Specific photodamage on HT-29 cancer cells leads to endolysosomal failure and autophagy blockage by cathepsin depletion.

Endolysosomes perform a wide range of cellular functions, including nutrient sensing, macromolecule digestion and recycling, as well as plasma membrane repair. Because of their high activity in cancerous cells, endolysosomes are attractive targets for the development of novel cancer treatments. Light-activated compounds termed photosensitizers (PS) can catalyze the oxidation of specific biomolecules and intracellular organelles. To selectively damage endosomes and lysosomes, HT-29 colorectal cancer cells were incubated with nanomolar concentrations of meso-tetraphenylporphine disulfonate (TPPS2a), an amphiphilic PS taken up via endocytosis and activated by green light (522 nm, 2.1 J.cm-1). Several cellular responses were characterized by a combination of immunofluorescence and immunoblotting assays. We showed that TPPS2a photosensitization blocked autophagic flux without extensive endolysosomal membrane rupture. Nevertheless, there was a severe functional failure of endolysosomes due to a decrease in CTSD (cathepsin D, 55%) and CTSB (cathepsin B, 52%) maturation. PSAP (prosaposin) processing (into saposins) was also considerably impaired, a fact that could be detrimental to glycosphingolipid homeostasis. Therefore, photosensitization of HT-29 cells previously incubated with a low concentration of TPPS2a promotes endolysosomal dysfunction, an effect that can be used to improve cancer therapies.

Activation of M2 macrophage autophagy by rapamycin increases the radiosensitivity of colorectal cancer xenografts.

BACKGROUND: Tumor-associated macrophages (TAMs) are intimately involved in cancer radiochemotherapy resistance. However, the mechanism by which macrophages affect radiosensitivity through autophagy remains unclear. The purpose of our study was to investigate how activating autophagy in type-II macrophages (M2) by using rapamycin (RAP) would affect the radiosensitivity of colorectal cancer (CRC) xenografts. MATERIALS AND METHODS: A nude mouse CRC model was established by injecting LoVo CRC cells. After tumor formation, supernatant from M2 cells (autophagy-unactivated), autophagy-activated M2 cells, or autophagy-downregulated M2 cells was injected peritumorally. All tumor-bearing mice were irradiated with 8-Gy X-rays twice, and the radiosensitivity of CRC xenografts was analyzed in each group. RESULTS: The mass, volume, and microvessel density (MVD) of tumors in the autophagy-unactivated M2 group significantly increased; however, supernatant from M2 cells that were autophagy-activated by rapamycin significantly decreased tumor weight, volume, and MVD compared with negative control. Combining bafilomycin A1 (BAF-A1) with RAP treatment restored the ability of the M2 supernatant to increase tumor mass, volume, and MVD. Immunohistochemical and Western blot results showed that compared with the negative control group, supernatant from M2 cells that were not activated by autophagy downregulated the expression of Livin and Survivin in tumor tissues; activation of M2 autophagy further downregulated the protein levels. CONCLUSIONS: Therefore, autophagy-activated M2 supernatant can downregulate the expression of the antiapoptotic genes Livin and Survivin in CRC xenografts, improving the radiosensitivity of CRC by inducing apoptosis in combination with radiotherapy and inhibiting the growth of transplanted tumors.

Alternative autophagy dampens UVB-induced NLRP3 inflammasome activation in human keratinocytes.

Sunlight exposure results in an inflammatory reaction of the skin commonly known as sunburn, which increases skin cancer risk. In particular, the ultraviolet B (UVB) component of sunlight induces inflammasome activation in keratinocytes to instigate the cutaneous inflammatory responses. Here, we explore the intracellular machinery that maintains skin homeostasis by suppressing UVB-induced inflammasome activation in human keratinocytes. We found that pharmacological inhibition of autophagy promoted UVB-induced NLRP3 inflammasome activation. Unexpectedly, however, gene silencing of Atg5 or Atg7, which are critical for conventional autophagy, had no effect, whereas gene silencing of Beclin1, which is essential not only for conventional autophagy but also for Atg5/Atg7-independent alternative autophagy, promoted UVB-induced inflammasome activation, indicating an involvement of alternative autophagy. We found that damaged mitochondria were highly accumulated in UVB-irradiated keratinocytes when alternative autophagy was inhibited, and they appear to be recognized by NLRP3. Overall, our findings indicate that alternative autophagy, rather than conventional autophagy, suppresses UVB-induced NLRP3 inflammasome activation through the clearance of damaged mitochondria in human keratinocytes and illustrate a previously unknown involvement of alternative autophagy in inflammation. Alternative autophagy may be a new therapeutic target for sunburn and associated cutaneous disorders.

