Acute stressor exposure facilitates innate immunity more in physically active than in sedentary rats

Most previous stress-immune research focused on the immunosuppressive effects of stress on acquired immunity. More recently, it has become clear that acute stressor exposure can potentiate innate, as well as suppress acquired, immunity. For example, acute stress improves recovery from bacterial inflammation, a classic in vivo measure of innate immunity. The previous work was done in sedentary organisms. Physical activity status can modulate the impact of stress on immune function. The following studies tested the hypothesis that the effect of stress on inflammation after subcutaneous challenge with bacteria (Escherichia coli) is facilitated by physical activity. The results were that sedentary, stressed rats resolved their inflammation 1-2 days faster and have increased circulating neutrophils compared with their nonstressed, sedentary counterparts. In contrast, physically active, stressed rats resolve their inflammation 3-4 days faster and have increased circulating and inflammatory site neutrophils compared with their nonstressed counterparts. Importantly, the beneficial impact of stress on inflammation recovery and neutrophil migration was greater in the physically active, than sedentary, stressed rats. Thus physical activity status facilitates the positive effect of acute stress on innate immunity.     

Habitual physical activity facilitates stress-induced HSP72 induction in brain,peripheral, and immune tissues

The mechanism(s) for how physically active organisms are resistant to many damaging effects of acute stressor exposure is unknown. Cellular induction of heat-shock proteins (e.g., HSP72) is one successful strategy used by the cell to survive the damaging effects of stress. It is possible, therefore, that the stress-buffering effect of physical activity may be due to an improved HSP72 response to stress. Thus the purpose of the current study was to determine whether prior voluntary freewheel running facilitates the stress-induced induction of HSP72 in central (brain), peripheral, and immune tissues. Adult male Fischer 344 rats were housed with either a mobile running wheel (Active) or a locked, immobile wheel [sedentary (Sed)] for 8 wk before stressor exposure. Rats were exposed to either inescapable tail-shock stress (IS; 100 1.6-mA tail shocks, 5-s duration, 60-s intertrial interval), exhaustive exercise stress (EXS; treadmill running to exhaustion), or no stress (controls). Blood, brain, and peripheral tissues were collected 2 h after stressor termination. The kinetics of HSP72 induction after IS was determined in cultured mesenteric lymph node cells. Activation of the stress response was verified by measuring serum corticosterone (RIA). Tissue and cellular HSP72 content were measured using HSP72 ELISA in cell lysates. Both Active and Sed rats had elevated levels of serum corticosterone after stress. In contrast, Active but not Sed rats exposed to IS and/or EXS had elevated HSP72 in dorsal vagal complex, frontal cortex, hippocampus, pituitary, adrenal, liver, spleen, mesenteric lymph nodes, and heart. In addition, Active rats exposed to IS demonstrated a faster induction of lymphocyte HSP72 compared with Sed rats. Thus Active rats responded to stress with both greater and faster HSP72 responses compared with Sed rats. These results indicate that previous physical activity potentiates HSP72 expression after a wide range of stressors. Facilitated induction of HSP72 may contribute to the increased stress resistance previously reported in physically active organisms.     

Physical activity alters the brain Hsp72 and IL-1beta responses to peripheral E. coli challenge

