The role of constitutive nitric-oxide synthase in ultraviolet B light-induced nuclear factor κB activity

Nitric oxide synthase regulates coelomocytes apoptosis through the NF-κB signaling pathway in the sea cucumber Apostichopus japonicus

Nitric oxide synthase (NOS) was initially discovered to participate in the generation of nitric oxide as a defense mechanism against pathogenic infections. In recent years, it has been found that NOS plays a pivotal role in regulating apoptosis and inflammation in mammals. However, the mechanisms underlying NOS-mediated apoptosis in invertebrates remain largely unclear. In this study, we found that the Apostichopus japonicus NOS (AjNOS) expression levels were upregulated by 2.20-fold and 3.46-fold after being challenged with Vibrio splendidus at concentrations of 107 CFU mL-1 and 108 CFU mL-1 for 12 h compared to the control group, respectively. Under these conditions, the rates of coelomocytes apoptosis were increased from 14.7% to 32.7% and 45.4%, respectively. Treatment with NOS inhibitor (l-NAME) resulted in a reduction of coelomocytes apoptosis rates from 32.6% to 26.5% in V. splendidus (107 CFU mL-1) groups and from 42.3% to 33.3% in V. splendidus (108 CFU mL-1) groups, respectively. NOS has been reported to regulate apoptosis through IκBα phosphorylation. Simultaneously, exposure to V. splendidus in conjunction with l-NAME resulted in down-regulation of AjIκBα phosphorylation levels compared to the group infected solely with V. splendidus. Furthermore, immunofluorescence analysis revealed that treatment with l-NAME or interference of AjNOS using siRNA inhibited translocation of AjNF-κB/p65 (RelA) into the nucleus. Previous studies have shown that NF-κB can down-regulate expression levels of Bcl-2 family members, which is an important pathway for regulating apoptosis. In the present study, treatment with l-NAME was found to promote anti-apoptotic AjBcl-2 mRNA increase to 1.41-fold and protein expression increase to 1.86-fold at 12 h post V. splendidus challenge. However, these effects were suppressed by PMA (an NF-κB activator). Overall, our findings demonstrate that AjNOS regulates coelomocytes apoptosis induced by V. splendidus through activation of the AjNF-κB signaling pathway and down-regulation of AjBcl-2 in A. japonicus.

Ultraviolet Light, Unfolded Protein Response and Autophagy†

The endoplasmic reticulum (ER) plays an important role in the regulation of protein synthesis. Alterations in the folding capacity of the ER induce stress, which activates three ER sensors that mediate the unfolded protein response (UPR). Components of the pathways regulated by these sensors have been shown to regulate autophagy. The last corresponds to a mechanism of self-eating and recycling important for proper cell maintenance. Ultraviolet radiation (UV) is an external damaging stimulus that is known for inducing oxidative stress, and DNA, lipid and protein damage. Many controversies exist regarding the role of UV-inducing ER stress or autophagy. However, a connection between the three of them has not been addressed. In this review, we will discuss the contradictory theories regarding the relationships between UV radiation with the induction of ER stress and autophagy, as well as hypothetic connections between UV, ER stress and autophagy.

Characterization of UVB and UVA-340 Lamps and Determination of Their Effects on ER Stress and DNA Damage

Ultraviolet B-light (UVB) has been often used as a "physiological" UV in photobiology studies. How representative and equivalent these studies are compared to the effect of the sunlight is always of great interest. We now characterized the spectrum and intensity of two commonly used UV sources, a UVB lamp and a UVA-340 lamp which simulate the solar spectrum in the UVB/UVA range in the presence or absence of a UVB band pass filter that reduces >80% UVA from the UVA-340 lamp. The spectrum of each lamp was used in computational modeling for skin penetration. The effects of the lamps on endoplasmic reticulum (ER)-stress response and DNA damage in cultured keratinocytes HaCaT cells were analyzed. Our data show that the UVB lamp is a better inducer for both eIF2α phosphorylation and PERK modification, as well as a better reducer of ATF6 expression. The UVB lamp is also the best inducer of gamma-H2AX expression and cyclobutane pyrimidine dimers formation. However, the UVA-340 lamp is a better inducer for ATF4 expression. Our results indicate that different spectral characteristics of UV lamps can produce different results for the activation of the ER-stress responses and the differences do not always follow a defined pattern.

