Purine nucleosides stimulate Na/K ATPase, and prolong survival in hemorrhagic shock

Inosine protects against impairment of memory induced by experimental model of Alzheimer disease: a nucleoside with multitarget brain actions

RATIONALE

Inosine is a naturally occurring purine nucleoside formed by adenosine breakdown. This nucleoside is reported to exert potent effects on memory and learning, possibly through its antioxidant and anti-inflammatory actions.

OBJECTIVE

The objective is to evaluate the effects of inosine on the behavioral and neurochemical parameters in a rat model of Alzheimer's disease (AD) induced by streptozotocin (STZ).

METHODS

Adult male rats were divided into four groups: control (saline), STZ, STZ plus inosine (50 mg/kg), and STZ plus inosine (100 mg/kg). STZ (3 mg/kg) was administered by bilateral intracerebroventricular injection. The animals were treated intraperitoneally with inosine for 25 days. Memory, oxidative stress, ion pump activities, acetylcholinesterase (AChE), and choline acetyltransferase (ChAT) activities and expression were evaluated in the cerebral cortex and hippocampus.

RESULTS

The memory impairment induced by STZ was prevented by inosine. An increase in the Na⁺, K⁺-ATPase, and Mg-ATPase activities and a decrease in the Ca²⁺-ATPase activity were induced by STZ in the hippocampus and cerebral cortex, and inosine could prevent these alterations in ion pump activities. Inosine also prevented the increase in AChE activity and the alterations in AChE and ChAT expression induced by STZ. STZ increased the reactive oxygen species, nitrite levels, and superoxide dismutase activity and decreased the catalase and glutathione peroxidase activities. Inosine treatment conferred protection from these oxidative alterations in the brain.

CONCLUSIONS

Our findings demonstrate that inosine affects brain multiple targets suggesting that this molecule may have therapeutic potential against cognitive deficit and tissue damage in AD.

Energy metabolism regulated by HDAC inhibitor attenuates cardiac injury in hemorrhagic rat model

A disturbance of energy metabolism reduces cardiac function in acute severe hemorrhagic patients. Alternatively, adequate energy supply reduces heart failure and increases survival. However, the approach to regulating energy metabolism conductive to vital organs is limited, and the underlying molecular mechanism remains unknown. This study assesses the ability of histone deacetylase inhibitors (HDACIs) to preserve cardiac energy metabolism during lethal hemorrhagic injury. In the lethally hemorrhagic rat and hypoxic myocardial cells, energy metabolism and heart function were well maintained following HDACI treatment, as evident by continuous ATP production with normal cardiac contraction. Valproic acid (VPA) regulated the energy metabolism of hemorrhagic heart by reducing lactate synthesis and protecting the mitochondrial ultrastructure and respiration, which were attributable to the inhibition of lactate dehydrogenase A activity and the increased myeloid cell leukemia-1 (mcl-1) gene expression, ultimately facilitating ATP production and consumption. MCL-1, the key target of VPA, mediated this cardioprotective effect under acute severe hemorrhage conditions. Our results suggest that HDACIs promote cardioprotection by improving energy metabolism during hemorrhagic injury and could therefore be an effective strategy to counteract this process in the clinical setting.

Activating Na+-K+ ATPase: a potential cardioprotective therapy during early hemorrhagic shock

Cell volume and resting potential are heavily affected by the activity of Na+-K+ ATPase (NKA, Na+-K+ pump), an essential membrane protein that regulates plasma K+ and Na+ levels. It is generally accepted that the ineffective perfusion of body tissues inhibits NKA activity and that NKA activity and heart failure are closely related. Recently, research has proven that the activation of NKA provides significant cardioprotection against ischemic injury. Based on these data, we propose that NKA stimulation could attenuate the development of heart arrhythmia during the early phase of hemorrhagic shock.

Hyperkalemia after packed red blood cell transfusion in trauma patients

BACKGROUND

Published analyses of clinical outcomes for patients requiring large-volume blood transfusion conflict with respect to the impact upon plasma potassium levels. We analyzed a cohort of trauma patients to ascertain the impact of component product transfusion upon plasma potassium values.

METHODS

We performed an observational analysis of previously, prospectively collected clinical data on 131 noncrush trauma patients undergoing resuscitation during the initial 12 hours after admission to a combat support hospital. Comparisons were made between those who received packed red blood cell (PRBC) transfusion and those who did not. Primary outcome was hyperkalemia (plasma potassium level >5.5 mmol/L).

