Alkaline phosphatase activity is expressed in murine splenic B-lymphocytes sensitized in vivo with Tetanus toxoid

Differential expression of alkaline phosphatase gene in proliferating primary lymphocytes and malignant lymphoid cell lines

Alkaline Phosphatase (APase) activity has been shown to be enhanced specifically in mitogen stimulated B lymphocytes committed to proliferation, but not in T lymphocytes. APase gene expression was analyzed in proliferating murine and human primary lymphocytes and human malignant cell lines using reverse transcriptase and real time PCR. In mitogen stimulated murine splenic lymphocytes, enhancement of APase activity correlated well with an increase in APase gene expression. However, in mitogen stimulated murine T lymphocytes and human PBL despite a vigorous proliferative response, no increase in APase enzyme activity or gene expression was observed. A constitutive expression of APase activity concomitant with APase gene expression was observed inhuman myeloma cell line, U266 B1. However, neither enzyme activity nor gene expression of APase were observed in human T cell lymphoma, SUPT-1. The results suggest a differential expression of APase activity and its gene in proliferating primary lymphocytes of mice and humans. The specific expression of APase activity and its gene only in human myeloma cells, but not in proliferating primary B cells can be exploited as a sensitive disease marker.

Anti-proliferative effect of levamisole on human myeloma cell lines in vitro

Levamisole has been employed as an immunomodulatory agent in conjunction with 5-fluorouracil in the treatment of colon cancer relapse. At high doses, levamisole has been shown to have both anti-cancer and immunosuppressive activities. In vitro, levamisole has been shown to potentiate the anti-proliferative effect of 5-fluorouracil in several types of tumor cell lines; however, its mechanism of cytotoxic action and its molecular targets in cells remains to be elucidated. Here, the effect of levamisole on the proliferative response of the human multiple myeloma cell lines RPMI 8226 and U266B1 was studied in vitro. Treatment of both lines with varying concentrations of levamisole for 48 and 72 h in culture resulted in a significant inhibition of proliferation (unstimulated) in a dose-dependent manner, as assessed by an 3-[(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide dye assay. Furthermore, measurements of cell viability (using a trypan blue dye exclusion assay) clearly showed that the levamisole was cytotoxic. The preliminary evaluation of the mechanism of this cytotoxic effect revealed that this drug induced apoptosis in the myeloma cells, as evidenced by increases in the levels of DNA fragmentation, release of cytochrome c into the cytoplasm, and the activation of caspase-3 activity in the cells. The results of these studies strongly suggest that levamisole could be a potent anti-myeloma agent and might be considered in the treatment of multiple myeloma in the future.

Immunomodulating activity of arabinogalactan and fucoidan in vitro

Many polysaccharides obtained from natural sources are considered to be biological response modifiers and have been shown to enhance various immune responses. Here, we investigated the immunomodulating effects of arabinogalactan (AG) and fucoidan (FU) in vitro. Mouse spleen lymphocytes became cytotoxic to tumor cells after culture with AG and FU at concentrations of 10-100 microg/mL. Also, AG and FU were mitogenic in spleen lymphocytes and peripheral macrophages. Macrophages treated with AG and FU (10-100 microg/mL) exhibited induced tumoricidal activity and increased phagocytosis, lysosomal enzyme activity, and production of nitrite, H2O2, tumor necrosis factor (TNF)-alpha, and interleukin (IL)-6. However, AG and FU had little effect on the level of IL-1beta. Thus, the tumoricidal effect of AG- and FU-activated macrophages appeared to be mainly mediated by production of free radicals (NO and H2O2) and cytokines (TNF-alpha and IL-6). These data suggest that AG and FU are activators of lymphocytes and macrophages. This property may contribute to their effectiveness in the immunoprevention of cancer.

Immune cell stimulating activity of mucopolysaccharide isolated from yam (Dioscorea batatas)

Mucopolysaccharide (YMP) of yam (Dioscorea batatas Decne) was tested for immunomodulatory activity in vitro. We examined the effect of YMP on the viability, cell-mediated cytotoxicity and IFN-gamma secretion of splenic lymphocytes. The cytotoxic activity of mouse splenocyte against leukemia cell was increased in the presence of YMP (10 microg/ml). However, YMP (10 microg/ml) did not affect the viability of splenocytes. The production of IFN-gamma was significantly increased in the YMP treated splenocytes, suggesting that YMP may induce cell-mediated immune responses. The effects of YMP on phagocytic activity were studied in relation to uptaking capacity and lysosomal phosphatase activity of the mouse peritoneal macrophages in vitro. YMP (50 microg/ml) was found to increase uptaking capacity and lysosomal phosphatase activity of peritoneal macrophages. In addition, YMP (10-100 microg/ml) significantly increased the viability of peritoneal macrophages (P<0.05). The data obtained demonstrate that the YMP may be used as sources of immunoactive polysaccharides.

Effect of synthetic lipids on apoptosis and expression of alkaline phosphatase in B-lymphocytes: influence on lipopolysaccharide action

Synthetic lipids were examined for their ability to mimic or to antagonize lipopolysaccharide (LPS) action in murine B-lymphocytes. Several recognized effects of LPS were analyzed: prevention of spontaneous apoptosis, expression of alkaline phosphatase (ALP) and stimulation of proliferation. Three synthetic lipids were used for that purpose: a lipopeptide (compound MTPP) which carries non-hydroxylated fatty acids, and is thus unrelated to LPS, and two glycolipids with hydroxylated fatty acids (compounds D2 and PPDm2-B), structurally related to the lipid A region of enterobacterial and Rhodopseudomonas LPS, respectively. We found that the ability of these lipids to induce LPS-like responses was not correlated with their structural analogy with LPS. Thus, the lipopeptide, MTPP, mimicked LPS in the three activities, whereas the glycolipid, D2, did not. In contrast, the ability of synthetic lipids to block LPS effects was correlated with their structural analogy with LPS. We thus observed that compound D2 selectively blocked LPS-induced ALP expression and that PPDm2-B selectively inhibited LPS-induced prevention of apoptosis. These synthetic lipids could therefore be useful for studying the LPS-mediated signals involved in B-cell activation and apoptosis.