The effects of the nitric oxide donor SIN-1 on ischemia-reperfused cutaneous and myocutaneous flaps

Ischemia-reperfusion injury causes tissue damage that leads to a decrease in bioavailability of nitric oxide. The authors hypothesized that an exogenous supply of nitric oxide will have beneficial effects on survival of skin and skeletal muscle subjected to ischemia-reperfusion injury. By using the nitric oxide donor SIN-1 (3-morpholino-sydnonimine) the effects of direct intraarterial infusion of an exogenous source of nitric oxide in reperfused flaps was studied. Bilateral island buttock skin flaps and latissimus dorsi myocutaneous flaps were elevated in eight pigs, for a total of 32 flaps. Flaps were subjected to 6 hours of ischemia followed by 18 hours of reperfusion. Flaps on one side of each animal were randomized to be treated with the nitric oxide donor (treatment group). The contralateral side was treated with an equivalent volume of saline vehicle (infusion control) SIN-1, or saline was administered as a continuous direct intraarterial infusion at the onset of reperfusion and continued during the observation period. Outcomes measured were tissue neutrophil accumulation by using myeloperoxidase assay and tissue survival (intravenous fluorescein and nitroblue tetrazolium for skin and muscle, respectively). In both skin and myocutaneous flaps, SIN-1 treatment caused a significant improvement in survival and a decrease in neutrophil accumulation. Nitric oxide may play an important role in the pathophysiologic process of ischemia-induced reperfusion injury in skin and skeletal muscle. Nitric oxide donors may be a promising family of therapeutic agents for the prevention of ischemia-induced reperfusion injury in cutaneous and myocutaneous flaps.     

Effects of L-NAME and L-arginine on ischemia-reperfusion injury in rat skeletal muscle

The involvement of nitric oxide in ischemia-reperfusion injury remains controversial and has been reported to be both beneficial and deleterious, depending on the tissue and model used. This study evaluated the effects of the nitric oxide synthase inhibitor N(G)-nitro-L-arginine-methyl ester (L-NAME) and the substrate for nitric oxide synthase, L-arginine on skeletal muscle necrosis in a rat model of ischemia-reperfusion injury. The rectus femoris muscle in male Wistar rats (250 to 500 g) was isolated on its vascular pedicle and subjected to 4 hours of complete arteriovenous occlusion. The animals were divided into five groups: (1) sham-raised control, no ischemia, no treatment (n = 6); (2) 4 hours of ischemia (n = 6); (3) vehicle control, 4 hours of ischemia + saline (n = 6); (4) 4 hours of ischemia + L-arginine infusion (n = 6); and (5) 4 hours of ischemia + L-NAME infusion (n = 6). The infusions (10 mg/kg) were administered into the contralateral femoral vein beginning 5 minutes before reperfusion and during the following 30 to 45 minutes. Upon reperfusion, the muscle was sutured in its anatomic position and all wounds were closed. The percentage of muscle necrosis was assessed after 24 hours of reperfusion by serial transections, nitroblue tetrazolium staining, digital photography, and computerized planimetry. Sham (group 1) animals sustained baseline necrosis of 11.9 +/- 3.0 (percentage necrosis +/- SEM). Four hours of ischemia (group 2) significantly increased necrosis to 79.2 +/- 1.4 (p < 0.01). Vehicle control (group 3) had no significant difference in necrosis (81.17 +/- 5.0) versus untreated animals subjected to 4 hours of ischemia (group 2). Animals treated with L-arginine (group 4) had significantly reduced necrosis to 34.6 +/- 7.5 versus untreated (group 2) animals (p < 0.01). Animals infused with L-NAME (group 5) had no significant difference in necrosis (68.2 +/- 6.7) versus untreated (group 2) animals. L-Arginine (nitric oxide donor) significantly decreased the severity of muscle necrosis in this rat model of ischemia-reperfusion injury. L-arginine is known to increase the amount of nitric oxide through the action of nitric oxide synthase, whereas L-NAME, known to inhibit nitric oxide synthase and decrease nitric oxide production, had comparable results to the untreated 4-hour ischemia group. These results suggest that L-arginine, presumably through nitric oxide mediation, appears beneficial to rat skeletal muscle subjected to ischemia-reperfusion injury.     