Physically active rats have facilitated heat shock protein 72 (Hsp72) responses after stressor exposure in both brain and peripheral tissues compared with sedentary rats. This study verifies that physically active animals do not have elevated Hsp72 levels compared with sedentary animals in the hypothalamus, pituitary, or dorsal vagal complex. We then examined whether 1) physically active rats respond more efficiently than sedentary rats to a bacterial challenge; 2) peripheral immune challenge elicits brain induction of Hsp72; 3) this induction is facilitated by prior freewheel running; and 4) Hsp72 upregulation produced by peripheral immune challenge results in a commensurate decrease in the proinflammatory cytokine IL-1beta. Adult male Fischer 344 rats were housed with either a mobile or locked running wheel. Six weeks later, rats were injected intraperitoneally with saline or Escherichia coli and killed 30 min, 2.5 h, 6 h, and 24 h later. Serum endotoxin and IL-1beta, and peritoneal fluid endotoxin and E. coli colony-forming units (CFUs) were measured. Hsp72 and IL-1beta were measured in hypothalamus, pituitary, and dorsal vagal complex. The results were that physically active rats had a faster reduction in endotoxin and E. coli CFUs and lower levels of circulating endotoxin and cytokines compared with sedentary rats. E. coli challenge elicited significantly greater time-dependent increases of both Hsp72 and IL-1beta in hypothalamus, pituitary, and dorsal vagal complex of physically active animals but not sedentary animals. Contrary to our hypothesis, increases in Hsp72 were positively correlated with IL-1beta. This study extends our findings that physical activity facilitates stress-induced Hsp72 to include immunological stressors such as bacterial challenge and suggests that brain Hsp72 and IL-1beta responses to peripheral immune challenge may contribute to exercise-mediated resistance to long-term sickness.     

Detectable levels of eHSP72 in plasma are associated with physical activity and antioxidant enzyme activity levels in hypertensive subjects

Previous studies reported that extracellular HSP72 (eHSP72) correlates with poor prognosis, markers of vascular dysfunction, and the severity of cardiovascular diseases, associated with a systemic oxidative and inflammatory profile. On the other hand, eHSP72 may represent immune-regulatory signaling that is related to exercise benefits, but the association between physical activity levels and eHSP72 levels is not established. Thus, since regular physical activity may avoid oxidative stress and inflammation, we investigate whether detectable levels of eHSP72 in plasma are associated with physical activity and antioxidant enzyme activity levels in hypertensive subjects. Physical activity levels of hypertensive subjects (n?=?140) were measured by tri-axial movement sensor pedometer for 24 h during 5 consecutive days. One day after, blood was collected into heparinized tubes for oxidative stress analyses (catalase—CAT and superoxide dismutase—SOD activities and malondialdehyde levels) or in disodium EDTA tubes for eHSP72 assays. Thus, hypertensive subjects were classified as physically inactive (<?10,000 footsteps/day) or active (>?than 10,000 footsteps/day) and according detectable or not detectable eHSP72 levels in plasma, performing the inactive/eHSP72^?, active/eHSP72^?, inactive/eHSP72⁺, and active/eHSP72⁺ groups. We found that detectable levels of eHSP72 in plasma were associated with physical activity levels and low oxidative stress profile (Higher CAT and SOD activities and low malondialdehyde levels). eHSP72 levels can be used as a biomarker of the amount of physical activity necessary to improve antioxidant defense and thus cardiovascular health in hypertensive subjects.     

Stress-induced extracellular Hsp72 is a functionally significant danger signal to the immune system

Extracellular heat-shock proteins (eHsp) such as those belonging to the 70-kDa family of Hsp (eg, Hsp72) have been hypothesized to act as a "danger signal" to immune cells, promote immune responses, and improve host defense. The current study tested this hypothesis. Adult male F344 rats were exposed to an acute laboratory stressor (100, 5-second, 1.6-mA inescapable tail shocks) and challenged with Escherichia coli. The number of colony-forming units (CFU) of bacteria at the site of injection, the levels of eHsp72, the immune response to eHsp72 and E. coli-derived lipopolysaccharide (LPS), and the amount of time required to recover from in vivo bacterial challenge were measured. CFUs were reduced 2, 4, and 6 hours after injection of E. coli in rats exposed to stress. Rats exposed to stress had elevated eHsp72 that was elevated rapidly (25 minutes) and remained elevated in the circulation and at the inflammatory site (2 hours after stressor termination). Both stressor exposure and eHsp72 administration in the absence of stress resulted in a facilitated pattern of recovery after bacterial inflammation induced by subcutaneous E. coli injection. Rats exposed to acute restraint (100 minutes) did not demonstrate elevated circulating eHsp72 or a facilitated pattern of recovery after bacterial challenge. In vitro stimulation of rat splenocytes and macrophages with eHsp72 elevated nitric oxide (NO), tumor necrosis factor alpha (TNF-alpha), interleukin (IL)-1beta, and IL-6, and this effect was specific to eHsp72 because it was not diminished by polymyxin B and was reduced by earlier heat-denature treatment. Stimulation of cells with eHsp72 combined with LPS resulted in a greater NO and cytokine response than that observed after stimulation with eHsp72 or LPS alone. In vivo, at the inflammatory site, the bacterial-induced NO response was potentiated by stress, and NO inhibition (L-NIO) reduced the stress-induced facilitation but had no effect on the control kinetics of bacterial inflammation recovery. Thus, these results lend support to the hypothesis that intense stressor exposure increases eHsp72, which acts as a danger signal to potentiate the NO response to bacterial challenge and facilitate recovery from bacterial inflammation.     

