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. Author manuscript; available in PMC: 2012 Apr 15.
Published in final edited form as: Arch Biochem Biophys. 2010 Dec 1;508(2):192–197. doi: 10.1016/j.abb.2010.11.021

The Roles of Akt and NOSs In Regulation of VLA-4-Mediated Melanoma Cell Adhesion To Endothelial VCAM-1 After UVB-irradiation

Wei Liu 1, Shiyong Wu 1,*
PMCID: PMC3073699  NIHMSID: NIHMS256644  PMID: 21129359

Abstract

UVB-reduced avidity between M624 melanoma and HUVEC cells is dependent on the interaction of VLA-4 with its endothelial ligand VCAM-1. Our previous studies suggested that a spatial organization of α4 integrin, one of the two subunits of VLA-4, on the melanoma cell surface contributed to the changes in avidity for VCAM-1 upon UVB-irradiation. In this study, we demonstrate that Akt plays an important role in regulation of the expression and surface level of α4 integrin on melanoma cells upon UVB-irradiation. While the cell surface level of α4 integrin is not significantly affected by UVB-irradiation or Akt inhibitor alone, it is dynamically altered after UVB-irradiation when Akt is inhibited. Inhibition of Akt also reverses the reduction of avidity of cells after the irradiation. Our data also shows that UVB reduces the level of Akt. The inhibition of Akt activity correlates with a reduced amount of coupled cNOS and reduced amount of iNOS after UVB-irradiation. However the effect of NOSs on melanoma cell adhesion appears due to their roles in regulation of apoptosis after UVB-irradiation. Base on these results, we propose that the UVB-induced reduction of avidity of melanoma cells is coordinatively regulated by NOSs and Akt through two differential mechanisms.

Introduction

The very late antigen-4 integrin (VLA-4, α4β1 integrin) expressed on human melanoma cells can potentially mediate tumor cell metastasis by tethering, rolling, and adhering to vascular cell adhesion molecule-1 (VCAM-1) expressed on endothelial cells, similar to peripheral blood mononuclear cell (PBMC) trafficking to lymphoid organs and to sites of inflammation [1–4]. The ability of melanoma cells to adhere to cytokine-activated endothelium correlates with VLA-4 expression [2, 5]. The avidity of VLA-4 to endothelia cells is regulated by several cytoplasmic proteins [6–8]. Phosphorylation and dephosphorylation of integrin α4 alters its binding affinity to paxillin, a cytosolic signaling adaptor protein, and thus regulates migration of cells [9, 10]. Protein kinase B (PKB, Akt) is a serine/threonine protein kinase, which has been shown to play important roles in regulation of cell adhesion via different mechanisms [11–15]. However, it has never been shown if Akt mediates adhesion by regulating an adhesion molecule such as α4 integrin upon UVB-irradiation.

Akt activity is often co-regulated with iNOS and eNOS. Akt can stimulate iNOS expression via the NF-κB pathway [16]. Akt can also phosphorylate eNOS to increase eNOS stability and coupling [17]. In return, an elevation of iNOS can cause feedback inhibition of Akt [18]. UVB-induced activation of Akt plays an important role in regulation of cell cycle progression and apoptosis [19–21]. However, it is not known if the Ultraviolet B light (UVB)-induced Akt activation can also affect adhesive affinity of the irradiated cells. A recent study indicated that UVB-irradiation leads to a readily observable redistribution of α4 but not β1 on the cell surface, resulting in reduced adhesion between M624 melanoma and endothelia cells [22]. Recent studies also indicated that UVB-irradiation dynamically regulates the activities of iNOS and cNOS, including nNOS and eNOS [23, 24], which can potentially affect adhesive affinity of cells [25–27]. However, little is known about the relationships among NOS, Akt and melanoma cell adhesion after UVB-irradiation. Using the same M624 melanoma model, this study was to elucidate the relationships of α4 integrin, Akt, eNOS and iNOS. Their effect on UVB-reduced melanoma cell adhesion to endothelium was also determined under hematogenous shear stress, a critical step for melanoma cells to establish distant metastases. Our results suggest that NOSs and Akt regulate avidity of melanoma cells after UVB-irradiation via independent signaling pathways.

