In vitro modulation of human neutrophil superoxide anion generation by various calcium channel antagonists used in ischemia-reperfusion resuscitation

Parkia speciosa empty pod prevents hypertension and cardiac damage in rats given N(G)-nitro-l-arginine methyl ester

Parkia speciosa Hassk is a plant found abundantly in Southeast Asia region. Its seeds with or without pods and roots have been used in traditional medicine in this region to treat hypertension. Therefore, we aimed to investigate the potential effect of the plant empty pod extract on hypertension development and changes in heart induced by N(G)-nitro-l-arginine methyl ester (l-NAME) administration in rats. Twenty-four male Sprague Dawley rats were divided into four groups. Groups 1 to 3 were given l-NAME (25mg/kg, intraperitoneally) for 8 weeks. Groups 2 and 3 were also given Parkia speciosa empty pods methanolic extract (800mg/kg, orally) and nicardipine (3mg/kg, orally), concurrently with l-NAME. The last group served as the control. l-NAME reduced plasma nitric oxide level and therefore, increased systolic blood pressure, angiotensin-converting enzyme and NADPH oxidase activities as well as lipid peroxidation in the heart. Parkia speciosa extract and nicardipine treatments had significantly prevented the elevations of blood pressure, angiotensin-converting enzyme, NADPH oxidase activities and lipid peroxidation in the heart induced by the l-NAME. Parkia speciosa extract but not nicardipine prevented the reduction in plasma nitric oxide level caused by l-NAME. In conclusion, Parkia speciosa empty pods methanolic extract has a potential to prevent the development of hypertension possibly by preventing the loss of plasma nitric oxide, as well as has cardioprotective effects by reducing angiotensin-converting enzyme activity and oxidative stress in the heart in rats administered l-NAME.

Molecular responses to ischemia and reperfusion in the liver

Ischemia/reperfusion (IR) injury occurs when oxygen is rapidly reintroduced into ischemic tissue, resulting in cell death and necrotic tissue damage. This is a major concern during liver transplantation procedures since there is an inevitable interruption and subsequent restoration of circulation. IR injury in liver tissue is initiated through reactive oxygen species (ROS), which are generated by hepatocytes during IR insult. Although these ROS are thought to play a protective roll since they are known to activate several pathways involved in the hypoxic response, they also trigger a localized sterile immune response that results in the recruitment of Kupffer cells and neutrophils to the site of IR insult. These immune cells generate larger quantities of ROS that trigger apoptosis and oncotic necrosis in liver tissue. In this review, we will summarize what is currently known about the response of liver tissue to IR insult at the molecular level.

Store-Operated Calcium Channel Inhibition Attenuates Neutrophil Function and Postshock Acute Lung Injury

BACKGROUND

A wide variety of neutrophil (PMN) functions are regulated by cytosolic calcium concentration. Calcium channel blockade might therefore decrease postshock inflammation but could also limit important cardiovascular compensations. PMN Ca2+ entry occurs, however, through store-operated calcium entry (SOCE) channels rather than the voltage operated (L-type) channels that regulate cardiovascular tone. We hypothesized that SOCE inhibition might suppress postshock PMN activation, lessening lung injury without compromising cardiovascular performance.

METHODS

Human PMNs were treated in vitro with N-propargyl-nitrendipine (MRS1845 [MRS]) a dihydropyridine Ca2+ channel blocker with relative specificity for SOCE channels. Calcium flux was measured by fura fluorescence. Chemotaxis was studied in modified Boyden chambers. Respiratory burst was studied by dihydrorhodamine fluorescence. Exploratory studies were then performed where rats were subjected to trauma and hemorrhagic shock (T/HS) (laparotomy, then hemorrhage to a mean arterial pressure of 30-40 mm Hg for 90 minutes) after pretreatment with MRS or vehicle given intraperitoneally at laparotomy. In vivo PMN CD11b expression was then assayed by flow cytometry and lung injury was assessed as percentage Evans blue dye leak 3 hours after resuscitation. The shed blood volume required to achieve standardized hypotension was measured.

