Effect of zinc protoporphyrin on carbon monoxide/heme oxygenase-1 system in rats subjected to recurrent febrile convulsion

BACKGROUND： Studies on febrile convulsion （FC）-caused brain injury are disputed in many aspects. How FC cause nervous system injury in the developmental period and what are the characteristics of these pathological injury are unknown. The current studies have demonstrated that berne oxygenase-1 （HO-1） exerts effects on brain injury mainly by catalyzing hemoglobin to produce degradation products, and HO-1 not only has neuroprotective effects, but also has neurotoxic effects during the FC-caused brain injury. Study on the effect of zinc protoporphyrin （ZnPP） on brain injury is still in the stage of animal experiment. OBJECTIVE： To observe the effects of ZnPP on carbon monoxide （CO）/HO-1 system of rats subjected to FC, and to analyze the action pathway of ZnPP in brain protective effect. DESIGN： A randomized controlled animal experiment. SETTING： Department of Pediatrics, First Hospital Affiliated to Jiamusi University. MATERIALS： Sixty-five Wistar rats, of either gender, were involved in this study. They were randomized into normal control group（ n =14, 37℃ water bath） and febrile treatment group （n =51, 44.5℃ hot water bath）. Febrile treatment group was sub-divided into febrile non-convulsion group （FNC group, n =16） and FC group （n =35）. FC group was further sub-divided into simple convulsion group （n =20） and ZnPP treatment group （n =15）. HO-1 mRNA in situ hybridization kit was provided by Boster Bioengineering Co.,Ltd. ZnPP（dark brown powder） was the product of Jingmei Bioengineering Company. METHODS： This study was carried out in the postgraduate laboratory of Jiamusi University between January 2004 and January 2007. Rats in the febrile treatment group were placed in the 44.5℃ hot water bath box. If rats did not convulse in the water within 5 minutes, they were taken out, namely FNC group （n = 16）, and those, which were convulsed within 5 minutes, were taken out immediately when they presented such a phenomenon, namely FC group （n =35）. Convulsion induction was conducted once every other day, totally 10 times. Rats were euthanized for analysis at 24 hours after the last induction. Rats in the control group were placed in the 37℃ water. Rats in the ZnPP treatment group were intraperitoneally injected with ZnPP at 45 μ mol/kg before FC attack. Rats in the simple convulsion group were only induced to be convulsed but not administrated. MAIN OUTCOME MEASURES： CO level in the brain tissue homogenate and plasma of rats in each group was detected with a spectrophotometer. HO-1 mRNA expression in the hippocampal CAI region, CA3 region and dentate gyrus of rats was observed by in situ hybridization technique. RESULTS： Sixty-five Wistar rats were involved in the study. Two rats died respectively due to drowning and convulsion in the FC group. One rat died due to convulsion drowning in the ZnPP treatment group. ①Plasma CO concentration of control group and ZnPP treatment group was significantly lower than that of the FC group （P 〈 0.01）, and was significantly higher in the ZnPP treatment group than in the FNC group （P 〈 0.05）. ②CO level in the brain tissue homogenate was significantly lower in the control group and ZnPP treatment group than in the FC group （P 〈 0.01）, and was very significantly higher in the ZnPP treatment group than in the control group （P 〈 0.01）. ③HO-1 mRNA expressions in the neuron of hippocampal CAl region, CA3 region and dentate gyrus of the control group were the lowerest, and those in the FC group were the highest. HO-1 mRNA expression in the neuron of dentate gyrus in the FC group was significantly higher than that in the ZnPP treatment group （P 〈 0.01）, and those in the FNC group and control group was significantly lower than that in the ZnPP treatment group （P 〈 0.01）. CONCLUSION： FC can cause brain injury. Over-expression of HO-I mRNA and the increase of CO are involved in the patho-physiological process of FC. ZnPP can inhibit HO-lmRNA activity and decrease CO level, which is one of pathways for protecting brain.

A Carbon Monoxide Sensing Film Based on Hemoglobin Allostery

Carbon monoxide (CO) is a gaseous mediator, which is generated via anenzymatic reaction of heme oxygenase, and it plays physiological roles to regulate cellular respiration and blood flow in the liver. The concentration and distribution of CO molecules in the living body is unknown owing to a lack of a suitable technique for measuring them in vivo. A needle-type CO sensor has been used for bioinstrumentation, but it is inappropriate for implantation in vivo and long-term monitoring. We developed a CO sensor sheet based on hemoglobin (Hb) allostery, as Hb undergoes a conformational change on CO binding. Hb was extracted from mice blood and mixed with agarose gel with a reducer to stabilize deoxy-Hb in the gel. CO-releasing molecules (CORM) were used to mimic CO-generating tissue, and the sensitivity of the Hb gel could be regulated by Hb concentration. We defined the CO–Hb index, an absorbance ratio at 539 and 557 nm, to estimate the accumulation of captured CO in the gel. It correlatively increased with CORM dose, indicating that gel-embedded Hb underwent a conformational change on CO binding, thereby acting as a CO sensor. We subsequently used the Hb-sensor sheet for two-dimensional imaging of CO distribution. CORM-containing gels with different sizes and doses were layered on this sheet. Size- and dose-dependent CO distribution was visualized by scanning the CO-Hb index in the sheet. Our Hb-based CO sensor sheet is composed of biocompatible materials and can be applied to detect low-level CO sources in the living body.