Background Renin Angiotensin System plays a complex role in regulating physiopathologic functional and morphological modifications at vascular level. While large information exist about Angiotensin (AT) II roles, namely in the development of vascular damage under early inflammatory conditions, little is known about AT 1-7 functions, supposed to play counteracting actions vs AT II
Objectives To evaluate if, in the early phases of an experimental inflammatory systemic condition namely the one induced by streptozotocin (SZ), the treatment with AT 1-7 could prevent inflammatory, pro-oxidative and structural vascular modifications, and further prevent the in vivo leukocyte trafficking activation, induced by local stimulation of well known arthritis-related proinflammatory mediators, such as thrombin (THR) or activated terminal complement complex (aTCC).
Methods In compliance with European (86/609/EEC) and the Italian (D.L.116/92) rules for animal experiments, 4 groups each of 10-12 male Wistar rats were randomly grouped and treated respectively with sterile saline, or AT 1-7 (576 μg/kg/day), either in the presence or absence (healthy control group) of a preliminary standardized bolus intra vein infusion of 50mg/kg SZ. Saline and AT 1-7 were daily infused by osmotic sc minipump. After 3 weeks, in 4 anesthesized rats from each group, the occurrence of either basal, or THR or aTCC-induced local inflammatory inflammatory stimulation, stable adherence to the endothelial layer and extravasation of circulating fluorescently-labelled leukocytes were assessed at microvascular level by using an in vivo videomicroscopy technique. In the other rats, the immunohistochemical staining (IHS) and gene expression ex vivo analysis of mesentery vascular content of IL-6, MCP-1, Nitrotyrosine, connective tissue growth factor (CTGF), proliferative cell nuclear antigen (PCNA), together with structural changes, assessed by median wall:total vessel area ratio (W/TV) and extracellular matrix content, were also assessed.
Results AT 1-7 did not induce any significant modification in control, healthy animals, differently AT 1-7 partly reduced the overall increase of leukocyte trafficking and extravasation in a time ranging from 15 to 60 minutes after topical exposure to THR and aTCC, while significantly inhibiting these effects (p<0.01) in rats previously treated with SZ. AT 1-7 also reduced the SZ induced percent increase of W/TV ratio (61±5 vs 87±6 of saline treated, p<0.001), local vascular content (ng/μg prot.) of IL-6 (7±1,2 vs 3±0.8, p<0.01) and MCP-1 (12±4 vs 7±2.5, p<0.05), and the percent IHS of Nitrotyrosine (25.5±6.7 vs 9.5±4, p<001), CTGF (21±4 vs 14.5±2.5, p<0.01) and PCNA (medial layer=8±3.2 vs 2.5±0.15, p<0.01). Gene expression assessments are still under evaluation
Conclusions These data suggest that AT 1-7 could play an immune modulating role even in the earlier phases of inflammatory conditions, with prevention of secondary structural tissue alterations. This could be of relevance in the development of arthritis disease, therefore our group has recently been starting new experiments with the aim of demonstrating any AT 1-7 protective effects also in experimental arthritis
Disclosure of Interest None declared