Elevated IL-1beta contributes to antibody suppression produced by stress.

Acute stressor exposure can facilitate innate immunity and suppress acquired immunity. The present study further characterized the potentiating effect of stress on innate immunity, interleukin-1beta (IL-1beta), and demonstrated that stress-induced potentiation of innate immunity may contribute to the stress-induced suppression of acquired immunity. The long-term effect of stress on IL-1beta was measured by using an ex vivo approach. Sprague-Dawley rats were challenged with lipopolysaccharide (LPS) in vivo, and the IL-1beta response was measured in vitro. Splenocytes, mesenteric lymphocytes, and peritoneal cavity cells had a dose- and time-dependent ex vivo IL-1beta response to LPS. Rats that were exposed to inescapable shock (IS, 100 1.6 mA, 5-s tail shocks, 60-s intertrial interval) and challenged with a submaximal dose of LPS 4 days later had elevated IL-1beta measured ex vivo. To test whether the acute stress-induced elevation in IL-1beta contributes to the long-term suppression in acquired immunity, IL-1beta receptors were blocked for 24 h after stress. Serum anti-keyhole limpet hemocyanin (KLH) immunoglobulin (Ig) was measured. In addition, the acute elevation (2 h post-IS) of splenic IL-1beta in the absence of antigen was verified. Interleukin-1 receptor antagonist prevented IS-induced suppression in anti-KLH Ig. These data support the hypothesis that stress-induced increases in innate immunity (i.e., IL-1beta) may contribute to stress-induced suppression in acquired immunity (i.e., anti-KLH Ig).     

Subacute exposure to residual oil fly ash (ROFA) increases eHSP70 content and extracellular-to-intracellular HSP70 ratio: a relation with oxidative stress markers

The purpose of this study was to evaluate whether exposure to particles induces an imbalance in 70-kDa heat shock proteins (HSP70). Since intracellularly (iHSP70) it has anti-inflammatory roles whereas extracellularly (eHSP70) it has pro-inflammatory roles, we evaluate the effect of residual oil fly ash (ROFA) exposure on eHSP70-to-iHSP70 ratio (H index), a biomarker of inflammatory status that is related to oxidative stress in plasma and lymphoid tissue. Wistar rats that received ROFA suspension for three consecutive days (750 μg) showed an increase in plasma eHSP70 levels (mainly the 72-kDa inducible form). Also, ROFA promoted alterations on plasma oxidative stress (increased protein carbonyl groups and superoxide dismutase activity, and decrease sulfhydryl groups). There was an increase in H index of the plasma/thymus with no changes in circulating leukocyte level, iHSP70, or oxidative stress markers in lymphoid tissues. Our results support the hypothesis that eHSP70 content and H index represent inflammatory and oxidative biomarkers.     