Materials and Methods

Cell Culture and Treatment

The M624 cells (human melanoma cell line) were cultured in 100 mm2 cell culture plates in Dulbecco’s modification of eagle’s medium (DMEM) (Mediatech, Manassas, VA) with 10% (v/v) fetal bovine serum (FBS) (Denville, Metuchen, NJ). Penicillin and streptomycin (Invitrogen, Carlsbad, CA) were added to the culture medium, and the cells were incubated at 37°C and 5% CO2.

UVB Irradiation

The power of the UVB lamp (UVP Inc., Upland, CA) was determined by a UVX digital radiometer (UVP Inc., Upland, CA) after the lamp was warmed up for 5 min. The cell culture medium was replaced with phosphate buffered saline (PBS, 1 ml/plate) during UVB irradiation (50 mJ/cm2). After the irradiation, the original medium was added to cell culture plates and the cells were returned to incubator for further analysis.

Cell Treatment

N-Nitro-L-Arginine Methyl Ester (L-NAME), N-Acetyl-L-Cysteine (L-NAC), N-([3-(Aminomethyl)phenyl]methyl)ethanimidamide dihydrochloride (1400w), Akt 1/2 kinase inhibitor (Akt I) were purchased from Sigma-Aldrich (St. Louis, MO). The final concentrations for the treatement were 2 mM L-NAME, 25 mM L-NAC, 25 µM 1400w, 200 nM Akt I. The cells were pre-treated with each chemical for 1 h and then UVB-irradiated. After the irradiation, the cells were incubated for 18 h in the same medium with each inhibitor.

Western Blotting

The antibodies against eNOS, iNOS, Akt 1, α4 integrin and mouse IgG were purchased from Santa Cruz Biotechnology (Santa Cruz, CA). The anti-β-actin was purchased from Sigma-Altrich (St. Louis, MO) and anti-rabbit IgG was purchased from Bio-Rad (Hercules, CA). Two different conditions were used for SDS-PAGE. The first one was low-temperature, SDS-resistant SDS-PAGE as previously described [24]. Generally, the protein samples were prepared in Laemmli buffer (0.32 M Tris-HCl, pH 6.8, 0.5 M glycine, 10% SDS, 50% glycerol, and 0.03% bromophenol blue) without boiling and separated on reducing SDS-PAGE (with 2.5% 2-mercaptoethanol) at 4°C. The second one was a regular SDS-PAGE. The protein samples in Laemmli buffer were boiled and separated on SDS-PAGE at room temperature. The proteins were then transferred onto a nitrocellulose membrane, which was then blocked with 5% (w/v) skim milk in TBST (20 mM Tris-HCl, pH 7.5, 150 mM NaCl, 0.1% Tween 20) for 1 h and then incubated with proper antibodies at 4°C overnight. After washing with TBST, the membrane was incubated with HRP–conjugated anti-rabbit antibody for 1 h at room temperature. The membrane was then washed three times in TBST, two times in TBS, and developed in West Pico Supersignal chemiluminescent substrate (Pierce, Rockford, IL).

Flow Cytometry

After treatment, cells were harvested in 15 ml tubes and washed with DPBS with Ca2+/Mg2+ twice. Then each sample with 106 cells was suspended in 100 µl DPBS with Ca2+/Mg2+ and was incubated with 5 µl FITC-conjugated CD49d antibody (BD sciences, Franklin Lakes, NJ) in the dark for 30 min. After incubation, the cells were washed twice again. The cell pellets were suspended in 400 µl DPBS with Ca2+/Mg2+ and ready for the analysis of FACSort analyzer (BD sciences, Franklin Lakes, NJ). 20,000 cells were counted for each sample.

