|Budget Amount *help
¥3,000,000 (Direct Cost: ¥3,000,000)
Fiscal Year 2003: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2002: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2001: ¥1,500,000 (Direct Cost: ¥1,500,000)
Granulocyte apoptosis and subsequent clearance by phagocytes is critical for the resolution of inflammation. However, no studies have addressed how the resolution proceed in the inflammatory site. We studied the time course of neutrophil apoptosis and the following ingestion by mononuclear leukocytes in rat carrageenin-induced pleurisy, detecting DNA fragmentation by the TUNEL method, by acridine orange staining and from the DNA ladder pattern on electrophoresis. Neutrophil accumulation started 3-5 hrs after carrageenin injection, then maintained a plateau until 24 hr. Neutrophils decreased steeply between days 1 and 3. Mononuclear leukocytes started to accumulate at 5 hr, and reached a peak at day 2. TUNEL-positive bodies and acridine orange-positive bodies first became detectable in the cytoplasm of the mononuclear leukocytes from 24 hr and 9 hr, respectively. Both methods indicated that mononuclear leukocytes containing fragmented DNA increased rapidly on days 1 and 2, and reached a peak at day 3. The characteristic ladder pattern of neutrophil DNA was observed from 5 hr. Furthermore, an apoptosis related protein, Bad, became detectable in the exudate leukocytes from 9 hr after carrageenin injection. These results indicate that neutrophils start to undergo apoptosis just after the beginning of their accumulation in the inflammation site. Thus, evolution and resolution processes may proceed concurrently in acute inflammation.
Parathymic lymph nodes enlarged with progression of inflammation. A large number of neutrophils and mononuclear leukocytes increasingly appeared in the enlarged lymph nodes. These cells expressed inducible nitric oxide synthase. In addition, cells possessing dendritic processes in the enlarged lymph nodes expressed cyclooxygenase-2. These results suggest that a part of neutrophils transmigrate into adjacent draining lymph nodes.