A new antithrombotic agent, aspalatone, attenuated cardiotoxicity induced by doxorubicin in the mouse; possible involvement of antioxidant mechanism

A new antithrombotic agent, aspalatone (APT; acetyl salicylic acid maltol ester), was synthesized by esterification of acetyl salicylic acid (ASP) and maltol (MAL). It was suggested that APT possessed an antioxidant effect in in vitro. To evaluate the putative antioxidant effect of APT in in vivo, we developed doxorubicin (DOX)-related cardiac damage, which might be implicated by oxidative stress. Vitamin E (Vit E) was included in the present study as an example of an antioxidant. Prolonged treatments with APT, MAL and Vit E significantly reduced the mortality in animals receiving multiple dose of DOX (3 mg/kg x 4). The potential role of APT, MAL and Vit E against DOX insult may be explained by the induction of glutathione peroxidase activity accompanied by the inhibition of lipid peroxidation. Prolonged treatments of APT, MAL and Vit E also ablated histopathological evidence of DOX cardiomyopathy. ASP challenge, however, did not affect the mortality, myocardial lesion and antioxidant deficit induced by DOX treatments. In conclusion, the protective effect of APT was equipotent to that of Vit E against DOX cardiotoxicity. The results also suggest that the antiperoxidative effect of APT plays a protective role in DOX-related cardiotoxic side effect.

Alpha-alpha diaspirin crosslinked hemoglobin, nitric oxide, and cerebral ischemic injury in rats

Prior studies indicate that alpha-alpha diaspirin crosslinked hemoglobin (DCLHb) decreases cerebral ischemia. One mechanism whereby DCLHb may ameliorate cerebral ischemia is by binding nitric oxide (NO), which has been implicated as neurotoxic. We assessed the effect of L-NAME (NO synthase inhibitor) and L-arginine (NO substrate) on ischemic brain injury after DCLHb infusion. Rats were randomized to one of the following groups: Control-no hematocrit manipulation; DCLHb-hematocrit decreased to 16% with 10% DCLHb; DCLHb/L-NAME-hematocrit decreased to 16% with DCLHb, and L-NAME given; DCLHb/L-arg-hematocrit decreased to 16% with DCLHb, and L-arginine given. After 90-min of middle cerebral artery occlusion and 4-hr of reperfusion, infarct volume was determined with TTC stain. Infarct volume (mm3, mean +/- SD) was greater in the Control group (142 +/- 16) than the DCLHb (43 +/- 12), DCLHb/L-NAME (45 +/- 14), and DCLHb/L-arg (71 +/- 18) groups (p < 0.05); was greater in the DCLHb/L-arg group than the DCLHb and DCLHb/L-NAME groups (p < 0.05); but was not different between the DCLHb and DCLHb/L-NAME groups. These data indicate that DCLHb decreases ischemic brain injury, and that binding NO may be one mechanism by which DCLHb decreases ischemic brain injury.

Effect of subarachnoid administration of alpha-alpha diaspirin crosslinked hemoglobin on cerebral blood flow in rats

As extravasated red blood cells have been implicated in the pathogenesis of perfusion deficits after subarachnoid hemorrhage, alpha-alpha diaspirin crosslinked hemoglobin (DCLHb) might have a detrimental effect on cerebral perfusion after subarachnoid hemorrhage. We evaluated the effect of subarachnoid administration of DCLHb on cerebral blood flow (CBF). Rats were randomized to receive one of the following solutions into the cisterna magna: Control-0.3 ml of mock cerebrospinal fluid; Blood-0.3 ml of autologous blood; DCLHb-0.3 ml of 10% DCLHb. After 20-min, the area of cerebral hypoperfusion was determined (CBF < 40 ml.100g-1.min-1). The area of hypoperfusion (% area of a coronal brain section, mean +/- SD) was greater in the Blood group (58 +/- 16) than the DCLHb (16 +/- 7) and Control (5 +/- 5) groups (p < 0.05), and was greater in the DCLHb group than the Control group (p < 0.05). These data support a hypothesis that extravasation of blood from the intravascular to the subarachnoid space induces cerebral hypoperfusion. Moreover, the data support the hypothesis that although extravasated molecular hemoglobin decreases CBF, the adverse effect is not as severe as a similar volume of blood.