Protective effects of pulsed electromagnetic field therapy attenuates autophagy and apoptosis in osteoporotic osteoarthritis model rats by activating PPARγ.

Osteoporotic osteoarthritis (OPOA) is a specific phenotype of OA with high incidence and severe cartilage damage. This study aimed to explore the protective efficacy of PEMF on the progression of OPOA and observed the effects of PEMF on PPARγ, autophagy- and apoptosis-related proteins in OPOA rats. Rats were randomly divided into three groups: control group, OPOA group, and PEMF group (n = 6). One week after surgery, the rats in PEMF group were subjected to PEMF (3.82 mT, 8 Hz, 40 min/day and 5 day/week) for 12 weeks. Results showed that PEMF retarded cartilage degeneration and bone loss, as evidenced by pathological staining image, decreased MMP-13 expression and increased bone mineral density. PEMF inhibited the serum levels of inflammatory cytokines, and the expressions of caspase-3 and caspase-8, while upregulated the expression of PPARγ. Moreover, PEMF significantly improved the autophagy disorders, represented by decrease expressions of Beclin-1, P62, and LC3B. The research demonstrates that PEMF can effectively prevent cartilage and subchondral bone destruction in OPOA rats. The potential mechanism may be related to upregulation of PPARγ, inhibition of chondrocyte apoptosis and inflammation, and improvement of autophagy disorder. PEMF therapy thus shows promising application prospects in the treatment of postmenopausal OA.

Osteoporotic osteoarthritis (OPOA) is a very common combination disease, that characterized by chronic pain, swollen joints and susceptibility to fractures. It is particularly common in postmenopausal women. At present, drug therapy is the main treatment method, but the adverse reactions are serious and can not stop the progression of the disease. PEMF is a safe physical therapy that has been shown to increase bone density, reduce pain, and improve joints mobility. In this study, we aimed to explore the protective effect and potential mechanism of PEMF on OPOA. We found that PEMF significantly inhibited the inflammatory response, ameliorated the damaged cartilage and subchondral bone in OPOA rats, that maybe related to the regulation of chondrocyte autophagy and apoptosis. This study provided a new vision for PEMF' treatment on OPOA and has positive significance for the clinical promotion of PEMF.

Enhancing autophagy leads to increased cell death in radiation-treated cervical cancer cells.

This study was carried out to determine the effect of autophagy modulation in radiation treatment of cervical cancer cells. HeLa and CaSki cells were irradiated with γ-rays (2 Gy/min) after treatment with an autophagy inducer (rapamycin) and inhibitor (3-MA). Expression of LC3 and cell death in two cell preparations were examined. In addition, expression of Caspase-3 and PARP were examined after radiation alone and with autophagy inhibitor treatment. A notable increment of LC3 expression was detected after radiation in both cell lines. Cell viability was observed to decrease in 3-MA-treated cells compared to radiation alone, and even further in rapamycin-treated cells. Apoptosis was confirmed to occur later than autophagy in radiation treatment, and inhibition of autophagy derived a decrease in apoptosis. In conclusion, radiation-induced autophagy may be regulated by modulators, and autophagy augmentation yields an increase in cervical cancer cell death under radiation.Impact statementWhat is already known on this subject? Autophagy is known to contribute both to tumour cell survival and death against radiation therapy. The effect of induction or inhibition of radiation-induced autophagy on cervical cancer cell death is not clear.What the results of this study add? Cell viability was observed to decrease in 3-MA-treated cells compared to radiation alone, and even further in rapamycin-treated cells. Apoptosis occurred later than autophagy in radiation treatment, and inhibition of autophagy derived a decrease in apoptosis.What the implications are of these findings for clinical practice and/or further research? Our results suggest that radiation-induced autophagy may be regulated by modulators, and autophagy augmentation yields an increase in cervical cancer cell death under radiation.

