The effects of membrane modification and hyperthermia on the survival of P-388 and V-79 cells

Synthesis of amide derivatives of chlorin e6 and investigation of their biological activity

In this work there is a synthesis of new photosensitizers which is based on amide derivatives of chlorin е6 . For the disclosure of an extra ring of the initial compound - pheophorbide a 1, we used primary aliphatic amines with 4-12 carbon atoms in the alkyl chain. The reaction is carried out under mild conditions in chloroform with heating to 40 ºС. The structure of all compounds obtained was confirmed by means of electronic, IR, 1Н-NMR spectroscopy and mass-spectrometry. The photoactivity and the dark toxicity of the compounds 2b-2h were investigated on two cancer cell lines: P-388 and K-562. The biological investigations revealed a good photoactivity and low dark toxicity of all compounds 2b-2f. The amide derivatives of chlorin е6 with 6 and 7 carbon atoms in the alkyl part showed the best results in our research. Thus, in this paper we propose a reliable scheme of synthesis of chlorin's photosensitizers which are promising agents for PDT.

Thermostability of biological systems: fundamentals, challenges, and quantification

This review examines the fundamentals and challenges in engineering/understanding the thermostability of biological systems over a wide temperature range (from the cryogenic to hyperthermic regimen). Applications of the bio-thermostability engineering to either destroy unwanted or stabilize useful biologicals for the treatment of diseases in modern medicine are first introduced. Studies on the biological responses to cryogenic and hyperthermic temperatures for the various applications are reviewed to understand the mechanism of thermal (both cryo and hyperthermic) injury and its quantification at the molecular, cellular and tissue/organ levels. Methods for quantifying the thermophysical processes of the various applications are then summarized accounting for the effect of blood perfusion, metabolism, water transport across cell plasma membrane, and phase transition (both equilibrium and non-equilibrium such as ice formation and glass transition) of water. The review concludes with a summary of the status quo and future perspectives in engineering the thermostability of biological systems.

Effect of dietary modulation of membrane lipid composition on the thermostability of HTC cells and of a membrane enzyme

Growth of hepatoma tissue culture (HTC) cells in the presence of linoleic (18:2) or arachidonic (20:4) acids for 36 h caused an increased cell thermosensitivity. Plasma membrane-rich fractions were purified (15-20-fold) with high yield (30%) from control and fatty acid-supplemented cells. Contamination with membranes from mitochondria, lysosomes and endoplasmic reticulum was low. Supplementation significantly increased the level of the supplemented fatty acid and decreased the level of oleic acid (18:1) in plasma membrane phospholipids (PL), causing a significant decrease in the oleic acid:PUFA (polyunsaturated fatty acid) ratio. No significant changes occurred in other parameters such as cholesterol:PL, cholesterol:protein or PL:protein ratios. Plasma membranes from PUFA-supplemented cells exhibited a lower membrane order, compared with control cell membranes, as determined by DPH fluorescence polarization over the temperature range 4-40 degrees C. Isothermal inactivation of alkaline phosphodiesterase I in plasma membranes from control and supplemented cells showed curvilinear kinetics. The change in membrane composition and order following supplementation with arachidonic acid was associated with increased thermosensitivity of this enzyme. These data are discussed with respect to the suggestion that the plasma membrane may be a target for cellular thermal injury and death.

Role of cellular membranes in hyperthermia: some observations and theories reviewed

We have re-examined critically the evidence for and against the involvement of membranes in determining the response of cells to acute and chronic heat stress. Although frequently dismissed by many in the past, we believe that the bulk of evidence presented supports the view that physical and compositional alterations of membrane lipid components, both during and subsequent to heat exposure may, at least in part, account for cell adaptation, malfunction and lethality. Our primary goal in this review is to generate renewed interest in testing the validity of this hypothesis.