Effect of hemodilution with diaspirin cross-linked hemoglobin on intracranial pressure, cerebral perfusion pressure, and fluid requirements after head injury and shock

Hemodilution has been shown to increase cerebral blood flow (CBF) and reduce lesion volume in models of occlusive cerebral ischemia, but it has not been evaluated in the setting of head trauma and shock in which ischemia is thought to play a role in the evolution of secondary injury. In a porcine model of brain injury and shock the authors compared hemodilution with diaspirin cross-linked hemoglobin (DCLHb) to a standard resuscitation regimen using Ringer's lactate solution and shed blood. After creation of a cryogenic brain injury followed by hemorrhage, the animals received a bolus of either 4 ml/kg of Ringer's lactate solution (Group 1, six animals) or DCLHb (Group 2, six animals), followed by infusion of Ringer's lactate solution to restore mean arterial pressure (MAP) to baseline. Group 1 received shed blood 1 hour after hemorrhage (R1) in the form of packed red blood cells. Group 2 received shed blood only for an Hb count of less than 5 g/dl. The animals were monitored for 24 hours. At R1, Group 2 had a significantly greater cerebral perfusion pressure ([CPP] 88 +/- 5.7 vs. 68 +/- 2.4 mm Hg, p < 0.05). By 3 hours after hemorrhage (R3) Group 2 had a significantly lower Hb concentration (8.5 +/- 0.4 vs. 12.1 +/- 0.3 g/dl, p < 0.05) and a significantly lower intracranial pressure ([ICP] 9 +/- 0.8 vs. 14 +/- 0.6 mm Hg, p < 0.05). The total 24-hour fluid requirement was significantly less in Group 2 (10,654 +/- 505 ml vs. 15,542 +/- 1094 ml, p < 0.05) There was no difference between the groups regarding levels of regional CBF in the injured hemisphere. Cerebral O2 delivery was not significantly different between groups at any time. Lesion volume as determined at postmortem examination was not significantly different between the groups. The increased MAP and CPP and lower ICP observed in the Group 2 animals indicate that hemodilution with DCLHb may be beneficial in the treatment of head injury and shock.

Cellular responses to surgical trauma, hemorrhage, and resuscitation with diaspirin cross-linked hemoglobin in rats

BACKGROUND

Resuscitation with acellular oxygen carrier solutions offers the potential advantage of improved oxygen delivery compared with crystalloid solutions, but the detailed consequences of improved resuscitation have not been fully evaluated. This study evaluated local and systemic cellular effects of trauma, hemorrhage, and resuscitation in a model of hemorrhage and surgical trauma.

METHODS

Rats with a 10 cm full-thickness incisional wound and a 15 mL/kg hemorrhage were either not resuscitated or resuscitated with blood or diaspirin cross-linked hemoglobin (DCLHb). Cellular proliferative responses were evaluated at 1.5, 6, 24, and 48 hours after wounding by labeling in vivo with 5-bromo-2'-deoxyuridine. Plasma levels of interleukin-6, tumor necrosis factor-alpha, and interferon-gamma were measured by bioassay or enzyme-linked immunosorbent assay (ELISA). Bacterial translocation was measured by culturing liver homogenates.

RESULTS

Trauma inhibited keratinocyte and hepatocyte proliferation at 1.5 and 6 hours, and stimulated subsequent proliferation of keratinocytes and liver nonparenchymal cells. DCLHb stimulated wound keratinocyte proliferation, attenuated the inhibition of hepatocyte proliferation, eliminated bacterial translocation to the liver, protected the intestine from ischemic damage, and induced a rapid increase of interleukin-6 during the early phase of injury.

CONCLUSIONS

Surgical trauma alone, or in combination with hemorrhage, modulated cell proliferation both in the wound and in the remote organs of intestine and liver. DCLHb enhanced wound healing and cell proliferation as well as, or better than, freshly drawn blood, which may be beneficial for trauma care.

Resuscitation with diaspirin crosslinked hemoglobin increases cerebral and renal blood perfusion in hemorrhaged rats

Diaspirin crosslinked hemoglobin (DCLHb Baxter Healthcare Corp., Round Lake, IL, USA), a hemoglobin-based blood substitute has been found to be an effective resuscitative agent following hemorrhage in animals. The present study was undertaken to determine the effect of DCLHb on microvascular perfusion in the brain and kidney following hemorrhage in anaesthetized, male Sprague Dawley rats using laser Doppler flowmetry. Hemorrhage was induced by withdrawal of arterial blood at a rate of 0.5 to 1.0 ml/min until blood pressure of 35-40 mmHg was achieved. This was maintained for up to 30 min. The arterial blood pH, pO2, pCO2 and total hemoglobin (THb) were monitored. Hemorrhage significantly decreased pH, pCO2 and THb and increased pO. Hemorrhage significantly decreased (26%) brain blood perfusion due to a decrease (17%) in the concentration of moving red blood cells (CMBC). In the kidney there was a greater decrease (65%) in blood perfusion due to a significant decrease in both CMBC (28%) and red blood cell velocity (49%). Resuscitation with vehicle (Ringer's lactate, 4 ml/kg, i.v.) did not produce any improvement in cerebral and renal blood perfusion. Resuscitation with DCLHb (400 mg/kg, i.v.) improved perfusion in the brain (112%) due to an increase in the CMBC (69%) and the velocity of red blood cells (33%). Similarly, in the kidney, DCLHb increased perfusion (178%) by increasing CMBC (55%) and red blood cell velocity (89%) of hemorrhaged rats. The increase in renal blood perfusion was more marked (p < 0.001) than the changes in cerebral blood perfusion following resuscitation with DCLHb in hemorrhaged rats. It is concluded that DCLHb can significantly increase cerebral and renal blood perfusion of hemorrhaged rats and this effect may contribute to its efficacy as a resuscitative solution.