L-精氨酸对任意型皮瓣成活的影响

目的　探讨L 精氨酸对任意型皮瓣的成活的影响。方法　以Wistar大鼠为实验对象 ,在其背部设计 7cm×2cm任意型皮瓣 ,于术后给予腹腔注射L 精氨酸 30 0mg/kg ,对照组给予 0 9%生理盐水。术后 7d ,通过图像分析技术观察皮瓣成活率 ;通过生物化学技术、组织学和免疫组织化学技术对不同时间皮瓣组织中一氧化氮含量、组织形态学变化、白细胞计数以及ICAM 1的表达进行观测。结果　外源性L 精氨酸可提高皮瓣组织一氧化氮含量 ,L 精氨酸组ICAM 1表达呈弱阳性、术后 12h皮瓣组织真皮中性粒细胞计数减少 ,L 精氨酸组皮瓣成活率明显高于对照组 (P <0 0 1)。结论　外源性L 精氨酸可提高皮瓣组织NO含量 ,ICAM 1表达下调 ,中性粒细胞浸润减少 ,提高任意皮瓣成活率。     

Presence and activity of nitric oxide synthase isoforms in ischemia-reperfusion-injured flaps

Nitric oxide is produced from the amino acid L-arginine by nitric oxide synthase, which has three known isoforms: (1) endothelial nitric oxide synthase and (2) brain nitric oxide synthase, both of which are constitutive nitric oxide synthase; and (3) inducible nitric oxide synthase. The authors' hypothesis is that after reperfusion injury, endothelial cell dysfunction leads to disruption of nitric oxide synthase-mediated nitric oxide production and that this may in part explain the deleterious effects of ischemia-reperfusion injury on tissue survival and blood reflow in flaps. An experiment was designed to study the effects of ischemia-reperfusion injury on the bioactivity of all three isoforms of nitric oxide synthase. Buttock skin flaps and latissimus dorsi myocutaneous flaps were elevated in eight pigs. Flaps on one side of the animal were randomized to receive 6 hours of arterial ischemia, whereas flaps on the other side served as controls. At 6 hours of ischemia and at 1, 4, and 18 hours after reflow, tissue biopsy specimens were obtained and were processed for both constitutive nitric oxide synthase and inducible nitric oxide synthase enzyme activity on the basis of the L-citrulline assay. In addition, specimens were processed for Western blot analysis of the three isoforms. The authors' results revealed three key findings: first, there was a statistically significant (p < 0.001) decrease in constitutive nitric oxide synthase activity of ischemia-reperfusion-injured flaps as compared with controls in both skin and muscle for all time intervals measured. Second, Western blot analyses of endothelial nitric oxide synthase and brain nitric oxide synthase showed a significant decrease in the signal intensity in ischemic and reperfused tissue as compared with controls. Third, the inducible nitric oxide synthase isoform's activity and protein remained undetectable in both tissue types for all time points measured. The authors' data demonstrated that following ischemia-reperfusion injury in the pig flap model there was a disruption of constitutive nitric oxide synthase expression and activity, which may lead to decreased nitric oxide production. The significant decrease in nitric oxide synthase activity found in the current study may partly explain the mechanism of tissue damage in flaps subjected to ischemia-reperfusion injury. Knowledge of the kinetics of nitric oxide synthase activity under conditions of ischemia-reperfusion injury has important implications for the choice and timing of delivery of therapeutic agents whose goal is to increase the bioavailability of nitric oxide in reperfused tissue.     

