Ma.Teresa González-Garza

High susceptibility of five axenic Entamoeba histolytica strains to gossypol

The antiamoebic potency of gossypol was tested against 5 axenic Entamoeba histolytica strains, in logarithmic phase growth in PEHPS medium. All of the strains were moderately susceptible to this polyphenolic drug. The 50% inhibitory concentration (IC50) was of the same order of magnitude in all strains: 0.015 microM (for strain HM-1) to 0.067 microM (for HM-38). The difference between the IC50 of HM-1 and the remaining 4 strains (HM-38, HK-9, HM-2 and HM-3) was significant, although it was greater between HM-1 and HM-38 (P less than 0.005) than between HM-1 and the other 3 strains (P less than 0.05), for which the IC50 was 0.03 microM, 0.049 microM and 0.38 microM respectively. Gossypol is more toxic in vitro for amoebae than other drugs widely used clinically, its pharmacological effects and safe dosage in humans are well known because of its antifertilizing effect, and it is accumulated mainly in the liver and colon. Accordingly, this compound could be a good antiamoebic agent if it is as potent in vivo as it is in vitro.

Leaf extracts of Carlowrightia cordifolia induce macrophage nitric oxide production.

Carlowrightia cordifolia (Acanthaceae) is a medicinal plant used in northeastern Mexico as a traditional remedy against inflammation. As tissue release of nitric oxide (NO) has been correlated with both inflammatory and anti-inflammatory processes, the aim of this study was to determine the effect of C. cordifolia leaf extracts on macrophage NO production. Lipopolysaccharide (LPS)-stimulated and non-LPS-stimulated mouse peritoneal macrophages were incubated with aqueous, ethanol, methanol and hexane extracts of C. cordifolia leaves. All extracts inhibited NO release from LPS-stimulated macrophages, with methanol and hexane extracts showing the greatest inhibition. On the other hand, macrophage cultures treated with extracts without LPS-stimulation produced high releases of NO. These unexpected results suggest two different ways by which leaf extracts may act, depending on cell status. On the other hand, data on NO activity in relation to inflammatory/anti-inflammatory auto-regulatory feedback and high concentrations of NO release by non-stimulated macrophages agreed with the hypothesis that NO may have an inhibitory effect in vascular inflammation.

Detection of a factor released by L5178Y lymphoblasts that inhibits mouse macrophage-activation induced by lipopolysaccharides.

BACKGROUND Several factors inhibit cellular immune response by deactivating macrophages, but very few, such as those described here, prevent macrophage activation. METHODS Ascites liquid from 12-day-old BALB/c mice bearing 5178Y lymphoma tumors was collected, and cell-free ascites liquid (CFAL) was separated from lymphoblasts. The supernatant (S1) was obtained from the homogenized and centrifuged lymphoblasts. Then, macrophage cultures containing 0.2 x 10(6) cells from lymphoma-bearing or healthy mice were added to 10 microL of CFAL or S1, plus 5 micrograms of lipopolysaccharides (LPS)/mL, 40 U interferon-gamma or a blend of both. Macrophages were incubated with CFAL or S1 prior to or after adding the activators to investigate whether any of the previously mentioned lymphoma fractions inhibited macrophage activation or whether they deactivated them. The effect of CFAL or S1 was estimated as the diminution of the amount of nitric oxide released by the experimental macrophage cultures with respect to controls (activated macrophages treated with none of the lymphoma fractions). RESULTS LPS, IFN-gamma, and the LPS/gamma blend activated macrophages from both lymphoma-bearing and healthy mice. None of the lymphoma fractions deactivated macrophages. CFAL, but not S1, inhibited the macrophage activation, i.e., the percentage of inhibition of nitric oxide releasing 76.7% and 78.1% in macrophages from healthy and lymphoma-bearing mice, respectively. In addition, CFAL was unable to inhibit the macrophage-activation effect of IFN-gamma or the LPS/IFN-gamma blend. CONCLUSIONS Mouse L5178Y lymphoma releases a factor that in vitro inhibits the macrophage activation induced by LPS, but not by IFN-gamma controls.

The macrophage-activation inhibitory factor (MAIF) from L5178Y murine lymphoma favors experimental amebic hepatic abscess development in Balb/c mice.

The development of amebic hepatic abscess usually implicates Entamoeba histolytica trophozoite migration from the bowel to the liver by passing through the intestine wall and blood vessels and traveling with the blood stream (1). The inflammatory response occurs immediately after the initial contact of trophozoites with the invaded tissues (2). In addition, E. histolytica has been shown to possess several mechanisms designed to disable the immune response of humans and susceptible experimental rodents such as hamsters and gerbils (3). Consequently, in a number of cases the affected host is unable to reject amebic invasion. Macrophages play an important role in the host immune response against amebiasis. The main effector molecule is nitric oxide (NO), which directly destroys amebas (4). We previously reported that L5178Y murine lymphoma cells produce in vivo a macrophage-activation inhibitory factor (MAIF), which specifically inhibits the NO production induced by lipopolyssacharides (LPS), but not by interferon g (INFg ) (5). Because mice are naturally resistant to develop amebic hepatic abscess (AHA), we designed the present in vivo study to assess whether MAIF could disable their immune response allowing AHA formation. Materials and Methods

In vitro anti-trichomonad effectiveness of a gossypol-metronidazol blend.

With the aid of the Basic Sequential Analytical Simplex Method the in vitro anti-trichomonad effectiveness of several metronidazole/gossypol blends was determined. While the combination that produced 50% of growth inhibition on trichomonad cultures (IC50) contained 15.1 microM gossypol and 0.087 microM metronidazole, the IC(50) of metronidazole and gossypol tested separately was 38.08 microM and 0.195 microM, respectively. Thus, the IC50 of mixed gossypol and metronidazole was, respectively 60.34 and 55.4% lower than that of each separated drug. Whereas metronidazole is usually administered orally, gossypol, used as spermicide, is formulated as pessary. In such conditions the absorption of metronidazole is very efficient while that of gossypol is strikingly poor. The above suggest that a gossypol-metronidazole anti-trichomoniasis therapeutic scheme could be as effective as metronidazole alone, but less toxic.