Effect of hyperthermia and X-irradiation on survival and occurrence of metastases in mice bearing P388 tumor

Survival of P388 lymphoid tumor-bearing mice and the occurrence of metastasis was studied after combined modality treatment with hyperthermia and X-irradiation. P388 ascites tumor cells were treated at 42 degrees C or 43.5 degrees C for 1 hr in vitro and transplanted on B6D2F1 mice intraperitoneally (i.p.) or intramuscularly (i.m.). Hyperthermic treatment at 43.5 degrees C increased the median survival time (MST). Increased life-span (ILS) was found after i.p. transplantation (54%) and after i.m. transplantation (30%). During the life-span of tumor-bearing animals, significantly fewer metastases were observed in liver and spleen after hyperthermia and 5-10% metastasis occurred after transplantation of ascites tumor cells treated at 43.5 degrees C in vitro compared with 90% in the untreated control animals. The lower occurrence of metastasis could not be ascribed to the higher cell-killing effect of hyperthermia. When both modalities were combined the best tumor growth retardation effect was obtained when ascites tumor cells were treated at 43.5 degrees C for 1 hr before being transplanted i.m. and 1 day later locally X-irradiated with 6 Gy. In this case, 77% ILS was found demonstrating a synergistic effect of the two modalities. While X-irradiation alone did not change the occurrence of metastasis, after combined modality treatment it was as low as with hyperthermia alone (5-10%). In connection with the significantly lower occurrence of metastasis, the possible alterations of P388 tumor cell membrane and surface proteins induced by in vitro hyperthermic treatment are discussed.

Incorporation of [3H]acetate into the membrane lipids of a murine tumour during the development of thermotolerance

The incorporation of [3H]acetate into the membrane lipids of a C3H mammary adenocarcinoma, grown s.c. in the hind paw of CBA mice, was followed to estimate the effects on the de novo synthesis of membrane lipids after hyperthermic treatments. Thermotolerance developed in response to a heat treatment at 43 degrees C for 20 min, as verified through growth rate studies of tumours exposed to fractionated heat treatments. Our results show that, during the development of thermotolerance, the relative rates of incorporation of [3H]acetate into the major lipid classes of the tumour cell membranes change significantly. The de novo synthesis of phospholipids decreased while that of cholesteryl esters plus triglycerides increased. The incorporation of [3H]acetate into cholesterol remained constant. Consequently, the ratio [3H]cholesterol/[3H]lecithin increased significantly during the development of thermotolerance. When the incorporation of [3H]acetate was followed 72-96 h after the heat treatment, i.e. at the interval at which heat resistance was observed to approach that of control tumours, the incorporation into cholesterol was significantly reduced while incorporation into phospholipids increased to control levels. Thus, the ratio [3H]cholesterol/[3H]lecithin was significantly lower, when compared to that of control tumours. The functional relationship between the heat-induced changes in the de novo synthesis of membrane lipids and the development of thermotolerance is discussed with regard to a mechanism based on homeoviscous adaptation of the membranes.

An approach to AIDS therapy using hyperthermia and membrane modification

Altering the biophysical characteristics of cell membranes by diet and membrane perturbing agents markedly influences thermosensitivity of cells. Likewise, manipulation of viral envelopes either by altering their lipid composition by diet or by the use of agents that perturb the lipid envelope influence infectivity of enveloped viruses and the progression of viral disease. The use of hyperthermia and envelope modification as a combined approach to treat AIDS has until now neither been suggested nor attempted. On the basis of my previous work and a review of the literature, I theorize that the combination of hyperthermia with procedures designed to alter the viral envelope will likely result in an increased viral sensitivity and be useful clinically for treatment of patients with enveloped viral diseases such as AIDS.

