Changes in filipin-sterol binding in the rat cingulate cortex after the administration of antidepressant drugs. A freeze-fracture study

Modulators of cellular cholesterol homeostasis as antiproliferative and model membranes perturbing agents

Cholesterol is an important component of mammalian cell membranes affecting their fluidity and permeability. Together with sphingomyelin, cholesterol forms microdomains, called lipid rafts. They play important role in signal transduction forming platforms for interaction of signal proteins. Altered levels of cholesterol are known to be strongly associated with the development of various pathologies (e.g., cancer, atherosclerosis and cardiovascular diseases). In the present work, the group of compounds that share the property of affecting cellular homeostasis of cholesterol was studied. It contained antipsychotic and antidepressant drugs, as well as the inhibitors of cholesterol biosynthesis, simvastatin, betulin, and its derivatives. All compounds were demonstrated to be cytotoxic to colon cancer cells but not to non-cancerous cells. Moreover, the most active compounds decreased the level of free cellular cholesterol. The interaction of drugs with raft-mimicking model membranes was visualized. All compounds reduced the size of lipid domains, however, only some affected their number and shape. Membrane interactions of betulin and its novel derivatives were characterized in detail. Molecular modeling indicated that high dipole moment and significant lipophilicity were characteristic for the most potent antiproliferative agents. The importance of membrane interactions of cholesterol homeostasis-affecting compounds, especially betulin derivatives, for their anticancer potency was suggested.

The effect of antidepressants on lipid homeostasis: a cardiac safety concern?

OBJECTIVE

The authors sought to summarise and synthesise results from investigations which report on the effect of antidepressants on serum lipid homeostasis.

METHOD

The authors conducted a MedLine search of all English-language articles from 1966 to March 2006 using the search terms: major depressive disorder, bipolar disorder, lipids, triglycerides, cholesterol, low-density lipoprotein, high-density lipoprotein, and the non-proprietary names of conventional antidepressants indicated for the treatment of major depressive disorder in North America as of March 2006. The search was supplemented with a manual review of retrieved articles for any further citations reporting the effects of antidepressants on lipid homeostasis.

RESULTS

Despite the paucity of well-characterised investigations, the unfavourable effect of weight gain promoting antidepressants (e.g., tricyclics, mirtazapine) on serum lipid parameters (i.e., triglycerides and low-density lipoprotein cholesterol) is a consistent finding. Weight-neutral antidepressants (e.g., bupropion, venlafaxine, duloxetine), however, are less likely to disrupt the lipid milieu. A weight-independent effect on lipid homeostasis is less consistently reported.

CONCLUSION

Some antidepressants unfavourably influence the lipid milieu; mediating factors other than weight gain are not well-established. Pivotal studies evaluating the therapeutic index of antidepressants need to systematically collect and report data on the lipid effects of antidepressants.

The effects of imipramine on the methylation of phosphatidylethanolamine (PE) in the cortical membranes of Wistar rats

This study investigates the effect of imipramine (IMI) on the methylation of phosphatidylethanolamine (PE) in crude cortical membranes of rat brain in vitro and ex vivo. It was found that IMI enhanced the formation of phosphatidyl-N-monomethylethanolamine (PME) and phosphatidyl-N,N-dimethylethanolamine (PDE) and inhibited the formation of phosphatidylcholine (PC) in the cortical membranes of rats in vitro. The same effect i.e. increased incorporation of methyl groups in PE and PME and decreased formation of PC was found in the cortical membrane of rats killed 1 hr after intraperitoneal administration of IMI at a single dose of 10 mg/kg. Chronic treatment of rats with IMI for 14 days with a daily dose of 10 mg/kg i.p. led to further inhibition of PC formation but did not affect the formation of PME and PDE and abolished the stimulating effect of IMI on the formation of PME and PDE in vitro.

Changes in the amount and distribution of neuronal alkaline and acid phosphatase after chronic exposure of cultures of cingulate cortex to antidepressant drugs

Enzyme histochemistry was used to examine alkaline and acid phosphatases in cultures of embryonic rat cingulate cortex after 14 days exposure in vitro to two tricyclic antidepressants (amitriptyline and desipramine) and two non-tricyclic antidepressants (mianserin and citalopram). An increased amount of acid phosphatase reaction product was observed in lysosomes of neurons in cultures treated chronically with the non-tricyclic antidepressants, mianserin or citalopram. More strikingly, reaction product was also present in the inner lamellae of the Golgi apparatus after this treatment, but never in controls. These observations suggest that non-tricyclic antidepressants significantly increase the rate of degradative processes in cingulate neurons. In cultures, treated chronically with desipramine or amitriptyline, pre- and postsynaptic membranes contained heavy deposits of alkaline phosphatase reaction product, whereas in control cultures not exposed to these drugs the corresponding membranes were entirely devoid of reaction product. An increase in the amount of alkaline phosphatase reaction product was also observed on the plasma membranes of neuronal cell bodies. These observations suggest that chronic exposure to antidepressants may influence transmembrane transport in cingulate neurons.