Parallel Plate Flow Chamber Cell Adhesion Analysis

Dynamic flow adhesion assays were performed using a parallel plate flow chamber in a laminar flow environment as previously described [1, 2, 28]. 50 µg/ml of VCAM-1 protein (R&D system, Minneapolis, MN) was placed on a 100 mm petri dish overnight at 4°C followed by blockade of non-specific binding sites with 0.1% bovine serum albumin (BSA) in DPBS containing Ca2+/Mg2+ for 2 h at room temperature. M624 melanoma cells (106/ml in DPBS flow buffer with Ca2+/Mg2+) were perfused through the chamber on immobilized VCAM-1 protein surface at 0.45 dyn/cm2. The movement of the cells was monitored and recorded by a video system for 5 min/sample. The total number of the attached cells in 5 min were counted [28].

Results and Discussion

UVB-irradiation reduces the expression of α4 integrin in M624 melanoma cells

Integrin α4β1 plays an important role in regulation of the avidity of melanoma to endothelia cells. Our recent report indicated that the surface levels of α4 and β1 integrins were not significantly changed after UVB-irradiation, while the spatial organization of α4 integrin was changed [29]. We now determined the effect of UVB on cellular level of α4 integrin in M624 melanoma cells. Western blot analysis showed that α4 integrin was reduced at 18 h post-irradiation (Fig. 1, Lane 2 vs. 1). Since UVB inhibits translation via NOS activation and oxidative stress signaling pathway [30], we determined whether the reduction of α4 integrin was regulated through NOS/oxidative stress-mediated translational inhibition. We used L-NAC to reduce oxidative stress, L-NAME to inhibit cNOS and 1400w to inhibit iNOS. Our data showed that treating each drug did not affect the expression of α4 integrin (Fig. 1, Lanes 3, 5, 7 vs. 1). However, while L-NAC did not have an impact on UVB-reduced α4 integrin expression (Fig. 1, Lane 4 vs. 2), inhibition of NOSs further reduced the α4 integrin level post-UVB (Fig. 1, Lanes 6, 8 vs. 2). Since L-NAC inhibits the UVB-induced phosphorylation of the alpha subunit of eukaryotic initiation factor 2 (eIF2α) and reverses the translation inhibition [30], the results suggest that the UVB-reduced α4 integrin expression is not due to the translational inhibition of the protein synthesis.

Fig. 1. The expression of α4 integrin.

Fig. 1

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M624 melanoma cells were treated with L-NAC, L-NAME, 1400w or Akt I in the presence or absence of UVB (50 mJ/cm2) as indicated. The total cellular levels of Akt and β-actin were determined by western blot analysis using corresponding antibodies.

The further decrease of α4 integrin by NOS inhibitors suggests that NOS activity partially protects the UVB-induced reduction of α4 integrin. Since iNOS and eNOS are involved in up- and down- stream signaling of Akt pathway, which can phosphorylate α4 integrin [9, 10] and has been shown to play a role in regulation of cell adhesion [13, 14], we also determined the effect of Akt inhibitor (Akt I) on UVB-induced reduction of α4 integrin. Unlike the other chemicals, treating the cells with Akt I significantly reduced α4 integrin without or with UVB-irradiation (Fig. 1, Lanes 9, 10 vs. 1, 2). The results suggest that Akt signaling pathway might play a critical role in regulation of α4 integrin expression upon UVB-irradiation.

Akt activity mediates eNOS coupling and iNOS expression after UVB-irradiation

To further determine the role of NOSs and Akt in regulation of melanoma adhesion, we analyzed the expression of NOSs and Akt. While both iNOS and Akt levels are reduced (Fig. 2A, Lane 2 vs. 1), nNOS is not detected (data not shown) and eNOS levels are not significantly changed after UVB-irradiation (Fig. 2B, Lane 2 vs. 1). It was a surprise to detect such a high level of iNOS in non-irradiated cells and it was even more surprising to see the level of iNOS was reduced after UVB-irradiation, which was opposite from what we and others reported for iNOS expression in none melanoma cells [24, 31–33]. Since elevated nitric oxide (NO•) produced by iNOS can inhibit UVB-induced apoptosis [24], our observation might explain the survival advantage of melanoma after UVB-irradiation.