Lack of Effects of Inhibition of Nitric Oxide Synthesis on Local Glucose Utilization in the Rat Brain

Abstract: The effects of chronic treatment with N ^G-nitro- l -arginine methyl ester, a potent inhibitor of nitric oxide synthase activity, on local cerebral glucose utilization were examined in conscious rats. Intraperitoneal injections of 50 mg/kg of the nitroarginine twice daily for 4 days have been found to result in almost complete inhibition of nitric oxide synthase activity in brain. Local cerebral glucose utilization was determined by means of the quantitative autoradiographic [¹⁴C]deoxyglucose method in an experimental group (n = 7) of rats that were treated with the nitroarginine according to this schedule and in a normal control group (n = 7) treated similarly with saline. The rats were conscious but partially restrained during the determinations of local cerebral glucose utilization. The nitroarginine treatment raised mean arterial blood pressure statistically significantly to 147 ± 3 mm Hg (mean ± SEM) from a level of 120 ± 5 mm Hg in the saline controls ( p < 0.001 by grouped t test), but there were no statistically significant effects on glucose utilization in any of 39 brain structures examined. It is concluded that nitric oxide normally exerts no significant influence on energy metabolism in the rat brain.     

Angiogenic growth factor expression in rat skeletal muscle in response to exercise training

Angiogenesis occurs in skeletal muscle in response to exercise training. To gain insight into the regulation of this process, we evaluated the mRNA expression of factors implicated in angiogenesis over the course of a training program. We studied sedentary control (n = 17) rats and both sedentary (n = 18) and exercise-trained (n = 48) rats with bilateral femoral artery ligation. Training consisted of treadmill exercise (4 times/day, 1-24 days). Basal mRNA expression in sedentary control muscle was inversely related to muscle vascularity. Angiogenesis was histologically evident in trained white gastrocnemius muscle by day 12. Training produced initial three- to sixfold increases in VEGF, VEGF receptors (KDR and Flt), the angiopoietin receptor (Tie-2), and endothelial nitric oxide synthase mRNA, which dissipated before the increase in capillarity, and a substantial (30- to 50-fold) but transient upregulation of monocyte chemoattractant protein 1 mRNA. These results emphasize the importance of early events in regulating angiogenesis. However, we observed a sustained elevation of the angiopoietin 2-to-angiopoietin 1 ratio, suggesting continued vascular destabilization. The response to exercise was (in general) tempered in high-oxidative muscles. These findings place importance on cellular events coupled to the onset of angiogenesis.     

Alterations in spontaneous contractions in vitro after repeated inflammation of rat distal colon

In inflammatory bowel disease, smooth muscle function reportedly varies with disease duration. The aim of these studies was to determine changes in the control of spontaneous contractions in a model of experimental colitis that included reinflammation of the healed area. The amplitude and frequency of spontaneous contractions in circular smooth muscle were determined after intrarectal administration of trinitrobenzenesulfonic acid in rat distal colon. With the use of a novel paradigm, rats were studied 4 h (acute) or 28 days (healed) after the initial inflammation. At 28 days, rats were studied 4 h after a second inflammation (reinflamed) of the colon. Colitis induced transient increases in the amplitude of spontaneous contractions coincident with a loss of nitric oxide synthase activity. The frequency of contractions was controlled by constitutive nitric oxide in controls. Frequency was increased in healed and reinflamed colon and was associated with a shift in the dominance of neural constitutive nitric oxide synthase control to that of inducible nitric oxide synthase (iNOS). The initial colitis induced a remodeling of the neural control of spontaneous contractions reflecting changes in their regulation by constitutive nitric oxide synthase and iNOS.     

VEGF(121)- and bFGF-induced increase in collateral blood flow requires normal nitric oxide production

