HSP70 and EndoG modulate cell death by heat in human skin keratinocytes in vitro

Energy-Based Skin Rejuvenation: A Review of Mechanisms and Thermal Effects

BACKGROUND

Energy-based photoelectric and ultrasonic devices are essential for skin rejuvenation and resurfacing in the field of plastic surgery and dermatology. Both functionality and appearance are impacted by factors that cause skin to age, and various energy types have variable skin penetration depths and modes of transmission.

AIM

The objective is to advise safe and efficient antiaging treatment while precisely and sensitively controlling and assessing the extent of thermal damage to tissues caused by different kinds of energy-based devices.

METHODS

A literature search was conducted on PubMed to review the mechanisms of action and thermal effects of photoelectric and ultrasonic devices in skin remodeling applications.

RESULTS

This paper reviews the thermal effects of energy-based devices in skin resurfacing applications, including the tissue level and molecular biochemical level. It seeks to summarize the distribution form, depth of action, and influencing factors of thermal effects in combination with the mechanisms of action of various types of devices.

CONCLUSION

Accurate control of thermal damage is crucial for safe and effective skin remodeling treatments. Thorough investigation of molecular biochemical indicators and signaling pathways is needed for real-time monitoring and prevention of severe thermal injury. Ongoing research and technological advancements will improve the accuracy and control of thermal damage during treatments.

Flavonoid compounds and their synergistic effects: Promising approaches for the prevention and treatment of psoriasis with emphasis on keratinocytes - A systematic and mechanistic review

Psoriasis, a chronic autoimmune skin disorder, causes rapid and excessive skin cell growth due to immune system dysfunction. Numerous studies have shown that flavonoids have anti-psoriatic effects by modulating various molecular mechanisms involved in inflammation, cytokine production, keratinocyte proliferation, and more. This study reviewed experimental data reported in scientific literature and used network analysis to identify the potential biological roles of flavonoids' targets in treating psoriasis. 947 records from Web of Sciences, ScienceDirect database, Scopus, PubMed, and Cochrane library were reviewed without limitations until June 26, 2023. 66 articles were included in the systematic review. The ten genes with the highest scores, including interleukin (IL)-10, IL-12A, IL-1β, IL-6, Tumor necrosis factor-α (TNF-α), Janus kinase 2 (JAK 2), Jun N-terminal kinase (JUN), Proto-oncogene tyrosine-protein kinase Src (SRC), Phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA), and Signal transducer and activator of transcription 3 (STAT3), were identified as the hub genes. KEGG pathway analysis identified connections related to inflammation and autoimmune responses, which are key characteristics of psoriasis. IL-6, STAT3, and JUN's presence in both hub and enrichment genes suggests their important role in flavonoid's effect on psoriasis. This comprehensive study highlights how flavonoids can target biological processes in psoriasis, especially when combined for enhanced effectiveness.

MicroRNAs involved in human skin burns, wound healing and scarring

MicroRNAs are small, non-coding RNAs that regulate gene expression, and consequently protein synthesis. Downregulation and upregulation of miRNAs and their corresponding genes can alter cell apoptosis, proliferation, migration and fibroproliferative responses following a thermal injury. This review summarises the evidence for altered human miRNA expression post-burn, and during wound healing and scarring. In addition, the most relevant miRNA targets and their roles in potential pathways are described. Previous studies using molecular techniques have identified 197 miRNAs associated with human wound healing, burn wound healing and scarring. Five miRNAs alter the expression of fibroproliferative markers, proliferation and migration of fibroblasts and keratinocytes post-burn: hsa-miR-21 and hsa-miR-31 are increased after wounding, and hsa-miR-23b, hsa-miR-200b and hsa-let-7c are decreased. Four of these five miRNAs are associated with the TGF-β pathway. In the future, large scale, in vivo, longitudinal human studies utilising a range of cell types, ethnicity and clinical healing outcomes are fundamental to identify burn wound healing and scarring specific markers. A comprehensive understanding of the underlying pathways will facilitate the development of clinical diagnostic or prognostic tools for better scar management and the identification of novel treatment targets for improved healing outcomes in burn patients.