Fig. 2. The expression of iNOS, eNOS and Akt, and coupling of eNOS.

Fig. 2

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M624 melanoma cells were treated with L-NAC, L-NAME, 1400w or Akt I in the presence or absence of UVB (50 mJ/cm2) as indicated. Panel A: The expression of iNOS and Akt was determined by western blot analysis using corresponding antibodies. Panel B: The monomers and dimers of eNOSs were first separated on a low-temperature SDS-resistant SDS-PAGE and then detected by western blot analysis using anti-eNOS antibody. The levels of β-actin were also probed as a loading control.

The UVB-induced reduction of iNOS and Akt was slightly reversed by treating the cells with L-NAC and L-NAME, which protects eIF2α from UVB-induced phosphorylation [30]. This suggested that UVB-induced translational inhibition might play a role in regulation of iNOS and Akt expression. Inhibition of Akt further decreased the expressions of iNOS and Akt post-UVB. Since Akt phosphorylates and activates eNOS [17], which plays a role in regulation of cell adhesion [34, 35], we analyzed the role of Akt in regulation of eNOS coupling after UVB-irradiation using a SDS-resistant reducing gel [24]. Our data showed that eNOS coupling was increased in an Akt-dependent manner after UVB-irradiation (Fig. 2B, Lane 10 vs. 2). Reduction of free radicals by L-NAC or inhibition of NOSs by L-NAME and 1400w did not significantly affect the UVB-induced eNOS coupling. These results suggest that Akt activity has a protective effect on UVB-reduced expressions of certain gene.

Regulation of surface α4 integrin on melanoma cells after UVB-irradiation

We previously showed that UVB-reduced avidity of melanoma to endothelia cells was not dependant on the surface level, but localization of α4 integrin [29]. Now we showed that the total expression of α4 integrin was reduced after UVB-irradiation, especially after treating the cells with NOS and Akt inhibitors (Fig. 1). To determine whether the significant reduction of total α4 integrin resulted in the decrease in surface level of the protein, we measured the surface α4 integrin on M624 melanoma cells using immunofluorescent staining followed by flow cytometry. Our data showed that the intensity of α4 Integrin on the cell surface was not significantly changed but the number of cells that contained surface α4 integrin was decreased after UVB-irradiation (Fig. 3A), which agreed with our previous report [29]. The reduction of surface α4 integrin could be due to apoptotic cell death, which has been shown to cause integrin endocytosis [36]. Treating the cell with L-NAC (free radical scavenger) or 1400w (iNOS inhibitor) reduced the numbers of cells that contained surface α4 integrin without or with UVB-irradiation (Fig. 3B and 3D). Reduction of oxidative stress also reduced the intensity of surface α4 integrin (Fig. 3B). These results suggested that keeping a certain level of oxidative stress could be important for maintaining surface levels of α4 integrin and protecting cells from apoptosis. Treating the cell with L-NAME did not affect the intensity of surface α4 integrin but slightly reversed UVB-induced reduction of the numbers of cells that contained surface α4 integrin (Fig. 3C). This result agreed with our previous report that eNOS promotes UVB-induced apoptosis [23].

Fig. 3. The cell surface level of α4 integrin.

Fig. 3

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M624 melanoma cells were treated with L-NAC, L-NAME, 1400w or Akt I in the presence or absence of UVB (50 mJ/cm2) as indicated. FITC-conjugated mouse anti-human α4 integrin antibody was added in each sample and the intensity of cell surface α4 integrin was determined by flow cytometry. 2×104 cells were counted for each sample. The data represents three independent experiments.

While treating the cells with Akt I alone did not affect surface α4 integrin, the expression of α4 integrin changed dramatically after UVB-irradiation. The number of cells that contained surface α4 integrin was significantly decreased, but the intensity of surface α4 integrin was significantly increased (Fig. 3E). The data indicated that inhibition of Akt increased the surface α4 integrin after UVB-irradiation. These results suggest that while Akt protects cells from UVB-induced apoptosis, Akt played an inhibitory role in the surface delivery of α4 integrin. These results also indicated that the surface level of α4 integrin was not always correlated with the total expression level of the integrin (Fig. 3 vs 1).

