Involvement of mast cells in the regulation of matrix metalloproteinase-9 and tissue inhibitor of metalloproteases-1 in 12-O-tetradecanoylphorbolacetate-induced inflammation in mice.

In this study, we investigated the involvement of mast cells in the regulation of matrix metalloproteinase-9 (MMP-9) in 12-O-tetradecanoylphorbolacetate (TPA)-induced inflammation, using mast cell-deficient (W/W(v)) mice and control (+/+) mice. Topical application of TPA to the ears induced acute inflammation, accompanied by mast cell degranulation in +/+ mice, which peaked at 6-12 h. There was no significant difference in ear thickness between the groups until 12 h, but the swelling was greater in W/W(v) mice than +/+ mice at 24-36 h. Western blot analysis revealed that TPA-induced marked increases in levels of proMMP-9 and tissue inhibitor of metalloproteinases-1 (TIMP-1), which existed as complexes with proMMP-9. The amount of proMMP-9-TIMP-1 complex was markedly smaller in +/+ mice than W/W(v) mice at 6 and 24 h, but had almost returned to control levels in both groups at 48 h. The free form of proMMP-9 was also slightly less abundant in +/+ mice than W/W(v) mice at 6, 24, and 48 h. Gelatin zymographic analysis revealed that levels of the active species of MMP-9 (approximately 74 and 83 kD), as well as free form of proMMP-9, increased time-dependently after the application of TPA and peaked at 24 h in +/+ mice. The 74-kD band was detected only in +/+ mice at 6 h. Our results therefore suggested that during inflammation degranulation of mast cells results in a reduction of the proMMP-9-TIMP-1 complex levels, together with a fall in the amount of free proMMP-9.

Possible involvement of mast cells in collagen remodeling in the late phase of cutaneous wound healing in mice.

We examined possible roles of mast cells in cutaneous wound healing using mast cell deficient (W/Wv) mice and their normal littermates (+/+). A round full-thickness wound was made on the back skin of these mice. The wounds closed completely within 20 days, and there was no difference in wound contraction between +/+ and W/Wv mice during the wound healing. While either chymase or tryptase activities were hardly detectable in W/Wv mice, chymase activities decreased at the impaired sites and recovered to the control level within 20 days in +/+ mice. Tryptase activities were higher than the control level on day 15 and day 20 in +/+ mice. Histological observations on day 15 and day 20 in +/+ mice revealed that mast cells were abundant at the wound edges but absent at the center. The latent and the active forms of MMP-2 and MMP-9 increased on day 10 and day 15 but recovered nearly to control levels on day 20 in both mice groups. The hydroxyproline contents in W/Wv mice were significantly higher than those in +/+ mice on day 15 and day 20. Furthermore, histological observations revealed that the collagen aggregation at the wound edges was tighter and less interwoven in W/Wv mice compared with +/+ mice. These results suggest that mast cells accumulated at the wound edge may participate in tissue remodeling in the late phase of wound healing.

Possible role of mucosal mast cells in the recovery process of colitis induced by dextran sulfate sodium in rats.

To clarify the role of mucosal mast cells in the lesion sites of colitis induced by dextran sulfate sodium (DSS) in rats, we investigated the histological changes and alterations relevant to mucosal mast cells in the spontaneous recovery process of colitis. Oral administration of 4% DSS solution for 11 days resulted in surface epithelial loss, crypt loss and goblet cell depletion in the rectal mucosa. A marked infiltration of inflammatory cells into the mucosa, which was consistent with a significant increase in myeloperoxidase (MPO) activity, was observed. In addition, mucosal mast cell number and rat mast cell protease (RMCP) I and II levels in the rectum increased at day 0 after DSS treatment, and most of the mucosal mast cells were degranulated. After replacing 4% DSS solution with water, re-epithelialization and restoration of goblet cells were observed at day 5 and day 10, respectively, but crypt damage was hardly recovered even at day 20. The elevated myeloperoxidase activity was significantly decreased from day 5 after DSS treatment. The increased number of mucosal mast cells was further elevated up to about 1.5-fold at day 10 and day 20 after DSS treatment and little degranulation was observed. In the spontaneous recovery process, the increased rat mast cell protease II level in the rectum was maintained for 20 days, while the increased rat mast cell protease I level was gradually decreased and recovered to control level. These results suggest that proliferated mucosal mast cells remained for 20 days, although most of infiltrated inflammatory cells disappeared in spontaneous recovery process of colitis. It may therefore be presumed that proliferated mucosal mast cells play a role in spontaneous recovery process of the colitis induced by DSS.

Altered gene expression profiles associated with enhanced skin inflammation induced by 12-O-tetradecanoylphorbol-13-acetate in streptozotocin-diabetic mice.

To examine the mechanisms of diabetes-enhanced inflammation, ear inflammation was induced by 12-O-tetradecanoylphorbol-13-acetate (TPA) in streptozotocin (STZ)-injected diabetic and control mice. The inflammatory response was determined from ear thickness and histology. The mRNA expression of several inflammation-related genes 8, 24 and 32 h after TPA treatment was determined by quantitative real-time RT-PCR. Ear thickness did not differ between the two groups at 8 h, but was greater in the diabetic mice than control mice at 24 and 32 h (late phase). STZ-diabetic conditions variously affected TPA-induced gene expression. The changes 8 h after TPA treatment probably reflected transcriptional regulation, and the genes were divided into three groups, up-regulated (IL-6, MCP-1, HO-1 and SOCS3), unregulated (IL-1beta, TNF-alpha and IL-10) and down-regulated (RANTES) genes. TPA-induced gene expression of cytokines, except for RANTES, peaked at 8 h and significantly declined in the late phase in control mice, while the expression of IL-1beta and TNF-alpha did not decline in the late phase in the diabetic mice. This result indicated the destabilization process for these mRNA, a type of post-transcriptional regulation, to be impaired under STZ-induced diabetic conditions; however, TPA-induced gene and protein expression of TTP, an RNA-binding protein involved in mRNA decay, were adversely enhanced in the diabetic mice. These findings suggested that STZ-induced diabetes affected the transcriptional and post-transcriptional control of TPA-induced inflammation, and greater mRNA levels of IL-1beta and TNF-alpha in the late phase were probably responsible for the diabetes-enhanced inflammation.