Curcumin protection against ultraviolet-induced photo-damage in Hacat cells by regulating nuclear factor erythroid 2-related factor 2.

Curcumin suppressed ultraviolet (UV) induced skin carcinogenesis and activated the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway. However, whether curcumin protects skin injury caused by UV is still unknown. A vitro model was established and curcumin effects on Hacat cells were detected. Nrf2 was knocked down in Hacat cells to verify the Nrf2 role in the protective effect of curcumin. Results indicated that ultraviolet A (UVA) (or ultraviolet B (UVB)) irradiation would lead to decreased cell proliferation, increased cell apoptosis, decreased catalase, heme oxygenase 1, and superoxide dismutase expression, and increased levels of protein carbonylation and malondialdehyde (p < 0.05). These adverse events could be reversed by adding 5-µM curcumin. Meanwhile, we found that the application of curcumin effectively induced Nrf2 nuclear accumulation in Hacat cells. While in the Nrf2 knockdown cells, the protective effects of curcumin against UVA (or UVB) were attenuated. Conclusively, curcumin protects Hacat cells against UV exposure-induced photo-damage by regulating Nrf2 expression.

Serum Protects Cells and Increases Intracellular Delivery of Molecules by Nanoparticle-Mediated Photoporation.

INTRODUCTION: Intracellular delivery of molecules is central to applications in biotechnology, medicine, and basic research. Nanoparticle-mediated photoporation using carbon black nanoparticles exposed to pulsed, near-infrared laser irradiation offers a physical route to create transient cell membrane pores, enabling intracellular delivery. However, nanoparticle-mediated photoporation, like other physical intracellular delivery technologies, necessitates a trade-off between achieving efficient uptake of exogenous molecules and maintaining high cell viability. METHODS: In this study, we sought to shift this balance by adding serum to cells during nanoparticle-mediated photoporation as a viability protectant. DU-145 prostate cancer cells and human dermal fibroblasts were exposed to laser irradiation in the presence of carbon black (CB) nanoparticles and other formulation additives, including fetal bovine serum (FBS) and polymers. RESULTS: Our studies showed that FBS can protect cells from viability loss, even at high-fluence laser irradiation conditions that lead to high levels of intracellular delivery in two different mammalian cell types. Further studies revealed that full FBS was not needed: viability protection was achieved with denatured FBS, with just the high molecular weight fraction of FBS (>30 kDa), or even with individual proteins like albumin or hemoglobin. Finally, we found that viability protection was also obtained using certain neutral water-soluble polymers, including Pluronic F127, polyvinylpyrrolidone, poly(2-ethyl-2-oxazoline), and polyethylene glycol, which were more effective at increased concentration, molecular weight, or hydrophobicity. CONCLUSION: Altogether, these findings suggest an interaction between amphiphilic domains of polymers with the cell membrane to help cells maintain viability, possibly by facilitating transmembrane pore closure. In this way, serum components or synthetic polymers can be used to increase intracellular delivery by nanoparticle-mediated photoporation while maintaining high cell viability.

Effect of Fish Bone Bioactive Peptides on Oxidative, Inflammatory and Pigmentation Processes Triggered by UVB Irradiation in Skin Cells.

In the present study, we evaluated for the first time the photoprotective effect of fish bone bioactive peptides (FBBP) preparation isolated from silver carp (Hypophthalmichthys molitrix) discarded tissue using in vitro experimental models of skin cells exposed to ultraviolet B (UVB) irradiation and stressing agents. FBBP preparation was obtained by papain treatment of minced bones and centrifugal ultrafiltration, and the molecular weight (MW) distribution was characterized by size exclusion and reversed-phase high performance liquid chromatography (RP-HPLC). In vitro assessment of the effect of FBBP pretreatment in UVB-irradiated L929 fibroblasts and HaCaT keratinocytes revealed their cytoprotective activity. Their capacity to efficiently reduce reactive oxygen species (ROS) production and lipid peroxidation varied in a dose-dependent manner, and it was greater in fibroblasts. A decrease of proinflammatory cytokines secretion, in particular of tumor necrosis factor alpha (TNF-α), was found after FBBP pretreatment of THP-1-derived inflamed macrophages. Melanin production and tyrosinase activity investigated in UVB-irradiated Mel-Juso cells were lowered in direct relation to FBBP concentrations. FBBP fractions with high radical scavenging activity were separated by ion exchange chromatography, and two collagenic sequences were identified. All these results offer new scientific data on aquaculture fish bone-derived peptides confirming their ability to control the antioxidant, anti-inflammatory and pigmentation processes developed during UV irradiation of skin cells and recommend their use as valuable natural ingredients of photoprotective cosmeceutical products.