Two potential mechanisms for regulation of avidity of melanoma cells after UVB-irradiation

The interaction of α4β1 integrin (VLA-4) and VCAM-1 was crucial for the adhesion of M624 melanoma to endothelia cells [29]. We previously showed that UVB-irradiation changed the surface distribution of α4 integrin and thus reduced the adhesive affinity of melanoma to endothelia cells [29]. To determine whether a change of surface α4 level can affect the avidity of melanoma cells, we analyzed the adhesion between melanoma and VCAM-1 protein using parallel plate flow chamber. Our data showed that the avidity of the cells decreased 68% after UVB-irradiation (Fig. 4), which agreed with our previous report [29]. Treating the cells with L-NAC or 1400w alone reduced the avidity of the cells by 71% or 57% respectively (Fig. 4), which correlated with the reduction of surface α4 integrin containing cells as observed (Fig. 3B and 3D). The avidity of the L-NAC or 1400w treated cells was further reduced after UVB-irradiation (Fig. 4), which was not correlated to the unchanged surface α4 integrin after UVB-irradiation (Fig. 3B and 3D). These results suggested that the reduced avidity of the melanoma cells after L-NAC or 1400w treatment might be mainly due to apoptosis. However, the reduced surface level of α4 integrin on L-NAC treated cells (Fig. 3B) also contributed to the reduction of avidity of the cells without or with UVB-irradiation (Fig. 4).

Fig. 4. The adhesive affinity of melanoma cells.

Fig. 4

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M624 melanoma cells were treated with L-NAC, L-NAME, 1400w or Akt I and then untreated or UVB irradiated. The cells were harvested for use in the flow adhesion assay at 18 h post-UVB. The cells were perfused over immobilized soluble VCAM-1 in the parallel plate flow chamber, at a physiologic shear stress of 0.45 dyn/cm2. The number of adhesive interactions in a single field of view was counted over a 5 min perfusion period. The experiments were repeated three times. The bars represented as mean±SD. The student t-test was used to compare the control with UVB irradiation with the inhibitor treatment after UVB irradiation. *: p<0.05.

Treating the cells with L-NAME or Akt inhibitor alone did not statistically significantly affect the avidity of the cells (Fig. 4), which correlated with the α4 integrin profile (Fig. 3C and 3E). Inhibition of eNOS reversed the UVB-induced decrease of adhesion between melanoma cells and VCAM-1 by 19% (Fig. 4), which correlated with increased numbers of α4 integrin contained cells after the same treatment (Fig. 3C). This result suggested that while the basal eNOS activity did not play a role in regulation of melanoma cell adhesion, the UVB-induced activation of eNOS led to the endocytosis of α4 integrin via promotion of apoptosis as we previously reported [23, 24]. Inhibition of Akt significantly increased avidity of the cells by 48% after UVB-irradiation (Fig. 4, Akt I vs. No Treat). This result indicated that the increased surface level of α4 integrin, but not the number of cells containing the integrin, contributed significantly to the adhesive affinity of melanoma cells.

In summary, our results suggested that the reduction of avidity of melanoma cells is regulated through two different mechanisms after UVB-irradiation. The first mechanism is through the internalization of α4 integrin, which is most likely due to cell apoptosis. Therefore these cells will not survive and contribute to melanoma cell metastasis. The second mechanism is regulated by an Akt-mediated inhibition of surface delivery of α4 integrin. Since Akt also suppressed apoptosis [20], the Akt pathway has potential in being significant in regulation of melanoma avidity and thus distance metastasis after UVB-irradiation.

Research Highlights

  • Akt activity is required for UVB-induced eNOS coupling.

  • Akt regulates iNOS expression in melanoma cells after UVB-irradiation.

  • Akt mediates expression and cell surface delivery of α4 integrin after UVB-irradiation.

