Development of an in Vivo Bioassay Method for Allergy-Preventive Substances Using Hen-Egg White Lysozyme (HEL)-Induced Blood Flow Decrease

Abstract

We discovered a phenomenon in which the blood flow in vein microcirculation markedly decreases in response to hen-egg white lysozyme (HEL)-sensitization without any change in blood pressure. Using this blood flow decrease as a guide, we developed an in vivo assay method to search for substances, which can prevent allergies. Antagonists of histamine, serotonin and platelet activating factor (PAF) did not affect the blood flow decrease in response to HEL-sensitization. On the other hand, cyclooxygenase (COX)-1, COX-2, thromboxane (TX) A 2 , endothelin-1 (ET-1), prostacyclin (PGI 2 ) and granulocytic elastase (GE) as well as nitric oxide (NO) from inducible NO synthase (iNOS) were involved in the blood flow decrease. Thus, these substances might injure vascular endothelial cells, and cause a decrease in blood flow in vein microcirculation. Our method can be used to search for preventive agents against allergies involving NO, COX-1, 2 and PGI 2 . This is the first report to applying to an assay method the specific blood flow decrease to occur in the promotion stage of allergy.

Development of an Assay Method to Search for Compounds Inhibiting Stress-Enhanced Allergy

“…3) An anti-allergic agent (DSCG, 10 mg/kg) was injected on days 0, 3, and 6 as previously reported. 1) Water was administered to the control group on the same schedule.…”

“…As stress is an important factor affecting blood flow (BF), we have developed a new assay system based upon our findings [1][2][3] on BF decrease in the induction phase of allergy in the tail vein of mice sensitized by use of hen egg-white lysozyme (HEL). We previously developed an in vivo assay to search natural resources for allergy-preventive substances.…”

“…We used it to assess BF during the allergy induction phase in the tail veins of mice that have been sensitized to HEL. [1][2][3] Blood flow in the model appears to be regulated by various factors such as nitric oxide, thromboxane A 2 (TXA 2 ), prostacyclin (PGI 2 ), and endothelin-1 (ET-1) together with cyclooxygenase-1 (COX-1), cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), and constitutive nitric oxide synthase (cNOS). 1) A reduction of BF occurs via two pathways.…”

“…[1][2][3] Blood flow in the model appears to be regulated by various factors such as nitric oxide, thromboxane A 2 (TXA 2 ), prostacyclin (PGI 2 ), and endothelin-1 (ET-1) together with cyclooxygenase-1 (COX-1), cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), and constitutive nitric oxide synthase (cNOS). 1) A reduction of BF occurs via two pathways. One is an iNOS-independent response involving TXA 2 and ET-1; and the other is an iNOS-dependent response involving cyclooxygenase COX-1, COX-2, and PGI 2 .…”

“…We believe this method can be used to analyze the mechanism of stress-enhanced allergies and will contribute to the search for new treatments. HEL Sensitization Sensitization with HEL was performed as previously described 1) with slight modifications. On day 0, male ddY mice were injected intraperitoneally with 12.5, 25, and 50 µg of HEL in 50% CFA.…”