Resveratrol protects intestinal epithelial cells against radiation-induced damage by promoting autophagy and inhibiting apoptosis through SIRT1 activation.

Intrinsic autophagy is important for the maintenance of intestinal homeostasis and intestinal regeneration. Ionizing radiation suppresses intrinsic autophagy and reduces damage-induced regeneration in the intestine, resulting in intestinal injury. Resveratrol, a sirtuin 1 (SIRT1) agonist, promotes autophagy and exerts radioprotective effect. In this study, the protective effect of resveratrol against radiation-induced intestinal injury and its potential mechanism were investigated. Intestinal epithelial cells (IEC-6) were exposed to 10 Gy ionizing radiation and resveratrol (0.1-40.0 µM). Cell viability was investigated using Cell Counting Kit 8 (CCK8), apoptosis was observed by Annexin V-fluorescein isothiocyanate/propidium iodide (PI) staining and flow cytometry, and the expression of apoptotic and autophagic proteins was determined by western blotting. Resveratrol exerted a high toxicity against IEC-6 cells, but at low concentrations, it inhibited ionizing radiation-induced apoptosis. Resveratrol increased SIRT1 expression after irradiation and inhibited ionizing radiation-induced p53 acetylation and pro-apoptotic protein, Bax, expression. Furthermore, resveratrol promoted autophagy via the phosphoinositide 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway, thereby protecting IEC-6 cells against radiation-induced damage. These results suggest that resveratrol reduces radiation-induced IEC-6 cell damage by inhibiting apoptosis and promoting autophagy via the activation of SIRT1, and that the PI3K/AKT/mTOR signaling pathway is involved in the induction of autophagy.

Carbon dioxide inhibits UVB-induced inflammatory response by activating the proton-sensing receptor, GPR65, in human keratinocytes.

Carbon dioxide (CO2) is the predominant gas molecule emitted during aerobic respiration. Although CO2 can improve blood circulation in the skin via its vasodilatory effects, its effects on skin inflammation remain unclear. The present study aimed to examine the anti-inflammatory effects of CO2 in human keratinocytes and skin. Keratinocytes were cultured under 15% CO2, irradiated with ultraviolet B (UVB), and their inflammatory cytokine production was analyzed. Using multiphoton laser microscopy, the effect of CO2 on pH was observed by loading a three-dimensional (3D)-cultured epidermis with a high-CO2 concentration formulation. Finally, the effect of CO2 on UVB-induced erythema was confirmed. CO2 suppressed the UVB-induced production of tumor necrosis factor-α (TNFα) and interleukin-6 (IL-6) in keratinocytes and the 3D epidermis. Correcting medium acidification with NaOH inhibited the CO2-induced suppression of TNFα and IL-6 expression in keratinocytes. Moreover, the knockdown of H+-sensing G protein-coupled receptor 65 inhibited the CO2-induced suppression of inflammatory cytokine expression and NF-κB activation and reduced CO2-induced cyclic adenosine monophosphate production. Furthermore, the high-CO2 concentration formulation suppressed UVB-induced erythema in human skin. Hence, CO2 suppresses skin inflammation and can be employed as a potential therapeutic agent in restoring skin immune homeostasis.

Adipocytes protect fibroblasts from radiation-induced damage by adiponectin secretion.