Bacterial Lipopolysaccharide Augments Febrile-Range Hyperthermia-Induced Heat Shock Protein 70 Expression and Extracellular Release in Human THP1 Cells

Sepsis, a devastating and often lethal complication of severe infection, is characterized by fever and dysregulated inflammation. While infections activate the inflammatory response in part through Toll-like receptors (TLRs), fever can partially activate the heat shock response with generation of heat shock proteins (HSPs). Since extracellular HSPs, especially HSP70 (eHSP70), are proinflammatory TLR agonists, we investigated how exposure to the TLR4 agonist, bacterial lipopolysaccharide (LPS) and febrile range hyperthermia (FRH; 39.5°C) modify HSP70 expression and extracellular release. Using differentiated THP1 cells, we found that concurrent exposure to FRH and LPS as well as TLR2 and TLR3 agonists synergized to activate expression of inducible HSP72 (HSPA1A) mRNA and protein via a p38 MAP kinase-requiring mechanism. Treatment with LPS for 6 h stimulated eHSP70 release; levels of eHSP70 released at 39.5°C were higher than at 37°C roughly paralleling the increase in intracellular HSP72 in the 39.5°C cells. By contrast, 6 h exposure to FRH in the absence of LPS failed to promote eHSP70 release. Release of eHSP70 by LPS-treated THP1 cells was inhibited by glibenclamide, but not brefeldin, indicating that eHSP70 secretion occurred via a non-classical protein secretory mechanism. Analysis of eHSP70 levels in exosomes and exosome-depleted culture supernatants from LPS-treated THP1 cells using ELISA demonstrated similar eHSP70 levels in unfractionated and exosome-depleted culture supernatants, indicating that LPS-stimulated eHSP70 release did not occur via the exosome pathway. Immunoblot analysis of the exosome fraction of culture supernatants from these cells showed constitutive HSC70 (HSPA8) to be the predominant HSP70 family member present in exosomes. In summary, we have shown that LPS stimulates macrophages to secrete inducible HSP72 via a non-classical non-exosomal pathway while synergizing with FRH exposure to increase both intracellular and secreted levels of inducible HSP72. The impact of increased macrophage intracellular HSP70 levels and augmented secretion of proinflammatory eHSP70 in the febrile, infected patient remains to be elucidated.     

AMP-activated Protein Kinase Attenuates Nitric Oxide-induced ��-Cell Death

During the initial autoimmune response in type 1 diabetes, islets are exposed to a damaging mix of pro-inflammatory molecules that stimulate the production of nitric oxide by β-cells. Nitric oxide causes extensive but reversible cellular damage. In response to nitric oxide, the cell activates pathways for functional recovery and adaptation as well as pathways that direct β-cell death. The molecular events that dictate cellular fate following nitric oxide-induced damage are currently unknown. In this study, we provide evidence that AMPK plays a primary role controlling the response of β-cells to nitric oxide-induced damage. AMPK is transiently activated by nitric oxide in insulinoma cells and rat islets following IL-1 treatment or by the exogenous addition of nitric oxide. Active AMPK promotes the functional recovery of β-cell oxidative metabolism and abrogates the induction of pathways that mediate cell death such as caspase-3 activation following exposure to nitric oxide. Overall, these data show that nitric oxide activates AMPK and that active AMPK suppresses apoptotic signaling allowing the β-cell to recover from nitric oxide-mediated cellular stress.     

Effect of ghrelin administration on phagocytic activity in acute cold-restraint stress exposed rats

Ghrelin, an endogenous ligand for growth hormone secretagogue receptor, was identified in the rat stomach. This peptide acts through nitric oxide (NO) by expressing endothelial nitric oxide synthase (eNOS) and down regulating inducible nitric oxide synthase (iNOS) at its gastroproprotective effect against restraint stress induced damage. Recently the ghrelin receptor has also been detected in peripheral systems including immune tissue. We have investigated the possible effect of ghrelin on phagocytic activity of peritoneal macrophages in acute cold-restraint stress (ACRS) exposed rats. The rats were divided into control, stress and ghrelin groups. In ghrelin groups, single dose and three days consecutive dose of ghrelin (20 microg/kg. i.p.) were applied to rats that were exposed to ACRS for 4 h. 1 ml of saline was injected i.p. after ACRS for 3 consecutive days to the rats of the stress groups. Ghrelin administration reduced the increased phagocytic activity induced by ACRS. We conclude that ghrelin exerts an important role at macrophage phagocytic activity in ACRS exposed rats.     

