liu.seSearch for publications in DiVA
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Regulation of UV induced apoptosis in human melanocytes
Linköping University, Department of Clinical and Experimental Medicine, Dermatology and Venerology . Linköping University, Faculty of Health Sciences.
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Malignant melanoma arises from the pigment producing melanocytes in epidermis and is the most aggressive type of skin cancer. The incidence of malignant melanoma is increasing faster than any other type of cancer in white population worldwide, with a doubling rate every 10-20 years. So far, the only identified external risk factor for malignant melanoma is UV exposure. Elimination of photodamaged cells by apoptosis (programmed cell death) is essential to prevent tumor formation. Melanocytes are considered relatively resistant to apoptosis, however, the regulation of apoptosis in melanocytes is still unknown.

The aim of this thesis was to investigate the apoptotic process following ultraviolet (UV) irradiation in primary cultures of human melanocytes. Focus was on regulation of mitochondrial stability by Bcl-2 family proteins and the possible participation of lysosomal proteases, cathepsins. UV irradiation activated the mitochondrial pathway of apoptosis, leading to cytochrome c release, caspase activation, and nuclear fragmentation. No change in protein expression of Bax and Bcl-2 was observed in response to UV. Instead, translocation of the Bcl-2 family proteins from cytosol to mitochondia was important in the regulation of survival and death of melanocytes. The findings further demonstrated permeabilization of the lysosomal membrane to occur early in the apoptotic process, resulting in cathepsin release into the cytosol. The cathepsins were potent pro-apoptotic mediators and triggered apoptosis upstream of Bax translocation and mitochondrial membrane permeabilization. In response to both heat and UV irradiation, there was a marked increase in expression of stress-induced heat shock protein 70 (Hsp70), which inhibited apoptosis by binding lysosomal and mitochondrial membranes and counteracting the release of cathepsins and cytochrome c. Furthermore, UV irradiation activated c-jun N-terminal kinase (JNK), which triggered apoptosis upstream of cathepsins release from the lysosomes. In addition, JNK mediated apoptosis through phosphorylation of pro-apoptotic Bim, which was released from anti-apoptotic Mcl-1, by UV induced Mcl-1 depletion.

This thesis illustrates that permeabilization of mitochondria and lysosomes and release of their constituents to the cytosol participates in UV induced apoptosis signaling in human melanocytes in vitro. The process is regulated by a complex network of pro- and anti-apoptotic proteins, exerting their effects through intracellular translocation and alteration of protein expression.

Place, publisher, year, edition, pages
Institutionen för biomedicin och kirurgi , 2007.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 997
Keyword [en]
apoptosis, UV, melanocyte, lysosome, cathepsin, Bcl-2, Bax, Hsp70, JNK
National Category
Dermatology and Venereal Diseases
Identifiers
URN: urn:nbn:se:liu:diva-8749ISBN: 978-91-85831-97-5 (print)OAI: oai:DiVA.org:liu-8749DiVA: diva2:23441
Public defence
2007-05-25, Berzeliussalen, Campus US, Linköpings Universitet, Linköping, 09:00 (English)
Opponent
Supervisors
Available from: 2007-05-14 Created: 2007-05-14 Last updated: 2017-08-30
List of papers
1. Wavelength specific effects on UVB induced apoptosis in melanocytes. A study of the Bcl-2/Bax expression and keratinocyte rescue effects
Open this publication in new window or tab >>Wavelength specific effects on UVB induced apoptosis in melanocytes. A study of the Bcl-2/Bax expression and keratinocyte rescue effects
2005 (English)In: Melanoma Research, ISSN 0960-8931, Vol. 15, no 1, 7-13 p.Article in journal (Refereed) Published
Abstract [en]