  • Akt regulates avidity of melanoma to endothelia cells after UVB-irradiation.

Acknowledgements

This work is partially supported by RO1 CA086928 (to S. W.).

Footnotes

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Reference

  • 1.Giavazzi R, Foppolo M, Dossi R, Remuzzi A. J Clin Invest. 1993;92:3038–3044. doi: 10.1172/JCI116928. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 2.Liang S, Dong C. Am J Physiol Cell Physiol. 2008;295:C701–C707. doi: 10.1152/ajpcell.00245.2008. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 3.DiVietro JA, Brown DC, Sklar LA, Larson RS, Lawrence MB. J Immunol. 2007;178:3903–3911. doi: 10.4049/jimmunol.178.6.3903. [DOI] [PubMed] [Google Scholar]
  • 4.Springer TA. Cell. 1994;76:301–314. doi: 10.1016/0092-8674(94)90337-9. [DOI] [PubMed] [Google Scholar]
  • 5.Martin-Padura I, Mortarini R, Lauri D, Bernasconi S, Sanchez-Madrid F, Parmiani G, Mantovani A, Anichini A, Dejana E. Cancer Res. 1991;51:2239–2241. [PubMed] [Google Scholar]
  • 6.Binsky I, Lantner F, Grabovsky V, Harpaz N, Shvidel L, Berrebi A, Goldenberg DM, Leng L, Bucala R, Alon R, Haran M, Shachar I. J Immunol. 184:4761–4769. doi: 10.4049/jimmunol.0904149. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 7.Sasaki K, Pardee AD, Okada H, Storkus WJ. Eur J Immunol. 2008;38:2865–2873. doi: 10.1002/eji.200838334. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 8.Goldfinger LE, Han J, Kiosses WB, Howe AK, Ginsberg MH. J Cell Biol. 2003;162:731–741. doi: 10.1083/jcb.200304031. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 9.Han J, Rose DM, Woodside DG, Goldfinger LE, Ginsberg MH. J Biol Chem. 2003;278:34845–34853. doi: 10.1074/jbc.M304691200. [DOI] [PubMed] [Google Scholar]
  • 10.Han J, Liu S, Rose DM, Schlaepfer DD, McDonald H, Ginsberg MH. J Biol Chem. 2001;276:40903–40909. doi: 10.1074/jbc.M102665200. [DOI] [PubMed] [Google Scholar]
  • 11.Wang S, Basson MD. Exp Cell Res. 2008;314:286–296. doi: 10.1016/j.yexcr.2007.08.005. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 12.Fayard E, Tintignac LA, Baudry A, Hemmings BA. J Cell Sci. 2005;118:5675–5678. doi: 10.1242/jcs.02724. [DOI] [PubMed] [Google Scholar]
  • 13.Irie HY, Pearline RV, Grueneberg D, Hsia M, Ravichandran P, Kothari N, Natesan S, Brugge JS. J Cell Biol. 2005;171:1023–1034. doi: 10.1083/jcb.200505087. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 14.Yoeli-Lerner M, Yiu GK, Rabinovitz I, Erhardt P, Jauliac S, Toker A. Mol Cell. 2005;20:539–550. doi: 10.1016/j.molcel.2005.10.033. [DOI] [PubMed] [Google Scholar]
  • 15.Dillon RL, Muller WJ. Cancer Res. 2010;70:4260–4264. doi: 10.1158/0008-5472.CAN-10-0266. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 16.Kao SJ, Lei HC, Kuo CT, Chang MS, Chen BC, Chang YC, Chiu WT, Lin CH. Immunology. 2005;115:366–374. doi: 10.1111/j.1365-2567.2005.02160.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 17.Li CJ, Elsasser TH, Kahl S. J Mol Signal. 2009;4:1–13. doi: 10.1186/1750-2187-4-1. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 18.Chan ED, Riches DW. Am J Physiol Cell Physiol. 2001;280:C441–C450. doi: 10.1152/ajpcell.2001.280.3.C441. [DOI] [PubMed] [Google Scholar]