UVB-induced eIF2α phosphorylation in keratinocytes depends on decreased ATF4, GADD34 and CReP expression levels

AIM

To elucidate the mechanism behind the sustained high levels of phosphorylated eIF2α in HaCaT cells post-UVB.

MAIN METHODS

In this study, expression levels of the machinery involved in the dephosphorylation of eIF2α (GADD34, CReP and PP1), as well as the PERK-eIF2α-ATF4-CHOP, IRE1α/XBP1s and ATF6α signaling cascades, were analyzed by western blot and fluorescence microscope.

KEY FINDINGS

Our data showed that UVB induces the phosphorylation of eIF2α, which induces the translation of ATF4 and consequently the expression of CHOP and GADD34. Nevertheless, UVB also suppresses the translation of ATF4 and GADD34 in HaCaT cells via a p-eIF2α independent mechanism. Therefore, the lack of ATF4, GADD34 and CReP is responsible for the sustained phosphorylation of eIF2α. Finally, our data also showed that UVB selectively modifies PERK and downregulates ATF6α expression but does not induce activation of the IRE1α/XBP1s pathway in HaCaT cells.

SIGNIFICANCE

Novel mechanism to explain the prolonged phosphorylation of eIF2α post-UVB irradiation.

Ultraviolet Radiation and Basal Cell Carcinoma: An Environmental Perspective

Ultraviolet radiation (UVR) is a known carcinogen participated for the development of skin cancers. Solar UVR exposure, particularly ultraviolet B (UVB), is the mostly significant environmental risk factor for the occurrence and progress of basal cell carcinoma(BCC). Both cumulative and intermittent high-grade UVR exposure could promote the uncontrolled replication of skin cells. There are also exsiting other contributing environmental factors that combine with the UVR exposure to promote the development of BCC. DNA damage in formation of skin cancers is considered to be a result of UVR toxicity. It is UVR that could activate a series of oncogenes simultaneously inactivating tumor suppressor genes and aberrant proliferation and survival of keratinocytes that repair these damages. Furthermore, mounting evidence demonstrates that inflammatory responses of immune cells in the tumor microenvironment plays crucial role in the skin tumorigenesis as well. In this chapter, we will follow the function of UVR in the onset and development of BCC. We describe the factors that influence BCC induced by UVR, and also review the recent advances of pathogenesis of BCC induced by UVR from the genetic and inflammatory aspects.

Role of constitutive nitric oxide synthases in the dynamic regulation of the autophagy response of keratinocytes upon UVB exposure

Ultraviolet B (UVB) radiation induces autophagy responses, which play a role in the regulation of the oncogenic processes of irradiated cells. However, the mechanism of autophagy responses post-UVB irradiation remains to be fully elucidated. Previous studies indicate that UVB radiation induces the activation and uncoupling of constitutive nitric oxide synthases (cNOS), which produce nitric oxide and peroxynitrite; both have been shown to regulate autophagy responses. In this study, the UVB-induced autophagy responses were analysed in cell line- and UVB dose-dependent manners, and the role of cNOS in UVB-induced autophagy responses was also studied. Our data showed that UVB induces both autophagosome formation and degradation, and that cNOS is involved in the regulation of autophagy responses post UVB exposure. Both nitric oxide and peroxynitrite, the two products that are produced in cells immediately after UVB exposure, could upregulate autophagy in a dose-dependent manner. Furthermore, cNOS is involved in the UVB-induced downregulation of SQSTM1/p62, a scaffold protein used as a reporter of the autophagy response. However, the cNOS-mediated reduction of SQSTM1/p62 is autophagy-independent post UVB irradiation. Our results indicated that autophagy responses post UVB exposure are a dynamic balance of autophagosome formation and degradation, with cNOS playing a role in the regulation of the balance.

