Chronic Caffeine Administration Attenuates Vascular Injury-Induced Neointimal Hyperplasia in Rats

Effects of dose-dependent chronic caffeine consumption in a rat burn wound model: Histopathological and immunohistochemical evaluation

Objectives

Using histopathological and immunohistochemical methods, we aimed to examine the dose-dependent effects of chronic caffeine consumption on the recovery of burn wounds in an in vivo rat model.

Materials and Methods

Forty-five rats were randomly assigned to a high-dose group (20 mg/kg per day for eight weeks; n=15), a low-dose group (10 mg/kg per day for eight weeks; n=15), or a control group (n=15). The burn model was created in rats. The groups were separated into three subgroups (n=5) based on the day after injury (7th, 14th, or 21st day). The wound area, wound closure percentage, and histopathological and immunohistochemical reactivity were evaluated.

Results

Successful wound healing was noted in rats treated with low doses of caffeine, similar to the control group. Pathology revealed low re-epithelization, low inflammation, and high granulation in the high-dose group. In addition, there was a significant difference between the control and high-dose groups regarding the immunohistochemical reactivity of αVβ3 integrin, vascular endothelial growth factor (VEGF), and matrix metalloproteinase 9 (MMP-9) (P<0.05).

Conclusion

We demonstrated that chronic caffeine consumption in rats adversely affects the recovery process of wounds in a dose-dependent manner. This effect may occur through delayed wound healing via the molecules MMP-9, αVβ3 integrin, and VEGF. Treatment that modulates these molecules can lead to enhanced and quicker recovery of damaged skin in coffee lovers.

Caffeine prevents restenosis and inhibits vascular smooth muscle cell proliferation through the induction of autophagy

Caffeine is among the most highly consumed substances worldwide, and it has been associated with decreased cardiovascular risk. Although caffeine has been shown to inhibit the proliferation of vascular smooth muscle cells (VSMCs), the mechanism underlying this effect is unknown. Here, we demonstrated that caffeine decreased VSMC proliferation and induced macroautophagy/autophagy in an in vivo vascular injury model of restenosis. Furthermore, we studied the effects of caffeine in primary human and mouse aortic VSMCs and immortalized mouse aortic VSMCs. Caffeine decreased cell proliferation, and induced autophagy flux via inhibition of MTOR signaling in these cells. Genetic deletion of the key autophagy gene Atg5, and the Sqstm1/p62 gene encoding a receptor protein, showed that the anti-proliferative effect by caffeine was dependent upon autophagy. Interestingly, caffeine also decreased WNT-signaling and the expression of two WNT target genes, Axin2 and Ccnd1 (cyclin D1). This effect was mediated by autophagic degradation of a key member of the WNT signaling cascade, DVL2, by caffeine to decrease WNT signaling and cell proliferation. SQSTM1/p62, MAP1LC3B-II and DVL2 were also shown to interact with each other, and the overexpression of DVL2 counteracted the inhibition of cell proliferation by caffeine. Taken together, our in vivo and in vitro findings demonstrated that caffeine reduced VSMC proliferation by inhibiting WNT signaling via stimulation of autophagy, thus reducing the vascular restenosis. Our findings suggest that caffeine and other autophagy-inducing drugs may represent novel cardiovascular therapeutic tools to protect against restenosis after angioplasty and/or stent placement.