat heart (of animals pretreated with 1 to 30 mg/kg pargyline). Inhibition of extraneuronal MAO caused a steep decline of the steady-state rate of deamination of 3H-(-)-adrenaline, but only a small rise in the steady-state tissue content. The decisive difference between the two deaminating systems lies in the fact that the ratio "kmao/kout" (where the two k-values characterize the activity of the unsaturated intracellular MAO and the ability of the 3H-catecholamine to leave the relevant cells, respectively) is much higher for the neuronal deaminating system exposed to 3H-(-)-noradrenaline than for the extraneuronal deaminating system exposed to 3H-(-)-adrenaline.(ABSTRACT TRUNCATED AT 250 WORDS)

Errors introduced by a tritium label in position 8 of catecholamines

The neuronal and extraneuronal disposition of 3H-7,8- and 3H-7-labelled (-)-noradrenaline and dopamine was compared in in vitro studies. In agreement with earlier studies, the present results show that the presence of a tritium label in position 8 (i.e., on the alpha-carbon) has two consequences: a) the rate of deamination declines and b) part of the deamination results in the formation of an unlabelled aldehyde plus tritium water; tritium water is recovered from the OMDA-fraction of the column chromatographic procedure of Graefe et al. (1973). Whenever the deamination of a 3H-catecholamine is reduced (by tritium in position 8), the intraneuronal 3H-catecholamine concentration is increased. This increase, in turn, partly masks the decline in neuronal deamination (rat vas deferens). Irrespective of whether one determines the spontaneous efflux, the release of 3H-noradrenaline by nerve stimulation or the release of 3H-(-)-noradrenaline by the reserpine-like compound Ro 4-1284, the presence of tritium in position 8 distorts the results (experiments with rat vasa deferentia and/or rabbit aorta). In the extraneuronal system of the rat heart, two intracellular enzymes inactivate 3H-(-)-noradrenaline and 3H-dopamine: catechol-O-methyl transferase (COMT) and monoamine oxidase (MAO). Any hindrance of deamination (by tritium in position 8, COMT intact) leads to a shift of the metabolism of the 3H-catecholamines from the exclusively deaminated to the exclusively O-methylated metabolites. No differences between 3H-7,8- and 3H-7-labelled catecholamines were found after inhibition of MAO and COMT (extraneuronal accumulation and rate constant for efflux from the extraneuronal compartment III of the rat heart).(ABSTRACT TRUNCATED AT 250 WORDS)

Furosemide-induced adverse reactions during hospitalization

The frequency and types of adverse reactions (ARs) occurring in hospitalized patients receiving furosemide were surveyed prospectively in a four-year study at the José Joaquin Aquirre Hospital in Santiago, Chile. A team of clinical pharmacists and clinical pharmacologists monitored 533 patients receiving furosemide and recorded patient characteristics, laboratory test results, drugs administered, and suspected ARs. Definite or probably furosemide-induced ARs were detected in 220 (39.8%) patients. No ARs were fatal but 7.6% of patients, all having cirrhosis of the liver, had severe ARs. Of the ARs recorded, 95.2% were dose-related. The most common ARs were electrolyte disturbances (23.5% of patients), extracellular volume depletion (9.0% of patients) and hepatic comma (3.6% of patients). Total and daily furosemide doses, lengthened hospitalization and hepatic disease were significantly associated with the frequency of ARs (p less than 0.001). The dosage of furosemide did not account for the increased frequency of ARs in patients with hepatic disease. The frequency of hypokalemia was not reduced significantly when furosemide was administered with potassium chloride or potassium-sparing diuretics (p less than 0.05). The frequency of severe furosemide-induced ARs is low, but ARs are more common in patients with cirrhosis of the liver. These patients should be closely monitored for furosemide-induced ARs.