Rapamycin Protects Skin Fibroblasts from Ultraviolet B-Induced Photoaging by Suppressing the Production of Reactive Oxygen Species

Abstract

Background/Aims: Ultraviolet B (UVB) irradiation alters multiple molecular pathways in the skin, thereby inducing skin photoaging. Murine dermal fibroblasts (MDFs) were subjected to a series of 4 sub-cytotoxic UVB doses (120 mJ/cm²), resulting in changes in cell shape, DNA damage, cell cycle arrest, extracellular matrix variations, reactive oxygen species (ROS) generation, and alterations in major intracellular antioxidant and cellular autophagy levels. Rapamycin (RAPA) is a new macrolide immunosuppressive agent that is primarily used in oncology, cardiology, and transplantation medicine and has been found to extend the lifespan of genetically heterogeneous mice. Several studies have shown that RAPA may have anti-aging effects in cells and organisms. Thus, in this study, we explored the effects and mechanisms of RAPA against the photoaging process using a well-established cellular photoaging model. Methods: We developed a stress-induced premature senescence (SIPS) model through repeated exposure of MDFs to ultraviolet B (UVB) irradiation. The cells were cultured in the absence or presence of RAPA for 48 h. Senescent phenotypes were assessed by examining cell viability, cell morphology, senescence-associated β-galactosidase (SA-β-gal) expression, cell cycle progression, intracellular ROS production, matrix metalloproteinase (MMP) synthesis and degradation, extracellular matrix (ECM) component protein expression, alterations in major intracellular antioxidant levels, and the cellular autophagy level. Results: Compared with the UVB group, pretreatment with RAPA (5 µM) significantly decreased the staining intensity and percentage of SA-β-gal-positive cells and preserved the elongated cell shape. Moreover, cells pretreated with RAPA showed inhibition of the reduction in the type I collagen content by blocking the UVB-induced upregulation of MMP expression. RAPA also decreased photoaging cell cycle arrest and downregulated p53 and p21 expression. RAPA application significantly attenuated irradiation-induced ROS release by modulating intracellular antioxidants and increasing the autophagy level. Conclusions: Our study demonstrated that RAPA elicited oxidative damage in vitro by reducing ROS accumulation in photoaged fibroblasts. The anti-aging effect can be attributed to the maintenance of normal antioxidant and cellular autophagy levels. However, determination of the definitive mechanism requires further study.

Genome-Protecting Compounds as Potential Geroprotectors

“…Modulation of intracellular antioxidants. [185,612,613] Aspirin and bis(aspirinato)zinc(II) Free radical scavenging. The decrease in intracellular ROS production.…”

Effect of antioxidants on the H2O2-induced premature senescence of human fibroblasts

“…For example, pretreatment with rapamycin decreased the extent of SIPS induced by UV exposure and this effect was ascribed to the modification of antioxidant defense by rapamycin and suppression of free radical production by irradiation [19]. We were interested in checking whether the mechanism of SIPS-induced cell death is dependent on the secondary production of ROS and if antioxidants can modulate the course of cellular changes following exposure to H2O2.…”

Autophagic Control of Skin Aging

“…UVB exposure, which promotes photoaging and senescence of dermal fibroblasts, induced proteasome inhibition and autophagy (Cavinato and Jansen-Dürr, 2017), whereas chronic UVA exposure led to blockage of autophagic flux (Lamore and Wondrak, 2013). In vitro , activation of autophagy by rapamycin prevented UVB induced senescence by limiting ROS production (Qin et al, 2018). Autophagy was proposed to be required for UV mediated senescence induction (Cavinato and Jansen-Dürr, 2017; Sample and He, 2017) but this hypothesis remains to be tested in different cells under different regimens of UV exposure.…”