Hypervolemic-hemodilution during cerebral ischemia in rats: effect of diaspirin cross-linked hemoglobin (DCLHb) on neurologic outcome and infarct volume

In a rat model of middle cerebral artery occlusion (MCAo) and reperfusion (120 min), previous studies have demonstrated that hemodilution with molecular hemoglobin decreases ischemic brain injury. However, long-term recovery data on the therapeutic efficacy of molecular hemoglobin for cerebral ischemia are lacking. Accordingly, we assessed the effect of hemodilution, with alpha-alpha diaspirin cross-linked hemoglobin (DCLHb, 10 g/dl) on neurologic outcome and infarct volume after 120 min of MCAo and 72 h of reperfusion. Ischemia was achieved by passing a 0.26-mm suture, via the external carotid artery, to internally occlude the middle cerebral artery. Immediately after MCAo, the rats were randomized to one of the following groups: Control-hematocrit not manipulated (44%); 30/Hct-hematocrit maintained at 30% with DCLHb; or 16/Hct-hematocrit maintained at 16% with DCLHb. After 120 min of MCAo, the suture was removed and the rats allowed to recover. Daily neurologic examinations were performed, and after 72 h, the brains were analyzed for infarct volume with TTC stain. Infarct volume (mm3) was less in the 30/Hct group (67 +/- 10; mean +/- SD) than in the Control group (141 +/- 17); and less in the 16/Hct group (40 +/- 12) than the other two groups (p < 0.05). Neurologic outcome was improved in both hemodilution groups versus the Control group (p < 0.05). These data are consistent with previous studies, performed in a model of short-term reperfusion, which indicate a dose-dependent decrease in ischemic injury by DCLHb.

Dose response effect of diaspirin crosslinked hemoglobin (DCLHb) on systemic hemodynamics and regional blood circulation in rats

Diaspirin crosslinked hemoglobin (DCLHb, Baxter Healthcare Corporation) a hemoglobin-based blood substitute has been found to increase mean arterial pressure (MAP) in a dose limiting manner. The present study was undertaken to determine dose-dependent effects of DCLHb on systemic hemodynamics and regional blood circulation. DCLHb (10% solution) in doses of 133, 400 and 1200 mg/kg i.v. was given to urethane anaesthetized rats. Normal saline (12 ml/kg) served as a control. Cardiovascular parameters were determined using a radioactive microsphere technique. DCLHb in the doses of 133, 400 and 1200 mg/kg i.v. produced a 46%, 67% and 65% increase in MAP, respectively. Total peripheral resistance (TPR) increased significantly with 133 and 400 mg/kg dose, while cardiac output increased significantly with 400 and 1200 mg/kg dose. There was no change in heart rate. A dose of 133 mg/kg of DCLHb produced a significant decrease in blood flow to the musculoskeletal system, kidney and liver. DCLHb in the dose of 400 and 1200 mg/kg significantly increased blood flow to the heart, gastrointestinal tract (GIT), mesentery & pancreas and skin. All doses of DCLHb produced a significant increase in vascular resistance to the musculoskeletal system and liver. DCLHb in the dose of 133 mg/kg increased resistance to the GIT. heart, skin and kidneys, while the dose of 400 mg/kg increased resistance to the kidneys. A dose of 1200 mg/kg decreased coronary vascular resistance. It is concluded that cardiovascular effects appear to be different with higher (1200 mg/kg) and lower (133 mg/kg) doses of DCLHb.

Complement activation in human serum by liposome-encapsulated hemoglobin: the role of natural anti-phospholipid antibodies

In exploring the occurrence and mechanism of liposome-encapsulated hemoglobin (LEH)-induced complement (C) activation, we found that normal human serum contained low titers of IgG and IgM class natural antibodies with reactivity against LEH, and that the amount of vesicle-bound IgM significantly correlated with LEH-induced C consumption. IgM binding to LEH was inhibited by phosphocholine and ATP, but not by choline chloride. These data suggest that naturally occurring antibodies play a key role in LEH-induced C activation, and that a major portion of these antibodies are directed against the phosphate moiety on the phospholipid headgroups of liposome bilayers.