Rapid Recovery of Marine Bacterioplankton Activity after Inhibition by UV Radiation in Coastal Waters

Laboratory and in situ experiments were performed in order to evaluate the role of UV radiation on bacterial activity. Particular attention was given to the determination of the role of UV-A and photosynthetic active radiation (PAR) and different nutrient conditions on the recovery of bacterial activity. Laboratory experiments with nearly natural radiation intensities indicated a 20 to 40% reduction from the initial level of bacterial activity after UV-B exposure for 2 to 4 h. Bacterial activity in freshly collected seawater showed a more pronounced inhibition and faster recovery than bacterial activity in aged, nutrient-depleted seawater. The results of in situ experiments with filtered water (0.8-(mu)m-pore-size filter) and natural surface solar radiation levels agreed with those of the laboratory experiments and revealed that UV-A and PAR are important for the recovery of bacterial activity and result in levels of bacterial activity that are higher than those prior to exposure to full solar radiation. Bacterioplankton exposed to full solar radiation for 3 h and subsequently incubated at different depths within the upper mixed water column showed an increase in bacterial activity with increased depth; the highest bacterial activity was detected at depths of 5.5 to 10.5 m, where the short-wavelength UV-B was already largely attenuated, but enough long wavelength UV-A and short PAR were available to allow recovery. This elevated bacterial activity following exposure to UV-B was attributed to the photolysis of dissolved organic matter (DOM) exposed to near-surface radiation and to the rapid recovery of bacteria from UV stress once they were mixed into deeper layers of the upper mixed water column, where they efficiently utilize the photolytically cleaved DOM. It is concluded that studies on the role of UV on the carbon and energy flux through the upper layer of the ocean should take into account the highly dynamic radiation conditions.     

In vivo exposure to carbon monoxide causes delayed impairment of activation of soluble guanylate cyclase by nitric oxide in rat brain cortex and cerebellum

Carbon monoxide induces delayed neurological and neuropathological alterations, including memory loss and cognitive impairment. The bases for the delay remain unknown. Activation of soluble guanylate cyclase by nitric oxide modulates some forms of learning and memory. Carbon monoxide binds to soluble guanylate cyclase, activating it but interfering with its activation by nitric oxide. The aim of this work was to assess whether exposure of rats to carbon monoxide alters the activity of soluble guanylate cyclase or its modulation by nitric oxide in cerebellum or cerebral cortex. Rats exposed chronically or acutely to carbon monoxide were killed 24 h or 7 days later. Acute carbon monoxide exposure decreased cyclic guanosine monophosphate (cGMP) content and reduced activation of soluble guanylate cyclase by nitric oxide. Cortex was more sensitive than cerebellum to chronic exposure, which reduced activation of soluble guanylate cyclase by nitric oxide in cortex. In cerebellum, chronic exposure induced delayed impairment of soluble guanylate cyclase activation by nitric oxide. Acute exposure effects were also stronger at 7 days than at 24 h after exposure. This delayed impaired modulation of soluble guanylate cyclase by nitric oxide may contribute to delayed memory loss and cognitive impairment in humans exposed to carbon monoxide.     

The features of lipid peroxidation and the antioxidant system of blood under the influence of different concentrations of nitric oxide in a chronic experiment

This paper presents the results of the study of oxidative metabolism of the blood of intact animals subjected to prolonged exposure to nitric oxide at concentrations of 20, 50, and 100 ppm. The experiment was carried out with Wistar rats. NO inhalation was performed for 30 days. The state of blood oxidative metabolism was evaluated after inhalation and a 30-day-long recovery period after discontinuation of NO oxidative stress. The intensity of lipid peroxidation was studied in plasma and erythrocytes by induced biochemiluminescence and the measurement of the level of malondialdehyde. The activity of superoxide dismutase was determined in the hemolysate of erythrocytes. It was established that the optimal dose of inhaled NO is 20 ppm: a maximum increase in the total antioxidant activity after 30 days and normalization of lipid peroxidation in the blood after the completion of the recovery period were observed at this concentration. High concentrations of nitric oxide (50 and 100 ppm) initiated lipid peroxidation in erythrocytes and plasma after discontinuation of NO oxidative stress (after the completion of the recovery period) thus enhancing catalytic properties of superoxide dismutase.     

