Curcumin targets YAP1 to enhance mitochondrial function and autophagy, protecting against UVB-induced photodamage

Abstract

Background: Ultraviolet B (UVB) radiation is a major environmental factor contributing to skin damage via DNA damage, oxidative stress, inflammation, and collagen degradation. It penetrates the epidermis, disrupts DNA integrity, and generates reactive oxygen species (ROS), activating pro-inflammatory pathways such as NF-κB and AP-1, and inducing matrix metalloproteinases (MMPs). These processes lead to structural skin changes, inflammation, and pigmentation disorders like melasma. Cumulative DNA damage from UVB also drives photocarcinogenesis, with nearly 90% of melanomas associated with UV radiation (UVR). Despite clinical interventions like phototherapy and antioxidants, effective treatments for UVB-induced damage remain limited due to side effects and efficacy issues.

Methods: This study investigates the protective effects of curcumin on UVB-induced skin damage using a mouse UVB irradiation model and HaCaT cells exposed to UVB in vitro. Skin damage was assessed through histopathological and immunohistochemical analyses. Cellular functional changes were evaluated using assays for cell viability, mitochondrial function, ROS levels, and apoptosis. Transcriptomic analysis was employed to elucidate the molecular mechanisms underlying curcumin's protective effects on HaCaT cells post-UVB exposure. This integrated approach provides a comprehensive understanding of curcumin's molecular-level protection against UVB-induced skin damage.

Results: Curcumin significantly alleviated UVB-induced skin lesions and inflammation in vivo. In vitro, it mitigated UVB-induced HaCaT cell damage, enhancing viability while reducing apoptosis and ROS levels. Transcriptomic analysis revealed that curcumin upregulated YAP signaling and mitochondrial autophagy while suppressing IL-18 expression.

Conclusion: Curcumin treatment markedly improved UVB-induced skin lesions and reduced epidermal inflammation and thickness in vivo. In vitro, curcumin intervention alleviated UVB-induced HaCaT cell damage, including reduced viability, increased apoptosis, elevated ROS and DNA damage, and enhanced inflammatory responses. Transcriptomic analysis demonstrated that curcumin upregulated the YAP signaling pathway and mitochondrial autophagy while inhibiting the IL-18 pathway. Further studies revealed that curcumin directly interacts with YAP1, promoting mitochondrial autophagy, an effect blocked by the YAP1 inhibitor Verteporfin. Additionally, curcumin enhances mitochondrial function through YAP1, maintaining mitochondrial integrity and preventing the release of mitochondrial DNA (mtDNA) and mitochondrial ROS (mtROS), thereby suppressing NLRP3/IL-18 pathway activation.

Keywords: UVB; YAP1; autophagy; curcumin; mitochondrial; photoprotection; skin damage.

Figure 1

Schematic diagram of curcumin treatment improving skin damage caused by UVB irradiation. Curcumin intervention significantly enhanced the YAP signaling pathway, led to increased mitochondrial autophagy, and inhibited the IL-18 pathway, thereby combating UVB-induced oxidative and inflammatory damage.

Figure 2

The mitigation of UVB-induced skin damage of curcumin. (A) Optical photos of mouse skin after different treatments, including Ctrl, UVB, UVB+0.05%DMSO, UVB+Cur-L, and UVB+Cur-H. (B) H&E staining results of mouse skin sections after different treatments, including Ctrl, UVB, UVB+0.05%DMSO, UVB+Cur-L, and UVB+Cur-H. (C, D) Quantitative results of skin epidermal thickness and skin dermal thickness of mouse skin sections after different treatments, including Ctrl, UVB, UVB+0.05%DMSO, UVB+Cur-L, and UVB+Cur-H (n=5). (E–G) The inflammatory cytokines level (IL-1β, TNF-α, and IL-18) of skin tissues after different treatments, including Ctrl, UVB, UVB+0.05%DMSO, UVB+Cur-L, and UVB+Cur-H (n=5). The data are presented as mean value ± SD. Statistical significance was calculated using one-way analysis of variance (ANOVA) with Tukey multiple comparison. #### P <0.0001 vs Ctrl, ns P >0.05 vs UVB, *** P <0.001 vs UVB, **** P <0.0001 vs UVB.