Engineering Nanoplatform for Combined Cancer Therapeutics via Complementary Autophagy Inhibition.

Despite advances in the development of tumor treatments, mortality from cancer continues to increase. Nanotechnology is expected to provide an innovative anti-cancer therapy, to combat challenges such as multidrug resistance and tumor recurrence. Nevertheless, tumors can greatly rely on autophagy as an alternative source for metabolites, and which desensitizes cancer cells to therapeutic stress, hindering the success of any current treatment paradigm. Autophagy is a conserved process by which cells turn over their own constituents to maintain cellular homeostasis. The multistep autophagic pathway provides potentially druggable targets to inhibit pro-survival autophagy under various therapeutic stimuli. In this review, we focus on autophagy inhibition based on functional nanoplatforms, which may be a potential strategy to increase therapeutic sensitivity in combinational cancer therapies, including chemotherapy, radiotherapy, phototherapy, sonodynamic therapy, and immunotherapy.

Fluvastatin sensitizes pancreatic cancer cells toward radiation therapy and suppresses radiation- and/or TGF-ß-induced tumor-associated fibrosis.

Pancreatic cancer (PC) is highly resistant to chemo and radiotherapy. Radiation-induced fibrosis (RIF) is a major cause of clinical concern for various malignancies, including PC. In this study, we aimed to evaluate the radiosensitizing and anti-RIF potential of fluvastatin in PC. Short-term viability and clonogenic survival assays were used to evaluate the radiosensitizing potential of fluvastatin in multiple human and murine PC cell lines. The expression of different proteins was analyzed to understand the mechanisms of fluvastatin-mediated radiosensitization of PC cells and its anti-RIF effects in both mouse and human pancreatic stellate cells (PSCs). Finally, these effects of fluvastatin and/or radiation were assessed in an immune-competent syngeneic murine model of PC. Fluvastatin radiosensitized multiple PC cell lines, as well as radioresistant cell lines in vitro, by inhibiting radiation-induced DNA damage repair response. Nonmalignant cells, such as PSCs and NIH3T3 cells, were less sensitive to fluvastatin-mediated radiosensitization than PC cells. Interestingly, fluvastatin suppressed radiation and/or TGF-ß-induced activation of PSCs, as well as the fibrogenic properties of these cells in vitro. Fluvastatin considerably augmented the antitumor effect of external radiation therapy and also suppressed intra-tumor RIF in vivo. These findings suggested that along with radiation, fluvastatin co-treatment may be a potential therapeutic approach against PC.

Radiosensitizing Pancreatic Cancer via Effective Autophagy Inhibition.

Despite aggressive treatments, pancreatic ductal adenocarcinoma (PDAC) remains an intractable disease, largely because it is refractory to therapeutic interventions. To overcome its nutrient-poor microenvironment, PDAC heavily relies on autophagy for metabolic needs to promote tumor growth and survival. Here, we explore autophagy inhibition as a method to enhance the effects of radiotherapy on PDAC tumors. Hydroxychloroquine is an autophagy inhibitor at the focus of many PDAC clinical trials, including in combination with radiotherapy. However, its acid-labile properties likely reduce its intratumoral efficacy. Here, we demonstrate that EAD1, a synthesized analogue of HCQ, is a more effective therapeutic for sensitizing PDAC tumors of various KRAS mutations to radiotherapy. Specifically, in vitro models show that EAD1 is an effective inhibitor of autophagic flux in PDAC cells, accompanied by a potent inhibition of proliferation. When combined with radiotherapy, EAD1 is consistently superior to HCQ not only as a single agent, but also in radiosensitizing PDAC cells, and perhaps most importantly, in decreasing the self-renewal capacity of PDAC cancer stem cells (PCSC). The more pronounced sensitizing effects of autophagy inhibitors on pancreatic stem over differentiated cells points to a new understanding that PCSCs may be more dependent on autophagy to counter the effects of radiation toxicity, a potential mechanism explaining the resistance of PCSCs to radiotherapy. Finally, in vivo subcutaneous tumor models demonstrate that combination of radiotherapy and EAD1 is the most successful at controlling tumor growth. The models also confirmed a similar toxicity profile between EAD1 and Hydroxychloroquine.

