Role of lipoxin A4 in the cell-to-cell interaction between all-trans retinoic acid-treated acute promyelocytic leukemic cells and alveolar macrophages.

Differentiation therapy with all-trans retinoic acid (ATRA) has been used successfully to treat acute promyelocytic leukemia (APL), but such treatment also causes differentiation syndrome (DS) by inducing APL cell infiltration into alveolar spaces. The mechanism underlying the clearance of infiltrated APL cells has not been investigated in detail. Lipoxin A(4) (LXA(4)) is an important anti-inflammatory mediator during the resolution of inflammation. In this study, the role of LXA(4) in the cell-cell interaction between alveolar macrophages (AMφ; NR8383 cells) and APL NB4 cells was investigated and found that conditioned medium (CM) harvested from ATRA-treated NR8383 (ATRA-NR8383) cells was able to induce the transmigration of ATRA-NB4 cells. However, the pro-migratory activity of CM was attenuated progressively when ATRA-NR8383 cells were co-cultured with increased cell dosages of apoptotic NB4 cells. A significantly higher amount of LXA(4) was released into the CM by ATRA-NR8383 cells when they were co-cultured with apoptotic ATRA-NB4 cells. Expression of a receptor for LXA(4) (ALX/FPR2) was enhanced in both ATRA-NB4 cells and ATRA-NR8383 cells. Exogenous LXA(4) treatment was able to inhibit the transmigration of ATRA-NB4 cells and induce the phagocytic clearance of apoptotic cells by ATRA-NR8383 cells. The anti-migratory activity of exogenous LXA(4) was attenuated by pre-treating ATRA-NB4 cells with an ALX/FPR2 inhibitor. We conclude that AMφ-derived LXA(4) plays an important role in the interaction between AMφ and APL cells and that this contributes to clearance of apoptotic APL cells.

Annexin A1 mediates the anti-inflammatory effects during the granulocytic differentiation process in all-trans retinoic acid-treated acute promyelocytic leukemic cells.

Annexin A1 (AnxA1) originating from mature neutrophils and their microparticles (MPs) plays an important anti-inflammatory role during the resolution phase of inflammation. However, the role of AnxA1 during the process of granulocytic differentiation is still unknown. All-trans retinoic acid (ATRA) can induce acute promyelocytic leukemic (APL) cells to differentiate along the granulocytic lineage and has been used successfully in treating APL patients. In this study, we investigated whether or not AnxA1 contributed to the anti-inflammatory properties of ATRA-treated APL (NB4; ATRA-NB) cells using the transmigratory and adhesive assays. We found that ATRA was able to enhance the surface expression of AnxA1 and its receptor (FPR2/ALX) and the release of AnxA1-containing MPs from ATRA-NB4 cells, while the expression of annexin V was not elevated on the latter cells. Further studies demonstrated that exogenous AnxA1 could inhibit ATRA-NB4 cells in their transmigratory activity and adhesion to endothelial cells. In addition, the transmigratory activity of ATRA-NB4 cells can be significantly enhanced by pretreatment with a FPR2/ALX neutralizing antibody, suggesting that endogenous AnxA1 may contribute to the anti-migratory effects. Finally, ATRA-NB4-derived MPs could also inhibit recipient cells in their transmigratory and adhesive activities and these anti-inflammatory effects could be inhibited by pretreatment of MPs with a specific anti-AnxA1 antibody. Flowcytometry studies further demonstrated that FITC-labeled AnxA1 could be transported from MPs to the membrane of recipient ATRA-NB4 cells. We conclude that biologically active AnxA1 may play a role in the anti-inflammatory properties of ATRA-treated APL cells during the process of granulocytic differentiation.

"Effects of high concentration oxygen treatment on traumatic pneumothorax in adult rabbits".

"We undertook this study to investigate the adequate oxygen concentration that can be applied safely to the treatment of pneumothorax. Complete unilateral pneumothorax was induced artificially in rabbits, which were subsequently treated with various inspired oxygen fractions (FIO2; 21%, 60%, 80% or 100%). The pneumothorax resolution time was measured together with the levels of IL-1ß and IL-8 in broncho-alveolar lavage (BAL) and plasma samples. Furthermore, the lungs from these animals were examined for histolopathological evidence of oxygen toxicity. The results showed that the resolution time was significantly faster in the pneumothorax rabbits when treated with higher FIO2. Significantly higher levels of IL-1 ß were detected in BAL samples collected from the pneumothorax-rabbits that had received FIO2 at levels of either 80% or 100% (P < 0.05), but not in those with FIO2 at the 60% level. However, there was no significant change in the level of IL-8 in the BAL when the pneumothorax-rabbits were treated with different FIO2 levels. In addition, no evidence of oxygen toxicity was found when the lung tissues were examined. The data indicated that higher FIO2 treatment can accelerate the resolution of pneumothorax, but caution should be exercised with regard to associated oxygen toxicity when the FIO2 used is greater than 80%. We conclude that treatment with 60% FIO2 is an appropriate concentration for oxygen therapy for the treatment of pneumothorax in this model."