Phase I study of the safety and pharmacologic effects of diaspirin cross-linked hemoglobin solution

OBJECTIVE

To evaluate the safety, pharmacokinetics, and pharmacodynamics of diaspirin cross-linked hemoglobin solution (DCLHb) in normal, healthy volunteers.

DESIGN

Randomized, double-blind, controlled, crossover study.

SETTING

Phase I research facility of a contract research organization.

PATIENTS

Twenty-four healthy adult volunteers.

INTERVENTIONS

Diaspirin cross-linked hemoglobin solution (25, 50, or 100 mg/kg) or equal volume of lactated Ringer's solution was infused on day 1; the alternate solution was infused 6 days later. Laboratory analyses, electrocardiograms, and Holter and telemetry monitoring were performed to assess organ function, pharmacokinetics, and potential toxicity. Vital signs, pulse oximetry, laser Doppler flowmetry, and toe temperature were measured to evaluate diaspirin cross-linked hemoglobin solution's pharmacodynamic effects.

MEASUREMENTS AND MAIN RESULTS

There were no serious adverse events associated with diaspirin cross-linked hemoglobin solution infusion. Abdominal pain occurred in three subjects after control infusion and in six subjects after diaspirin cross-linked hemoglobin solution infusion; no treatment was required. A dose-related increase in lactic dehydrogenase (LDH)-5 isoenzyme concentrations was observed in 12 subjects after diaspirin cross-linked hemoglobin solution infusion. There were no associated increases in the circulating concentrations of total LDH, aspartate aminotransferase, alanine aminotransferase, or alkaline phosphatase. Total serum creatine kinase concentrations increased significantly after infusion of 100 mg/kg of diaspirin cross-linked hemoglobin solution; the isoenzyme creatine kinase-myocardial band (CK-MB) was not increased, nor were there any abnormal electrocardiogram findings. There were no differences in laser Doppler, pulse oximetry, or toe temperature measurements during or after either infusion. The half-life of diaspirin cross-linked hemoglobin solution was 2.5 hrs for the 25- and 50-mg/kg doses and 3.3 hrs for the 100-mg/kg dose. A dose-related increase in blood pressure occurred with diaspirin cross-linked hemoglobin solution.

CONCLUSIONS

Diaspirin cross-linked hemoglobin solution doses of 25, 50, and 100 mg/kg are well tolerated, without evidence of organ dysfunction or toxicity. Diaspirin cross-linked hemoglobin solution's pressor effect is without evidence of decreased peripheral perfusion. Further investigations of its use in certain patient populations are warranted.

Lysine acetylsalicylate modifies aphagia and thermogenic changes induced by lateral hypothalamic lesion

These experiments test the effect of intraperitoneal injection of lysine acetylsalicylate on 1) food intake and 2) the sympathetic and thermogenic changes induced by lesion of the lateral hypothalamus (LH). Food intake, firing rate of the nerves innervating interscapular brown adipose tissue (IBAT), and IBAT and colonic temperatures (TIBAT and TC) were monitored in male Sprague-Dawley rats lesioned in the LH. These variables were measured before and after intraperitoneal injection of lysine acetylsalicylate. The same variables were also monitored in 1) lesioned rats with intraperitoneal administration of saline, 2) sham-lesioned animals with intraperitoneal injection of lysine acetylsalicylate, and 3) sham-lesioned rats with intraperitoneal injection of saline. The results show that lysine acetylsalicylate modifies the aphagia by increasing food intake and also reduces the enhancements in firing rate, TIBAT, and TC induced by LH lesion. These findings suggest that prostaglandin synthesis plays a key role in the control of eating behavior in LH-lesioned rats by acting on the sympathetic and thermogenic changes induced by LH lesion.