Ionizing Radiation-Induced Brain Cell Aging and the Potential Underlying Molecular Mechanisms.

Population aging is occurring rapidly worldwide, challenging the global economy and healthcare services. Brain aging is a significant contributor to various age-related neurological and neuropsychological disorders, including Alzheimer's disease and Parkinson's disease. Several extrinsic factors, such as exposure to ionizing radiation, can accelerate senescence. Multiple human and animal studies have reported that exposure to ionizing radiation can have varied effects on organ aging and lead to the prolongation or shortening of life span depending on the radiation dose or dose rate. This paper reviews the effects of radiation on the aging of different types of brain cells, including neurons, microglia, astrocytes, and cerebral endothelial cells. Further, the relevant molecular mechanisms are discussed. Overall, this review highlights how radiation-induced senescence in different cell types may lead to brain aging, which could result in the development of various neurological and neuropsychological disorders. Therefore, treatment targeting radiation-induced oxidative stress and neuroinflammation may prevent radiation-induced brain aging and the neurological and neuropsychological disorders it may cause.

Evaluating Whether Radiofrequency Irradiation Attenuated UV-B-Induced Skin Pigmentation by Increasing Melanosomal Autophagy and Decreasing Melanin Synthesis.

Autophagy is involved in the degradation of melanosomes and the determination of skin color. TLR4 and tumor necrosis factor (TNF) signaling upregulates NF-kB expression, which is involved in the upregulation of mTOR. The activation of mTOR by UV-B exposure results in decreased autophagy, whereas radiofrequency (RF) irradiation decreases TLR4 and TNF receptor (TNFR) expression. We evaluated whether RF decreased skin pigmentation by restoring autophagy by decreasing the expression of TLR4 or TNFR/NF-κB/mTOR in the UV-B-irradiated animal model. UV-B radiation induced the expressions of TNFR, TLR, and NF-κB in the skin, which were all decreased by RF irradiation. RF irradiation also decreased phosphorylated mTOR expression and upregulated autophagy initiation factors such as FIP200, ULK1, ULK2, ATG13, and ATG101 in the UV-B-irradiated skin. Beclin 1 expression and the expression ratio of LC3-I to LC3-II were increased by UV-B/RF irradiation. Furthermore, melanin-containing autophagosomes increased with RF irradiation. Fontana-Masson staining showed that the amount of melanin deposition in the skin was decreased by RF irradiation. This study showed that RF irradiation decreased skin pigmentation by restoring melanosomal autophagy, and that the possible signal pathways which modulate autophagy could be TLR4, TNFR, NF-κB, and mTOR.

High-Dose Irradiation Inhibits Motility and Induces Autophagy in Caenorhabditis elegans.

Radiation damages many cellular components and disrupts cellular functions, and was previously reported to impair locomotion in the model organism Caenorhabditis elegans. However, the response to even higher doses is not clear. First, to investigate the effects of high-dose radiation on the locomotion of C. elegans, we investigated the dose range that reduces whole-body locomotion or leads to death. Irradiation was performed in the range of 0-6 kGy. In the crawling analysis, motility decreased after irradiation in a dose-dependent manner. Exposure to 6 kGy of radiation affected crawling on agar immediately and caused the complete loss of motility. Both γ-rays and carbon-ion beams significantly reduced crawling motility at 3 kGy. Next, swimming in buffer was measured as a motility index to assess the response over time after irradiation and motility similarly decreased. However, swimming partially recovered 6 h after irradiation with 3 kGy of γ-rays. To examine the possibility of a recovery mechanism, in situ GFP reporter assay of the autophagy-related gene lgg-1 was performed. The fluorescence intensity was stronger in the anterior half of the body 7 h after irradiation with 3 kGy of γ-rays. GFP::LGG-1 induction was observed in the pharynx, neurons along the body, and the intestine. Furthermore, worms were exposed to region-specific radiation with carbon-ion microbeams and the trajectory of crawling was measured by image processing. Motility was lower after anterior-half body irradiation than after posterior-half body irradiation. This further supported that the anterior half of the body is important in the locomotory response to radiation.