The angiogenic proteins basic fibroblast growth factor (bFGF; FGF-2) and vascular endothelial growth factor 121 (VEGF(121)) are each able to enhance the collateral-dependent blood flow after bilateral femoral artery ligation in rats. To study the effect of nitric oxide (NO) synthase (NOS) inhibition on bFGF- or VEGF(121)-induced blood flow expansion, the femoral arteries of male Sprague-Dawley rats were ligated bilaterally, and the animals were given tap water [non-N(G)-nitro-L-arginine methyl ester (L-NAME) group; n = 36] or water that contained L-NAME (L-NAME group; 2 mg/ml, n = 36). Animals from each group were further divided into three subgroups: vehicle (n = 12), bFGF (5 microg x kg(-1) x day(-1), n = 12), or VEGF(121) (10 microg x kg(-1) x day(-1), n = 12). Growth factors were delivered via intra-arterial infusion with osmotic pumps over days 1-14. On day 16, after a 2-day delay to permit clearance of bFGF and VEGF from the circulation, maximal collateral blood flow was determined by (85)Sr- and (141)Ce-labeled microspheres during treadmill running. L-NAME (approximately 137 mg x kg(-1) x day(-1)) for 18 days increased systemic blood pressure (approximately 26%, P<0.001). In the absence of L-NAME, collateral-dependent blood flows to the calf muscles were greater in the VEGF(121)- and bFGF-treated subgroups (85 +/- 4.5 and 80 +/- 2.9 ml x min(-1) x 100 g(-1), respectively) than in the vehicle subgroup (49 +/- 3.0 ml x min(-1) x 100 g(-1), P<0.001). In the presence of NOS inhibition by L-NAME, blood flows to the calf muscles were essentially equivalent among the three subgroups (54 +/- 3.0, 56 +/- 5.1, and 47 +/- 2.0 ml x min(-1) x 100 g(-1) in the bFGF-, VEGF(121)-, and vehicle-treated subgroups, respectively) and were not different from the blood flow in the non-L-NAME vehicle subgroup. Our results therefore indicate that normal NO production is essential for the enhanced vascular remodeling induced by exogenous bFGF or VEGF(121) in this rat model of experimental peripheral arterial insufficiency. These results imply that a blunted endothelial NO production could temper vascular remodeling in response to these angiogenic growth factors.     

Cardiac malformations are associated with altered expression of vascular endothelial growth factor and endothelial nitric oxide synthase genes in embryos of diabetic mice

The aim of this study was to investigate the role of nitric oxide (NO), and the expression of endothelial nitric oxide synthase (eNOS) and vascular endothelial growth factor (VEGF) genes in developing hearts at embryonic day 13.5 of embryos from diabetic mice. The protein and mRNA expression levels of eNOS and VEGF were significantly altered in the developing hearts of embryos from diabetic mice. The NO level was significantly decreased, whereas the VEGF concentration was significantly increased in the developing hearts of the embryos from diabetic mice. In vitro study showed a significant reduction in eNOS expression and cell proliferation in cardiac myoblast cells exposed to high glucose concentrations. Further, high glucose induced apoptosis in myoblast cells. Ultrastructural changes characteristics of apoptosis, including cell blebbing, aggregation of ribosomes and vacuoles in the cytoplasm were also evident in myoblast cells exposed to high glucose. It is suggested that hyperglycemia alters the expression of eNOS and VEGF genes that are involved in the regulation of cell growth and vasculogenesis, thereby contributing to the cardiac malformations seen in embryos from diabetic mice.     

Zinc deficiency during growth: influence on renal function and morphology

This study was designed to investigate the effects of moderate zinc deficiency during growth on renal morphology and function in adult life. Weaned male Wistar rats were divided into two groups and fed either a moderately zinc-deficient diet (zinc: 8 mg/kg, n=12) or a control diet (zinc: 30 mg/kg, n=12) for 60 days. We evaluated: renal parameters, NADPH-diaphorase and nitric oxide synthase activity in kidney, renal morphology and apoptotic cells in renal cortex. Zinc-deficient rats showed a decrease in glomerular filtration rate and no changes in sodium and potassium urinary excretion. Zinc deficiency decreased NADPH diaphorase activity in glomeruli and tubular segment of nephrons, and reduced activity of nitric oxide synthase in the renal medulla and cortex, showing that zinc plays an important role in preservation of the renal nitric oxide system. A reduction in nephron number, glomerular capillary area and number of glomerular nuclei in cortical and juxtamedullary areas was observed in zinc deficient kidneys. Sirius red staining and immunostaining for alpha-smooth muscle-actin and collagen III showed no signs of fibrosis in the renal cortex and medulla. An increase in the number of apoptotic cells in distal tubules and cortical collecting ducts neighboring glomeruli and, to a lesser extent, in the glomeruli was observed in zinc deficient rats. The major finding of our study is the emergence of moderate zinc deficiency during growth as a potential nutritional factor related to abnormalities in renal morphology and function that facilitates the development of cardiovascular and renal diseases in adult life.     