Apoptosis and alterations in Bcl-2 and Bax messenger RNA (mRNA) and protein expression were examined in cultured human epidermal melanocytes following UVB irradiation (50 mJ/cm2). The effects of various spectral ranges within UVB were investigated. A co-culture system was set up to study the interplay between melanocytes and keratinocytes in response to UVB. Melanocytes expressed high basal levels of the anti-apoptotic protein Bcl-2 compared with keratinocytes. Different wavelengths within the UVB spectrum induced diverse response patterns of Bcl-2 and Bax mRNA and had different apoptotic power. Both Bcl-2 and Bax mRNA were upregulated to preserve protein levels and only a slight increase in apoptosis was noted 24 h after UVB ([lambda]>305 nm). Increasing UVB between 280 and 305 nm enhanced apoptosis and upregulated Bcl-2, whilst Bax mRNA was unaltered. However, no change in protein levels was detected. A redistribution of Bax protein from different compartments within the cell may be more important than direct upregulation for the acceleration of apoptosis, but it cannot be excluded that other apoptotic pathways may be induced by shorter UVB wavelengths. The increase in apoptosis was significantly lower in melanocytes co-cultured with irradiated matched keratinocytes than in melanocytes from pure cultures, indicating that melanocytes are protected from UVB-induced apoptosis by the release of substance(s) from keratinocytes. This rescue response concurred with a fast and significant increase in Bcl-2 mRNA level in melanocytes.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-14399 (URN)10.1097/00008390-200502000-00003 (DOI)
Available from: 2008-11-13 Created: 2008-11-13 Last updated: 2009-04-28
2. UVA/B induced apoptosis in human melanocytes involves translocation of cathepsins and Bcl-2 family members
Open this publication in new window or tab >>UVA/B induced apoptosis in human melanocytes involves translocation of cathepsins and Bcl-2 family members
Show others...
2006 (English)In: Journal of Investigative Dermatology, ISSN 0022-202X, Vol. 126, no 5, 1119-1127 p.Article in journal (Refereed) Published
Abstract [en]

We demonstrate UVA/B to induce apoptosis in human melanocytes through the mitochondrial pathway, displaying cytochrome c release, caspase-3 activation, and fragmentation of nuclei. The outcome of a death signal depends on the balance between positive and negative apoptotic regulators, such as members of the Bcl-2 protein family. Apoptotic melanocytes, containing fragmented nucleus, show translocation of the proapoptotic proteins Bax and Bid from the cytosol to punctate mitochondrial-like structures. Bcl-2, generally thought to be attached only to membranes, was in melanocytes localized in the cytosol as well. In the fraction of surviving melanocytes, that is, cells with morphologically unchanged nucleus, the antiapoptotic proteins Bcl-2 and Bcl-XL were translocated to mitochondria following UVA/B. The lysosomal proteases, cathepsin B and D, which may act as proapoptotic mediators, were released from lysosomes to the cytosol after UVA/B exposure. Proapoptotic action of the cytosolic cathepsins was confirmed by microinjection of cathepsin B, which induced nuclear fragmentation. Bax translocation and apoptosis were markedly reduced in melanocytes after pretreatment with either cysteine or aspartic cathepsin inhibitors. No initial caspase-8 activity was detected, excluding involvement of the death receptor pathway. Altogether, our results emphasize translocation of Bcl-2 family proteins to have central regulatory functions of UV-induced apoptosis in melanocytes and suggest cathepsins to be proapoptotic mediators operating upstream of Bax.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-14400 (URN)10.1038/sj.jid.5700124 (DOI)
Available from: 2008-11-13 Created: 2008-11-13 Last updated: 2017-08-30
3. Hsp70 protects against UVB induced apoptosis by preventing release of cathepsins and cytochrome c in human melanocytes
Open this publication in new window or tab >>Hsp70 protects against UVB induced apoptosis by preventing release of cathepsins and cytochrome c in human melanocytes
2007 (English)In: Carcinogenesis, ISSN 0143-3334, Vol. 28, no 3, 537-544 p.Article in journal (Refereed) Published
Abstract [en]