Prostate and colon cancers are among the most common cancers diagnosed annually, and both often require treatment with radiation therapy. Advancement in radiation delivery techniques has led to highly accurate targeting of tumor and sparing of normal tissue; however, in the pelvic region it is anatomically difficult to avoid off-target radiation exposure to other organs. Chronically the effects of normal urogenital tissue exposure can lead to urinary frequency, urinary incontinence, proctitis, and erectile dysfunction. Most of these symptoms are caused by radiation-induced fibrosis and reduce the quality of life for cancer survivors. We have observed in animal models that the severity of radiation-induced fibrosis in normal tissue correlates to damaged fat reservoirs in the pelvic region. We hypothesize that adipocytes may secrete a factor that prevents the induction of radiation-associated fibrosis in normal tissues. In these studies we show that the adipokine, adiponectin, is secreted by primary mouse adipocytes and protects fibroblasts from radiation-induced cell death, myofibroblast formation, and senescence. Further, we demonstrated that adiponectin does not protect colorectal or prostate cancer cells from radiation-induced death. Thus, we propose that adiponectin, or its downstream pathway, would provide a novel target for adjuvant therapy when treating pelvic cancers with radiation therapy.

Protecting HaCaT cells from ionizing radiation using persimmon tannin-Aloe gel composite.

Context: Persimmon tannin (extract of Diospyros kaki L.f [Ebenaceae]) and Aloe gel (extract of Aloe vera (L.) Burm.f. [Asphodelaceae]) are known as anti-radiation agents. However, radiation resistance of the persimmon tannin-Aloe gel composite remains inconclusive.Objective: To investigate the capacity of the persimmon tannin-Aloe gel composite to protect against ionising radiation at the cellular level.Materials and methods: HaCaT (human epidermal keratinocytes) cells were pre-treated with PT-A-1 (the mass ratio of persimmon tannin and Aloe gel was 2:1) or the single component (persimmon tannin or Aloe gel) at various concentrations (0, 50, 100, 200, 400, 800 µg/mL. Control group: medium with no HaCaT cells), and then radiated with X-rays (radiation dose: 4, 8, 12, 16, and 20 Gy). Cell viability, cell apoptosis, and radiation-induced intracellular reactive oxygen species (ROS) generation were analysed by CCK-8, Hoechst 33258 staining/flow cytometry, and 2',7'-dichlorfluorescein diacetate (DCFH-DA) assay, respectively, for 12 or 24 h incubation after radiation.Results: The optimal radiation dose and post-radiation incubation period were determined to be 8 Gy and 12 h. CCK-8 activity detection showed that the cell activity was 77.85% (p < 0.05, IC50 = 55.67 µg/mL). The apoptotic rate was the lowest (4.32%) at 200 µg/mL of PT-A-1 towards HaCaT cells. ROS production was the most effectively suppressed by 200 µg/mL PT-A-1 towards HaCaT cells.Discussion and conclusions: The persimmon tannin-Aloe gel composite has good radioprotective effect, and which will facilitate its clinic application as a potential natural anti-radiation agent in future.

Protective effects of Ginkgo biloba L. against natural toxins, chemical toxicities, and radiation: A comprehensive review.

Nowadays in our developing and industrial world, humans' health or even their life is threatened by exposure to poisons. In this situation, detecting a protective compound could be helpful and interesting. In the present article, we collected and reviewed all studies, which have been conducted so far about the protective effects of Ginkgo biloba L. (GB), one of the most ancient medicinal tree species, against toxicities induced by chemical toxic agents, natural toxins, and also radiation. In overall, investigations showed that GB exerts the antioxidant, antiinflammatory, antiapoptotic, and antigenotoxicity effects in different toxicities. There are also some special mechanisms about its protective effects against some specific toxic agents, such as acetylcholine esterase inhibition in the aluminium neurotoxicity or membrane-bond phosphodiesterase activation in the triethyltin toxicity. Ginkgolide A was the most investigated active ingredient of G. biloba leaf extract as a protective compound against toxicities, which had the similar effects of total extract. A few clinical studies have been conducted in this field, which demonstrated the beneficial effects of GB against toxic agents. However, the promising effects of this valuable herbal extract will practically remain useless without carrying out more clinical studies and proving its effects on human beings.

Repair-independent functions of DNA-PKcs protect irradiated cells from mitotic slippage and accelerated senescence.