RESULTS

In vitro, MRS suppressed human PMN SOCE without affecting calcium store release; it suppressed chemotaxis (60 +/- 6 vs. 150 +/- 15 x 10(3) PMNs/well, p = 0.002) and suppressed respiratory burst (62 +/- 11% vs. 100%, p < 0.05) at IC50 concentrations similar to those needed to suppress SOCE. In subsequent in vivo rat studies, MRS decreased postshock PMN CD11b expression from 397 +/- 93 to 268 +/- 39 MFU mean flourescent units (p < 0.05) and decreased lung Evans blue dye permeability from 8.1 +/- 1.9% to 3.4 +/- 0.1% (p < 0.05). MRS had no noticeable effect on the relationship between blood pressure and blood loss, with shed blood volume remaining almost identical (26 +/- 2 mL/kg vs. 27 +/- 3 mL/kg, p = not significant).

CONCLUSION

Modulation of PMN Ca2+ entry by means of selective SOCE channel inhibition attenuates PMN inflammatory responses in vitro. In vivo, SOCE channel blockade attenuates trauma and hemorrhagic shock-induced PMN priming and lung injury without gross evidence of hemodynamic side effects. The relative specificity of SOCE channel blockade for "nonexcitable" cells such as PMNs may make it a valuable form of chemoprophylaxis for the inflammatory consequences of hemorrhagic shock in trauma patients.

Simultaneous measurements of cytoplasmic Ca2+ responses and intracellular pH in neutrophils of localized aggressive periodontitis (LAP) patients

In view of the reports that polymorphonuclear leukocytes (PMN) of patients with localized aggressive periodontitis (LAP) exhibit hyper-responsiveness to stimulation, it has been suggested that such abnormalities could lead to PMN-mediated tissue damage during inflammation. To determine whether these abnormalities include signal transduction, we compared cytoplasmic calcium concentration (Delta[Ca2+](i)) and cytoplasmic pH (DeltapH(i)) changes, early stimulus responses to chemotactic agents, of LAP versus control (C)-PMN and explored whether these could be modulated by sensitizing cytokines or calcium channel-blocking agents. PMN responses of LAP patients were compared with age- and gender-matched controls. Delta[Ca2+](i) and DeltapH(i) were measured fluorimetrically using 1H-indole-6-carboxylic acid, 2-[4-[bis[2-[(acetyloxy)methoxy]-2-oxoethyl]amino]-3-[2-[2-[bis[2-[(acetyloxy)methoxy]-2-oxoethyl]amino]-5-methylphenoxy]ethoxy]phenyl]-1 and 2',7'-bis-(carboxyethyl)-5(6)-carboxyfluorescein as respective probes. Not only was the maximal calcium response to chemoattractants higher in LAP-PMN, but also their subsequent intracellular calcium redistribution was significantly slower. The slower calcium redistribution of LAP-PMN, but not their higher maximal calcium response, was successfully mimicked in C-PMN treated with Nifedipine or 1-[b-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl]-1H-imidazole-HCl, both known to be inhibitors of membrane-associated calcium influx, but this redistribution was not affected when inhibitors of other calcium influx mechanisms, Diltiazem or Verapamil, were used. Taken together, our findings indicate that certain early stimulus responses are aberrant in LAP-PMN, that internal redistribution of cytoplasmic-free calcium is compromised, and, additionally, that a membrane-associated Ca2+ transport defect may be present.

Reperfusion injury after focal myocardial ischaemia: polymorphonuclear leukocyte activation and its clinical implications

The only way to rescue ischaemic tissue is to re-instate the oxygen supply to the tissue. However reperfusion of the ischaemic area not only oxygenates the tissue but also initiates a cascade of processes, which may in some cases result in temporary dysfunction of the myocardium. In order to devise protective measures, it is essential to understand the mechanisms and the triggers of this reperfusion phenomenon. In this review we will mainly focus on the inflammatory response caused by reperfusion. We will cover the different steps of polymorphonuclear leukocyte activation and will briefly discuss the molecular biology of the receptors involved. The currently used pharmacological medications in acute cardiology will be reviewed and in particular their actions on polymorphonuclear leukocyte activation, adhesion and degranulation. This review is a compilation of the current knowledge in the field and the therapeutic progress in the prevention of reperfusion injury made today.