RESULTS

Ninety-six of one hundred thirty-one patients (73.3%) received PRBCs (mean number of PRBC units 11.2, range, 0-55.0). For transfusion versus nontransfusion patients, baseline plasma potassium value (3.7 +/- 0.57 mmol/L vs. 3.6 +/- 0.36 mmol/L, p = 0.22) rose significantly after transfusion (5.3 +/- 1.2 mmol/L, vs. 4.0 +/- 0.78 mmol/L, p < 0.001). During the study period, 38.5% of transfusion patients developed hyperkalemia, versus 2.9% of those who did not (p = 0.003). In multivariate logistic regression analysis, transfusion of greater than 7 units of PRBCs was independently associated with the development of hyperkalemia (RR 4.72, 95% CI 1.01-21.97, p = 0.048). Transfusion of other cell-based products, baseline base deficits, and plasma bicarbonate levels were not. Spearman's rank correlation coefficient for the relationship of number of transfused PRBC units to the highest recorded potassium value was 0.554 (p < 0.001). The predictive accuracy of the logistic regression model for hyperkalemia was 0.824 (95% CI 0.747-0.901, p < 0.001).

CONCLUSIONS

Hyperkalemia is common after PRBC transfusion, and often severe. PRBC transfusion is independently associated with the development of hyperkalemia. The findings suggest the need for interventional studies examining the impact of alternative resuscitative approaches after severe trauma.

Hemorrhagic Shock in the Rat: Comparison of Carotid and Femoral Cannulation

BACKGROUND

The reservoir model of rat hemorrhagic shock is widely used. In this model, either the carotid or femoral artery can be cannulated to withdraw blood and measure pressure. In animals undergoing hemorrhage using the carotid approach, we observed seizure activity during the post-shock period, suggesting some degree of brain damage. The hypothesis of the present study is that survival in a model of severe hemorrhagic shock would be higher with femoral cannulation than with carotid cannulation.

MATERIALS AND METHODS

All animals (n = 90) were anesthetized with isoflurane using an anesthesia vaporizer while breathing spontaneously. In group 1, the left carotid artery and jugular vein were cannulated; in group 2, the left femoral artery and vein were cannulated. Following a period of hemorrhagic shock (20 to 30 mmHg for 30, 60, or 50-90 min), resuscitation was performed through the venous cannula by giving L-lactated Ringer's (21 mL/kg) and returning the shed blood.

RESULTS

In the carotid cannulation group, nearly 50% of the animals had seizures after resuscitation, and most of those animals died following the seizures. The 24-h survival rate in the femoral artery cannulation group was significantly higher than in the carotid artery cannulation group. Femoral cannulated animals had no seizures following reperfusion.

CONCLUSIONS

Femoral artery cannulation was associated with considerably better survival than carotid artery cannulation in this rodent model of hemorrhagic shock. The occurrence of seizures in animals undergoing carotid cannulation suggests brain damage from inadequate cerebral perfusion or subsequent reperfusion damage.

Inosine infusion prevents mortality in endotoxic shock

BACKGROUND

Substances that inhibit Na/K ATPase activity appear in plasma during severe septic shock causing Na and fluid to move into cells and K to move out, resulting in cell swelling and an elevation of plasma K. These changes contribute to the morbidity of sepsis. Recently, we reported that inosine and other purine nucleosides stimulate Na/K ATPase activity, prolong survival in hemorrhagic shock, and lower the plasma potassium in that condition. Here, we determine whether inosine prolongs survival in lipopolysaccharide-induced sepsis shock.

METHODS

Pentobarbital-anesthetized rats underwent cannulation of a femoral artery and vein, and lipopolysaccharide was injected by intravenous bolus (10 mg/kg). Rats were than resuscitated (5 mL/hr) with inosine (5 mmol/L) in saline, saline alone, inosine with S-4-nitrobenzyl-6-thioinosine (NBTI, 10 micromol/L, an equilibrative nucleoside transporter blocker), NBTI alone, or no resuscitation.

RESULTS

Inosine significantly and dramatically prolongs survival of rats in endotoxic shock as compared with saline resuscitation or to no resuscitation. Furthermore, resuscitation with NBTI (10 micromol/L) prevented prolonged survival with inosine.

CONCLUSION

Inosine prevents mortality in lipopolysaccharide-induced septic shock in rats. The mechanism of action must be intracellular, as blockers of the equilibrative nucleoside transporter prevented prolonged survival with inosine.