Stress-induced heat shock protein 70 (Hsp70) effectively protects cells against apoptosis, although the anti-apoptotic mechanism is still undefined. Exposure of human melanocytes to heat and subsequent UVB irradiation increased the level of Hsp70 and pre-heating reduced UVB induced apoptosis. Immunofluorescence staining of Hsp70 in combination with staining of lysosomes (Lamp2) or mitochondria (Mitotracker®) in pre-heated UVB exposed cells showed co-localization of Hsp70 with both lysosomes and mitochondria in the surviving cell population. Furthermore, UVB induced apoptosis was accompanied by lysosomal and mitochondrial membrane permeabilization, detected as release of cathepsin D and cytochrome c, respectively, which were prevented by heat pre-treatment. In purified fractions of lysosomes and mitochondria, recombinant Hsp70 attached to both lysosomal and mitochondrial membranes. Moreover, in apoptotic cells Bax was translocated from a diffuse cytosolic location into punctate mitochondrial-like structures, which was inhibited by Hsp70 induction. Such inhibition of Bax translocation was abolished by transfection with Hsp70 siRNA. Furthermore, Hsp70 siRNA eliminated the apoptosis preventive effect observed after pre-heating. These findings show Hsp70 to rescue melanocytes from UVB induced apoptosis by preventing release of cathepsins from lysosomes, Bax translocation and cytochrome c release from mitochondria.

 

Abbreviations: AIF, apoptosis-inducing factor; Hsp, heat shock protein; NAG, ß-N-acetylglucosaminidase; tBid, truncated Bid; UV, ultraviolet

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-14401 (URN)10.1093/carcin/bgl152 (DOI)
Available from: 2007-05-14 Created: 2007-05-14 Last updated: 2017-08-30
4. JNK mediates UVB-induced apoptosis upstream lysosomal membrane permeabilization and Bcl-2 family proteins
Open this publication in new window or tab >>JNK mediates UVB-induced apoptosis upstream lysosomal membrane permeabilization and Bcl-2 family proteins
2008 (English)In: Apoptosis (London), ISSN 1360-8185, Vol. 13, no 9, 1111-1120 p.Article in journal (Refereed) Published
Abstract [en]

UVB irradiation induced phosphorylation of JNK and subsequent apoptosis in human melanocytes. Depletion of both JNK1 and JNK2 expression using siRNA transfection, protected against apoptosis, as detected by decreased nuclear fragmentation and caspase-3 activity, as well as reduced translocation of Bax to mitochondria. Moreover, release of cathepsin B and D from lysosomes to the cytosol was reduced when JNK expression was suppressed by siRNA, demonstrating a JNK dependent regulation of lysosomal membrane permeabilization. In unirradiated control melanocytes, coimmunoprecipitation showed that Bim was sequestered by Mcl-1, which had a pro-survival function. After UVB irradiation, a significant decrease in Mcl-1 protein level was found, which was prevented by addition of a proteasome inhibitor. The interaction between Bim and Mcl-1 was reduced in response to UVB irradiation and Bim was phosphorylated in a JNK dependent manner. In conclusion, these findings Suggest JNK to have an important pro-apoptotic function following UVB irradiation in human melanocytes, by acting upstream of lysosomal membrane permeabilization and Bim phosphorylation.

Keyword
UV, Cathepsin, JNK, Mcl-1, Bim
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-16886 (URN)10.1007/s10495-008-0240-7 (DOI)
Note
The original publication is available at www.springerlink.com: Cecilia Bivik and Karin Öllinger, JNK mediates UVB-induced apoptosis upstream lysosomal membrane permeabilization and Bcl-2 family proteins, 2008, Apoptosis (London), (13), 9, 1111-1120. http://dx.doi.org/10.1007/s10495-008-0240-7 Copyright: Springer Science Business Media http://www.springerlink.com/ Available from: 2009-04-29 Created: 2009-02-20 Last updated: 2017-08-30Bibliographically approved

Open Access in DiVA

fulltext(1112 kB)4304 downloads
File information
File name FULLTEXT01.pdfFile size 1112 kBChecksum SHA-1
4fe8e491dbc9b6952295c4acf8e6bda495767f27d5f82cd7b47a3380e8bd08562c0a17e8
Type fulltextMimetype application/pdf
popular summary(10 kB)170 downloads
File information
File name POPULARSUMMARY01.pdfFile size 10 kBChecksum SHA-1
36eef30c287bebfd4e8e08277422b68d2ba8833e4c19395a0ce2211549ff0cbe4f4a2879
Type popularsummaryMimetype application/pdf

Authority records BETA

Bivik, Cecilia

Search in DiVA

By author/editor
Bivik, Cecilia
By organisation
Dermatology and Venerology Faculty of Health Sciences
Dermatology and Venereal Diseases

Search outside of DiVA

GoogleGoogle Scholar
Total: 4304 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 3734 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf