Binding of a spin-labelled chlorpromazine analogue to calmodulin

Effects of chlorpromazine, pentoxifylline and dexamethasone on mRNA expression of lipopolysaccharide-induced inflammatory cytokines in bovine peripheral blood mononuclear cells

The effects of chlorpromazine (CPZ), pentoxifylline (PTX) and dexamethasone (DEX) on mRNA expression of lipopolysaccharide (LPS)-induced proinflammatory cytokines were examined in bovine peripheral blood mononuclear cells (PBMCs) in vitro. The expression of inflammatory cytokine mRNAs was analyzed by RT-PCR and Southern blot hybridization in bovine PBMCs. CPZ and DEX decreased the expression of cytokine mRNA (such as interleukin-1 beta and tumor necrosis factor-alpha) after stimulation with LPS in a dose-dependent manner. However, pretreatment with PTX had no inhibitory effect on the mRNA expression of proinflammatory cytokines. These results indicated that pretreatment with CPZ and DEX might be effective to reduce the production of LPS-induced inflammatory cytokines in bovine PBMCs in vitro.

The antagonistic effect of chlorpromazine on cadmium toxicity

Adult male rats were injected sc with cadmium chloride (CdCl(2)) in a single dose of 7 mg/kg body wt. Twenty-four hours postinjection, exposure to CdCl(2) increased the hemoglobin absorbance of the testes from 0.36 +/- 0.01 to 2.46 +/- 0.02. Pretreatment of rats with chlorpromazine (CPZ) 3 mg/kg ip either for 1 or 2 days before exposure to CdCl(2) significantly (p < 0.05) reduced the testicular damage and the hemoglobin absorbance decreased to 1.03 +/- 0.02 and 0.92 +/- 0.04, respectively. After CdCl(2) injection there was a progressive increase in serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities. CdCl(2) injection induced hemorrhage and a diffuse area of coagulative necrosis in liver. Pretreatment with CPZ partially protected liver from the effect of CdCl(2). Two months postinjection, exposure to CdCl(2) significantly decreased the weights of testes, epididymis, and accessory sex organs. Furthermore, CdCl(2) induced a highly significant (p < 0.01) decrease in sperm cell concentration and the percentage of mobile cells. Moreover CdCl(2) induced degenerative changes in testes, epididymis, and seminal vesicles. Pretreatment with CPZ partially protected these organs from the toxic effects of CdCl(2). It could be concluded that chlorpromazine partially antagonized the toxic effects of cadmium on liver, testes, and other male reproductive organs of rats.

Chlorpromazine inhibits tumour necrosis factor synthesis and cytotoxicity in vitro

Chlorpromazine (CPZ) has been previously shown to protect against endotoxin [lipopolysaccharide (LPS)] lethality and inhibit the release of tumour necrosis factor in vivo. We investigated at the cellular level whether this was due to direct inhibition of tumour necrosis factor-alpha (TNF-alpha) synthesis, using LPS-stimulated THP-1 human monocytic leukemia cells. We also studied the effect of CPZ on human TNF-alpha action by assessing TNF-alpha cytotoxicity on mouse fibrosarcoma L929 cells. CPZ (1-100 microM) inhibited TNF-alpha production in THP-1 cells in a dose dependent manner by a maximum of 80%. This effect was comparable to that of two well-known inhibitory drugs, dexamethasone and cyclicAMP. Inhibition was also evident at the mRNA level. On the other hand CPZ (10-25 microM) also inhibited TNF-alpha activity: in fact it reduced the cytotoxicity of TNF-alpha on L929 cells (EC50 was increased four times) and could provide protection even as a post-treatment. CPZ inhibited TNF-induced apoptosis in L929 cells, as detected by analysis of nuclear morphology. However, since we showed that apoptosis was very limited, and was not the main mode of cell death in our conditions, this could not explain the overall protection. Since CPZ did not interfere with either the oligomerization state of TNF-alpha or its receptor binding, our data suggest that it reduced cytotoxicity by inhibiting some steps in the TNF-alpha signalling pathways.

Chlorpromazine inhibits nitric oxide-mediated increase in intracellular cGMP in a mouse teratocarcinoma cell line

Chlorpromazine is a phenothiazine with a structure similar to that of methylene blue. Since methylene blue is a well known inhibitor of nitric oxide-induced cyclic GMP accumulation, we investigated whether chlorpromazine had the same effect. Cyclic GMP accumulation, induced in a mouse teratocarcinoma cell line (P19) by sodium nitroprusside (a nitric oxide releasing agent), was inhibited by both methylene blue (IC50 0.34 microM) and chlorpromazine (IC50 35 microM). Chlorpromazine's action was probably directed specifically at soluble guanylate cyclase, since the drug had no effect on ADP-ribosylation in rat hippocampus, another nitric oxide-affected, but cGMP-independent event.

Chlorpromazine protection against interleukin-1 and tumor necrosis factor-mediated activities in vivo

Interleukin (IL-1) and tumor necrosis factor (TNF) are thought to play a key role in septic shock and inflammation. We had previously shown that chlorpromazine (CPZ) has a protective effect in various models of endotoxic shock and IL-1 toxicity. We have tested the effect of CPZ on several activities of IL-1 in vivo. CPZ (4 mg/kg) inhibited increases in serum corticosterone, triglycerides and serum amyloid A (SAA). Chlorpromazine also antagonized these same effects when they were induced by endotoxin or TNF, suggesting that this activity could be implicated in the protective effect of CPZ in various models of endotoxic shock and IL-1 lethality.