CDK4, CDK6/cyclin-D1 Complex Inhibition and Radiotherapy for Cancer Control: A Role for Autophagy.

The expanding clinical application of CDK4- and CDK6-inhibiting drugs in the managements of breast cancer has raised a great interest in testing these drugs in other neoplasms. The potential of combining these drugs with other therapeutic approaches seems to be an interesting work-ground to explore. Even though a potential integration of CDK4 and CDK6 inhibitors with radiotherapy (RT) has been hypothesized, this kind of approach has not been sufficiently pursued, neither in preclinical nor in clinical studies. Similarly, the most recent discoveries focusing on autophagy, as a possible target pathway able to enhance the antitumor efficacy of CDK4 and CDK6 inhibitors is promising but needs more investigations. The aim of this review is to discuss the recent literature on the field in order to infer a rational combination strategy including cyclin-D1/CDK4-CDK6 inhibitors, RT, and/or other anticancer agents targeting G1-S phase cell cycle transition.

TRIM44 mediated p62 deubiquitination enhances DNA damage repair by increasing nuclear FLNA and 53BP1 expression.

Cancer cells show increases in protein degradation pathways, including autophagy, during progression to meet the increased protein degradation demand and support cell survival. On the other hand, reduced autophagy activity during aging is associated with a reduced DNA damage response and increased genomic instability. Therefore, it is a puzzling how DNA repair can be increased in cancer cells that are resistant to chemotherapies or during progression when autophagy activity is intact or increased. We discovered that tripartite motif containing 44 (TRIM44) is a pivotal element regulating the DNA damage response in cancer cells with intact autophagy. TRIM44 deubiquitinates p62, an autophagy substrate, which leads to its oligomerization. This prevents p62 localization to the nucleus upon irradiation. Increased cytoplasmic retention of p62 by TRIM44 prevents the degradation of FLNA and 53BP1, which increases DNA damage repair. Together, our data support TRIM44 a potential therapeutic target for therapy-resistant tumor cells with intact autophagy.

Plasma Rich in Growth Factors Promotes Autophagy in ARPE19 Cells in Response to Oxidative Stress Induced by Blue Light.

Age-related macular degeneration (AMD) causes the degeneration of photoreceptors and retinal cells leading to vision loss in older subjects. Among possible exogenous risk factors, it has been recently proposed that long-term exposure to blue light could aggravate the course of AMD. In the search for therapeutic options, plasma rich in growth factors (PRGF) has been shown to enhance cell antioxidant pathways and protect photoreceptors against the harm produced by blue light, although its mechanism of action remains unknown. One possible mechanism, autophagy, is one of the most conservative cell renewal systems used in eukaryotes to destroy cellular components that have been damaged by some kind of insult. The oxidative stress of exposure to blue light is known to induce cell autophagy. In this study, we examined the combined effects on autophagy of blue light and PRGF in a retinal cell line, ARPE19. In response to treatment with both PRGF and blue light, we detected the modulated expression of autophagy markers such as NF-kB, p62/sqstm1, Atg5, LC3 and Beclin1, and inflammatory markers such as IL1B and IL18. Our findings suggest that PRGF promotes cell autophagy in response to exposure to blue light.

Radiation-Induced Autophagy in Human Pancreatic Cancer Cells is Critically Dependent on G2 Checkpoint Activation: A Mechanism of Radioresistance in Pancreatic Cancer.

