Age-dependence of the lateral mobility of lipids in hepatocyte plasma membrane of male rats and the effect of life-long dietary restriction

Pharmacological interventions against aging through the cell plasma membrane: a review of the experimental results obtained in animals and humans

As was shown in a recent review by this author (Ann. N.Y. Acad. Sci., 928: 187-199, 2001), oxyradicals cannot be considered only as harmful by-products of the oxidative metabolism, but living cells and organisms implicitly require their production. This idea is supported by numerous facts and arguments, the most important of which is that the complete inhibition of the oxyradical production by KCN (or by any block of respiration) kills the living organisms long before the energy reserves would be exhausted. This new theoretical approach not only helps our understanding of the normal functions of the living organisms, such as the basic memory mechanisms in the brain cells, but also helps in identifying the site-specific, radical-induced damaging mechanisms that represent the undesirable side effects of oxygen free radicals. First of all, these effects make the cell plasma membrane vulnerable and cause a series of intracellular functional disorders, as described by the membrane hypothesis of aging (MHA). The logical way for any antiaging intervention therefore should be to increase the available number of loosely bound electrons inside the plasma membrane that are easily accessible for OH(*) free radical scavenging. The present review summarizes the available knowledge regarding the theory of the use of membrane-related antiaging pharmaca, like centrophenoxine (CPH), tested in both animal experiments and human clinical trials. A modified, developed version of CPH coded as BCE-001 is also reported.

Comparison of the lateral diffusion coefficient of hepatocyte plasma membrane proteins in three strains of sensescence accelerated mouse (SAM)

The lateral diffusion coefficients of proteins (D(p)) were measured in hepatocyte plasma membrane in freshly prepared liver smears by means of the fluorescence recovery after photobleaching (FRAP) method. D(p) was measured after development of peroxide-induced autofluorescence (PIAF) in a total of 115 senescence accelerated mice (SAM), distributed in three strains, at least five age-groups in each, as follows: (i) SAMR1TA (25 males and 22 females), medium life span (MLS) in months, under specific pathogen free (SPF) conditions, MLS(spf) 20.1 and 20.0, respectively, while under conventional conditions, MLS(Deltapf)=18.9 in average for both sexes; (ii) SAMP6/Ta (18 males and 17 females), MLS(spf)=17.1 and 15.3, respectively, and MLS(cc)=8.1 for both sexes; (iii) SAMP6/Ta (17 males and 16 females), MLS(spf)=15.6 and 14.7, respectively, and MLS(cc)=10.0 for both sexes. A highly significant negative linear age-correlation of D(p) (R=0.975 or higher) was found in each strain, being roughly proportional with the MLS(cc) values. Since the studied mice kept under SPF conditions survived longer, than under conventional conditions, the actual age-dependent decay rates of D(p) values did not differ significantly in two pairs of comparisons (female R1/P6 and female R1/P8), whereas they did in all other possible pairs, including also the normal C57BL/6 mice. The main conclusion can be drawn that the D(p) of hepatocyte membranes is a good biomarker of aging and survival also in SAM, as in all other inbred and outbred rodents, studied so far.

Pharmacological modifications of endogenous antioxidant enzymes with special reference to the effects of deprenyl: a possible antioxidant strategy

Limited information is available on the upregulation of endogenous antioxidant enzymes by means of administering various pharmaceuticals and/or chemicals. It has been reported that ursodeoxycholic acid (UDCA), a bile acid originally identified from black bear bile (a Chinese medicine, Yutan) increased glutathione S-transferase (GST) activities in mouse livers, resulting in a decrease in systemic lethal toxicity of orally challenged 1-2-dichloro-4-nitrobenzene (DCNB). Also, ursolic acid found in herbal medicines (e.g. leaves of loquat) was reported to increase catalase (CAT) activities in mouse liver. Interestingly, the chemical structures of these two compounds are surprisingly similar to each other, despite the difference in their original sources. These results suggest that in the future, more and more compounds will be found to have effects on increasing endogenous antioxidant enzyme activities. Deprenyl is a monoamine oxidase B inhibitor but also possesses many other different pharmacological activities. Among these various pharmacological effects of deprenyl, a possible causal relationship between two effects of deprenyl, namely the prolongation of the survival of animals and upregulation of antioxidant enzymes in selective brain regions, has been postulated by the authors. In at least four different animal species (rats, mice, hamsters and dogs), a significant prolongation of survival by chronic administration of the drug has been reported by different groups including that of the authors. This group has reported that repeated administration of the drug for 2-3 weeks can significantly increase activities of both types of superoxide dismutase (SODs) (Cu, Zn-, and Mn-SODs) as well as of CAT selectively in brain dopaminergic regions. Both effects are dose dependent but excessive dosages become less effective and even cause an adverse effect (i.e. a decrease in enzyme activities and shortening of life span). The parallelism of the dose-effect relationship between the two phenomena suggests that modification of SOD and CAT levels is one possible mechanism for deprenyl's ability to prolong the life span of animals.

Lateral mobility of proteins and lipids of cell surface membranes during aging: do the data support 'The Membrane Hypothesis of Aging'?

Many previous studies regarding the change with age in surface membrane fluidity of different cell types, including hepatocytes, as determined by the fluorescence anisotropy method, are in conflict, demonstrating decreased, unchanged or even increased fluidity with age. In contrast, the results of our series of works using the fluorescence recovery after photobleaching (FRAP) technique, which measures protein lateral diffusion coefficients of hepatocyte surface membranes (Dp), have demonstrated that Dp generally declines in a linear fashion with age in hepatocytes of all animal strains and species examined. The major coworker (I. Zs.-Nagy) of these studies insists that our observations support his original hypothesis, 'The Membrane Hypothesis of Aging' (MHA), the primary assumption of which is that changes in cell surface membranes with age cause a general decline in intracellular enzyme activities. However, while it seems clear that cell surface membrane changes do occur with age, a number of past observations including those from the laboratory of this author, provide strong evidence that intracellular enzyme activities do not generally decline with age. This paper presents the data in detail, along with the author's view that the results do not support the main assumption of the MHA, but are more likely related to alterations in membrane functions with age.

Age-dependence of the lateral diffusion coefficient of Con-A receptor protein in the skeletal muscle membrane of C57BL/6J mice

The lateral diffusion coefficient (Dp) of the Con-A receptor protein was measured in the sarcolemma of the quadriceps femoris (QF) muscle of male and female C57BL/6JNia mice in four age groups between 2 and 26 months. Freshly prepared, ex vivo taken muscle strips were stained with Con-A-FL conjugate for 10 min, and fluorescence recovery after photobleaching (FRAP) measurements were carried out on 20-30 cells per animal, at 37 degrees C. Using this technique, Dp, and the fractional recovery (mobile fraction = FR%) of these proteins can be measured. In the youngest male and female age groups, Dp values of 5.72E-10 and 5.43E-10 cm2/s, and FR% values of 43.3 and 36.3%, were found, respectively. Dp displayed a characteristic, significant, negative, linear correlation with age in both sexes. The slope of the linear regression line calculated per month of age was 1.06E-11 and 0.96E-11 cm2/s for males and females, respectively; both of them differ from zero highly significantly. FR% values tended to increase slightly with age, yet the estimated average Dp = D(FR), calculated for the total Con-A receptor pool, maintained its significant, negative, linear age-correlation. The physiological significance of these changes needs to be clarified in the future.