The binding of DNA-dependent protein kinase catalytic subunit (DNA-PKcs, also known as PRKDC) to Ku proteins at DNA double-strand breaks (DSBs) has long been considered essential for non-homologous end joining (NHEJ) repair, providing a rationale for use of DNA-PKcs inhibitors as cancer therapeutics. Given lagging clinical translation, we reexamined mechanisms and observed instead that DSB repair can proceed independently of DNA-PKcs. While repair of radiation-induced DSBs was blocked in cells expressing shRNAs targeting Ku proteins or other NHEJ core factors, DSBs were repaired on schedule despite targeting DNA-PKcs. Although we failed to observe a DSB repair defect, the γH2AX foci that formed at sites of DNA damage persisted indefinitely after irradiation, leading to cytokinesis failure and accumulation of binucleated cells. Following this mitotic slippage, cells with decreased DNA-PKcs underwent accelerated cellular senescence. We identified downregulation of ataxia-telangiectasia mutated kinase (ATM) as the critical role of DNA-PKcs in recovery from DNA damage, insofar as targeting ATM restored γH2AX foci resolution and cytokinesis. Considering the lack of direct impact on DSB repair and emerging links between senescence and resistance to cancer therapy, these results suggest reassessing DNA-PKcs as a target for cancer treatment.

[Hydrogen Sulfide Donor NaHS Protects Mesenchymal Stem and Melanoma Cells from the Negative Effects of Infrared Laser Irradiation].

We have established earlier that 835-nm infrared laser irradiation results in a dose-dependent growth inhibition of human mesenchymal stem and melanoma cells and is able to induce cell death. In this work we have demonstrated that hydrogen sulfide donor NaHS is able to protect both cell types from the negative action of laser irradiation and the magnitude of protection depends on NaHS concentration. The mechanism of cell protection by NaHS is primarily attributable to its effects on intracellular processes occurring after irradiation, since the protective effect does not depend on whether NaHS is added before or after irradiation. Moreover, NaHS is able to exert its protective effect even when added 6 hours post irradiation.

microRNA-4532 inhibition protects human lens epithelial cells from ultra-violet-induced oxidative injury via activating SIRT6-Nrf2 signaling.

Ultra-violet radiation (UVR) can induce significant oxidative injury to human lens epithelial cells (HLECs). Sirtuin 6 (SIRT6) is shown to directly bind to Nrf2, essential for Nrf2 signaling activation. In the present study, we show that microRNA-4532 (miR-4532) targets SIRT6 to regulate Nrf2 signaling in HLECs. Ectopic overexpression of miR-4532 in HLECs decreased SIRT6 3'-UTR activity, causing SIRT6 downregulation and Nrf2 signaling inhibition. Conversely, miR-4532 inhibition, by a lentiviral construct, enhanced SIRT6 3'-UTR activity, SIRT6 expression and Nrf2 signaling activation. Functional studies show that UVR-induced cytotoxicity and apoptosis in HLECs were potentiated by miR-4532 overexpression, Nrf2 depletion or SIRT6 shRNA. Conversely, miR-4532 inhibition or ectopic SIRT6 overexpression attenuated UVR-induced oxidative injury in HLECs. Importantly, miR-4532 overexpression or inhibition was ineffective in SIRT6-KO or Nrf2-KO HLECs. Taken together, the results show that inhibition of miR-4532 protects HLECs from UVR-induced oxidative injury via activation of SIRT6-Nrf2 pathway. Targeting the miR-4532-SIRT6-Nrf2 pathway could be a novel strategy to protect HLECs from UVR and possible other oxidative stresses.

Radiation resistance of normal human astrocytes: the role of non-homologous end joining DNA repair activity.

Radiotherapy is a common modality for treatment of brain cancers, but it can induce long-term physiological and cognitive deficits. The responses of normal human brain cells to radiation is not well understood. Astrocytes have been shown to have a variety of protective mechanisms against oxidative stress and have been shown to protect neurons. We investigated the response of cultured normal human astrocytes (NHAs) to X-ray irradiation. Following exposure to 10 Gy X-irradiation, NHAs exhibited DNA damage as indicated by the formation of γ-H2AX foci. Western blotting showed that NHAs displayed a robust increase in expression of non-homologous end joining DNA repair enzymes within 15 min post-irradiation and increased expression of homologous recombination DNA repair enzymes ~2 h post-irradiation. The cell cycle checkpoint protein p21/waf1 was upregulated from 6-24 h, and then returned to baseline. Levels of DNA repair enzymes returned to basal ~48 h post-irradiation. NHAs re-entered the cell cycle and proliferation was observed at 6 days. In contrast, normal human mesenchymal stem cells (MSCs) failed to upregulate DNA repair enzymes and instead displayed sustained upregulation of p21/waf1, a cell cycle checkpoint marker for senescence. Ectopic overexpression of Ku70 was sufficient to protect MSCs from sustained upregulation of p21/waf1 induced by 10 Gy X-rays. These findings suggest that increased expression of Ku70 may be a key mechanism for the radioresistance of NHAs, preventing their accelerated senescence from high-dose radiation. These results may have implications for the development of novel targets for radiation countermeasure development.