Burn Injury: Mechanisms of Keratinocyte Cell Death

Cutaneous burn injury is associated with epidermal loss in the zone of coagulation zone and delayed tissue loss in the zone of stasis. Thus, thermal stress can trigger both necrosis and regulated cell death (RCD) or apoptosis. Experimental in vitro and in vivo work has clearly demonstrated apoptotic events of thermally injured keratinocytes that are accompanied by morphological and biochemical markers of regulated cell death. However, in vivo data for the different pathways of regulated cell death are sparse. In vitro experiments with heat-stressed human keratinocytes have demonstrated death receptor involvement (extrinsic apoptosis), calcium influx, and disruption of mitochondrial membrane potential (intrinsic apoptosis) in regulated cell death. In addition, caspase-independent pathways have been suggested in regulated cell death. Keratinocyte heat stress leads to reduced proliferation, possibly as a result of reduced keratinocyte adhesion (anoikis) or oncogene involvement. Understanding the underlying mechanisms of RCD and the skin’s responses to thermal stress may lead to improved strategies for treating cutaneous burn trauma.

Heat shock proteins in the physiology and pathophysiology of epidermal keratinocytes

Heat shock proteins (HSPs), a large group of highly evolutionary conserved proteins, are considered to be main elements of the cellular proteoprotection system. HSPs are encoded by genes activated during the exposure of cells to proteotoxic factors, as well as by genes that are expressed constitutively under physiological conditions. HSPs, having properties of molecular chaperones, are involved in controlling/modulation of multiple cellular and physiological processes. In the presented review, we summarize the current knowledge on HSPs in the biology of epidermis, the outer skin layer composed of stratified squamous epithelium. This tissue has a vital barrier function preventing from dehydratation due to passive diffusion of water out of the skin, and protecting from infection and other environmental insults. We focused on HSPB1 (HSP27), HSPA1 (HSP70), HSPA2, and HSPC (HSP90), because only these HSPs have been studied in the context of physiology and pathophysiology of the epidermis. The analysis of literature data shows that HSPB1 plays a role in the regulation of final steps of keratinization; HSPA1 is involved in the cytoprotection, HSPA2 contributes to the early steps of keratinocyte differentiation, while HSPC is essential in the re-epithelialization process. Since HSPs have diverse functions in various types of somatic tissues, in spite of multiple investigations, open questions still remain about detailed roles of a particular HSP isoform in the biology of epidermal keratinocytes.

The different axes of the mammalian mitochondrial unfolded protein response

Mitochondria are sensitive to numerous environmental stresses, which can lead to activation of mitochondrial stress responses (MSRs). Of particular recent interest has been the mitochondrial unfolded protein response (UPR^mt), activated to restore protein homeostasis (proteostasis) upon mitochondrial protein misfolding. Several axes of the UPR^mt have been described, creating some confusion as to the nature of the different responses. While distinct molecularly, these different axes are likely mutually beneficial and activated in parallel. This review aims at describing and distinguishing the different mammalian MSR/UPR^mt axes to define key processes and members and to examine the involvement of protein misfolding.

Thermal stress in Danio rerio: a link between temperature, light, thermo-TRP channels, and clock genes

It is believed that the biological systems perceiving temperature and light daily cycles were subjected to the simultaneous selective pressures, which resulted in their co-evolutionary association. We investigated the influence of 1h 33°C heat shock on the expression of clock and heat shock protein genes, as well as the role of the thermo-TRP channel, TRPV1, in ZEM-2S cells of the teleost Danio rerio, in constant dark (DD) or light-dark cycles (LD). After heat shock, we observed an acute increase of hsp90 aa1 levels in both DD and LD conditions. Interestingly, the expression of hsp90 aa1 was two-fold lower in LD than in DD, what suggests an antagonistic effect of white light on heat shock action. Regarding clock genes, no effect was found in cells subjected to the heat shock in DD. When cells were kept in LD, the expression of per1, per2, cry1a, and cry1b increased in response to heat shock, indicating that heat shock only affects clock core of LD-synchronized ZEM-2S cells. We then evaluated whether TRPV1 played a role in heat-mediated hsp90 aa1 and per2 responses: hsp90 aa1 increase was unaffected whereas per2 increase was partially blocked by TRPV1 inhibitor, demonstrating the channel participation in clock gene regulation by heat shock. Taken together, our results open a novel investigative perspective regarding the relationship between temperature and clock genes, placing a new player in the regulation of this phenomenon: the TRPV1 channel.