Hemoglobin-induced contraction of pig pulmonary veins

The effects of hemoglobin Ao (HbAo), alpha alpha cross-linked hemoglobin (alpha alphaHb), cyanomet alpha alpha cross-linked hemoglobin (cyanomet alpha alphaHb), and human serum albumin (HSA) were compared under basal conditions and during relaxation with acetylcholine (ACh), sodium nitroprusside (SNP), and papaverine (PAP) in porcine pulmonary veins. Isometric tension changes were recorded in isolated rings (3 to 4 mm) that were suspended in Krebs solution bubbled with 95% O2/5% CO2. Increasing concentrations of HbAo and alpha alphaHb (10(-9) - 3 x 10(-6) mol/L) caused concentration-dependent increases in tension that reached a maximum of 4.20 +/- 0.3 gm and 3.78 +/- 0.6 gm, respectively. Cyanomet alpha alphaHb and HSA (10(-9) - 3 x 10(-6) mol/L) did not cause significant increases in tension. The maximum responses to HbAo and alpha alphaHb were significantly increased during relaxation with ACh and SNP but not with PAP. In contrast, SNP (10(-4) mol/L) and PAP (10(-5) mol/L), but not ACh, reversed contractions induced by HbAo and alpha alphaHb. These studies support the concept that hemoglobin-induced vascular contraction is primarily mediated by inactivation of the vasodilator nitric oxide in vitro. We suggest that this mechanism is common to acellular hemoglobins in which the ligand binding site is unimpaired and in which the heme iron is in the ferrous (+2) state.

Epileptogenic activity induced by combined treatment with antiinflammatory drugs and enoxacin and its inhibition by a calcium antagonist, nicardipine

Epileptogenic activity induced by combined treatment with antiinflammatory drugs and enoxacin was investigated in chronic electrode-implanted rats. Ferubinac ethyl and aspirin DL-lysine showed a spike and wave complex in EEG without showing remarkable behavioral changes when they were injected intraventricularly, although a relatively high dose was needed. Enoxacin, on the other hand, elicited potent epileptogenic activity characterized by uninterrupted high voltage spike and wave complex at doses of 50 and 100 micrograms. At the same time, rats showed hyperactivity, jumping and violent convulsion. Combined treatment with enoxacin (p.o.) and ferubinac ethyl (i.v.) caused potent epileptogenic activity characterized by uninterrupted burst of high voltage spike and wave complex. Behaviorally, animals showed forelimb clonus, head nodding and generalized convulsion. High voltage spike and wave complex was also observed after combined treatment with enoxacin (i. vent.) and ferubinac ethyl (i.v. or i. vent.) in association with hyperactivity and jumping and violent convulsion. Nicardipine remarkably inhibited epileptic seizures induced by combined treatment with enoxacin (p.o.) and ferubinac ethyl (i.v.). It is concluded that simultaneous treatment with enoxacin and ferubinac ethyl produced epileptogenic activity when injected intraventricularly, and nicardipine inhibited convulsions induced by combined use of enoxacin (p.o.) and ferubinac ethyl (i.v.).

Mapping cross-linking sites in modified proteins with mass spectrometry: an application to cross-linked hemoglobins

The combined use of trypsin digestion and peptide mass mapping by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is reported here as an effective and rapid means for identifying the cross-linking sites in human oxy hemoglobin A (HbA) cross-linked with either bis(3,5-dibromosalicyl)-succinate or -glutarate. MALDI-MS analysis of a nondigested sample of oxy HbA modified with bis(3,5-dibromosalicyl)-glutarate showed that cross-linking only occurred between the beta 1- and beta 2-protomers and not between alpha 1- and alpha 2- or alpha- and beta-protomers, along with a modification reaction on an un-cross-linked beta-chain. Results of the MALDI tryptic peptide mass maps of cross-linked hemoglobins showed several cross-linked peptides having masses consistent with: beta Val67-Lys95-XL-beta Val67-Lys95, beta Val67-Lys95-XL-beta Val67-Arg104, beta Val67-Arg104-XL-beta Val67-Arg104, where XL represents the succinyl or glutaryl bridging span moiety. Each of these peptides contains Lys82, the targeted residue for these reagents, substantiating the cross-linking sites at beta 1Lys82-beta 2Lys82. This approach in general will enable rapid identification of the cross-linking sites in engineered proteins or intracellularly recombinant cross-linked proteins when the mass of the cross-linker and the protein primary structure are known.

Diaspirin cross-linked hemoglobin resuscitation improves cerebral perfusion after head injury and shock

BACKGROUND

Shock associated with traumatic brain injury (TBI) doubles the mortality of TBI alone by inducing a secondary ischemic injury. Rapid correction of cerebral perfusion pressure (CPP) is thought to be essential to improving outcome. Diaspirin cross-linked hemoglobin (DCLHb) has been shown to improve cerebral blood flow, increase mean arterial pressure (MAP), and reduce lesion size in models of occlusive cerebral ischemia but has not been evaluated in a model of TBI combined with hemorrhagic shock.

