[Evaluation of time course and inter-relationship of inflammatory mediators in experimental inflammatory reaction]

Inflammatory signs, such as heat, redness, swelling and pain, have been described from the Greek era. In these phenomena various endogenous active substances, i.e., inflammatory mediators, could cause and manifest vascular dilatation, a vascular permeability increase and sensitization of pain receptors, etc. In order to evaluate the roles of inflammatory mediators, we have studied the time courses of inflammatory reaction along with detection of various active substances directly or indirectly in the experimental animal model of pleurisy, such as rat carrageenin-induced, and zymosan-induced pleurisy. These pleurisies showed almost similar time courses of pleural exudate accumulation and neutrophil migration. However, mediators detected in the exudates of such pleurisies were different; in carrageenin-induced pleurisy bradykinin and prostacyclin (PGI2) caused exudate formation, while zymosan-induced pleurisy showed early degradation of mast cells and activation of complements, followed by an increase in platelet activating factor (PAF). In both pleurisies TNF alpha, IL-1, IL-6 and CINC (cytokine-induced neutrophil chemoattractant) appeared similarly in the exudates to cause chemoattractant for neutrophils. TNF alpha and IL-1 could stimulate to produce IL-6 and IL-8. While prostaglandins may regulate cytokine production via a cellular cAMP-dependent mechanism. Thus one should consider the time for application of anti-inflammatory drugs, such as cyclooxygenase inhibitor, indomethacin, since it causes increases in TNF alpha and IL-1 production by reducing PGI2 and prostaglandin E2 (PGE2) levels. In conclusion, inflammatory reaction has its own automatic regulation mechanism through complex cross talks between inflammatory mediators.