Flavonoid genistein protects bone marrow sinusoidal blood vessels from damage by methotrexate therapy in rats

Cancer chemotherapy can cause significant damage to the bone marrow (BM) microvascular (sinusoidal) system. Investigations must now address whether and how BM sinusoidal endothelial cells (SECs) can be protected during chemotherapy. Herein we examined the potential protective effects of genistein, a soy-derived flavonoid, against BM sinusoidal damage caused by treatment with methotrexate (MTX). The groups of young adult rats were gavaged daily with genistein (20 mg/kg) or placebo. After 1 week, rats also received daily injections of MTX (0.75 mg/kg) or saline for 5 days and were killed after a further 4 days. Histological analyses showed that BM sinusoids were markedly dilated ( p < 0.001) in the MTX-alone group but were unaffected or less dilated in the genistein+MTX group. In control rats, genistein significantly enhanced expression of vascular endothelial growth factor (VEGF; p < 0.01), particularly in osteoblasts, and angiogenesis marker CD31 ( p < 0.001) in bone. In MTX-treated rats, genistein suppressed MTX-induced apoptosis of BM SECs ( p < 0.001 vs MTX alone group) and tended to increase expression of CD31 and VEGF ( p < 0.05). Our in vitro studies showed that genistein in certain concentrations protected cultured SECs from MTX cytotoxic effects. Genistein enhanced tube formation of cultured SECs, which is associated with its ability to induce expression of endothelial nitric oxide synthase and production of nitric oxide. These data suggest that genistein can protect BM sinusoids during MTX therapy, which is associated, at least partially, with its indirect effect of promoting VEGF expression in osteoblasts and its direct effect of enhancing nitric oxide production in SECs.     

Effects of nitric oxide synthase inhibitors on the febrile response to muramyl dipeptide and lipopolysaccharide in rats

We have administered aminoguanidine, a relatively specific inhibitor of inducible nitric oxide synthase, and N-nitro-L-arginine methyl ester (L-NAME), an unspecific nitric oxide synthase inhibitor, to rats made febrile with the gram-positive pyrogen, muramyl dipeptide and gram-negative pyrogen, lipopolysaccharide. Sprague-Dawley rats, housed individually at approximately 25 degrees C with a 12:12 h light:dark cycle (lights on 0700 hours), were injected (at 0900 hours) intraperitoneally with 50 mg/kg aminoguanidine, 25 mg/kg or 50 mg/kg L-NAME, and intramuscularly with 500 microg/kg muramyl dipeptide or 100 microg/kg lipopolysaccharide. Pyrogen injections were spaced at least 14 days apart. Body temperature was measured throughout the study in unrestrained animals using radio-telemetry. Neither muramyl dipeptide nor lipopolysaccharide-induced fevers were affected by aminoguanidine. However, L-NAME administration inhibited muramyl dipeptide and lipopolysaccharide-induced fevers, but only for the 1st 2-4 h of the fevers (two-way ANOVA, P<0.05). After the initial inhibition, lipopolysaccharide fevers developed normally. Therefore, constitutively expressed nitric oxide synthase appears to be involved in the initial phases of fever genesis of gram-negative and gram-positive fevers in rats. On the other hand, inducible nitric oxide synthase appears not to play a role in these fevers.     

Nitric oxide is responsible for oxidative skin injury and modulation of cell proliferation after 24 hours of UVB exposures

Nitric oxide (NO) is produced by various mammalian cells and plays a variety of regulatory roles in normal physiology and in pathological processes. This article provides evidence regarding the participation of NO in UVB-induced skin lesions and in the modulation of skin cell proliferation following UVB skin irradiation. Hairless mice were subjected to UVB irradiation for 3 hours and the skin evaluated immediately, 6 and 24 hours postirradiation. The skin lipid peroxidation, and NO levels evaluated by chemiluminescence and inducible nitric oxide synthase (iNOS) and nitrotyrosine immunolabelling increased significantly 24 hours after irradiation and decreased under the treatment with aminoguanidine (AG). On the other hand, cell proliferation markers, PCNA and VEGF showed a strong labelling index when AG was used. The data indicate that NO mediates, at least in part, the lipid peroxidation and protein nitration and also promotes the down regulation of factors involved in cell proliferation. This work shows that the NO plays an important role in the oxidative stress damage and on modulation of cell proliferation pathways in UVB irradiated skin.     