Heat-mediated reduction of apoptosis in UVB-damaged keratinocytes in vitro and in human skin ex vivo

Background

UV radiation induces significant DNA damage in keratinocytes and is a known risk factor for skin carcinogenesis. However, it has been reported previously that repeated and simultaneous exposure to UV and heat stress increases the rate of cutaneous tumour formation in mice. Since constant exposure to high temperatures and UV are often experienced in the environment, the effects of exposure to UV and heat needs to be clearly addressed in human epidermal cells.

Methods

In this study, we determined the effects of repeated UVB exposure 1 kJ/m² followed by heat (39 °C) to human keratinocytes. Normal human ex vivo skin models and primary keratinocytes (NHEK) were exposed once a day to UVB and/or heat stress for four consecutive days. Cells were then assessed for changes in proliferation, apoptosis and gene expression at 2 days post-exposure, to determine the cumulative and persistent effects of UV and/or heat in skin keratinocytes.

Results

Using ex vivo skin models and primary keratinocytes in vitro, we showed that UVB plus heat treated keratinocytes exhibit persistent DNA damage, as observed with UVB alone. However, we found that apoptosis was significantly reduced in UVB plus heat treated samples. Immunohistochemical and whole genome transcription analysis showed that multiple UVB plus heat exposures induced inactivation of the p53-mediated stress response. Furthermore, we demonstrated that repeated exposure to UV plus heat induced SIRT1 expression and a decrease in acetylated p53 in keratinocytes, which is consistent with the significant downregulation of p53-regulated pro-apoptotic and DNA damage repair genes in these cells.

Conclusion

Our results suggest that UVB-induced p53-mediated cell cycle arrest and apoptosis are reduced in the presence of heat stress, leading to increased survival of DNA damaged cells. Thus, exposure to UVB and heat stress may act synergistically to allow survival of damaged cells, which could have implications for initiation skin carcinogenesis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12895-016-0043-4) contains supplementary material, which is available to authorized users.

CHIP has a protective role against oxidative stress-induced cell death through specific regulation of endonuclease G

Oxidative stress is implicated in carcinogenesis, aging, and neurodegenerative diseases. The E3 ligase C terminus of Hsc-70 interacting protein (CHIP) has a protective role against various stresses by targeting damaged proteins for proteasomal degradation, and thus maintains protein quality control. However, the detailed mechanism by which CHIP protects cells from oxidative stress has not been demonstrated. Here, we show that depletion of CHIP led to elevated Endonuclease G (EndoG) levels and enhanced cell death upon oxidative stress. In contrast, CHIP overexpression reduced EndoG levels, and resulted in reduced or no oxidative stress-induced cell death in cancer cells and primary rat cortical neurons. Under normal conditions Hsp70 mediated the interaction between EndoG and CHIP, downregulating EndoG levels in a Hsp70/proteasome-dependent manner. However, under oxidative stress Hsp70 no longer interacted with EndoG, and the stabilized EndoG translocated to the nucleus and degraded chromosomal DNA. Our data suggest that regulation of the level of EndoG by CHIP in normal conditions may determine the sensitivity to cell death upon oxidative stress. Indeed, injection of H₂O₂ into the rat brain markedly increased cell death in aged mice compared with young mice, which correlated with elevated levels of EndoG and concurrent downregulation of CHIP in aged mice. Taken together, our findings demonstrate a novel protective mechanism of CHIP against oxidative stress through regulation of EndoG, and provide an opportunity to modulate oxidative stress-induced cell death in cancer and aging.

Inducible hsp70 in the regulation of cancer cell survival: analysis of chaperone induction, expression and activity

Understanding the mechanisms that control stress is central to realize how cells respond to environmental and physiological insults. All the more important is to reveal how tumour cells withstand their harsher growth conditions and cope with drug-induced apoptosis, since resistance to chemotherapy is the foremost complication when curing cancer. Intensive research on tumour biology over the past number of years has provided significant insights into the molecular events that occur during oncogenesis, and resistance to anti-cancer drugs has been shown to often rely on stress response and expression of inducible heat shock proteins (HSPs). However, with respect to the mechanisms guarding cancer cells against proteotoxic stresses and the modulatory effects that allow their survival, much remains to be defined. Heat shock proteins are molecules responsible for folding newly synthesized polypeptides under physiological conditions and misfolded proteins under stress, but their role in maintaining the transformed phenotype often goes beyond their conventional chaperone activity. Expression of inducible HSPs is known to correlate with limited sensitivity to apoptosis induced by diverse cytotoxic agents and dismal prognosis of several tumour types, however whether cancer cells survive because of the constitutive expression of heat shock proteins or the ability to induce them when adapting to the hostile microenvironment remains to be elucidated. Clear is that tumours appear nowadays more "addicted" to heat shock proteins than previously envisaged, and targeting HSPs represents a powerful approach and a future challenge for sensitizing tumours to therapy. This review will focus on the anti-apoptotic role of heat shock 70kDa protein (Hsp70), and how regulatory factors that control inducible Hsp70 synthesis, expression and activity may be relevant for response to stress and survival of cancer cells.

