Development of an assay method to search for compounds inhibiting stress-enhanced allergy

Allergic disorders, such as atopic dermatitis and asthma, become severe or relapse due to stress. As stress is an important factor affecting blood flow (BF), we developed a new assay system based upon our findings on BF decrease in the induction phase of allergy in mice sensitized using egg-white lysozyme (HEL) [1, 2]. Male ddY mice were sensitized i.p. with 12.5, 25 or 50 µg/head of HEL emulsified in complete Freund's adjuvant on 0 day. BF of the venous microcirculation of the tail hypodermic of un-anesthetized mouse was monitored using a Laser Doppler BF Meter of the contact type as previously described [1]. The stress load was given using a modification of the method of Castilla-Ortega E et al [3]. Mice in the stressed groups were restrained 1h or 1.5h daily for 5 – 10 consecutive days in a modified 50 ml clear polystyrene conical centrifuge tube (2.8 cm x11.2 cm in length) with multiple air holes for ventilation. No significant difference of BF decreases between previously reported sensitized mice [1] and stress-enhanced sensitized mice was found. Therefore, we examined the quantity of HEL needed for the sensitization and concluded that we could evaluate stress-enhanced allergy even if the amount of HEL was reduced to 12.5 µg/head. With respect to the stress exposure time, BF showed a significant decrease by the 8th to 10th day on exposure for 60 min/day and by the 5th to 7th day on exposure for 90 min/day. We finally established 90 min/day for 7 days (every other day) as being suitable for an assay system of stress-enhanced allergy. Using this novel assay system, we evaluated natural herbal medicines that are clinically used to treat stress or allergic disorders. Our model should be useful for identifying potential anti-stress-enhanced allergy drugs.

Keywords: allergy, stress, blood flow, natural medicine, assay method

References:

[1] Ishiguro K, Oku H, Ueda Y et al. Development of an in vivo Bioassay Method for Allergy-Preventive Substances Using Hen-Egg White Lysozyme (HEL)-Induced Blood Flow Decrease. Biol Pharm Bull 2005; 28:1490 – 1495

[2] Oku H, Ogawa Y, Iwaoka E, Kunitomo M et al. Involvement of inducible Nitric Oxide Synthase in Blood Flow Decrease in vein induced by Hen-egg White Lysozyme. Biol Pharm Bull 2007; 30:1324 – 1328

[3] Castilla-Ortega E. et al. Aggravation of Chronic Stress Effects on Hippocampal Neurogenesis and Spatial Memory in LPA1 Receptor Knockout Mice. PLoS One. 2011; 6: e25522