METHODS

We studied the effects of DCLHb resuscitation in a porcine model of cryogenic TBI and hemorrhagic shock (MAP = 50 mmHg). After combined insults, animals were randomized to receive a bolus of 4 mliters/kg of either lactated Ringer's solution (n = 5) or DCLHb (n = 6). Lactated Ringer's solution was then infused in both groups to maintain MAP at baseline. Shed blood was returned 1 hour after the initiation of resuscitation (R1). Animals were studied for 24 hours.

RESULTS

DCLHb infusion resulted in a significantly greater MAP at R1 and R24 (95 +/- 4 vs. 82 +/- 2 and 99 +/- 3 vs. 85 +/- 3 mm Hg, respectively) and a significantly greater CPP at R1 and R24 (83 +/- 10 vs. 68 +/- 5 and 89 +/- 6 vs. 71 +/- 11 mm Hg, respectively). Intracranial pressure was lower in the DCLHb group, but this difference was not significant. There was no significant difference between the groups in cerebral oxygen delivery. DCLHb animals required less fluid to maintain MAP (12,094 +/- 552 vs. 15,542 +/- 1094 mliters, p < 0.05).

CONCLUSION

These data suggest that DCLHb is beneficial in the early resuscitation of head injury and shock and that further investigation is warranted. Key Words: Diaspirin cross-linked hemoglobin, Head injury, Shock, Cerebral perfusion pressure.

The antiplatelet effects of a new nitroderivative of acetylsalicylic acid--an in vitro study of inhibition on the early phase of platelet activation and on TXA2 production

We studied in vitro the antiplatelet activity of a new nitroderivative chemically related to acetylsalicylic acid: 2 acetoxybenzoate 2-[1-nitroxy-methyl]-phenyl ester (NCX 4016), in order to identify any effects due to the release of nitric oxide and the blockade of cyclo-oxygenase. The effects of scalar doses of NCX 4016 on the early phase of platelet activation, platelet aggregation and thromboxane A2 production were investigated. We observed inhibitory effects of NCX 4016 on platelet adhesion (IC50 = 7.3 x 10(-5) M), platelet cytosolic calcium concentration, assayed by fluorescent probe Fura 2, and the expression of glycoprotein IIb/IIIa (CD41/alpha IIb beta 3) (IC50 = 3.4 x 10(-5) M) and P-selectin (CD62/GMP-140) (IC50 = 4.9 x 10(-5) M) measured by flow cytometry. NCX 4016 also prevented thrombin-induced platelet aggregation (IC50 = 3.9 x 10(-5) M). None of these parameters were affected by acetylsalicylic acid. These inhibitory activities of NCX 4016 were abolished by oxyhaemoglobin and methylene blue. Intracellular cyclic GMP observed during thrombin-induced aggregation was increased by incubation with NCX 4016. These results appear to be attributable to the release of nitric oxide, which activates soluble platelet guanylylcyclase and promotes intracellular cyclic GMP increase. NCX 4016 almost completely inhibited platelet thromboxane A2 production and arachidonic acid-induced platelet aggregation. This also occurred in the presence of oxyhaemoglobin and methylene blue, indicating that its antiplatelet activity can be attributed not only to nitric oxide release but also to cyclo-oxygenase inhibition.

Diaspirin cross-linked hemoglobin does not alter isolated human umbilical artery or vein tone

Diaspirin cross-linked hemoglobin (DCLHbTM; Baxter Healthcare Corp., Round Lake, IL, USA) is undergoing clinical trials as a blood substitute. Administration of DCLHb is associated with an increase of mean arterial pressure in vivo and contraction of selected adult isolated blood vessels of from certain species in vitro. The mechanisms of these pressor effects may be due to scavenging of the endothelium derived relaxing factor, nitric oxide (NO), by hemoglobin. Unlike adult blood vessels, prostacyclin (PGI2) rather than EDNO is the important relaxing agent in human umbilical vessels. In this study, we examined if DCLHb had vasoconstrictor effects on isolated human umbilical vessels. Human umbilical veins and arteries were excised, cut into rings and placed in organ chambers filled with 25 ml Krebs-Ringer solution (37 degrees C). 5-hydroxytryptamine (5-HT, 0.01-10 microM) increased the tension of human umbilical arteries (HUA, from 0.4 +/- 0.2 g to 2.6 +/- 0.4g) and veins (HUV, from 0.8 +/- 0.4g to 2.5 +/- 0.4g) in a dose-dependent manner. DCLHb (0.01-10 microM) did not have a significant effect on HUA and HUV. Substance P (1 microM, via prostanoid synthesis) and nitroglycerin (NG, 1 microM) but not acetylcholine (ACh, 1 microM) caused relaxation of both HUA and HUV. The NO synthase inhibitor L-NA did not have significant effects on HUA and HUV. DCLHb did not alter 5-HT preconstricted tension of HUA and HUV. The basal cGMP contents of HUA and HUV were low. These results support our previous finding that DCLHb-induced vasoconstriction in isolated vessels is dependent primarily on the binding of NO by hemoglobin.