Hypoxia-induced expression of HIF-1alpha and its target genes in umbilical venous endothelial cells of Tibetans and immigrant Han

The better adaptation of native Tibetans to hypoxia is thought to be partly due to improved umbilical circulation, which results in reduced pre- and postnatal fatalities. We hypothesized that the difference in umbilical circulation between native Tibetans and other high-altitude inhabitants was due to differences in the expression of hypoxia-induced factor (HIF-1) and its target genes vascular endothelial growth factor (VEGF) and inducible nitric oxide synthase (iNOS). We tested this hypothesis by examining the effect of hypoxia on the expression of HIF-1alpha, VEGF, and iNOS in cultured umbilical venous endothelial cells (UVECs) from native Tibetans and immigrant Hans. UVECs were collected and cultured under hypoxic (0.5% oxygen) or normoxic conditions for 2, 4, 12 and 24 h. The mRNA levels of HIF-1alpha, VEGF, endothelial nitric oxide synthase (eNOS) and iNOS and the protein level of HIF-1alpha were determined with RT-PCR and Western blot analyses, respectively. In both immigrant Han and Tibetans, HIF-1alpha mRNA was constitutively expressed under normoxic condition, and remained constant after hypoxic exposure. In contrast, HIF-1alpha protein was undetectable under normoxic condition, but underwent dynamic changes in response to hypoxia. It was induced at 4 h, peaked at 12 h, and remained elevated at 24 h. Concurrent with the induction of HIF-1alpha protein, the mRNA levels of VEGF and iNOS were also up-regulated whereas that of eNOS was down-regulated. The lack of a hypoxia-related difference in the expression of HIF-1alpha and its target genes suggests that HIF-1alpha does not play a critical role in high altitude adaptation. Alternative mechanisms may be responsible for the better adaptation of native Tibetans.     

Nitric oxide mediates the mitogenic effects of insulin and vascular endothelial growth factor but not of leptin in endothelial cells

The regulation of vascular wall homeostasis by nitric oxide (NO) generated by endothelium is being intensively studied. In the present paper, the involvement of NO in the vascular endothelial growth factor (VEGF), insulin or leptin-stimulated proliferation of human endothelial cells (HUVEC) was measured by [3H]thymidine or bromodeoxyuridine incorporation. VEGF and insulin, but not leptin, increased NO generation in HUVEC, as detected with ISO-NO electrode. Proliferation of HUVEC induced by leptin was not changed or was higher in the presence of N(omega)-nitro-L-arginine methyl ester (L-NAME) a nitric oxide synthase (NOS) inhibitor. In contrast, L-NAME blunted the proproliferative effect of VEGF and insulin. Furthermore, we demonstrated that, in human arterial smooth muscle cells (hASMC) transfected with endothelial NOS (eNOS) gene, the generation of biologically active VEGF protein was NO-dependent. Inhibition of NO generation by L-NAME decreased the synthesis of VEGF protein and attenuated HUVEC proliferation induced by conditioned media from transfected hASMC. Endothelium-derived NO seems to participate in VEGF and insulin, but not leptin, mitogenic activity. Additionally, the small amounts of NO released from endothelial cells, as mimicked by eNOS transfection into hASMC, may activate generation of VEGF in sub-endothelial smooth muscle cells, leading to increased synthesis of VEGF protein necessary for turnover and restitution of endothelial cells.     