  • 19.Han W, He YY. Photochem Photobiol. 2009;85:997–1003. doi: 10.1111/j.1751-1097.2008.00531.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 20.Ibuki Y, Goto R. Biochem Biophys Res Commun. 2000;279:872–878. doi: 10.1006/bbrc.2000.4018. [DOI] [PubMed] [Google Scholar]
  • 21.Mildner M, Eckhart L, Lengauer B, Tschachler E. J Biol Chem. 2002;277:14146–14152. doi: 10.1074/jbc.M110687200. [DOI] [PubMed] [Google Scholar]
  • 22.Wang L, Tang Z, Sun H. Zhonghua Zhong Liu Za Zhi. 2000;22:301–303. [PubMed] [Google Scholar]
  • 23.Wu S, Wang L, Jacoby AM, Jasinski K, Kubant R, Malinski T. Photochem Photobiol. 2010;86:389–396. doi: 10.1111/j.1751-1097.2009.00682.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 24.Liu W, Wu S. Nitric Oxide. 2010;23:199–205. doi: 10.1016/j.niox.2010.06.003. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 25.Conran N, Ferreira HH, Lorand-Metze I, Thomazzi SM, Antunes E, de Nucci G. Br J Pharmacol. 2001;134:632–638. doi: 10.1038/sj.bjp.0704295. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 26.Faruqi TR, Erzurum SC, Kaneko FT, DiCorleto PE. Am J Physiol. 1997;273:H2490–H2497. doi: 10.1152/ajpheart.1997.273.5.H2490. [DOI] [PubMed] [Google Scholar]
  • 27.Lahiri M, Martin JH. Oncol Rep. 2009;21:275–281. [PubMed] [Google Scholar]
  • 28.Burdick MM, Chu JT, Godar S, Sackstein R. J Biol Chem. 2006;281:13899–13905. doi: 10.1074/jbc.M513617200. [DOI] [PubMed] [Google Scholar]
  • 29.Wang L, Venktesh SS, Burdick MM, Wu S. Mol. Carcinogenesis. 2010 In Press. [Google Scholar]
  • 30.Lu W, Laszlo CF, Miao Z, Chen H, Wu S. The Journal Of Biological Chemistry. 2009;284:24281–24288. doi: 10.1074/jbc.M109.008821. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 31.Sasaki M, Yamaoka J, Miyachi Y. Exp Dermatol. 2000;9:417–422. doi: 10.1034/j.1600-0625.2000.009006417.x. [DOI] [PubMed] [Google Scholar]
  • 32.Seo SJ, Choi HG, Chung HJ, Hong CK. Br J Dermatol. 2002;147:655–662. doi: 10.1046/j.1365-2133.2002.04849.x. [DOI] [PubMed] [Google Scholar]
  • 33.Kuhn A, Fehsel K, Lehmann P, Krutmann J, Ruzicka T, Kolb-Bachofen V. J Invest Dermatol. 1998;111:149–153. doi: 10.1046/j.1523-1747.1998.00253.x. [DOI] [PubMed] [Google Scholar]
  • 34.Pandolfi A, Di Pietro N, Sirolli V, Giardinelli A, Di Silvestre S, Amoroso L, Di Tomo P, Capani F, Consoli A, Bonomini M. J Cell Physiol. 2007;213:699–709. doi: 10.1002/jcp.21138. [DOI] [PubMed] [Google Scholar]
  • 35.Kaminski A, Ma N, Donndorf P, Lindenblatt N, Feldmeier G, Ong LL, Furlani D, Skrabal CA, Liebold A, Vollmar B, Steinhoff G. Lab Invest. 2008;88:58–69. doi: 10.1038/labinvest.3700693. [DOI] [PubMed] [Google Scholar]
  • 36.Tsai WH, Chang CW, Lin YS, Chuang WJ, Wu JJ, Liu CC, Tsai PJ, Lin MT. Infect Immun. 2008;76:1349–1357. doi: 10.1128/IAI.01162-07. [DOI] [PMC free article] [PubMed] [Google Scholar]

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