Plasma and lipids from stored packed red blood cells cause acute lung injury in an animal model

Transfusion-related acute lung injury (TRALI) is a serious complication of hemotherapy. During blood storage, lipids are generated and released into the plasma. In this study, the role of these lipids in TRALI was investigated using an isolated, perfused rat lung model. Rats were pretreated with endotoxin (LPS) or saline in vivo and the lungs were isolated, ventilated, and perfused with saline, or (a) 5% (vol/ vol) fresh human plasma, (b) plasma from stored blood from the day of isolation (D.0) or from the day of outdate (D.42), (c) lipid extracts from D.42 plasma, or (d) purified lysophosphatidylcholines. Lungs from saline or LPS-pretreated rats perfused with fresh (D.0) plasma showed no pulmonary damage as compared with saline perfused controls. LPS pretreatment/D.42 plasma perfusion caused acute lung injury (ALI) manifested by dramatic changes in both pulmonary artery pressure and edema. Incubation of LPS pre-tx rats with mibefradil, a Ca2+ channel blocker, or WEB 2170, a platelet-activating factor (PAF) receptor antagonist, inhibited ALI caused by D.42 plasma. Lung histology showed neutrophil sequestration without ALI with LPS pretreatment/saline or D.0 plasma perfusion, but ALI with LPS pretreatment/D.42 plasma perfusion, and inhibition of D.42 plasma induced ALI with WEB 2170 or mibefradil. A significant increase in leukotriene E4 was present in LPS-pretreated/D.42 plasma-perfused lungs that was inhibited by WEB 2170. Lastly, significant pulmonary edema was produced when lipid extracts of D.42 plasma or lysophosphatidylcholines were perfused into LPS-pretreated lungs. Lipids caused ALI without vasoconstriction, except at the highest dose employed. In conclusion, both plasma and lipids from stored blood produced pulmonary damage in a model of acute lung injury. TRALI, like the adult respiratory distress syndrome, may be the result of two insults: one derived from stored blood and the other from the clinical condition of the patient.

Azotemia, TNF alpha, and LPS prime the human neutrophil oxidative burst by distinct mechanisms

The oxidative burst of neutrophils from azotemic patients (AzoPMNs) is primed for an enhanced response compared to neutrophils from normal subjects (NorPMNs). The mechanism for this priming is unknown, although TNF alpha does not further prime AzoPMNs. The present study examines the hypothesis that azotemia and TNF alpha prime neutrophils by the same mechanism. Formyl peptide receptor expression and degranulation were not primed in AzoPMNs, but were primed by both LPS and TNF alpha. LPS was also able to prime the AzoPMN oxidative burst. Guanine nucleotide exchange by multiple guanine nucleotide binding proteins, including heterotrimeric G-proteins and low molecular weight GTP-binding proteins (LMWGs), was increased in AzoPMNs, as demonstrated by GTP gamma S binding and azidoanilide GTP photoaffinity labeling. The plasma membrane density of G-protein alpha i2, alpha i3, and alpha s subunits and the density in the cytosol of the LMWG, Rap1A, was present in significantly greater amounts on plasma membranes from AzoPMNs. FMet-Leu-Phe-stimulated phospholipase D activity, but not basal activity, was significantly greater in AzoPMNs. Finally, incubation of NorPMNs in plasma from azotemic patients resulted in a significant increase in basal GTP gamma S binding. These results demonstrate that priming of AzoPMNs is restricted to oxidative burst activity and that it occurs by a mechanism distinct from that utilized by TNF alpha and LPS. While the exact mechanism remains unknown, it appears to involve a plasma factor and changes in LMWG expression or activity.

Characterization of drugs as antioxidant prophylactics

There is growing interest in the evaluation of drugs (prescription only medicines and over-the-counter medicines) as antioxidant prophylactics. Although free radical mechanism in human degenerative diseases is now generally recognised, the mechanisms of tissue injury in humans are very complex and it may not be possible to clearly identify the role played by free radicals in the process. This review examines the current evidence to support the notion that drugs for a particular therapeutic category might possess useful antioxidant capacity hence minimising tissue injury due to free radicals.

Effect of activation on adhesion of flowing neutrophils to cultured endothelium: time course and inhibition by a calcium channel blocker (nitrendipine)

