Fig 2: Curcumin treatment altered the expressions of mitochondrial proteins. Mitochondrial proteins including UCP2, UCP3 and mtTFA were determined by the western blotting assay. The COX IV was used as the internal control. (A) The blots of UCP2, UCP3 and mtTFA. (B) The relative expression of the protein level of UCP2. (C) The relative expression of the protein level of UCP3. (D) The relative expression of the protein level of mtTFA Cur: curcumin; Con: control; UCP2: mitochondrial uncoupling protein 2; UCP3: mitochondrial uncoupling protein 3; mtTFA: mitochondrial transcription factor A; *p < 0.05 vs. the Sham; #p < 0.05 vs. the Con.

Fig 3: Autophagic flux evaluation in UCP2-silenced cells exposed to high-salt.A Autophagic flux evaluation in microvascular brain endothelial cells exposed to high-salt (20 mM NaCl for 72 h) and treated for the last 3 h with 100 nM bafilomycin (N = 4). B Autophagic flux evaluation in UCP2-silenced endothelial cells (siUCP2) exposed to high-salt (20 mM NaCl for 72 h) and treated for the last 3 h with 100 nM bafilomycin (N = 4). C Autophagic flux evaluation in renal proximal tubular epithelial cells exposed to high-salt (20 mM NaCl for 72 h) and treated for the last 3 h with 100 nM bafilomycin (N = 4). D Autophagic flux evaluation in UCP2-silenced renal proximal tubular epithelial cells (siUCP2) exposed to high-salt (20 mM NaCl for 72 h) and treated for the last 3 h with 100 nM bafilomycin (N = 4). Representative western blots for LC3-I/II and corresponding quantification are reported. *p < 0.05, obtained using the one-way ANOVA followed by Bonferroni post hoc analysis. Data are reported as mean ± SEM.

Fig 4: Knocking down or inhibiting endogenous UCP2 exacerbated senescence. (A) Representative images and quantification of SA-β-gal–positive cells in HRECs cultured in NG and HG with or without UCP2 knockdown (shUCP2). Scale bar: 50 µm. (B) Western blot analysis of P21 in HRECs cultured in NG and HG with or without shUCP2. (C) Cell-cycle analysis of HRECs cultured in NG and HG with or without shUCP2. (D) Representative images and quantification of SA-β-gal–positive cells in HRECs cultured in NG and HG with or without UCP2 inhibition (genipin). Scale bar: 50 µm. (E) Western blot analysis of P21 in HRECs cultured in NG and HG with or without genipin. (F) Cell-cycle analysis of HRECs cultured in NG and HG with or without genipin. All of the results were analyzed by ANOVA with Tukey's multiple comparison test and are presented as mean ± SD. *P < 0.05, **P < 0.01, ***P < 0.001.

Fig 5: Knockout of Ucp2 exacerbates myocardial I/R injury. a, b Representative images of TTC staining 2 h after reperfusion. c Representative images of H&E staining after I/R injury (scale bar = 40 μm). d, e Representative images of Masson’s trichrome staining of heart tissues after 4 weeks of reperfusion (scale bar = 40 μm). f, g Representative images of Sirius red-stained heart tissues after 4 weeks of reperfusion (scale bar = 40 μm). The values are presented as the mean ± SD (n = 6 per group). *p < 0.05, **p < 0.01 versus WT + I/R group; #p < 0.05, ##p < 0.01 versus Ucp2−/− + I/R group; +p < 0.05, ++p < 0.01 versus WT.