Anticancer Activity of Rosmarinus officinalis L.: Mechanisms of Action and Therapeutic Potentials

Alternative treatments for neoplastic diseases with new drugs are necessary because the clinical effectiveness of chemotherapy is often reduced by collateral effects. Several natural substances of plant origin have been demonstrated to be successful in the prevention and treatment of numerous tumors. Rosmarinus officinalis L. is a herb that is cultivated in diverse areas of the world. There is increasing attention being directed towards the pharmaceutical capacities of rosemary, utilized for its anti-inflammatory, anti-infective or anticancer action. The antitumor effect of rosemary has been related to diverse mechanisms, such as the antioxidant effect, antiangiogenic properties, epigenetic actions, regulation of the immune response and anti-inflammatory response, modification of specific metabolic pathways, and increased expression of onco-suppressor genes. In this review, we aim to report the results of preclinical studies dealing with the anticancer effects of rosemary, the molecular mechanisms related to these actions, and the interactions between rosemary and anticancer drugs. The prospect of utilizing rosemary as an agent in the treatment of different neoplastic diseases is discussed. However, although the use of rosemary in the therapy of neoplasms constitutes a fascinating field of study, large and controlled studies must be conducted to definitively clarify the real impact of this substance in clinical practice.

Potential Immunoregulatory and Antiviral/SARS-CoV-2 Activities of Nitric Oxide

Nitric oxide (NO) represents a key signaling molecule in multiple regulatory pathways underlying vascular, metabolic, immune, and neurological function across animal phyla. Our brief critical discussion is focused on the multiple roles of the NO signaling pathways in the maintenance of basal physiological states of readiness in diverse cell types mediating innate immunological functions and in the facilitation of proinflammatory-mediated adaptive immunological responses associated with viral infections. Prior studies have reinforced the critical importance of constitutive NO signaling pathways in the homeostatic maintenance of the vascular endothelium, and state-dependent changes in innate immunological responses have been associated with a functional override of NO-mediated inhibitory tone. Accordingly, convergent lines of evidence suggest that dysregulation of NO signaling pathways, as well as canonical oxidative effects of inducible NO, may provide a permissive cellular environment for viral entry and replication. In immunologically compromised individuals, functional override and chronic rundown of inhibitory NO signaling systems promote aberrant expression of unregulated proinflammatory pathways resulting in widespread metabolic insufficiencies and structural damage to autonomous cellular and organ structures. We contend that restoration of normative NO tone via combined pharmaceutical, dietary, or complex behavioral interventions may partially reverse deleterious physiological conditions brought about by viral infection linked to unregulated adaptive immune responses.

PM2.5 exposure induces vascular dysfunction via NO generated by iNOS in lung of ApoE-/- mouse

PM2.5 exposure exacerbates cardiovascular diseases via oxidative stress and inflammation, the detailed mechanism of which is unclear. In this study, the effects of oxidative stress and inflammation, as well as vascular structure and function were studied by multiple PM2.5 exposure model of ApoE-/- mice. The results indicated that NO produced by iNOS not cNOS might play important roles in inducing vascular dysfunction after PM2.5 exposure. The occurrence order and causality among NO, other oxidative stress indicators and inflammation is explored by single PM2.5 exposure. The results showed that NO generated by iNOS occurred earlier than that of other oxidative stress indicators, which was followed by the increased inflammation. Inhibition of NOS could effectively block the raise of NO, oxidative stress and inflammation after PM2.5 exposure. All in all, we firstly confirmed that NO was the initiation factor of PM2.5 exposure-induced oxidative stress, which led to inflammation and the following vascular dysfunction.