[Comparative trial of lysine acetylsalicylate and paracetamol on pain in daily medical practice]

We performed a randomized double-blind controlled study in community medical practice comparing lysine acetylsalicylate (LAS) and paracetamol (PAR). Both drugs were given at the same dose (1 g, thrice daily) during two days; from the third to the seventh day, the patients could freely take the same drug if necessary. The analgesic effect of drugs was measured by two means: an analog scale of pain during day 1 & 2 and the count of drugs units taken during days 3 to 7. The side effects were reported. We included 473 patients (167 men, 306 women) by means of a group of 54 general practitioners. 470 patients were stratified according to the site of pain: head (n = 113), joints (n = 80), back (n = 193), thorax (n = 11), teeth (n = 48), ENT (n = 25). The pain was either acute (73%) or chronic (27%) and scored an average +/- SD of 76 +/- 12 mm on an analog visual scale from 0 to 100 mm. Response was defined as a decrease of at least 50% of the pain score. Before intake of active drugs, all patients were given placebo. Only 14% responded. Under LAS or PAR, although the difference is not statistically significant, the number of responders was slightly higher with LAS than with PAR. Moreover, the study yields some interesting differences. During day 1 and day 2, the patients of the LAS group had less pain than those of the PAR group. This difference became statistically significant at D2 H12 (p < 0.05). LAS was significantly more effective than PAR in patients with back pain (p < 0.01), and there was a trend in favor of LAS in dental and ENT pain, and for intense pain. PAR never yielded better response levels than LAS. Among the placebo-unresponsive patients, the amount of drug taken from day 3 to day 7 was significantly lower in the LAS group than in the PAR group (p < 0.05). The side effects were comparable in both groups. According to the investigators' point of view both drugs were similarly well accepted by the patients (89.3% in LAS group, 94% in PAR group). The fact that LAS seems more effective than PAR in some kinds of pain is to bring near to the anti-inflammatory action of LAS and to its better bioavailability.

Development and validation of a reversed-phase liquid chromatographic method for analysis of aspirin and warfarin in a combination tablet formulation

A stability-indicating liquid chromatographic method for the simultaneous analysis of aspirin and warfarin in warfarin sodium/aspirin combination (DuP 647) tablets has been developed and validated. This paper presents linearity, accuracy, precision, robustness, recovery, limits of detection and quantitation, and cross-validation data. The method has been shown to be specific and stability-indicating, and to give results comparable to existing methods for the individual components. Solution stability has been optimized for routine analysis.

Mechanism of the contractile effect of diaspirin-cross-linked hemoglobin in rat isolated aorta strip denuded of endothelium as revealed using an oil-immersion procedure

Diaspirin-cross-linked hemoglobin (DCLHb) is a chemically modified hemoglobin (Hb) (i.e., alpha-subunits are cross-linked by a covalent bond) currently being tested as a potential oxygen-carrying blood substitute. It was examined for possible vasoactive properties, using the rat isolated aorta strip denuded of endothelium. In this experimental model, DCLHb (1.6-155 microM) was found to be inactive as a vasoconstrictor when added to the Krebs medium but to elicit contractile responses once the Krebs medium containing DCLHb was replaced by mineral oil, a procedure that favors the sequestration of a fixed amount of DCLHb within a substantially reduced volume of extracellular fluid. The contractile activity of DCLHb in our experimental model (i.e., prior exposure of tissues to drugs in the Krebs medium followed by replacement of the Krebs medium by mineral oil) was mimicked by methemoglobin and metmyoglobin, but not by cytochrome c, albumin, hemin, hematin, Fe2+, and a variety of hemorphins. It was abolished by indomethacin, SQ-29548 (prostaglandin H2-thromboxane A2 receptor antagonist), thiourea, or N-2-mercaptopropionylglycine (MCPG), reduced partially by verapamil, but not affected by dazmegrel, MK-886 (leukotriene biosynthesis inhibitor), dimethylsulfoxide, vitamin C or E, deferoxamine, NG-nitro-L-arginine, naloxone, and a variety of other drug receptor antagonists (e.g., prazosin) and protease inhibitors (e.g., pepstatin). Rat aorta strips denuded of endothelium exhibited contractile responses to arachidonic acid added in the Krebs medium (i.e., with no mineral oil added afterwards). Such contractile activity was reduced by SQ-29548, thiourea, or MCPG. Addition of U-46619 (prostaglandin H2-thromboxane A2 mimetic) to the Krebs medium also elicited contractile responses in rat aorta strips denuded of endothelium. Such contractile activity was reduced by SQ-29548, thiourea, or verapamil but not by MCPG. Within the limitations of our experimental approach, these results suggest that (1) the contractile activity of DCLHb in rat aorta strips denuded of endothelium following replacement of the Krebs medium by mineral oil involves the participation of a secondary mediator, which could be a vasoconstrictor metabolite of arachidonic acid; (2) the participation of reactive oxygen species, potential degradation products of DCLHb (e.g., heme, Fe2+, hemorphins), or other mediators in the contractile activity of DCLHb is unlikely; and (3) Ca2+ entry into target cells might be involved in the process by which DCLHb elicits its contractile activity in our experimental model.

