Inhibition of granuloma‐associated angiogenesis by controlling mast cell mediator release: role of mast cell protease‐5

1 We investigated the role of mast cells in granuloma‐associated angiogenesis in rat by using: (i) a mast cell membrane stabilizer, ketotifen; (ii) a mast cell depleting agent, compound 48/80. Moreover, we focused on the role of chymases, which exhibit proinflammatory and proangiogenic properties by using: (i) chymostatin, an inhibitor of chymase activity; (ii) a specific antisense oligonucleotide (AS‐ODN) designed against rat mast cell protease‐5 (rMCP‐5), the most abundantly expressed chymase in the skin. 2 The formation of granuloma was evaluated, as wet weight, 96 h after the subcutaneous implant of two λ‐carrageenin (1%)‐soaked sponges on the back of male Wistar rats. Angiogenesis was evaluated as haemoglobin content in the granulomatous tissue and as level of tumour necrosis factor‐α (TNF‐α) in the exudates. 3 A single injection of ketotifen (1–5–25 mg kg−1 i.p.) significantly reduced granuloma formation by 31.6, 44.6 and 71.9%, and haemoglobin content by 17.0, 35.0 and 66.2%, suggesting that the release of mediator(s) from mast cells modulates the process. Chymostatin (5–10 nmol−1 site−1 day−1) reduced granuloma‐associated angiogenesis by 57.3 and 70.0%. 4 RT–PCR analysis showed that rMCP‐5 mRNA amounts were significantly reduced by rMCP‐5 AS‐ODN (1.25–2.5–5.0 nmol site−1) by 69.5, 72.5 and 81.8%. In parallel experiments, rMCP‐5 AS‐ODN (1.25, 2.5, 5.0 nmol site−1) strongly reduced granuloma weight (26.1, 45.0 and 56.3%) and haemoglobin content (22.2, 50.4, 62.03%), suggesting that the observed effect is mediated through an antisense mechanism. 5 In conclusion, these data suggest that: (i) inhibition of mast cell mediators release may represent a novel strategy to modulate angiogenesis; (ii) among the chymase family, rMCP‐5 is a key promoter of angiogenesis in the rat. British Journal of Pharmacology (2005) 145, 24–33. doi:10.1038/sj.bjp.0706112