Inhibition of vascular endothelial growth factor-induced retinal neovascularization by retinoic acid in experimental retinopathy of prematurity

Vascular endothelial growth factor (VEGF) has an important role in the pathogenesis of retinopathy of prematurity (ROP) and inhibition of VEGF expression in the neovascular phase might prevent destructive neovascularization in ROP. It is suggested that retinoids exert a highly potent antiangiogenic activity by inhibiting VEGF expression. The aim of this study was to demonstrate the preventive effect of retinoic acid (RA) on the VEGF-induced retinal neovascularization in a rat model of ROP. Wistar albino rats were placed into incubators at birth and exposed to an atmosphere alternating between 50 % and 10 % O(2) every 24 hours. After 14 days, the animals were removed to room air and received either an intraperitoneal injection of RA (5 mg/kg/day) (n=9) or saline (n=4) daily for six days, and sacrificed at 21 days. Other rats (n=4) were raised in room air and served as age-matched controls. The globe of each eye was cut through the cornea and embedded in paraffin. Serial sections were stained with hematoxylin-eosin for quantification of neovascular nuclei. The avidin-biotin peroxidase method was performed for evaluation of VEGF expression. The average number of neovascular nuclei was significantly lower in the control group compared to that in the ROP groups. In addition, it significantly decreased in the RA-treated ROP group compared to that of the saline-administrated ROP group. VEGF immunostaining was overall negative in room air-exposed rats. The VEGF immunostaining score significantly decreased in the RA-treated ROP group compared to that in the saline-administered ROP group. RA treatment might be beneficial in preventing neovascularization resulting from oxygen-induced retinopathy by downregulation of VEGF expression.     

The role of iNOS inhibitors on lung injury induced by gastrointestinal decontamination agents aspiration

Aspiration is a devastating complication during decontamination procedure in poisoning patients. We have investigated whether S-methylisothiourea protects different pulmonary aspiration gastrointestinal decontamination agent-induced lung injury in rats. Forty-two male Sprague-Dawley rats were assigned to one of six groups (n = 7): normal saline, activated charcoal, polyethylene glycol, normal saline + S-methylisothiourea treated activated charcoal + S-methylisothiourea treated and polyethylene glycol + S-methylisothiourea treated. Normal saline, activated aharcoal and polyethylene glycol were instilled into the lungs. The rats received S-methylisothiourea i.p twice daily for 7 days. Serum surfactant protein D, oxidative stress products and inducible nitric oxide synthase expression in the lung were investigated. The aspiration of activated charcoal significantly increased all histopathological scores (P < 0.01). Only peribronchial inflammatory cell infiltration, alveolar edema, and alveolar histiocytes were increased in the polyethylene glycol groups as compared to the normal saline group (P < 0.05). Pulmonary aspiration increased serum malondialdehyde (P < 0.001), and surfactant protein D (P < 0.05) levels and decreased serum superoxide dismutase levels (P < 0.05). S-methylisothiourea treatment decreased all histopathological scores in the activated charcoal treated S-methylisothiourea group (P < 0.01) and only decreased alveolar edema and alveolar histiocytes in the polyethylene glycol-treated S-methylisothiourea group (P < 0.05). S-methylisothiourea treatment reduced elevated oxidative factors, inducible nitric oxide synthase activity and serum surfactant protein D levels. Our findings showed that S-methylisothiourea may be a protective drug against Activated Charcoal and Polyethylene Glycol-induced lung injury.     

Nitric oxide is responsible for oxidative skin injury and modulation of cell proliferation after 24 hours of UVB exposures

Abstract

Nitric oxide (NO) is produced by various mammalian cells and plays a variety of regulatory roles in normal physiology and in pathological processes. This article provides evidence regarding the participation of NO in UVB-induced skin lesions and in the modulation of skin cell proliferation following UVB skin irradiation. Hairless mice were subjected to UVB irradiation for 3 hours and the skin evaluated immediately, 6 and 24 hours postirradiation. The skin lipid peroxidation, and NO levels evaluated by chemiluminescence and inducible nitric oxide synthase (iNOS) and nitrotyrosine immunolabelling increased significantly 24 hours after irradiation and decreased under the treatment with aminoguanidine (AG). On the other hand, cell proliferation markers, PCNA and VEGF showed a strong labelling index when AG was used. The data indicate that NO mediates, at least in part, the lipid peroxidation and protein nitration and also promotes the down regulation of factors involved in cell proliferation. This work shows that the NO plays an important role in the oxidative stress damage and on modulation of cell proliferation pathways in UVB irradiated skin.