Local and systemic responses to iron-dextran injected into a granuloma pouch in the rat

Many inflammatory processes are accompanied by anemia and repeated hemorrhages, but the local and systemic effect of the iron present in the inflamed area and the availability of this iron are not known. The experimental model used to mimic the above situation was the carrageenan-induced granuloma in rats with simultaneous iron-dextran injection into the granuloma pouch. We studied the effect of iron-dextran on leukocytes from the inflammatory exudate and the location of iron in the granuloma tissue. We also evaluated the systemic responses by studying several iron parameters in blood and in iron-storage organs. The results showed a reduction in the number of leukocytes present in the exudate and a reduction in their viability and also extensive damage to the granuloma tissue, essentially to macrophages, caused by local iron-induced oxidative stress. A small percentage of iron reaches the systemic circulation, and this is eventually stored in the liver and spleen as hemosiderin, which is unlikely to have any effect on anemia. In spite of its local toxicity, the accumulation of iron in inflamed areas can be interpreted as a protective mechanism against systemic oxidative radical reactions induced by iron mobilization.

Use of almond mesocarp for production of the entomopathogenic fungus Verticillium lecanii

Almond mesocarp (AM) has been evaluated for production of Verticillium lecanii. Microbial flora of AM has been studied. After ground AM dilution plating, 5.3 x 10(5) +/- 2.6 x 10(4) fungal CFU.g-1 of dry AM were found. Common fungal saprophytes (Rhizopus sp. and Alternaria spp.) were found in more than 80% of the samples. Aspergillus sp. and yeasts were found less commonly. Rhizopus sp., Alternaria spp., and Aspergillus sp. inhibited growth of several V. lecanii; therefore, AM was treated with sterilization agents to eliminate endogenous mycoflora. Small samples (10 g) of AM saturated in distilled water treated with steam (120 degrees C and 100 kPa) were completely sterilized after 15 min. Ground AM incorporated on agar increased the biomass of V. lecanii compared with controls. This suggested AM as suitable substrate for the production of the fungus. In petri dishes, 9.7 x 10(7) +/- 2.9 x 10(7) conidia.g-1 of dry AM were produced after inoculating 10 conidia.g-1 of AM and incubating for 2 weeks. Viability of conidia produced was more than 90%. These conidia (5 x 10(4) conidia per larvae) caused Galleria mellonella mortality, calculated as median lethal time (LT50 5.3 +/- 1.6 days), that was significantly higher (F = 10.93; P < 0.05) than untreated controls (LT50 11.3 +/- 1.1 days). Larger scale tests have to be optimized before mass production.

Use of almond mesocarp for production of the entomopathogenic fungus Verticillium lecanii

Almond mesocarp (AM) has been evaluated for production of Verticillium lecanii. Microbial flora of AM has been studied. After ground AM dilution plating, 5.3 × 105 ± 2.6 × 104 fungal CFU·g-1 of dry AM were found. Common fungal saprophytes (Rhizopus sp. and Alternaria spp.) were found in more than 80% of the samples. Aspergillus sp. and yeasts were found less commonly. Rhizopus sp., Alternaria spp., and Aspergillus sp. inhibited growth of several V. lecanii; therefore, AM was treated with sterilization agents to eliminate endogenous mycoflora. Small samples (10 g) of AM saturated in distilled water treated with steam (120°C and 100 kPa) were completely sterilized after 15 min. Ground AM incorporated on agar increased the biomass of V. lecanii compared with controls. This suggested AM as suitable substrate for the production of the fungus. In petri dishes, 9.7 × 107 ± 2.9 × 107 conidia·g-1 of dry AM were produced after inoculating 10 conidia·g-1of AM and incubating for 2 weeks. Viability of conidia produced was more than 90%. These conidia (5 × 104 conidia per larvae) caused Galleria mellonella mortality, calculated as median lethal time (LT50 5.3 ± 1.6 days), that was significantly higher (F = 10.93; P < 0.05) than untreated controls (LT50 11.3 ± 1.1 days). Larger scale tests have to be optimized before mass production.Key words: Verticillium lecanii, almond mesocarp, production, entomopathogenic fungi, bioassays.

