Alteration of lymphocyte membrane phospholipids and intracellular free calcium concentrations in hyperlipidemic subjects

The role of paraoxonase 1 in regulating high-density lipoprotein functionality during aging

Pharmacological interventions to increase the concentration of high-density lipoprotein (HDL) have led to disappointing results and have contributed to the emergence of the concept of HDL functionality. The anti-atherogenic activity of HDLs can be explained by their functionality or quality. The capacity of HDLs to maintain cellular cholesterol homeostasis and to transport cholesterol from peripheral cells to the liver for elimination is one of their principal anti-atherogenic activities. However, HDLs possess several other attributes that contribute to their protective effect against cardiovascular diseases. HDL functionality is regulated by various proteins and lipids making up HDL particles. However, several studies investigated the role of paraoxonase 1 (PON1) and suggest a significant role of this protein in the regulation of the functionality of HDLs. Moreover, research on PON1 attracted much interest following several studies indicating that it is involved in cardiovascular protection. However, the mechanisms by which PON1 exerts these effects remain to be elucidated.

Hyperlipidemia is involved in apoptosis in rat submandibular glands

OBJECTIVE

The aim of the present study was to investigate the effects of hyperlipidemia on histological changes and apoptosis in submandibular glands using apolipoprotein E (apoE)-deficient rats.

DESIGN

Histopathological findings related to induced apoptosis in the submandibular glands were compared between apoE-deficient rats (n=6; male; age, 16 weeks) and the corresponding wild-type rats (n=6).

RESULTS

ApoE-deficient rats showed significantly higher plasma levels of oxidized low-density lipoprotein (LDL), total cholesterol, very LDL and LDL, and lower plasma levels of high-density lipoprotein when compared to control rats (P<0.05). Lipid deposition in the submandibular gland was observed in apoE-deficient rat group and in none of the control group. Significant increases in vacuolization and apoptosis in acinar cells were observed in apoE-deficient rats, as compared to control rats (P<0.05). The number of active caspase-3-positive cells was also higher in the apoE-deficient rat group when compared with the control group (P<0.01).

CONCLUSIONS

According to our results, hyperlipidemia induced apoptosis in apoE-deficient rat submandibular glands. Oxidized LDL generation in case of hyperlipidemia may trigger off a reaction of apoptotic acinar cells with vacuolization in the submandibular glands.

Ganoderma lucidum beta 1,3/1,6 glucan as an immunomodulator in inflammation induced by a high-cholesterol diet

BACKGROUND

Binding of beta 1,3/1,6 glucan of Ganoderma lucidum (G. lucidum) with the receptor results in a series of signal transfers (signalling cascades), which activates the transcription factors for regulating inflammation. Excess cholesterol intake leads to an increase in the distance between fat cells and capillaries, which may cause hypoxia in the fat tissue of obese mice. This hypoxia induces the death of fat cells, resulting in the inflammation of adipose tissue or an increase in the inflammatory gene expression associated with obesity.

METHODS

The current study examined the immunomodulation effect of G. lucidum beta 1,3/1,6 glucan according to immunoglobulin, poly-Ig receptor expression, Nature Killer cell (NK cell) activity, lymphocytes proliferation and cytokines expression.

RESULTS

Our present study shows that feeding G. lucidum beta 1,3/1,6 glucan to mice induces IgA or IgG expression in the serum and small intestine washing fluid and enhances poly-Ig receptor expression in the small intestine moreover, the observation of the IL-2 and Nature killer cell activity were exchanged.

CONCLUSIONS

The effect of a high-cholesterol diet in the inflammatory response was observed in heart, liver, kidney, spleen, and colon tissues through histopathological evaluations. The presented evidence demonstrates that the inflammation response in the high-cholesterol diet group was much higher than in the other groups and the beta 1,3/1,6 glucan reduces inflammation in obese mice fed a high-cholesterol diet.

Association between Paraoxonase 1 (PON1) Polymorphisms and the Risk of Acute Coronary Syndrome in a North African Population

The purpose of the present study was to investigate the distribution of PON1 Q192R and L55M polymorphisms and activities in a North African population and to determine their association with cardiovascular complications. The prevalence of the QQ, QR, RR, LL, LM, and MM genotypes in the study population was 55.4%, 34.09%, 9.83%, 41.97%, 48.20%, and 9.83% respectively. The Q, R, L, and M alleles had a gene frequency of 0.755, 0.245, 0.67, and 0.33, respectively. The PON1 192 RR genotype was significantly more prevalent among ACS patients than among healthy subjects. There was a 4.33-fold increase in the risk of ACS in subjects presenting the PON1 192 RR genotype compared to those with the QQ genotype (OR=4.33; 95% CI=1.27–17.7). There was a significantly different distribution of PON1 L55M in the ACS patient groups (UA, STEMI, NSTEMI). Moreover, individuals presenting the PON1 55MM genotype present a higher risk for ACS than those with LL genotype (OR=3.69; 95% CI=1.61–11.80). Paraoxonase activities were significantly lower in coronary patients than in healthy subjects. The decrease in PON1 activity was inversely correlated with the number of concomitant risk factors for CVD (r=0.57, p<0.0001). The results of the present study suggested that the PON1 R and M alleles may play a role in the pathogenesis of cardiac ischemia in our North African population and that a decrease in PON1 activity may be a valuable marker for monitoring the development of the atherosclerosis process and the associated cardiovascular complications.

