Alterations in membrane fluidity during keratinocyte differentiation measured by fluorescence polarization

Abstract

The epidermis shows a distinctive pattern of differentiation wherein keratinocytes proliferate in the basal cell layer and mature into spinous and granular cells. Using a discontinuous density-gradient centrifugation method, guinea-pig keratinocytes were separated into high (HDF), intermediate (IDF), and low (LDF) density fractions. Morphological and flow cytometrical observations demonstrated that HDF, IDF, and LDF were basal, spinous, and granular cell-rich fractions, respectively. Membrane fluidity of the fractionated keratinocytes was measured by diphenylhexatriene fluorescence polarization. Polarization (p)-value of keratinocytes was negatively correlated with temperature. At each temperature, HDF cells showed a lower p-value than IDF or HDF cells except at 40 degrees C. Since a low p-value indicates a high degree of Brownian motion, membrane fluidity is higher in basal cells and lower in spinous and granular cells. Our results indicate that membrane fluidity of guinea-pig keratinocytes decreases during their maturation.

Caged Fluorescent Haptens Reveal the Generation of Cryptic Epitopes in Allergic Contact Dermatitis

“…The reactivity pattern of the bromobimanes can be explained by the availability of protein targets, e.g., free thiols, in combination with changes in the cell membrane integrity, e.g., formation of cornified envelope across the epidermis (Figure 3; Sun and Green, 1978;Candi et al, 2005). Also, because of the lipid composition of the basal cell membrane (Hachisuka et al, 1990), it has a relatively high fluidity, facilitating cell penetration and reaction with intracellular free thiols, forming HPCs. This distribution correspond to that observed in skin biopsies obtained from human volunteers exposed to 1-chloro-2,4-dinitrobenzene, a very potent thiol-reactive hapten (EC3 ¼ 0.05% (w/v; Gawkrodger et al, 1989;Kimber et al, 2002)).…”

Plant pentacyclic triterpenic acids as modulators of lipid membrane physical properties

“…One important aspect of the above mentioned molecular mechanisms is the fact that membrane-related processes are frequently an integral part of them [19,24], which is demonstrated by the following examples: i) inflammation and lipid peroxidation are phenomena, which to a large extent take place at the cell-surface, ii) membrane proteins of organelles, such as endoplasmatic reticulum or lysosomes, participate in pro-apoptotic signalling events [26], iii) permeabilization of the mitochondrial membrane is a pivotal step in the apoptotic pathway cascades [27] and iv) the differentiation process of some cell types has been related to alterations in the plasma membrane fluidity [28,29]. Based on these observations, one may hypothesize that part of the molecular mechanism to explain the distinct biological activities of TTPs may be related to a direct effect of this compound class on the cell membrane.…”

The human papillomavirus type 16 (HPV-16) E5 protein sensitizes human keratinocytes to apoptosis induced by osmotic stress

“…In fact, changes in the phospholipid composition and phospholipase activities have been described in cells expressing the viral gene (Crusius et al, 1999). For keratinocytes a strong correlation between membrane¯uidity and temperature has been reported (Hachisuka et al, 1990). Presumably, incorporation of E5 increases membrane¯uidity leading to changes in the cellular response upon sorbitol treatment in a temperaturedependent manner.…”