Nitric oxide inhibits superoxide production by inflammatory polymorphonuclear leukocytes

Nitric oxide (NO.) has a complex role in the inflammatory response. In this study, we modified the levels of endogenous NO. in vivo in an acute model of inflammation and evaluated the interactions between NO. and superoxide anion (O2-.) produced by polymorphonuclear leukocytes (PMNs) accumulated in the inflamed area. We injected phosphate-buffered saline (control group), 6 mumol of L-N5-(1-iminoethyl)ornithine (L-NIO group), or 6 mumol of L-arginine (L-arginine group) into the granuloma pouch induced by carrageenan in rats. NO2- plus NO3- (indicative of NO. generation) was 188 nmol in the exudate of the control group, but it decreased in the L-NIO group (P < 0.05) and increased in the L-arginine group (P < 0.05). When PMNs from treated rats were incubated in vitro, the production of superoxide anion (O2-.) decreased by approximately 46% in the L-arginine group. Furthermore, O2-. was inhibited in PMNs when L-arginine was added to the incubation medium before phorbol 12-myristate 13-acetate stimulation but not when added simultaneously. Our results suggest a protective role for NO. in inflammation, through the inactivation of NADPH oxidase and the consequent impairment of O2-. production for cell-mediated injury.

Fish oil and oxidative stress by inflammatory leukocytes

We investigated the effects of diets with different fatty acid composition upon the oxidative stress of inflammatory leukocytes of rats. After weaning, two groups of rats were fed isoenergetic semipurified diets for five weeks containing 5% of corn oil or menhaden oil. Polymorphonuclear leukocytes from rats fed menhaden oil diet incorporated n-3 polyunsaturated fatty acids into phospholipid membranes at the expense of arachidonic acid. These cells showed diminished superoxide production and, as a consequence, the total antioxidant status in the inflammatory exudate was increased. However, nitric oxide production was not affected by diet. Free malondialdeyde concentration increased in the exudate because of lower mitochondrial activity. These results add new aspects that help clarifying the anti-inflammatory mechanisms of n-3 polyunsaturated fatty acids.

Factors influencing the acid-base changes in the air-pouch exudate following carrageenan induced inflammation in rats

The interactions between the acid-base variables that contribute to exudate acidosis were studied in the subcutaneous air-pouch after carrageenan injection in rats. We studied the concurrent changes of exudate gases (PCO2 and PO2), main ions ([Na+], [K+], [Ca2+], [Mg2+], [Cl-] and [Lac-]), inorganic phosphate (P(i)) and albumin in acutely inflamed rats (4, 8, 12, 24 and 48 h of inflammation). A notable hypercapnia was found in the exudate after only 8 h (exudate PCO2 = 64.3 +/- 2.9 mm Hg) but this hypercapnia decreased after 48 h (32.9 +/- 12.7 mm Hg), coincident with the greatest increase in exudate cells. With respect to the metabolic acid-base variables, the most important changes found were a parallel decrease in the strong ion difference ([SID]) and exudate pH, as well as increases in the exudate weak acid buffers ([ATOT]) due to albumin and inorganic phosphate (P(i)) increases. However, after 12 h, the exudate acidosis was stable at around pH 7. A similar acid pH was obtained after 24 h of inflammation when the carrageenan solution injected was previously adjusted to a physiological pH (7.4). This pH, analogous to that of the exudate, was the result of compensation by the acid-base independent variables, a fact which suggests that acid pH may be a beneficial condition for cells taking part in inflammatory processes.

Conditions to study nitric oxide generation by polymorphonuclear cells from an inflammatory exudate in rats

Superoxide and nitric oxide release by leukocytes has been usually performed after exposure to a particular stimulus. We measured the generation of superoxide and nitric oxide by cells isolated from an inflammatory exudate of rats in either the absence or the presence of a variety of stimuli. Nonstimulated leukocytes generated superoxide radical (1.2 nmol x 10(6) cells(-1)) and nitric oxide (3.8 nmol x 10(6) cells(-1)) after 2 h incubation. When cells were incubated with lipopolysaccharides, opsonized zymosan or phorbol 12-myristate 13-acetate, superoxide level increased while nitric oxide decreased. Phorbol 12-myristate 13-acetate (100 ng/ml) induced a decrease of 0.88 nmol x 10(6) cells(-1) compared with nonstimulated cells, and incubation with N-iminoethyl-L-ornithine increased superoxide production by 0.81 nmol x 10(6) cells(-1). These results provide clear evidence that cells from an inflammatory exudate which are already triggered are able to generate a considerable amount of nitric oxide and in less proportion superoxide, that the measure of nitric oxide must be performed without a further stimulus, and that both molecules react in an equimolar proportions to give peroxynitrite anion.