1. Adhesion of neutrophils to vascular endothelium plays an important role in inflammation and thrombosis. Modulation of adhesion may be therapeutic in these conditions. 2. A flow model was used to quantify adhesion of neutrophils to human cultured umbilical vein endothelial cells. The time course of the neutrophil response to activation by N-formyl-methionyl-leucylphenylalanine (fMLP, 10(-7) M) was studied and the inhibitory effects of the calcium-channel blockers, nitrendipine and nifedipine, were investigated. 3. Neutrophils adhered firmly to the endothelial cells without rolling, but initial attachment was highly dependent on shear stress; doubling the stress from 0.05 to 0.1Pa decreased the number of neutrophils adhering by over 80%. 4. Adhesion rapidly increased after activation of neutrophils by fMLP, peaking at 1-3 min post-treatment, and then decreased over the next 10-12 min. A monoclonal antibody to the beta 2-integrin component CD18 inhibited adhesion by over 80% for activated or unactivated cells. 5. The Ca-channel blocker, nitrendipine, but not nifedipine, significantly inhibited the fMLP-induced increase of adhesion in a dose-dependent manner (10(-8) to 10(-6) M). Dihydropyridines may be useful agents for modifying neutrophil function.

The relationship between excitotoxicity and oxidative stress in the central nervous system

Excitotoxicity and oxidative stress are two phenomena that have been repeatedly described as being implicated in a wide range of disorders of the nervous system. Such disorders include several common idiopathic neurological diseases, traumatic brain injury, and the consequences of exposure to certain neurotoxic agents. While there is evidence that metabolic derangements can lead to these adverse processes, and that these processes may synergize in their damaging effects, the degree of interdependence, and the causal relation between them is not clear. The intent of this review is to delineate potential mechanisms which may unit hyperexcitation to the excessive generation of reactive oxygen species. The degree of linkage between these events appears rather strong. It is likely that excitoxicity frequently leads to a pro-oxidant condition but that high rates of these events appears rather strong. It is likely that excitoxicity frequently leads to a pro-oxidant condition but that high rates of generation of reactive oxygen species are not invariably accompanied by a hyperexcited neuronal state Both excitoxic and 'oxidotoxic' states result from the failure of normal compensatory antiexcitatory and antioxidant mechanisms to maintain cellular homeostasis.

Beta-adrenoceptor antagonists enhance white blood cell aggregation in patients with ischaemic heart disease

The effects of beta-adrenoceptor antagonists, calcium channel blockers and long acting nitrates on white blood cell (WBC) aggregation were studied in patients with ischaemic heart disease. WBC aggregation was significantly increased by beta-adrenoceptor antagonists (P = 0.011) but was unaffected by either calcium channel blockers or long acting nitrates. Enhanced WBC aggregation promotes microvascular occlusion and damage.

Pharmacological modulation of the antioxidant enzymes activities and the concentration of peroxidation products in fibroblasts stimulated with elastin peptides

1. Elastin peptides (kappa-elastin) prepared by alcoholic potassium hydroxide degradation of insoluble elastin were shown to increase the activities of antioxidant enzymes (SOD, CAT, GSH-Px) and the lipid peroxide concentration within fibroblasts. 2. The preincubation of cells with nifedipine (calcium channel antagonist) and trifluoperazine (calmodulin antagonist) caused the decrease in the activities of studied enzymes and the concentration of TBA-reactive products in fibroblasts stimulated with kappa-elastin. 3. The preincubation with ketotifen (antiallergic drug) has no effect on the activities of SOD, CAT, GSH-Px and the lipid peroxide concentration in stimulated cells. 4. These data suggest the possibilities of pharmacological modulation of the biological effects induced by elastin-derived peptides.

Inhibition by calcium channel blockers of the binding of platelet-activating factor to human neutrophil granulocytes

The inhibitory action of calcium channel blockers on platelet-activating factor (PAF)-induced activation of human polymorphonuclear granulocytes (PMNL) and on the binding of [3H]PAF to neutrophils was studied. Verapamil and diltiazem inhibited PAF (10(-8)-10(-15) M)-induced degranulation and superoxide production in a dose-dependent manner, with pA2 values of 5.6 and 6.1 for verapamil and 5.9 and 6.2 for diltiazem, respectively. Both channel blockers inhibited the specific binding of [3H]PAF to PMNL in dose-dependent fashion, with Ki values of 3.9 +/- 0.6 X 10(-5) M and 3.2 +/- 0.4 X 10(-5) M for verapamil and diltiazem, respectively. Scatchard analysis of the binding data revealed that both calcium channel blockers decreased the receptor binding affinity and slightly increased the number of high-affinity PAF receptors, whereas they did not affect the binding affinity and number of low-affinity receptors. These results indicate that calcium channel blockers can inhibit neutrophil responses elicited by PAF by a mechanism other than inhibition of calcium influx and suggest that the PAF receptor may be closely associated with calcium channels.