Effect of gender differences and voluntary exercise on antioxidant capacity in rats

The effects of gender difference and voluntary exercise on antioxidant capacity in rats were evaluated. The subjects were divided into two groups, physically active and sedentary. In the sedentary group, the level of hydroxyl radical in the liver was higher (P<0.001) in male rats than in female rats, however, in the physically active group, the level in male rats was lower (P<0.05) than in female rats. The levels of reduced glutathione (GSH) in physically active males and females were higher compared to those in the sedentary group. The physically active group also showed an increase in antioxidant enzymes, such as glutathione peroxidase (GPx), glutathione reductase (GR) and superoxide dismutase activities. The level of liver GSH was higher in physically active females than in physically active males. For both groups, GPx and GR activities in females were significantly higher than in males. These results indicate that female rats have an intrinsically higher antioxidant capacity, which resulted in increased levels of GSH via the glutathione redox cycle and gamma-glutamyl cycle enzymes. The adaptation to altered antioxidant capacity, induced by physical activity, appeared to be affected by gender differences.     

Effect of inhaled crystalline silica in a rat model: time course of pulmonary reactions

Numerous investigations have been conducted to elucidate mechanisms involved in the initiation and progression of silicosis. However, most of these studies involved bolus exposure of rats to silica, i.e. intratracheal instillation or a short duration inhalation exposure to a high dose of silica. Therefore, the question of pulmonary overload has been an issue in these studies. The objective of the current investigation was to monitor the time course of pulmonary reactions of rats exposed by inhalation to a non-overload level of crystalline silica. To accomplish this, rats were exposed to 15 mg/m3 silica, 6 h/day, 5 days/week for up to 116 days of exposure. At various times (5-116 days exposure), animals were sacrificed and silica lung burden, lung damage, inflammation, NF-KB activation, reactive oxygen species and nitric oxide production, cytokine production, alveolar type II epithelial cell activity, and fibrosis were monitored. Activation of NF-KB/DNA binding in BAL cells was evident after 5 days of silica inhalation and increased linearly with continued exposure. Parameters of pulmonary damage, inflammation and alveolar type II epithelial cell activity rapidly increased to a significantly elevated but stable new level through the first 41 days of exposure and increased at a steep rate thereafter. Pulmonary fibrosis was measurable only after this explosive rise in lung damage and inflammation, as was the steep increase in TNF-alpha and IL-1 production from BAL cells and the dramatic rise in lavageable alveolar macrophages. Indicators of oxidant stress and pulmonary production of nitric oxide exhibited a time course which was similar to that for lung damage and inflammation with the steep rise correlating with initiation of pulmonary fibrosis. Staining for iNOS and nitrotyrosine was localized in granulomatous regions of the lung and bronchial associated lymphoid tissue. Therefore, these data demonstrate that the generation of oxidants and nitric oxide, in particular, is temporally and anatomically associated with the development of lung damage, inflammation, granulomas and fibrosis. This suggests an important role for nitric oxide in the initiation of silicosis.     

Influence of exercise on dilatation of the basilar artery during diabetes mellitus.