PURPOSE: Autophagy and cell-cycle checkpoints act in concert to confer cellular radioresistance. We investigated the functional interaction between radiation-induced autophagy and G2 checkpoint activation in highly radioresistant human pancreatic ductal adenocarcinoma (PDAC) cells. METHODS AND MATERIALS: Four human PDAC cell lines (MIA PaCa-2, KP-4, Panc-1, and SUIT-2) were analyzed. These cells were first irradiated using x-rays, and their cell cycle status, autophagy, and cell cycle checkpoint marker expression and ATP production levels were evaluated. Autophagic flux assays and siRNA knockdown were used to evaluate autophagy activity. Double thymidine block experiments were performed to synchronize the cells. Two inhibitors (MK-1775 and SCH 900776) were used to attenuate G2 checkpoint activation. Cell survival assays and animal experiments were performed to evaluate the radiosensitizing effects of the G2 checkpoint inhibitors. RESULTS: Autophagy and G2/M accumulation were synchronously induced in human PDAC cells with an activated G2 checkpoint at 12 hours after x-ray irradiation of 6 Gy. Radiation-induced autophagy produced the ATP levels required for cell survival. Double thymidine block experiments revealed that no autophagy occurred in cells that were solely in G2 phase. MK-1775 or SCH 900776 exposure attenuated not only G2 checkpoint activation but also postirradiation autophagy, indicating the dependence of radiation-induced autophagy on an activated G2 checkpoint. The inhibitors demonstrated a higher radiosensitizing effect in the PDAC cells than the autophagy inhibitor chloroquine. MK-1775 in combination with x-rays significantly suppressed the tumor growth of MIA PaCa-2 xenografts compared with other treatment groups, including radiation or drug exposure alone, to enhance the radiosensitivity of PDAC cells in vivo. CONCLUSIONS: Biological crosstalk exists between the G2 checkpoint activation and radiation-induced autophagy processes that are believed to independently contribute to the radioresistance of human PDAC cells. These findings have important implications for the development of future radiation therapy strategies for PDAC.

Sulforaphane inhibits blue light-induced inflammation and apoptosis by upregulating the SIRT1/PGC-1α/Nrf2 pathway and autophagy in retinal pigment epithelial cells.

The present study elucidated mechanisms through which sulforaphane (SFN) protects retinal pigment epithelial (RPE) cells from blue light-induced impairment. SFN could activate the nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2) and increase the expression of the heme oxygenease-1 (HO-1) gene and production of glutathione. SFN reduced blue light-induced oxidative stress, and effectively activated cytoprotective components including Nrf-2, HO-1, thioredoxin-1, and glutathione. The protective effect of SFN on blue light-induced injury was blocked by the Nrf2 inhibitor ML385, suggesting that the SFN-induced Nrf2 pathway is involved in the cytoprotective effect of SFN. SFN inhibited intercellular adhesion molecule-1 expression induced by TNF-α or blue light, suggesting the anti-inflammatory activity of SFN. The inhibitory effect of SFN was associated with the blocking of NF-κB p65 nuclear translocation in blue light-exposed RPE cells. SFN protected RPE cells from blue light-induced interruption of the mitochondrial membrane potential and reduction of the Bcl-2/Bax ratio and cleaved caspase-3 and PARP-1 expression, suggesting the antiapoptotic activity of SFN. SFN alone or together with blue light exposure increased the expression of the autophagy-related proteins LC3BII and p62. An autophagy inhibitor, 3-MA, inhibited the protective effect of SFN on blue light-induced cell damage. SFN increased sirtuin-1 (SIRT1) expression; however, treatment with blue light induced peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α) expression. Our study results demonstrated that SFN exerts its protective effect under blue light exposure by maintaining the Nrf2-related redox state and upregulating SIRT1 and PGC-1α expression and autophagy.

Crocetin Mitigates Irradiation Injury in an In Vitro Model of the Pubertal Testis: Focus on Biological Effects and Molecular Mechanisms.

Infertility is a potential side effect of radiotherapy and significantly affects the quality of life for adolescent cancer survivors. Very few studies have addressed in pubertal models the mechanistic events that could be targeted to provide protection from gonadotoxicity and data on potential radioprotective treatments in this peculiar period of life are elusive. In this study, we utilized an in vitro model of the mouse pubertal testis to investigate the efficacy of crocetin to counteract ionizing radiation (IR)-induced injury and potential underlying mechanisms. Present experiments provide evidence that exposure of testis fragments from pubertal mice to 2 Gy X-rays induced extensive structural and cellular damage associated with overexpression of PARP1, PCNA, SOD2 and HuR and decreased levels of SIRT1 and catalase. A twenty-four hr exposure to 50 µM crocetin pre- and post-IR significantly reduced testis injury and modulated the response to DNA damage and oxidative stress. Nevertheless, crocetin treatment did not counteract the radiation-induced changes in the expression of SIRT1, p62 and LC3II. These results increase the knowledge of mechanisms underlying radiation damage in pubertal testis and establish the use of crocetin as a fertoprotective agent against IR deleterious effects in pubertal period.