Engineered nanoceria cytoprotection in vivo: mitigation of reactive oxygen species and double-stranded DNA breakage due to radiation exposure.

Cerium oxide nanomaterials are known to absorb ionizing radiation energy, as well as to neutralize free radicals in solution, by undergoing redox changes. We, therefore, proposed that ceria nanoparticles could be used in biomedical applications as an injectable, radio-protectant material. In this study, we examine the effectiveness of engineered nanoparticles in protecting germ cells from the damaging effects of irradiation-induced cell death, in vivo. C57BL/6J male mice were used as a model and irradiation was localized to the scrotal region at 2.5, 5, and/or 10 Gy intensities. Ceria nanoparticles were introduced as 100 µL injections at 100 nM and 100 µM via tail vein injections, weekly, for one month. Following this, the animals were sacrificed and their organs (heart, brain, kidneys) were harvested. Tissues were fixed, sectioned, and stained for instances of cell death, DNA damage (TUNEL assay), and ROS (nitro-tyrosine evolution). Tissues from mice treated with ceria nanoparticles showed significantly less (∼13% decrease; *P < 0.05) tissue damage (per immunohistochemistry) over controls at up to 5 Gy radiation. DNA damage and ROS also decrease substantially with ceria treatment, confirming ceria's capacity as an injectable, radio-protectant material. The study also highlights the ability of ceria nanoparticles to protect cells/tissues from both direct and indirect effects of ionizing radiation.

A protective Langerhans cell-keratinocyte axis that is dysfunctional in photosensitivity.

Photosensitivity, or skin sensitivity to ultraviolet radiation (UVR), is a feature of lupus erythematosus and other autoimmune and dermatologic conditions, but the mechanistic underpinnings are poorly understood. We identify a Langerhans cell (LC)-keratinocyte axis that limits UVR-induced keratinocyte apoptosis and skin injury via keratinocyte epidermal growth factor receptor (EGFR) stimulation. We show that the absence of LCs in Langerin-diphtheria toxin subunit A (DTA) mice leads to photosensitivity and that, in vitro, mouse and human LCs can directly protect keratinocytes from UVR-induced apoptosis. LCs express EGFR ligands and a disintegrin and metalloprotease 17 (ADAM17), the metalloprotease that activates EGFR ligands. Deletion of ADAM17 from LCs leads to photosensitivity, and UVR induces LC ADAM17 activation and generation of soluble active EGFR ligands, suggesting that LCs protect by providing activated EGFR ligands to keratinocytes. Photosensitive systemic lupus erythematosus (SLE) models and human SLE skin show reduced epidermal EGFR phosphorylation and LC defects, and a topical EGFR ligand reduces photosensitivity. Together, our data establish a direct tissue-protective function for LCs, reveal a mechanistic basis for photosensitivity, and suggest EGFR stimulation as a treatment for photosensitivity in lupus erythematosus and potentially other autoimmune and dermatologic conditions.

Protection from UV light is an evolutionarily conserved feature of the haematopoietic niche.