Influence of hyperthermia, pH and culturing conditions on the electrical parameters of Chinese hamster V79 cells

Conductivity measurements in the frequency range 10 kHz-100 MHz have been performed on Chinese hamster fibroblasts V79 exposed to hyperthermia in different experimental conditions. The membrane electrical conductivity is decreased when cells are heated for 1 h at 44 degrees C or 3 h at 43 degrees C at pH 7.25. This effect has not been observed on cell samples following heating for 1 h at 43 degrees C at pH 7.25. However, if the pH of the culture medium is adjusted to 6.50 or 6.0 before hyperthermic exposure, a substantial decrease of membrane conductivity is observed. In cells maintained in partially spent medium before heating, a 3 h treatment at 43 degrees C at pH 7.25 does not produce any effect on membrane conductivity. The results of all these experiments seem to indicate that some alteration of the energy-driven mechanisms involved in active transport across the plasma membranes may be responsible for the observed effects.

Heat-induced changes in the incorporation of [H3]acetate in membrane lipids

The effects of heat treatments at temperatures from 42 to 47 degrees C on the rate of incorporation of [3H]acetate into different classes of lipids have been studied in V-79 Chinese hamster cells. Thermotolerance induction and subtoxic heat treatments decreased the incorporation of [3H]acetate into phospholipids and caused the ratio [3H]cholesterol/[3H]phospholipids to increase several fold, and a positive correlation between heat dose and the ratio [3H]cholesterol/[3H]phospholipids was obtained for subtoxic hyperthermic treatments. The duration of this hyperthermic effect on the incorporation of [3H]acetate into the different lipid fractions was followed in pulse-label experiments. The highest increase of the ratio [3H]cholesterol/[3H]phospholipids was obtained during the first 24 h, but a significant elevation was also present for the 24-72 h pulse-labelled group. Thermotolerance induction was maximal 24 h after the heat treatment and then declined during the next 24 h. The increased [3H]cholesterol/[3H]phospholipid ratio observed in response to hyperthermia resembles the processes that serve to provide homeoviscous adaptation to sustain thermosensitive membrane-located functional groups, in analogy with the mechanisms responsible for thermal adaptation. However, the lack of a positive correlation between thermotolerance induction and the changes in lipid synthesis, for the whole time interval studied, remains to be further explored before any mechanistic interpretation of the data can be found.

Heat-induced alterations in cell membrane permeability and cell inactivation of transformed mouse fibroblasts

Hyperthermia, has recently been extended in many permutations as a modality of anticancer treatment, but the mechanisms underlying heat-induced cell inactivation are poorly understood. In this study, the role of the cell permeability barrier in the process of heat cytotoxicity are examined. Changes in cell membrane permeability were determined by following the efflux of normally impermeant metabolites, e.g. nucleotides, in cultures of Swiss mouse 3T3 cells, and their transformed derivatives, 3T6 cells. The increase in cell membrane permeability as a function of temperature and exposure duration was found to be characterized by a sigmoid curve, with a threshold value, above which the permeability markedly increased. A correlation was found between cell membrane permeabilization and cell inactivation. Both heat-induced permeabilization and heat cytotoxicity were more pronounced in the transformed cells, as compared to their untransformed counterparts. The temperature-dependent permeabilization was more effective in the presence of the ionophore amphotericin B. The data suggest that heat-induced lesion in the cell membrane has a major role in hyperthermia cytotoxicity.

Membrane effects of ionizing radiation and hyperthermia

Results of numerous studies demonstrate that membranes are important sites of cell damage by both ionizing radiation and hyperthermia. Modification of membrane properties (mainly lipid fluidity) affects the cellular responses to radiation and hyperthermia but former concepts that membrane rigidification sensitizes cells to radiation while membrane fluidization potentiates hyperthermic damage have now been seriously challenged. It seems that the effects of membrane fluidity on cell responses to hyperthermia and radiation are due to an indirect influence on functional membrane proteins. The major role of lipid peroxidation in radiation damage to membranes has also been questioned. The existing evidence makes it unlikely that the interaction between radiation and hyperthermia is determined by the action of both agents on the same membrane components.