TRPV channel expression in human skin and possible role in thermally induced cell death

Cell death via necrosis and apoptosis is a hallmark of deep dermal to full-thickness cutaneous burn injuries. Keratinocytes might act as thermosensory cells that transmit information regarding ambient temperature via heat-gated transient receptor potential vanilloid (TRPV) ion channels. The aim of this study was to investigate the distribution of TRPV1, 2, 3, and 4 in uninjured and thermally burned skin. The authors investigated warmth-evoked currents in keratinocytes and cell kinetics of thermally injured keratinocytes in culture with agonists and antagonists of TRPV channels. Specimens of uninjured normal skin and discarded tissue of thermally injured skin were stained for TRPV1, 2, 3, and 4. Cultured primary human keratinocytes were heated for 5 minutes at the following temperatures: 37°C (control), 42°C, and 60°C and thereafter cultured for 24 or 48 hours at 37°C. Thermally stressed cells were treated with TRPV antagonists capsazepine or ruthenium red, and cell viability capacity was determined. TRPV1, TRPV2, TRPV3, and TRPV4 immunoreactivity was differentially identified on basal and suprabasal keratinocytes of healthy human skin. Patch clamp analysis showed a functional response of human keratinocytes at temperatures >40°C. Cell death of keratinocytes after heating at 42°C was reduced by 15 and 5% with ruthenium red and by 20 and 30% by capsazepine at 24 and 48 hours, respectively. Cell death after treatment at 60°C was significantly reduced at 24 hours with capsazepine (22%) or ruthenium red (18%) but only minimally affected after 48 hours postinjury. Interaction with TRPV channels on keratinocytes may offer a new strategy to counteract cell death after thermal injury.

Vacuolar H+-ATPase inhibitors overcome Bcl-xL-mediated chemoresistance through restoration of a caspase-independent apoptotic pathway

The anti-apoptotic oncoproteins Bcl-2 and Bcl-xL play crucial roles in tumorigenesis and chemoresistance, and are thus therapeutic cancer targets. We searched for small molecules that disturbed the anti-apoptotic function of Bcl-2 or Bcl-xL, and found vacuolar H(+)-ATPase (V-ATPase) inhibitors, such as bafilomycin A1 (BMA), that showed such activity. Bcl-xL-overexpressing Ms-1 cells displayed resistance to anticancer drugs, but underwent apoptosis following treatment with a combination of V-ATPase inhibitors at doses similar to those that caused inhibitory activities of V-ATPase. We investigated the apoptosis mechanism induced by cotreatment of Bcl-xL-overexpressing Ms-1 cells with BMA as a V-ATPase inhibitor and taxol (TXL) as an anticancer drug. With BMA, TXL triggered mitochondrial membrane potential loss and cytochrome c release, whereas downstream caspase activation was not observed. In contrast, pronounced nuclear translocation of mitochondrial apoptosis-inducing factor and endonuclease G, known as effectors of caspase-independent apoptosis, was observed with BMA and TXL cotreatment. Moreover, depletion of apoptosis-inducing factor and endonuclease G using each siRNA significantly rescued cells from BMA- and TXL-induced apoptosis. Hence, the apoptosis-inducing factor- and endonuclease G-dependent pathway was critical for apoptosis induction by BMA and TXL cotreatment. Our data suggest that V-ATPase inhibitors could not only suppress anti-apoptotic Bcl-2 nor Bcl-xL but could also facilitate the caspase-independent apoptotic pathway. V-ATPase inhibition will be a promising therapeutic approach for Bcl-2- or Bcl-xL-overexpressing malignancies.