Figure 3

UVB-induced cell damage alleviation of curcumin in vitro. (A) Cell viability of HaCaT cells after different treatments, including Ctrl, UVB, UVB+0.05%DMSO, UVB+Cur-L, and UVB+Cur-H (n=3). (B) Western blot analysis for apoptotic markers, including Bax, Bcl-2, and Cleaved Caspase-3. (C–E) The relative expression of Cleaved Caspase-3, Bcl-2, and Bax of cells after different treatments (n=3). (F) The progression of cell migration in HaCaT cells at 0 and 24 h after different treatments, including Ctrl, UVB, UVB+0.05%DMSO, UVB+Cur-L, and UVB+Cur-H. (G) Quantitative analysis results of cell scratch assay from (B) (n=3). The data are presented as mean value ± SD. Statistical significance was calculated using one-way analysis of variance (ANOVA) with Tukey multiple comparison. ### P < 0.001 vs Ctrl, #### P < 0.0001 vs Ctrl, ns P > 0.05 vs UVB, * P<0.05 vs UVB, ** P <0.01 vs UVB, *** P <0.001 vs UVB, **** P < 0.0001 vs UVB.

Figure 4

UVB-induced oxidative stress damage reduction of curcumin in vitro. (A) CLSM images of HaCaT cells stained with DCFH-DA probe after different treatments, including Ctrl, UVB, UVB+0.05%DMSO, UVB+Cur-L, and UVB+Cur-H. (B) Quantification of CLSM images results (n=5). (C) JC-1 staining of HaCaT cells after different treatments for MMP assessment. (D–F) The cytokines level (IL-1β, TNF-α, and IL-18) of HaCaT cells after different treatments, including Ctrl, UVB, UVB+0.05%DMSO, UVB+Cur-L, and UVB+Cur-H (n=3). (G) γ-H2AX and DAPI staining for DNA damage evaluation of HaCaT cells after different treatments, including Ctrl, UVB, UVB+0.05%DMSO, UVB+Cur-L, and UVB+Cur-H. The data are presented as mean value ± SD. Statistical significance was calculated using one-way analysis of variance (ANOVA) with Tukey multiple comparison. ### P < 0.001 vs Ctrl, #### P <0.0001 vs Ctrl, ns P > 0.05 vs UVB, ** P < 0.01 vs UVB, **** P < 0.0001 vs UVB.

Figure 5

Molecular docking and RNA-seq. (A) Molecular interaction network between YAP1 and curcumin. (B) Volcano plot of DEGs between UVB and curcumin+UVB groups. (|Fold Change|≥2, p<0.05). (C) GO enrichment of DEGs between UVB and curcumin+UVB groups. (|Fold Change|≥2, p<0.05). (D–F) GSEA analysis of DEGs between UVB and curcumin+UVB groups. (|Fold Change|≥2, p<0.05).

Figure 6

YAP1 signal pathway regulation of curcumin. (A) Cell viability of HaCaT cells after different treatments, including Ctrl, UVB, UVB+Cur, and Cur+Verteporfin (n=3). (B–D) The cytokines level (IL-1β, TNF-α, and IL-18) of HaCaT cells after different treatments, including Ctrl, UVB, UVB+Cur, and Cur+Verteporfin (n=3). (E, F) Immunofluorescence staining for γ-H2AX and the corresponding fluorescence quantitative analysis (n=3). (G, H) Immunofluorescence staining for EdU and the corresponding fluorescence quantitative analysis (n=3). The data are presented as mean value ± SD. Statistical significance was calculated using one-way analysis of variance (ANOVA) with Tukey multiple comparison. ### P < 0.001 vs Ctrl, #### P < 0.0001 vs Ctrl, ns P > 0.05 vs UVB, ** P < 0.01 vs UVB, *** P < 0.001 vs UVB, **** P < 0.0001 vs UVB.

Figure 7

(A) Western blot analysis of NLRP3, ASC, cleaved Caspase-1, IL-18, and IL-1β. (B–F) Relative expression of NLRP3, ASC, Cleaved Caspase-1, IL-18, and IL-1β (n=3). (G) Western blot analysis of P62, PINK1, Parkin, LC3-I, and LC3-II. (H–L) Relative expression of P62, PINK1, Parkin, LC3-I, and LC3-II (n=3). The data are presented as mean value ± SD. Statistical significance was calculated using one-way analysis of variance (ANOVA) with Tukey multiple comparison. ns P > 0.05, * P < 0.05, ** P < 0.01, *** P < 0.001, **** P < 0.0001.