Haematopoietic stem and progenitor cells (HSPCs) require a specific microenvironment, the haematopoietic niche, which regulates HSPC behaviour1,2. The location of this niche varies across species, but the evolutionary pressures that drive HSPCs to different microenvironments remain unknown. The niche is located in the bone marrow in adult mammals, whereas it is found in other locations in non-mammalian vertebrates, for example, in the kidney marrow in teleost fish. Here we show that a melanocyte umbrella above the kidney marrow protects HSPCs against ultraviolet light in zebrafish. Because mutants that lack melanocytes have normal steady-state haematopoiesis under standard laboratory conditions, we hypothesized that melanocytes above the stem cell niche protect HSPCs against ultraviolet-light-induced DNA damage. Indeed, after ultraviolet-light irradiation, unpigmented larvae show higher levels of DNA damage in HSPCs, as indicated by staining of cyclobutane pyrimidine dimers and have reduced numbers of HSPCs, as shown by cmyb (also known as myb) expression. The umbrella of melanocytes associated with the haematopoietic niche is highly evolutionarily conserved in aquatic animals, including the sea lamprey, a basal vertebrate. During the transition from an aquatic to a terrestrial environment, HSPCs relocated into the bone marrow, which is protected from ultraviolet light by the cortical bone around the marrow. Our studies reveal that melanocytes above the haematopoietic niche protect HSPCs from ultraviolet-light-induced DNA damage in aquatic vertebrates and suggest that during the transition to terrestrial life, ultraviolet light was an evolutionary pressure affecting the location of the haematopoietic niche.

A new copper ionophore DPMQ protects cells against ultraviolet B irradiation by inhibiting the TRPV1 channel.

Copper is more likely than iron to generate reactive oxygen species (ROS) in a redox reaction due to its higher electrochemical reactivity. This study examined the effect of a newly synthesized Cu2+ binding compound, (E)-2-(4-(dimethylamino)phenylimino)methyl)quinolin-8-ol (DPMQ), on ultraviolet B (UVB) irradiation-induced cytotoxicity in human dermal fibroblasts. DPMQ induced Cu2+ influx as effectively as disulfiram, a Cu2+ ionophore anticancer drug. However, disulfiram induced ROS generation, mitochondrial dysfunction, and apoptosis in fibroblasts in a Cu2+ -dependent manner, whereas DPMQ was not only nontoxic, but protected cells against UVB irradiation-induced apoptosis in a Cu2+ -independent manner. UVB irradiation induced a Ca2+ -dependent increase in ROS generation, a decrease in Nrf2 levels, and activation of the mitochondrial apoptotic pathway, and these effects were prevented by DPMQ, which also increased Nrf2 nuclear translocation in a Cu2+ -independent manner. UVB irradiation activated 12-lipoxygenase and 12-hydroxyeicosatetraenoic acid (12-HETE), a product of 12-lipoxygenase, activated the TRPV1 channel. DMPQ did not act as a Ca2+ chelator, but inhibited the cytosolic Ca2+ increase induced by 12-HETE or capsaicin, but not that induced by bradykinin or ATP. Blockade of Ca2+ influx by pharmacological inhibition or silencing of the TRPV1 channel or chelation of cytosolic Ca2+ inhibited the UVB irradiation-induced Nrf2 reduction, ROS generation, mitochondrial dysfunction, and apoptosis. Taken together, our results suggest that Ca2+ influx via the TRPV1 channel is responsible for UVB irradiation-induced cytotoxicity and that DPMQ protects cells against UVB irradiation by inhibiting the TRPV1 channel and stabilizing Nrf2, and could thus be a potentially useful compound for the treatment of free radical-induced diseases.

Thrombopoietin protects hematopoietic stem cells from retrotransposon-mediated damage by promoting an antiviral response.

Maintenance of genomic integrity is crucial for the preservation of hematopoietic stem cell (HSC) potential. Retrotransposons, spreading in the genome through an RNA intermediate, have been associated with loss of self-renewal, aging, and DNA damage. However, their role in HSCs has not been addressed. Here, we show that mouse HSCs express various retroelements (REs), including long interspersed element-1 (L1) recent family members that further increase upon irradiation. Using mice expressing an engineered human L1 retrotransposition reporter cassette and reverse transcription inhibitors, we demonstrate that L1 retransposition occurs in vivo and is involved in irradiation-induced persistent γH2AX foci and HSC loss of function. Thus, RE represents an important intrinsic HSC threat. Furthermore, we show that RE activity is restrained by thrombopoietin, a critical HSC maintenance factor, through its ability to promote a potent interferon-like, antiviral gene response in HSCs. This uncovers a novel mechanism allowing HSCs to minimize irradiation-induced injury and reinforces the links between DNA damage, REs, and antiviral immunity.

Spliceosomal components protect embryonic neurons from R-loop-mediated DNA damage and apoptosis.

