Particulate matter (PM), which refers to the mixture of particles present in the air, can have harmful effects. Damage to cells by PM, including disruption of organelles and proteins, can trigger autophagy, and the relationship between autophagy and PM has been well studied. However, the cellular regulators of PM-induced autophagy have not been well characterized, especially in keratinocytes. The Aryl Hydrocarbon Receptor (AhR) is expressed in the epidermis and is activated by PM. In this study, we investigated the role of the AhR in PM-induced autophagy in HaCaT cells. Our results showed that PM led to AhR activation in keratinocytes. Activation of the AhR-target gene CYP1A1 by PM was reduced by co-treatment with α-naphthoflavone (α-NF), an AhR inhibitor. We also evaluated activation of the autophagy pathway in PM-treated keratinocytes. In HaCaT cells, treatment with PM treatment led to the induction of microtubules-associated proteins light chain 3 (LC3) and p62/SQSTM1, which are essential components of the autophagy pathway. To study the role of the AhR in mediating PM-induced autophagy, we treated cells with α-NF or used an siRNA against AhR. Expression of LC3-ІІ induced by PM was decreased in a dose dependent manner by α-NF. Furthermore, knockdown of AhR with siAhR diminished PM-induced expression of LC3-ІІ and p62. Together, these results suggest that inhibition of the AhR decreases PM-induced autophagy. We confirmed these results using the autophagy-inhibitors BAF and 3-MA. Taken together, our results indicate that exposure to PM induces autophagy via the AhR in HaCaT keratinocytes.

The role of particulate matter (PM) in health problems including cardiovascular diseases (CVD) and pneumonia is becoming increasingly clear. Polycyclic aromatic hydrocarbons, major components of PM, bind to aryl hydrocarbon receptor (AhRs) and promote the expression of CYP1A1 through the AhR pathway in keratinocytes. Activation of AhRs in skin cells is associated with cell differentiation in keratinocytes and inflammation, resulting in dermatological lesions. Oleanolic acid, a natural component of L. lucidum , also has anti-inflammation, anticancer, and antioxidant characteristics. Previously, we found that PM 10 induced the AhR signaling pathway and autophagy process in keratinocytes. Here, we investigated the effects of oleanolic acid on PM 10 -induced skin aging. We observed that oleanolic acid inhibits PM 10 -induced CYP1A1 and decreases the increase of tumor necrosis factor–alpha and interleukin 6 induced by PM 10 . A supernatant derived from keratinocytes cotreated with oleanolic acid and PM 10 inhibited the release of matrix metalloproteinase 1 in dermal fibroblasts. Also, the AhR-mediated autophagy disruption was recovered by oleanolic acid. Thus, oleanolic acid may be a potential treatment for addressing PM 10 -induced skin aging.

Melanophilin (Mlph) forms an interaction with Rab27a and the actin‐based motor protein MyosinVa (MyoVa) on mature melanosome membranes and the tripartite complex regulates melanosome transport in melanocytes. In this study, we found that Rab27a siRNA decreased Mlph and Rab27a protein levels, but Mlph mRNA levels were not changed. Other Rab27a siRNA sequences also showed the same results. When Rab27a siRNA was treated with melan‐a melanocytes, Rab27a protein was decreased within 6 hours and Mlph protein was decreased within 24 hours. To determine whether the absence of Rab27a promotes Mlph degradation, we inhibited protein degradation by treatment with proteasome (MG132) and lysosomal enzyme (E64D and Pepstatin A) inhibitors in melan‐a melanocytes. MG132 inhibited the degradation of Mlph, but E64D and Pepstatin A had no effect on Mlph. The absence of Rab27a enhanced ubiquitination of Mlph and induced proteasomal degradation. From these results, we concluded that Mlph interaction with Rab27a is important for Mlph stability and melanosome transport.