The Effect of Endothelial Cells on UVB-induced DNA Damage and Transformation of Keratinocytes In 3D Polycaprolactone Scaffold Co-culture System

Nitric oxide ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup><mml:mrow><mml:mi>NO</mml:mi></mml:mrow> <mml:mo>·</mml:mo></mml:msup> </mml:math> ) plays an important role in the regulation of redox balance in keratinocytes post-UVB exposure. Since endothelial cells releases <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup><mml:mrow><mml:mi>NO</mml:mi></mml:mrow> <mml:mo>·</mml:mo></mml:msup> </mml:math> for a prolonged time post-UVB, we determined whether human umbilical vein endothelial cells (HUVEC) could have an effect on UVB-induced DNA damage and transformation of their adjacent keratinocytes (HaCaT) using a 3D cell co-culturing system. Our data show that the levels of DNA breaks and/or cyclobutane pyrimidine dimer (CPD) along with γH2AX are higher in the co-cultured than in the mono-cultured keratinocytes post-UVB. The <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup><mml:mrow><mml:mi>NO</mml:mi></mml:mrow> <mml:mo>·</mml:mo></mml:msup> </mml:math> level in the co-cultured cells is increased approximately 3-fold more than in mono-cultured HaCaT cells within 1-hour post-UVB but then is reduced quickly in co-cultured HaCaT cells comparing to mono-cultured cells from 6 to 24 h post-UVB. However, the peroxynitrite (ONOO^- ) level is higher in the co-cultured than in the mono-cultured HaCaT cells in whole period post-UVB. Furthermore, while expression level of inducible nitric oxide synthase (iNOS) is increased, the ratio of coupled/uncoupled eNOS is reduced in co-cultured HaCaT cells compared to mono-cultured HaCaT cells. Finally, the co-cultured cells have a significantly increased transformation efficiency after repeating UVB exposure compared to mono-culture HaCaT cells. Our results suggest that endothelial cells could enhance <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup><mml:mrow><mml:mi>NO</mml:mi></mml:mrow> <mml:mo>·</mml:mo></mml:msup> </mml:math> /ONOO^- imbalance and promote transformation of adjacent keratinocytes.

The Mechanisms of Carnosol in Chemoprevention of Ultraviolet B-Light-Induced Non-Melanoma Skin Cancer Formation

Carnosol is a natural compound extracted from rosemary and sage, which has been demonstrated to have anti-inflammatory, anti-oxidant, and anti-cancer properties. In this report, we evaluated the therapeutic potential and elucidated the potential mechanism of action of carnosol in chemoprevention of ultraviolet B-light (UVB) induced non-melanoma skin cancer formation. Our data indicated that carnosol could partially reduce UVB-induced reactive oxygen species (ROS) elevation and thus reduce DNA damage. It could also reduce UVB-induced formation of cyclobutane pyrimidine dimers (CDP) in keratinocytes possibly through its ability in absorbing UVB radiation. In addition, carnosol could inhibit the UVB-induced activation of NF-κB and also reduce UVB-induced transformation of keratinocytes. Taken together, the results indicate the role of carnosol as a potential chemopreventive agent upon UVB radiation.

The mechanism of CIRP in inhibition of keratinocytes growth arrest and apoptosis following low dose UVB radiation

UV induces CIRP expression and subsequent Stat3 activation, but the biological function and mechanism of CIRP and Stat3 in mediating UVB-induced skin carcinogenesis have not been fully elucidated. In this study, we demonstrate that CIRP is elevated in all tested melanoma and non-melanoma skin cancer cell lines; and the expression of CIRP is upregulated in keratinocytes after being irradiated with relatively low dose (<5 mJ/cm² ), but not high dose (50 mJ/cm² ), UVB acutely and chronically. The increased expression of CIRP, either induced by UVB or through overexpression, leads to resistance of keratinocytes to UVB-induced growth arrest and death; and reduced expression of CIRP by RNA knockdown sensitizes keratinocyte cells to the low dose UVB radiation. We also demonstrated that CIRP expression is required for the low dose UVB-induced Tyr705-phosphorylation, but not total amount, of Stat3. The p-Stat3 level is correlated with the expression levels of cyclin D1 and VEGF, two known downstream cell growth regulators of Stat3, as well as Bag-1/S, an apoptosis regulator. Inhibition of Stat3 DNA-binding activity by S3I-201 leads to a reduction of the p-Stat3 and Bag-1/S along with growth and survival of keratinocytes post-UVB; and the effect of S3I-201 on the UVB-irradiated cells can be partially inhibited by overexpression of CIRP or Bag-1/S. Furthermore, the overexpression of Bag-1/S can totally inhibit UVB-induced PARP cleavage and caspase 3 activation. The results presented above led us to propose that CIRP-p(705)Stat3 cascade promotes cell proliferation and survival post-UVB via upregulating the expression of cyclin D1 and Bag-1/S, respectively. Published 2017. This article is a U.S. Government work and is in the public domain in the USA.