Hyperlipidemia impaired innate immune response to periodontal pathogen porphyromonas gingivalis in apolipoprotein E knockout mice

A finely-tuned innate immune response plays a pivotal role in protecting host against bacterial invasion during periodontal disease progression. Hyperlipidemia has been suggested to exacerbate periodontal health condition. However, the underlying mechanism has not been addressed. In the present study, we investigated the effect of hyperlipidemia on innate immune responses to periodontal pathogen Porphyromonas gingivalis infection. Apolipoprotein E-deficient and wild-type mice at the age of 20 weeks were used for the study. Peritoneal macrophages were isolated and subsequently used for the study of viable P. gingivalis infection. ApoE^−/− mice demonstrated inhibited iNOS production and impaired clearance of P. gingivalis in vitro and in vivo; furthermore, ApoE^−/− mice displayed disrupted cytokine production pattern in response to P. gingivalis, with a decreased production of tumor necrosis factor-α, interleukin-6 (IL-6), IL-1β and monocyte chemotactic protein-1. Microarray data demonstrated that Toll-like receptor (TLR) and NOD-like receptor (NLR) pathway were altered in ApoE^−/− mice macrophages; further analysis of pattern recognition receptors (PRRs) demonstrated that expression of triggering receptors on myeloid cells-1 (TREM-1), an amplifier of the TLR and NLR pathway, was decreased in ApoE^−/− mice macrophages, leading to decreased recruitment of NF-κB onto the promoters of the TNF-α and IL-6. Our data suggest that in ApoE^−/− mice hyperlipidemia disrupts the expression of PRRs, and cripples the host’s capability to generate sufficient innate immune response to P. gingivalis, which may facilitate immune evasion, subgingival colonization and establishment of P. gingivalis in the periodontal niche.

Aging, immunosenescence and membrane rafts: the lipid connection

The decreased efficiency of immune responses in older people is partly a consequence of alterations in T lymphocyte functions caused by modifications in the early events of signal transduction. Several alterations in the signaling pathways of T lymphocytes have been described in older humans and animals. A unifying cause could be modifications in the physicochemical properties of the plasma membrane resulting from changes in its lipid composition and the distribution and function of lipid rafts (LR). The latter serve to assemble the initial components of the signaling cascade. Accumulating data suggest that the function of plasma membrane LR is altered with aging; we hypothesize that this would significantly contribute to immune dysregulation. The role of aging and cholesterol in LR functions in T lymphocytes is reviewed and discussed here.

Hydrophobic but not hydrophilic statins enhance phagocytosis and decrease apoptosis of human peripheral blood cells in vitro

The engulfing ability of phagocyting cells is related to the fluidity of the cell membrane that in turn depends on its chemical composition. Changes in membranal lipid content may increase or decrease membranal fluidity with a subsequent enhanced or impaired phagocytosis, respectively. Statins are recognized as potent inhibitors of cholesterol synthesis and therefore, are successfully administered to patients with hypercholesterolemia. Since it is considered that cholesterol affects cell function via changes in membrane composition, the present study was designed to examine the in vitro effect of three hydrophobic statins--atorvastatin, lovastatin and simvastatin, and a hydrophilic one--pravastatin, on the engulfing capacity, phagocytic index and apoptosis of peripheral blood phagocytes from healthy volunteers. Peripheral white blood cells obtained from 20 healthy normocholesterolemic individuals were incubated for 2h with 10 and 50 microM of the four statins and phagocytosis of fluorescent latex particles was detected by flow cytometry. Apoptosis was examined using annexin V and propidium iodide staining. An increase in the percentage of phagocyting cells was observed after incubation with 50 microM of lovastatin and simvastatin. On the other hand, all three hydrophobic statins induced a dose-dependent increase in the phagocytic index. The hydrophilic pravastatin did not affect phagocytosis, phagocytic index and apoptosis. All three hydrophobic statins at 50 microM exerted a slight, but significant decrease of apoptosis. The results suggest that the effect of hydrophobic statins on the engulfing capacity of human peripheral blood phagocytes and apoptosis is dependent on their dosage and physiochemical properties. This observation is an additional contribution to the statins' pleiotropic effect.

