Augmentation of in vitro antibody response by disulfide compounds. I. Comparison between intermolecular and intramolecular disulfides

Potential alteration of tumor microenvironments by β-mercaptoethanol

The therapeutic effectiveness of immune checkpoint inhibitors in cancer patients is quite profound. However, it is generally accepted that further progress is curtailed by accompanying adverse events and by low cure rates linked to the tumor microenvironment. The multitudes of immune processes altered by low-molecular-weight thiols published over the past decades suggest they have potential to alter tumor microenvironment processes which could result in an increase in immune checkpoint inhibitor survival rates. Based on one of the most studied and most potent low-molecular-weight thiols, β-mercaptoethanol (BME), it is proposed that clinical assessment be undertaken to identify any BME benefits with relevance for proliferation/differentiation of immune cells, lymphocyte exhaustion, immunogenicity of tumor antigens and inactivation of suppressor cells/factors. The BME alterations projected to be most effective are: maintenance/replacement of glutathione in lymphocytes via facilitation of cysteine uptake, inhibition of suppressor cells/soluble factors and inactivation of free-radical, reactive oxygen species.

A review: alteration of in vitro reproduction processes by thiols -emphasis on 2-mercaptoethanol

Descriptions of organosulfurs altering biologically relevant cellular functions began some 40 years ago when murine in vitro cell mediated and humoral immune responses were shown to be dramatically enhanced by any of four xenobiotic, sulfhydryl compounds-2-mercaptoethanol (2ME), dithiothreitol (DTT), glutathione, and L-cysteine; the most effective were 2ME and DTT. These findings triggered a plethora of reports defining 2ME benefits for a multitude of immunological processes. This in turn led to investigations on 2ME alterations of (a) immune functions in other species, (b) activities of other cell-types, and (c) in vivo diseases. In addition, these early findings preceded the identification of previously undefined anticarcinogenic chemicals in specific foods as organosulfurs. Taken all together, there is little doubt that organosulfur compounds have enormous benefits for cellular functions and for a multitude of diseases. Issues of importance still to be resolved are (a) clarification of mechanisms that underlie alteration of in vitro and in vivo processes and perhaps more importantly, (b) which if any in vitro alterations are relevant for (i) alteration of in vivo diseases and (ii) identification of other diseases that might therapeutically benefit from organosulfurs. As one means to address these questions, reviews of different processes impacted by thiols could be informative. Therefore, the present review on alterations of in vitro fertilization processes by thiols (mainly 2ME, since cysteamine alterations have been reviewed) was undertaken. Alterations found to occur in medium supplemented with 2ME were enhancement, no effect, or inhibition. Parameters associated with which are discussed as they relate to postulated thiol mechanisms.

Immunomodulatory action of levamisole--I. Structural analysis and immunomodulating activity of levamisole degradation products

In our laboratory we observed that solutions of levamisole (LMS) stored at 4 degrees C consistently enhanced the lymphocyte proliferation response to concanavalin A (Con A) more than freshly prepared solutions did. To determine if the increased immunopotentiation observed with the stored solutions of LMS was due to products formed from LMS, we assessed the stability of LMS when stored at 4 or 37 degrees C at pH 6, 7, 7.5 and 8. Analysis of the various solutions by high pressure liquid chromatography demonstrated that LMS decomposes during storage in neutral and alkaline conditions to form three products. The formation of the products was accelerated by increasing the temperature from 4 to 37 degrees C. The three degradation products were purified by preparative high pressure liquid chromatography and their structures determined by mass spectrometry, infrared spectrometry and homo- and heteronuclear two dimensional nuclear magnetic resonance spectroscopy. The degradation products, denoted as No. 1, No. 2 and No. 3, based on their high pressure liquid chromatography retention times, were identified as: No. 1, 3-(2-mercaptoethyl)-5-phenylimidazolidine-2-one; No. 2, 6-phenyl-2,3-dihydroimidazo (2,1-b) thiazole and No. 3, bis [3-(2-oxo-5-phenylimidazolidin-1-yl) ethyl] disulfide. Product 2 significantly enhanced murine lymphocyte proliferation responses to concanavalin A (Con A) at concentrations between 0.5 and 10.0 micrograms/ml (whereas the optimum concentration of LMS is 10-100 fold higher (50-100 micrograms/ml)). Products 1, 2 and 3 significantly inhibited the lymphocyte proliferative response at concentrations greater than 2.2, 10.0 and 10.0 micrograms/ml, respectively. These studies indicate that under relatively mild conditions, including physiological conditions, LMS may decompose to products which inhibit or enhance lymphocyte responses to Con A.

CuSO4 as an inhibitor of B cell proliferation

In the course of investigating the mechanisms of the in vitro immunosuppressive effect of D-penicillamine in the presence of copper ion with murine spleen cells, we observed that copper ion, by itself, exhibited a strong immunosuppressive effect at a low concentration. Namely, the addition of CuSO4 at a concentration of 0.1 to 2 microM markedly inhibited the development of SRBC-specific plaque forming cells (PFC) without causing cytotoxicity. CuSO4, at the same concentration range, suppressed the lipopolysaccharide (LPS)-induced proliferative response, but not the response induced by concanavalin A (Con A). The suppressive effect of CuSO4 on the antibody production was reversed by 500 U/ml of catalase, but that on the LPS-induced proliferative response was not. CuSO4 also substantially suppressed the pokeweed mitogen-induced proliferative response. These findings suggest that CuSO4 acts as an inhibitor of B cell proliferation and, through this effect, markedly inhibits the antibody production in murine spleen cells.

Augmentation of the antibody response by lipoic acid in mice. I. Analysis of the mode of action in an in vitro cultures system

Lipoic acid (Lip), a naturally occurring disulfide compound, was found to augment markedly in vitro antibody responses to sheep erythrocytes (SRBC), dinitrophenyl-Ficoll and trinitrophenyl-lipopolysaccharide (TNP-LPS) as effectively as 2-mercaptoethanol (2-ME) in murine lymphocytes. The mitogenic response to LPS or concanavalin A (Con A) was augmented by Lip only slightly. 2-ME has been reported to facilitate cystine utilization by the lymphocytes, but Lip did not, indicating that the mode of action of Lip is different from that of 2-ME. Lip-augmentation of anti-SRBC response was markedly abrogated when murine lymphocytes were depleted of T cells and cultured in the presence of Con A-conditioned medium containing T cell-replacing factor. The effect of Lip was also diminished in the response to TNP-LPS when the spleen cells were depleted of T cells. These observations suggest that Lip could augment the antibody response by stimulating a T cell subpopulation. This idea was confirmed by the experiment that Lip could enhance helper T cell activity which was induced by culturing murine lymphocytes with the antigen.