Blood acid-base changes during acute experimental inflammation in rats

Acidosis has often been reported in inflamed tissues, and changes in strong relevant ions at the site of inflammation may provoke alterations in blood acid-base status. We measured changes in blood acid-base variables during carrageenan-induced inflammation in rats. We found a mixed acid-base disorder in rat blood during acute inflammation (12, 24, and 48 h). A metabolic acid contribution was found during the first 12 h and maintained further, as revealed by a decrease in plasma strong ion concentration difference ([SID]) and an increase in plasma weak acid concentration due to a rise in inorganic phosphate ([ATOT]P(i)). Plasma [SID] and [ATOT]P(i) changes were probably due to exchange of Na+ and P(i) between the inflammatory exudate and rat blood. A secondary respiratory compensation for the metabolic acid changes occurred in the blood of inflamed rats, resulting in significant hypocapnia. Furthermore, a progressive decrease in the total weak acid buffer concentration due to a decrease in plasma albumin ([ATOT]Alb) also counteracted the impact of changes in [SID] and P(i) to increase blood acidity. Therefore, despite the metabolic acid-base disorders induced by inflammatory processes, hydrogen ion (H+) homeostasis was maintained, and blood pH remained essentially unchanged in the inflamed rats.

Simultaneous generation of nitric oxide and superoxide by inflammatory cells in rats

It has recently been shown that peroxynitrite anion is a powerful oxidant than can initiate lipid peroxidation. As this oxidant is the product of the reaction between nitric oxide and superoxide, we have studied whether cells isolated from an inflammatory exudate can release both radicals simultaneously under physiological conditions. The carrageenin-induced granuloma model in rats was used. Cells from the inflammatory pouch were stimulated with opsonized zymosan in the absence or in the presence of exogenous L-arginine. Nitric oxide production without exogenous L-arginine was detectable after 15 min (0.29 nmol NO2-) and increased with time (1.65 nmol NO2- at 4 h). When nitrite released from cells was expressed as a rate a burst was shown in the first few minutes. Between 0 and 15 min, cells produced NO2- at the following rates: 20 pmol NO2-/1 x 10(6) cells/min without exogenous L-arginine and 83 pmol NO2-/1 x 10(6) cells/min with exogenous L-arginine. Production was further stimulated with opsonized zymosan (92 pmol NO2-/1 x 10(6) cells/min), and inhibited by L-NMMA and L-NIO. The production of superoxide increased for up to 2 h and then stabilized. A significant increase in nitrite was observed in the presence of SOD, whereas L-NIO increased superoxide generation. These results suggest that peroxynitrite anion may be formed by inflammatory cells.

Carrageenan-induced granuloma and iron status in rats with dietary polyunsaturated fatty acid deficiency

Sprague-Dawley rats were fed for 4 months on a control diet or a polyunsaturated-fatty-acid (PUFA)-deficient diet. The combined effects of iron overload (Fe dextran) or Fe deficiency (desferrioxamine) on carrageenan-induced granuloma were studied. PUFA deficiency induced changes in Fe metabolism, but no alterations in lipid peroxidation variables were observed. Inflammation implied an increase in lipid peroxidation, Fe storage and caeruloplasmin concentration, together with symptoms of anaemia. PUFA deficiency in inflamed rats gave rise to a lower inflammatory response (granuloma weight and prostaglandin E2 concentration) and ethane exhalation. Fe overload potentiated inflammatory and lipid peroxidation processes, whereas Fe deficiency decreased them.

Modulation of exudate inflammation parameters in rat carrageenan-induced granuloma by modification of exudate iron levels

We have used the carrageenan-induced pouch-granuloma in rats to investigate how changes in low-molecular-mass iron chelate levels in the exudate, induced by iron loading (iron-dextran) or chelation (desferrioxamine) influence cellular and systemic inflammatory parameters. In the iron-treated group we observed a rapid decrease in the number of leukocytes and exudate volume; there was also an increase in ferritin iron and low-molecular-mass iron chelates, and on the eighth day a systemic response. In the desferrioxamine-treated group we detected a decrease in low-molecular-mass iron chelates, ferritin iron, and an increase in the number of leukocytes. We describe the protective effects of desferrioxamine against the deleterious effects of ferrous iron and relate this to its chelating and scavenging activity. The results suggest that the levels of low-molecular-mass iron chelates modulate the inflammatory response, possibly through their contribution to the oxygen free radical generation, which is responsible for the cell membrane damage and subsequently its death. The modulatory action of iron-dextran and desferrioxamine support our hypothesis.