Effect of pravastatin, simvastatin and atorvastatin on the phagocytic activity of mouse peritoneal macrophages

Since cholesterol and lipid content may affect cell membrane fluidity, we assumed that treatment of mice with lipid lowering statins would enhance the engulfing capacity of their macrophages. Four groups of animals were examined. Group I-treated with pravastatin, group II--with simvastatin--both drugs in a dosage of 40 mg/kg daily, 5 days/week for a total of 3 weeks. Mice in group III received atorvastatin 5 mg/kg for the same time period. Group IV--untreated animals serving as controls. The phagocytic capacity of the peritoneal macrophages was evaluated by their ability to engulf latex particles. In addition, the mitogen response of the peripheral blood mononuclear cells (PBMC) and splenocytes to Con A and PHA was examined. Compared to the controls, the percentage of phagocyting cells in pravastatin-treated mice was enhanced by 18%, with simvastatin--by 24% and in atorvastatin-treated animals by 8%. The three statins increased the phagocytic index by 79.5%, 88.8% and 62%, respectively. The mitogen response of splenocytes from mice treated with the three statins to Con A increased by 68%, 48% and by 40%, respectively. Compared with the controls the response to PHA was higher in animals treated with pravastatin (84%), simvastatin (73%) and atorvastatin (57%). The response of PBMC from statin-treated animals to both mitogens did not differ from that of the controls. The results suggest that statins, at least those hereby investigated, may exert a beneficial effect on the immune function of the macrophages.

Modulation of human lymphocyte proliferative response with aging

Previously, we have demonstrated age-associated alterations in transmembrane signaling. One of the most reproducible alterations found in the immune response with aging is the decrease of lymphocyte proliferation on stimulation with various different mitogens. Here, we confirm that proliferative responses to stimulation with phytohaemagglutin (PHA), recombinant human IL-2, or anti-CD3 monoclonal antibody are all greater in the young (20-25 years) than old (60-87 years) population. We attempted to modulate the proliferative response using various agents acting at different levels of transmembrane signaling (pertussis toxin, cholera toxin, isoproterenol, PMA, Ca ionophore A23187), as well as at the level of the lymphocyte plasma membrane (methyl-beta-cyclodextrin, MBCD), or by using antioxidant vitamins (Vitamin E or C). None of these agents was able to restore effectively the proliferative response of lymphocytes from the aged to the level of young subjects. Even the combination of A23187 and PMA acting directly on calcium metabolism and protein kinase C activity was insufficient to restore the decreased mitogenic capacity of T cells from elderly subjects. Cyclodextrin, which decreases the cholesterol content of the membrane, increased the proliferative response of lymphocytes of elderly subjects, but not to the level of the young. Vitamin E had a very strong inhibitory effect on lymphocyte stimulation in both the age groups, except in combination with MBCD in T cells of the elderly, while Vitamin C had no significant modulatory effect. MAPK ERK and p38 activation was found to be decreased with aging in T cells after anti-CD3 mAb stimulation. Vitamin E but not Vitamin C strongly inhibited MAPK ERK or p38 activation. The direct activation of certain molecules or the modulation of the cholesterol content of the membrane seems to be effective immunomodulatory interventions with aging.

Cyclodextrin modulation of T lymphocyte signal transduction with aging

There is an alteration of the immune response in aging that leads to the increased incidence of infections, cancers and autoimmune disorders. The aim of the present study was to investigate whether there exists changes in signal transduction under the IL-2 receptor stimulation and the role of plasma membrane cholesterol in the activation of T cells with aging. We report age-related changes in the JAK-STAT signalling pathway that results in decreased tyrosine phosphorylation of STAT5. We present evidence for the importance of cholesterol content in regulating signalling pathways in T cells and in modulating their proliferation by using the plasma membrane cholesterol-depleting agent methyl-beta-cyclodexrin (MBCD). MBCD treatment (0.5 mM) induced a significant decrease in the cholesterol content of T cells of elderly subjects whereas it was increased in T cells of young subjects. MBCD induced changes in the phosphorylation of p56(lck), especially in T cells of elderly subjects. The proliferation of MBCD-treated T cells decreased in lymphocytes of young subjects but did not change in T cells of elderly subjects. These results suggest a role for plasma membrane cholesterol in the regulation of the TcR signalling pathways with differential effects related to aging. However, the data suggest that modulation of the plasma membrane cholesterol content alone may not be enough to restore signal transduction changes with aging.

Biogerontological research in Canada

There is an ever increasing interest in the study of the aging process. This review is aimed to make an overview of the biological aging research in Canada. I will summarize, to the best of my knowledge, the biological aging research undertaken actually in Canadian institutions dealing with various aspects of this research using many different experimental approaches, models from animals to humans and a huge array of techniques. The biological aging research is developing continuously in Canada, however, it is very important that we assist in a near future to its huge explosion if we would respond to the needs of an ever increasing aging population. Initiatives recently proposed by the Canadian government concerning the creation of Canadian Institutes on Health Research will provide good opportunities to establish a performant, cost-effective, and innovative biological aging research.

The role of calcium in the etiology of the affective disorders

Calcium abnormalities are some of the more consistent findings in platelets of affective disorder patients. While medication status does not correlate with this finding, antidepressants do modulate intracellular calcium. This, in combination with reports that calcium channel inhibitors may have antidepressant potential, suggests that calcium may play an important role in this disorder. This paper reviews the specificity of calcium abnormalities for the affective disorders and also discusses possible mechanisms of action.