HucMSC exosome-delivered 14-3-3ζ alleviates ultraviolet radiation-induced photodamage via SIRT1 pathway modulation.

Exosomes derived from human umbilical cord mesenchymal stem cells (hucMSC-ex) are nano-sized membrane-bound vesicles that have been reported to facilitate skin regeneration and repair. However, the roles played by hucMSC-ex in ultraviolet (UV) radiation-induced skin photodamage and the underlying mechanisms remain unknown. To investigate the functions of hucMSC-ex in a rat model of acute skin photodamage, immunofluorescence and immunohistochemical staining, quantitative real-time-polymerase chain reaction (qRT-PCR), western blot, and gene silencing assays were performed. We found that the in vivo subcutaneous injection of hucMSC-ex elicited antioxidant and anti-inflammatory effects against UV radiation-induced DNA damage and apoptosis. Further studies showed that the sirtuin 1 (SIRT1) expression level in skin keratinocytes (HaCaT) decreased in a time- and dose-dependent manner under in vitro UV radiation induced-oxidative stress conditions, which could be reversed by treatment with hucMSC-ex. The activation of SIRT1 significantly attenuated UV- and H2O2-induced cytotoxic damage by inhibiting oxidative stress and promoting the activation of autophagy. Our study found that 14-3-3ζ protein, which was delivered by hucMSC-ex, exerted a cytoprotective function via the modulation of a SIRT1-dependent antioxidant pathway. Collectively, our findings indicated that hucMSC-ex might represent a new potential agent for preventing or treating UV radiation-induced skin photodamage and aging.

Marliolide Derivative Induces Melanosome Degradation via Nrf2/p62-Mediated Autophagy.

Nuclear factor erythroid 2-related factor 2 (Nrf2), which is linked to autophagy regulation and melanogenesis regulation, is activated by marliolide. In this study, we investigated the effect of a marliolide derivative on melanosome degradation through the autophagy pathway. The effect of the marliolide derivative on melanosome degradation was investigated in α-melanocyte stimulating hormone (α-MSH)-treated melanocytes, melanosome-incorporated keratinocyte, and ultraviolet (UV)B-exposed HRM-2 mice (melanin-possessing hairless mice). The marliolide derivative, 5-methyl-3-tetradecylidene-dihydro-furan-2-one (DMF02), decreased melanin pigmentation by melanosome degradation in α-MSH-treated melanocytes and melanosome-incorporated keratinocytes, evidenced by premelanosome protein (PMEL) expression, but did not affect melanogenesis-associated proteins. The UVB-induced hyperpigmentation in HRM-2 mice was also reduced by a topical application of DMF02. DMF02 activated Nrf2 and induced autophagy in vivo, evidenced by decreased PMEL in microtubule-associated proteins 1A/1B light chain 3B (LC3)-II-expressed areas. DMF02 also induced melanosome degradation via autophagy in vitro, and DMF02-induced melanosome degradation was recovered by chloroquine (CQ), which is a lysosomal inhibitor. In addition, Nrf2 silencing by siRNA attenuated the DMF02-induced melanosome degradation via the suppression of p62. DMF02 induced melanosome degradation in melanocytes and keratinocytes by regulating autophagy via Nrf2-p62 activation. Therefore, Nrf2 activator could be a promising therapeutic agent for reducing hyperpigmentation.

Two Faces of Autophagy in the Struggle against Cancer.

Autophagy can play a double role in cancerogenesis: it can either inhibit further development of the disease or protect cells, causing stimulation of tumour growth. This phenomenon is called "autophagy paradox", and is characterised by the features that the autophagy process provides the necessary substrates for biosynthesis to meet the cell's energy needs, and that the over-programmed activity of this process can lead to cell death through apoptosis. The fight against cancer is a difficult process due to high levels of resistance to chemotherapy and radiotherapy. More and more research is indicating that autophagy may play a very important role in the development of resistance by protecting cancer cells, which is why autophagy in cancer therapy can act as a "double-edged sword". This paper attempts to analyse the influence of autophagy and cancer stem cells on tumour development, and to compare new therapeutic strategies based on the modulation of these processes.