Effects of calcium and calcium analogs on calmodulin: a Fourier transform infrared and electron spin resonance investigation

Fourier transform infrared (FTIR) and electron spin resonance (ESR) spectroscopies have been used to monitor changes in the conformation of calmodulin induced by Ca2+ and Ca2+ analogs. Using FTIR spectroscopy we observe that Ca2+: (i) favors the alpha-helical conformation and decreases the flexibility of the molecule; (ii) multiplies the intramolecular hydrogen bonds (the ratio of freely vibrating NH/hydrogen bound NH groups decreases); (iii) induces changes in the C-terminal tyrosine environment; and (iv) increases compactness of the molecule (less NH groups in the peptide bonds can be deuterated). As proved by ESR, Ca2+ binding induces exposure of hydrophobic domains allowing binding of a spin-labelled phenothiazine on calmodulin. When the experiments are performed in the presence of increasing amounts of Ca2+, both ESR and FTIR provide evidence that major conformational changes result after the filling of only two Ca2+-binding sites. But achievement of the spectroscopical changes is only observed when the four binding sites are filled (Ca2+/calmodulin = 4). The effects of analogs are monitored with the same spectroscopical parameters. Zn+ does not induce structural modifications of calmodulin but all other analogs studied mimic the calcium effects to some extent. As regards the amplitude of the spectroscopical effects, analogs rank in the following order: Ca2+ greater than Cd2+ greater than Tb3+ = Eu3+ greater than Gd3+ greater than La3+ greater than Zn2+ = cation depleted. Except for Zn2+, ranking for their activating potency of MLCK, the analogs can be arranged in a similar order.

Trifluoperazine increases fatty acid turnover in phospholipids in cultured human fibroblasts

A 24-hr pretreatment of cultured human fibroblasts with trifluoperazine induced a marked increase in incorporation of saturated (stearic, palmitic) and unsaturated (oleic, arachidonic) fatty acids into phospholipids (1.5- to 2-fold for 5.10(-5) M trifluoperazine). Concomitantly, incorporation into cholesteryl esters was strongly inhibited (20% of control for 5.10(-5) M trifluoperazine). The drug did not change the phospholipid composition of treated cells. The effect of trifluoperazine on oleic acid incorporation into phospholipids was time-dependent and reached a maximum after a six-hr preincubation with the drug. Trifluoperazine also induced an increase in the rate of chase of oleic acid from the different phospholipid classes. In vitro preincubation of cell-free extracts with trifluoperazine resulted in activation of phospholipid acyltransferases, whereas cholesterol acyltransferase activity was decreased. The rapid effect of trifluoperazine together with its effect on a cell-free system suggests a direct action of this amphiphilic drug on the acyltransferase activities, probably by modification of the structural organization of cellular membranes.

Relationship between the displacement of phosphatidate phosphohydrolase from the membrane-associated compartment by chlorpromazine and the inhibition of the synthesis of triacylglycerol and phosphatidylcholine in rat hepatocytes

Glycerolipid synthesis was studied in isolated hepatocytes by using 177 microM [14C]oleate and 1 mM [3H]glycerol. Chlorpromazine (25-400 microM) inhibited the synthesis of phosphatidylcholine and triacylglycerol. This was accompanied by an average increase of 12-fold in the accumulation of the labelled precursors in phosphatidate at 200 microM chlorpromazine and a decrease in the conversion of phosphatidate to diacylglycerol of 76%. These results indicate that part of the inhibition of the synthesis of phosphatidylcholine and triacylglycerol occurs at the level of phosphatidate phosphohydrolase. The relative rate of triacylglycerol synthesis at different concentrations of chlorpromazine was approximately proportional to the rate of conversion of phosphatidate to diacylglycerol. Phosphatidylcholine synthesis increased at higher rates of conversion of phosphatidate to diacylglycerol, but it was relatively independent of the latter rate when this was inhibited by more than about 30% with chlorpromazine. The addition of oleate to the hepatocytes caused a translocation of phosphatidate phosphohydrolase from the cytosol to the membrane-associated compartment. Chlorpromazine had the opposite effect and displaced the phosphohydrolase from the membranes in the presence or absence of oleate. There was a highly significant correlation between the activity of phosphatidate phosphohydrolase that was associated with the membranes of the hepatocytes and the calculated conversion of [3H]phosphatidate to diacylglycerol. Chlorpromazine also antagonized the association of the phosphohydrolase with microsomal membranes when cell-free preparations were incubated with combinations of oleate and spermine. Furthermore, it inhibited the transfer of the soluble phosphohydrolase to microsomal membranes that were labelled with [14C]phosphatidate and thereby decreased diacylglycerol production. It is concluded that part of the action of chlorpromazine in inhibiting the synthesis of triacylglycerol and phosphatidylcholine occurs because it prevents the interaction of the soluble phosphatidate phosphohydrolase with the membranes on which glycerolipid synthesis occurs. This in turn prevents the conversion of phosphatidate to diacylglycerol.

Interaction between calmodulin and five different spin-labelled chlorophenothiazines

The binding to purified calmodulin of five spin-labelled derivatives of chlorophenothiazine was investigated by e.s.r. spectrometry and by the antagonizing potency on the calmodulin-dependent activation of myosin light chain kinase. The results of a comparative study and the influence of pH and ionic strength on the binding support the occurrence of an electrostatic binding involving the terminal amino group of the side-chain of the chlorophenothiazine. These results are discussed in relation to the specificity of the interaction that holds the antipsychotic drug-calmodulin complex together.