Comparative pharmacokinetics of Aspegic 1000 mg i.v. versus 1000 mg i.m. thrice daily

The comparative pharmacokinetics of Aspegic, the lysine salt of acetylsalicylic acid, administered in multi doses either through i.v. or i.m. route was studied. 1 g of drug was injected each time with a frequency of 3 times a day. The pharmacokinetic parameters were determined using the experimental data in the literature. From these results, three categories of patients were considered, depending on their response to the drug. A numerical model was established in order to evaluate the following results: the drug level in the blood compartment obtained with the i.v. or i.m. administration, as well as the area under the curve for the first day and the third day when the so-called stationary state was obtained. Approximately similar values for AUC were obtained for each route of administration, for a given category of patients. The effect of the inter-variability of the patients characterised by their response to the drug was found to be of prime importance.

Combined neuroprotection and reperfusion therapy for stroke. Effect of lubeluzole and diaspirin cross-linked hemoglobin in experimental focal ischemia

BACKGROUND AND PURPOSE

In search of a better treatment for acute ischemic stroke, we evaluated the use of lubeluzole and hemodilution with diaspirin cross-linked hemoglobin (DCLHb) therapy to test whether treatment with two complementary acting compounds provides more potent protection than either treatment alone.

METHODS

We used unilateral reversible middle cerebral artery (MCA) and common carotid artery (CCA) occlusion of various durations in Long-Evans rats to produce ischemic cortical lesions. We calculated the average maximal lesion volume (Volmax) and the time required to produce half maximal lesion size (T50) in control animals (n = 31) and evaluated the effects on cerebral perfusion and infarct size of treatment with lubeluzole (n = 23), hemodilution (to 30% hematocrit) with albumin (n = 17) or DCLHb (n = 23), and combined lubeluzole + DCLHb therapy initiated 15 minutes after MCA/CCA occlusion.

RESULTS

The Volmax produced by MCA/CCA occlusion in control animals was 138.5 +/- 7.7 mm3, and T50 was 98.5 +/- 10.2 minutes. Lubeluzole alone reduced Volmax by 53% with no significant effect on T50. In contrast to lubeluzole, DCLHb hemodilution prolonged T50 by 68% with no significant effect on Volmax. Prolongation of T50 by DCLHb was not due to hemodilution itself, since a similar degree of hemodilution with albumin had no effect. Finally, combined lubeluzole+DCLHb rescued 72% of the tissue and augmented the effect of lubeluzole alone by 40% (Volmax, 66.3 +/- 13.0 versus 39.4 +/- 12.2 mm3) while prolonging T50 by 31%.

CONCLUSIONS

Combination therapy for acute stroke using compounds with complementary action can result in more complete attenuation of neuronal damage and demonstrates the possible clinical utility of combined neuroprotective and reperfusion therapies.

The cytotoxic activities of human hemoglobin and diaspirin crosslinked hemoglobin

It is well known that hemoglobin (Hb) possesses many oxidative enzyme activities, including a pseudo-peroxidase activity. It has also been shown by many investigators that various peroxidases in the presence of hydrogen peroxide and a halide ion exert a potent cytotoxic activity toward various mammalian cell types. It has further been observed by various investigators that the administration of relatively large amounts of purified Hb or a Hb derivative to a host animal during resuscitation experiments leads to a number of unrelated types of tissue damage and cell damage in the host. The first objective of this investigation was to determine if the observed tissue and cell damage may be due to a cytotoxic activity that Hb may exert in vivo analogous to that of the peroxidases. We also showed some time ago that peroxidases are able to activate peritoneal macrophages to the cytocidal state. Hence, we also addressed the question whether or not Hb is able to activate macrophages in a similar manner. Our results were negative with regard to both questions. Further investigations indicated that, unlike the peroxidases, ferryl-Hb is unable to oxidize iodide to iodine at a measurable rate, which appears to be the reason for the lack of cytotoxic activity.