RNA splicing factors are essential for the viability of all eukaryotic cells; however, in metazoans some cell types are exquisitely sensitive to disruption of splicing factors. Neuronal cells represent one such cell type, and defects in RNA splicing factors can lead to neurodegenerative diseases. The basis for this tissue selectivity is not well understood owing to difficulties in analyzing the consequences of splicing factor defects in whole-animal systems. Here, we use zebrafish mutants to show that loss of spliceosomal components, including splicing factor 3b, subunit 1 (sf3b1), causes increased DNA double-strand breaks and apoptosis in embryonic neurons. Moreover, these mutants show a concomitant accumulation of R-loops, which are non-canonical nucleic acid structures that promote genomic instability. Dampening R-loop formation by conditional induction of ribonuclease H1 in sf3b1 mutants reduced neuronal DNA damage and apoptosis. These findings show that splicing factor dysfunction leads to R-loop accumulation and DNA damage that sensitizes embryonic neurons to apoptosis. Our results suggest that diseases associated with splicing factor mutations could be susceptible to treatments that modulate R-loop levels.

Cholinergic and cytoprotective signaling cascades mediate the mitigative effect of erythropoietin on acute radiation syndrome.

The present investigation aimed to evaluate the radiomitigative efficacy of the recombinant human erythropoietin (EPO) against acute radiation syndrome (ARS) in a rat model. Rats were irradiated with a single sublethal dose of γ-radiation (7 Gy; total body irradiation; TBI) on the 1st day of experimental course, then received EPO (5000 IU/kg; i.p.) 24 h after irradiation, and rats were observed for 30 days of survival analysis. Administration of EPO improved 30-day survival, alleviated TBI-induced myelosuppression and pancytopenia, by augmenting lymphocytes and other white blood cells in the peripheral blood of rats, while bone marrow and spleen cellularity were restored. EPO post-exposure treatment alleviated hepatotoxicity biomarkers and restored splenic function. EPO abrogated radiation-induced oxidative stress through the upregulation of the cholinergic anti-inflammatory nicotinic acetylcholine receptor (α-7-nAChR) and the pro-survival Janus kinase-2 and signal transducers and activators of transcription JAK-2/STAT-3 signaling mediated via enhancing nuclear factor erythroid-2 related factor-2 (Nrf-2) cytoprotective machinery in liver and spleen of irradiated rats. Moreover, EPO treatment prevented hepatic and splenic apoptosis. The present study establishes the implication of α-7-nAChR-JAK-2/STAT-3-Nrf-2 signaling cascade in the radiomitigative potential of EPO against ARS.

Photochemoprotective effect of a fraction of a partially purified extract of Byrsonima crassifolia leaves against UVB-induced oxidative stress in fibroblasts and hairless mice.

Ultraviolet B (UVB) irradiation increases the risk of various skin disorders, leading to inflammation and oxidative stress and thereby increasing the risk of skin photoaging and carcinogenesis. The use of photochemoprotectors such as natural products with antioxidant and anti-inflammatory properties represents a strategy for preventing UVB-induced skin damage. We investigated the photochemoprotective effect of a fraction of a partially purified extract of Byrsonima crassifolia leaves (BCF) on fibroblasts and hairless mice exposed to UVB radiation. The mixture of phenolic compounds in BCF prevented the decrease in reduced glutathione (GSH) levels in fibroblast cultures induced by UVB radiation more than some of their individual standards ((+)-catechin (CAT), epigallocatechin gallate and quercetin 3-O-ß-d-glucopyranoside). Prepared gel formulations increased skin antioxidant activity, and BCF components and the CAT standard were retained in the HRS/J hairless mice epidermis 2h after application. Topical treatment with the BCF or CAT formulations (1%) significantly reduced the decrease in GSH levels and decreased myeloperoxidase activity and the secretion of pro-inflammatory cytokines IL-1ß and IL-6 induced by UVB radiation (P<0.05), indicating that both BCF and CAT had anti-inflammatory effects. BCF inhibited UVB-induced metalloproteinase (MMP)-9 secretion/activity, whereas CAT had no effect on MMP-9 activity in the skin of treated animals. These results therefore suggest that BCF can be used as a photochemoprotective agent and antioxidant in the prevention/treatment of inflammation and oxidative stress of the skin induced by UVB radiation.