Fig 2: The effect of KAL on oxidative stress and apoptosis in CaPO4 induced and AngII-induced AAA mouse models and in vitro. (A) Quantitative data showing mean fluorescence was quantified and expressed as DHE staining intensity (%). Data expressed as median and interquartile range with maximum and minimum data points (whiskers) for positive staining area relative to total specimen area (%); *P < 0.05, **P < 0.01 by Mann–Whitney U test (n = 6 aorta/group). (B) Quantitative data showing TUNEL staining, shown is data expressed as median and interquartile range with maximum and minimum data points for positive staining area relative to total specimen area (%); **P < 0.01 by Mann–Whitney U test (n = 6 aorta/group). (C, D) VSMCs were plated at 1 × 106 cells/ml in 500 µl DMEM + 5% FBS and allowed to adhere overnight. Exposure of VSMCs to AAA thrombus-derived conditioned medium for 24 h (n = 6/group) promoted both apoptosis (C) and upregulation of ROS activity (D) in these cells as assessed by mean relative luminescence unit (RLU). Addition of 10 nM rhKAL to the conditioned media resulted in significant reduction in both apoptosis and ROS activity (C,D). All experiments were performed in triplicate (n = 6/group). Analysis performed by Kruskal Wallis test and post hoc analysis and statistical significance shown as *P < 0.05; **P < 0.01; ***P < 0.001. AngII, angiotensin II; DHE, dihydroethidium; Kal-Tg, kallistatin transgenic; rhKAL, recombinant human Kallistatin; SRA, suprarenal aortic diameter; IRA, infrarenal aortic diameter; ROS, reactive oxygen species; VC, vehicle control; WT, wild type.

Fig 3: KAL upregulates SIRT1 activity and fenofibrate upregulates KAL expression. (A) SIRT1 activity was assessed in the nuclear extract from IRA and SRA segments. Compared to the respective controls, the nuclear protein extract obtained from the CaPO4 administered KS-Tg mice and rhKAL-administered AngII-induced ApoE-/- mice showed increased SIRT1 activity (n = 8/group). (B) Relative SIRTI mRNA expression in AAA-neck (n = 6) and AAA-body (n = 12) tissues. Aortic tissues were collected in the RNAlater and total RNA isolated to perform quantitative real time PCR (QRT–PCR). (C) AAA-Body and AAA-neck tissues (n = 6) were used for isolating VSMCs using established protocol. AAA-VSMCs were collected in the RNA later and total RNA isolated to perform QRT-PCR to assess SIRT1 mRNA expression. (D,E) Incubation of VSMCs with increasing concentration of fenofibrate upregulated KAL protein expression. Cells were plated at 0.5 × 106 cells in 500 µl DMEM + 5% FBS and incubated with fenofibrate (0–100 µM) over 24 h after which protein and mRNA was assayed (n = 6/group). Incubation of VSMCs with increasing concentration of fenofibrate (0–100 µM) dose-dependently stimulated (D) SERPINA4 protein and (E) SERPINA4 mRNA expression. Protein concentrations were assessed by Bradford method and SERPINA4 concentration levels were assessed in the cell culture supernatants by ELISA. QRT-PCR was performed on extracted total mRNA using SERPIN4A primers and normalised to GAPDH expression. (n = 6 replicates). (F) AAA-VSMCs (n = 6) were incubated with fenofibrate (100 µM) for 24 h. Total RNA was isolated from the cells SERPINA4 mRNA expression was assessed by QRT-PCR. Analysis performed by Mann Whitney U or Kruskal Wallis tests and statistical significance shown as *P < 0.05; **P < 0.01; ***P < 0.001. GAPDH, glyceraldehyde 3 phosphate; IRA, infrarenal aorta; KS-Tg, kallistatin transgenic; rhKAL, recombinant human kallistatin; RFU, relative fluorescent unit; SERPINA4, serpin-A4; SIRT1, sirutuin-1; SRA, suprarenal aorta; VC, vehicle control; VSMC, vascular smooth muscle cell; WT, wild type.

Fig 4: The effect of KAL in the aorta of CaPO4 induced and AngII-induced AAA mouse models. (A) Ex vivo morphometry measurement of ascending aortic aneurysm measured using an en face method. (B) Percent atherosclerosis lesion area of thoracic aorta measured by en face Sudan IV staining method. (C) Quantification graph showing elastin filament degradation (n = 6 aorta/group). Aortic wall elastin filament degradation was graded based on the degree of breaks in elastin filaments (graded on a scale of 1–4) as described in the materials and methods. (D) Quantification of polarisation images for collagen content expressed as a percentage (%) of the total IRA and SRA section areas in the CaPO4 and AngII models, respectively (n = 6 aorta/group). Data shown as median and interquartile range and analysed by Mann–Whitney U test. Statistical significance shown as *P < 0.05, **P < 0.01. AngII, angiotensin II; n.s., not significant; rhKAL, recombinant human Kallistatin; Kal-Tg, kallistatin transgenic; SRA, suprarenal aortic diameter; IRA, infrarenal aortic diameter; VC, vehicle control; WT, wild type; ApoE-/-, apolipoprotein E deficient; CaPO4, calcium phosphate.

Fig 5: KAL attenuated the expression of extracellular matrix regulating genes in VSMCs. VSMCs were plated at 1 × 106 cells/ml in 500 µl DMEM + 5% FBS and allowed to adhere overnight. Subsequently, the cells were incubated with 2 nm AngII or AAA thrombus-derived media for 24 h. At the end of the experiment, VSMCs were collected in the RNAlater and total RNA isolated to perform quantitative real time PCR (QRT–PCR). (A,B) Incubating VSMCs with 2 nm AngII resulted in significant upregulation of MMP-9 and VEGF gene expressions. Co-incubation with 10 nM rhKAL for 24 h attenuated AngII-induced upregulation of MMP-9 and VEGF. (C,D) VSMCs exposed to AAA thrombus-derived conditioned medium for 24 h promoted MMP-9 and VEGF expression. Addition of 10 nM rhKAL to the conditioned media resulted in a significant reduction in both MMP-9 and VEGF expressions. All experiments were performed in triplicate (n = 6/group). Analysis performed by Kruskal Wallis test and post-hoc analysis and statistical significance shown as *P < 0.05; **P < 0.01. AngII, angiotensin II; rhKAL, recombinant human kallistatin; MMP, Matrix metalloproteinase; VEGF, vascular endothelial growth factor; VSMC, vascular smooth muscle cell; n.s, non-significant.