Antitumoral gene-based strategy involving nitric oxide synthase type III overexpression in hepatocellular carcinoma

Hepatocellular carcinoma develops in cirrhotic liver. The nitric oxide (NO) synthase type III (NOS-3) overexpression induces cell death in hepatoblastoma cells. The study developed gene therapy designed to specifically overexpress NOS-3 in cultured hepatoma cells, and in tumors derived from orthotopically implanted tumor cells in fibrotic livers. Liver fibrosis was induced by CCl4 administration in mice. The first-generation adenoviruses were designed to overexpress NOS-3 or green fluorescent protein, and luciferase complementary DNA under the regulation of murine alpha-fetoprotein (AFP) and Rous Sarcoma Virus (RSV) promoters, respectively. Both adenovirus and Hepa 1-6 cells were used for in vitro and in vivo experiments. Adenoviruses were administered through the tail vein 2 weeks after orthotopic tumor cell implantation. AFP-NOS-3/RSV-luciferase increased oxidative-related DNA damage, p53, CD95/CD95L expression and caspase-8, -9 and -3 activities in cultured Hepa 1-6 cells. The increased expression of CD95/CD95L and caspase-8 activity was abolished by Nω-nitro-l-arginine methyl ester hydrochloride, p53 and CD95 small interfering RNA. AFP-NOS-3/RSV-luciferase adenovirus increased cell death markers, and reduced cell proliferation of established tumors in fibrotic livers. The increase of oxidative/nitrosative stress induced by NOS-3 overexpression induced DNA damage, p53, CD95/CD95L expression and cell death in hepatocellular carcinoma cells. The effectiveness of the gene therapy has been demonstrated in vitro and in vivo.

Ultraviolet radiation-induced non-melanoma skin cancer: Regulation of DNA damage repair and inflammation

Exposure to ultraviolet (UV) radiation is associated with approximately 65% of melanoma cases, and 90% of non-melanoma skin cancers (NMSC), including basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). While the incidence of most other malignancies has either stabilized or declined, that of NMSC has increased and is developing even in younger age groups. NMSCs account for nearly 15,000 deaths, 3.5 million new cases, and more than 3 billion dollars a year in medical costs in the United States alone, representing a major public health concern. As sun protection efforts have not been proven effective, targeted chemoprevention strategies are much needed. Skin carcinogenesis by DNA damage is considered a predominant paradigm for UV toxicity. Exposure to UV radiation can activate various oncogenes while inactivating tumor suppressor genes, resulting in inappropriate survival and proliferation of keratinocytes that harbor these damages. Moreover, increasing evidence demonstrate that inflammatory responses by the immune cells within the tumor microenvironment also contribute significantly to skin tumorigenesis. Initiation and progression of skin carcinogenesis mediated by UV radiation involve complex pathways, including those of apoptosis, proliferation, autophagy, DNA repair, checkpoint signaling, metabolism, and inflammation. In this review, we highlight the recent advances in two of these key molecular processes that result in UV-mediated skin carcinogenesis. In particular, we discuss 1) pathways that regulate DNA damage repair and 2) the regulation of the inflammatory process its crosstalk with DNA repair potentially leading to non-melanoma skin carcinogenesis.