Alterations in membrane fluidity and dynamics in experimental colon cancer and its chemoprevention by diclofenac
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We examined the role of membrane fluidity and dynamics as important early events in the carcinogenic transformation of colonic epithelial cells. 1,2-Dimethylhydrazine dihydrochloride (DMH) was used to induce initial stages of colon cancer and diclofenac was used for chemoprevention. To determine alterations of membrane fluidity of rat colonic epithelial cells, fluidity (inverse of fluorescence polarization) and order parameter were studied with 1,6-diphenylhexatriene (DPH) polarization. Order parameter as well as fluorescence polarization was found to be significantly decreased, thus demonstrating an increase in the fluidity of the membrane. To further confirm the fluidity changes, microviscosity of the cell membrane was studied using pyrene excimer formation, which showed a significant decrease in microviscosity and hence elevated membrane fluidity (translational diffusion). The colonocytes were stained with merocyanine 540 (MC540) to further elaborate the changes in membrane fluidity and lipid packing. The increased number of colonocytes showing high MC540 fluorescence pointed towards the wide spaces and hence, high fluidity in the membrane after DMH treatment. Membrane dynamics studies, i.e., lipid phase separation and membrane phase state were carried out using N-NBD-PE and Laurdan, respectively. We saw a transition from the gel to a more liquid crystalline state of the membrane in the Laurdan experiment. Further more percentage quenching (%Q) value of N-NBD-PE showed less phase separation (or domain formation). Diclofenac co-administration with DMH was successful in reverting the changes observed, confirming the role of these anti-inflammatory drugs in considerable lipid affinity and consequently in the chemoprevention of early stages of colon cancer.
KeywordsMembrane fluidity Phase separation Colon cancer Diclofenac
Financial assistance from the Council of Scientific and Industrial Research (CSIR), Government of India (37(1308)/07/EMR-II) is gratefully acknowledged.
- 1.Raghuraman H, Kelkar D, Chattopadhyay A (2003) Novel insights into membrane protein structure and dynamics utilizing the wavelength-selective fluorescence approach. Proc Indian Natl Sci Acad 69A(1):25–35Google Scholar
- 4.German JB, Dillard CJ, Whelan J (1995) Symposium: biological effects of dietary arachidonic acid. J Nutr 126:1076S–1080SGoogle Scholar
- 9.Kaur J, Sanyal SN (2009b) Induction of apoptosis as a potential chemopreventive effect of dual cyclooxygenase inhibitor, diclofenac in early colon carcinogenesis. J Env Pathol Toxicol Oncol (in press)Google Scholar
- 23.Ambrosini A, Zolese G, Wozniak M, Genga D, Boscaro M, Mantero F, Balerica G (2003) Idiopathic infertility: susceptibility of spermatozoa to in vitro capacitation, in the presence and the absence of palmitylethanolamide (a homologue of anandamide), is strongly correlated with membrane polarity studies by Laurdan fluorescence. Mol Hum Reprod 9:381–388CrossRefPubMedGoogle Scholar
- 31.McEvoy L, Schlegel RA, Williamson P, Del Buono BJ (1998) Merocyanine 540 as a flow cytometric probe of membrane lipid organization in leukocytes. J Leukoc Biol 44:337–344Google Scholar
- 39.Kusumi A, Nakada C, Ritchie K, Murase K, Suzuki K, Murakoshi H, Kasai RS, Kondo J, Fujiwara T (2005) Paradigm shift of the plasma membrane concept from the two-dimensional continuum fluid to the partitioned fluid: high-speed single-molecule tracking of membrane molecules. Annu Rev Biophys Biomol Struct 34:351–378CrossRefPubMedGoogle Scholar
- 44.Kanwar SS, Roy KR, Nehru B, Reddanna P, Sanyal SN (2009) Na+-stimulated Na+/H+ exchange and an unfavorable Ca2+ homeostasis initiate the cycloxygenase-2 inhibitors-induced apoptotic signals in colonic epithelial cells during the early stage of colon carcinogenesis. Oncol Res 18:1–15CrossRefGoogle Scholar