## 2 Results
### IMD Protected the Adherent Junctions in HUVECs by Activating the cAMP/Rac1 Pathway  
ELISA assays measuring cAMP levels indicated that, compared to basal levels in the control group, the cAMP concentration rapidly and significantly increased within 5 min of exposure to IMD (10 nmol/L) (Figure 2A). Western blot analysis was employed to detect the expression levels of Rac1 and VE-cadherin in groups treated with IMD, iohexol + IMD, and iohexol + IMD + NSC23766 (a specific Rac1 inhibitor [28]) (Figure 2B). Compared with  
Figure 1: IMD can antagonize damage to HUVEC viability and apoptosis induced by iohexol. (**A**) HUVECs were preincubated with IMD (0, 1, 10, 100 nmol/L) for 30 min and then treated with iohexol (10, 20, 40, 80 mgl/mL) for 12 h. A CCK-8 kit was used to test cell viability. (**B**) HUVECs were preincubated with IMD (10 nmol/L) for 30 min, then were treated with iohexol (40 mgl/mL) or iohexol (40 mgl/mL) +NSC23766(50 uM) for 12 h. Apoptosis was detected using flow cytometry. (**C**) The apoptosis rate in each group was quantified (\(n\) = 6). The results were analyzed using ANOVA, followed by [PERSON]’s multiple comparisons test for subgroup analysis. All data are expressed as mean SD, \({}^{\star}\)\(p\) < 0.05 compared to the control group, # \(p\) < 0.05. For comparison between groups, ns: not significant. the iohexol group, the expression of Rac1 and VE-cadherin were elevated in the iohexol + IMD treatment group, but the improvement effect of IMD disappeared after Rac1 was inhibited (Figure 2C). These findings suggest that IMD activates the cAMP/Rac1 pathway and protects the adherens junctions between HUVECs, while the application of the Rac1 inhibitor significantly diminishes this protective effect. Figure 2: IMD can protect the adherens junction of HUVECs by activating the cAMP/Rac1 pathway. (**A**) Intermedin induces cAMP production in HUVECs. The concentration of cAMP was measured using ELISA, \(n=4\). (**B**,C**) HUVECs were treated with 10 nmol of IMD and/or 40 mgl/mL iohexol or 50 uM NSC23766 for 12 h. Whole-cell lysates of HUVECs were collected for immunoblotting analysis of Rac1, VE-cadherin, and GAPDH. The results were analyzed using ANOVA, with [PERSON]’s multiple comparisons test applied for subgroup analysis. All data are expressed as mean SD, \({}^{*}\)\(p<0.05\) compared to the control group, \({}^{\#}\)\(p<0.05\). For comparison between groups, ns: not significant. IMD Attenuated Renal Injury in Rat CIAKI Models and Inhibition of Rac1 Negated This Protective Effect  
SD rats were randomly divided into five groups (\(n=6\)): a control group, an IMD group, an iohexol group, an iohexol + IMD group, and an iohexol + IMD + NSC23766 group. The treatment protocol for each group is illustrated in Figure 3A. Serum creatinine levels, a marker of renal function, were measured. Kidney sections from the rats were stained with HE (Figure 3B) and PAS (Figure 3C), and the extent of renal tubular injury was assessed through pathological scoring (Figure 3D). The HE staining results indicated that the iohexol group exhibited significant tubular vacuolar degeneration and tubular dilation compared to the control group. Notably, the addition of IMD resulted in a marked improvement in pathological damage. However, when Rac1 was inhibited, the protective effects of IMD were abrogated. Serum creatinine levels in the iohexol group were significantly elevated compared to the control group. However, in the IMD + iohexol group, serum creatinine levels were notably reduced compared to the iohexol group, indicating that IMD mitigates iohexol-induced renal dysfunction. Conversely, the addition of NSC23766 led to a significant increase in serum creatinine, implying that the protective effect of IMD was nullified by Rac1 inhibition (Figure 3E). Moreover, the pathological score for renal tubular injury in the IMD + iohexol group was significantly lower than in the iohexol group and the IMD + iohexol + NSC23766 group.