Our goal was to examine whether exercise training alleviates impaired nitric oxide synthase (NOS)-dependent dilatation of the basilar artery in Type 1 diabetic rats. To test this hypothesis, we measured in vivo diameter of the basilar artery in sedentary and exercised nondiabetic and diabetic rats in response to NOS-dependent (acetylcholine) and -independent (nitroglycerin) agonists. To determine the potential role for nitric oxide in vasodilatation in sedentary and exercised nondiabetic and diabetic rats, we examined responses after NG-monomethyl-l-arginine (l-NMMA). We found that acetylcholine produced dilatation of the basilar artery that was similar in sedentary and exercised nondiabetic rats. Acetylcholine produced only minimal vasodilatation in sedentary diabetic rats. However, exercise alleviated impaired acetylcholine-induced vasodilatation in diabetic rats. Nitroglycerin produced dilatation of the basilar artery that was similar in sedentary and exercised nondiabetic and diabetic rats. l-NMMA produced similar inhibition of acetylcholine-induced dilatation of the basilar artery in sedentary and exercised nondiabetic and diabetic rats. Finally, we found that endothelial NOS (eNOS) protein in the basilar artery was higher in diabetic compared with nondiabetic rats and that exercise increased eNOS protein in the basilar artery of nondiabetic and diabetic rats. We conclude that 1) exercise can alleviate impaired NOS-dependent dilatation of the basilar artery during diabetes mellitus, 2) the synthesis and release of nitric oxide accounts for dilatation of the basilar artery to acetylcholine in sedentary and exercised nondiabetic and diabetic rats, and 3) exercise may exert its affect on cerebrovascular reactivity during diabetes by altering levels of eNOS protein in the basilar artery.     

Inducible nitric oxide synthase and control of intracellular bacterial pathogens

Inducible nitric oxide synthase (iNOS) has important functions in innate immunity and regulation of immune functions. Here, the role of iNOS in the pathogenesis of various intracellular bacterial infections is discussed. These pathogens have also evolved a broad array of strategies to repair damage by reactive nitrogen intermediates, and to suppress or inhibit functions of iNOS.     

Lifelong exposure to dietary fish oil alters macrophage responses in Walker 256 tumor-bearing rats

Supplementation of the diet with fish oil (FO) decreases growth of the Walker 256 tumor and decreases the cachexia associated with tumor-bearing. The mechanisms by which FO inhibits tumor growth and cachexia are unknown. Macrophages are very important in host defence against tumors since they produce several anti-tumor agents which in turn have been shown to be modified by dietary FO, but rarely in the setting of tumor bearing and never in relation to lifelong exposure. In this study, we compared the effects of supplementation of the diet of pregnant and lactating rats and subsequent supplementation of the offspring with coconut fat or FO on macrophage activities involved in anti-tumor defence. FO supplementation was able to induce an increase in phagocytosis, in O2-, H2O2, nitric oxide, and TNF-alpha production by macrophages and in lysosomal volume in non-tumor-bearing rats. However, phagocytosis, production of O2- and H2O2 and lysosomal volume were not affected by the FO diet when rats were bearing tumors, although nitric oxide production was higher in these animals. It appears that tumor bearing activates the innate immune system and that dietary FO has little effect on innate immunity in the presence of Walker 256 tumors. Thus, it is still unclear how FO decreases the growth of Walker 256 tumors and the associated cachexia.     

Changes of renal function and structure in rats exposed to cold

The kidney appears to play a crucial role in both initiating and maintaining the high blood pressure in cold-induced hypertension (CIH). The aim of the present study was to evaluate the changes of renal function and structure in rats exposed to cold for 2, 4 and 6 weeks. Systolic blood pressure increased significantly after 2 weeks of cold exposure and was maintained throughout the whole experiment. Upregulation of angiotensin type 1 receptor (AT₁R) expression was seen in the vascular zone and distal tubule after 4 and 6 weeks of cold exposure. This was accompanied by an increase in malondialdehyde (MDA) levels and decreases in superoxide dismutase (SOD), nitric oxide synthase (NOS) activities and nitric oxide (NO) content in kidney. Structural changes were also observed in glomeruli, tubules and arteries in cold-treated rats. These results suggest that upregulation of kidney AT₁R plays a critical role in the development of CIH, and its interaction with oxidative stress, NO and NOS may be involved in changes of renal function and structure.