Role of butyric acid and its derivatives in the treatment of colorectal cancer and hemoglobinopathies.

Butyric acid, a short chain fatty acid (SCFA), is a natural component of the animal metabolism. Physiological concentrations induce multiple and reversible biological effects. They concern regulatory mechanisms of gene expression conducing to promote markers of cell differentiation, apoptosis and cell growth control. The described hyperacetylation of histones and the induction of several immune or non-immune cell-activating mediators are consistent with the pleiotropic stimulatory effect of the agent. Butyric acid is considered as a biological response modifier (BRM) and is an interesting tool for biological studies. The history of butyric acid as a putative medication in human health is spanning since 60 years and is confusing in part because of conflicting data between exciting experimental results and clinical trials. In light of minimal impact of systemic therapy and the short half-life of the saline molecule used, it is evident that continuous infusions of butyrate are required to improve the efficacy of the treatment. Butyric acid has been viewed with skepticism because of less convenient for long-term chronic therapy. New experimental data from several studies conduced within the past decade with butyric derivatives, delivery systems, and long-acting prodrugs, have demonstrated the practical value of the therapeutic concept. To support issues regarding clinical development, it was of interest to evaluate the recent information, showing butyric acid currently considered as therapeutic purposes in the treatment of colorectal cancer and hemoglobinopathies.

Selective potentiation of cytokine expression in human whole blood by murabutide, a muramyl dipeptide analogue.

Murabutide is a synthetic muramyl peptide which is in clinical stage of development. Its effect on cytokine production was analysed in human whole blood to reproduce the natural environment. Induced gene transcription within 2 h was associated with the release of cytokines such as tumour necrosis factor (TNF), interleukin-1 beta (IL-1 beta), IL-6, IL-8, and also the anti-inflammatory mediator IL-1ra. This synthesis was not associated with the release of IL-4, IL-12, interferon gamma (IFN-gamma), the three colony-stimulating factors (CSFs) or the soluble TNF receptors. The same series of cytokines were assayed to determine the effect of some recombinant cytokines in association with murabutide. Thus, in the presence of IL-2, IL-6, IL-3 or granulocyte-macrophage colony-stimulating factor (GM-CSF), the level of cytokines induced by murabutide was enhanced with no change in the other cytokines profile. IL-3 and GM-CSF were more potent in increasing the murabutide-induced response, eliciting synergistic effects on IL-8 and IL-1Ra production, at both the mRNA accumulation and the protein release. Although neither IL-12 nor IFN-gamma were produced in cells stimulated with murabutide alone, some mRNA expression was found with combined treatments. The results indicate that association of murabutide with a cytokine could exert synergistic effects, thus reducing effective doses of the recombinant protein, increasing the release of anti-inflammatory mediators, and triggering efficient cellular immunity.

Enhancement in vivo of the antiinflammatory and antitumor activities of type I interferon by association with the synthetic immunomodulator murabutide.

The therapeutic efficacy of type I interferon (IFN) has been reported to vary considerably in different indications. The use of the cytokine as adjuvant therapy has been suggested to enhance its efficacy and reduce the toxicity frequently associated with long-term and high-dose administration. In this study, we have assessed the activity of type I IFN in the protection against and treatment of acute hepatitis induced in mice by the administration of concanavalin-A (ConA). At the same time, we have evaluated the efficacy of the synthetic immunomodulator murabutide when administered alone or in combination with type I IFN to protect against ConA hepatitis and in the treatment of tumors in MethA sarcoma-bearing mice. Our results demonstrate a prophylactic effect as well therapeutic effects of type I IFN and of murabutide in the inflammation-mediated model of liver damage. The use of combination therapy presented enhanced efficacy in inhibiting the ConA-induced elevation of plasma transaminases. Both compounds were found to suppress IFN-gamma mRNA accumulation in the livers of ConA treated mice. This activity is discussed with respect to the mechanism of action of the two immunomodulators. In addition, the combination of murabutide with type I IFN exhibited synergistic antitumor activity that was clearly seen in the significant regression of MethA tumors and resulted in almost 50 percent tumor-free mice. The potential clinical application of combination therapies using a cytokine and a safe immunomodulator is analyzed in terms of enhancing the cytokine efficacy and extending its use to new indications.

Enhancement by muramyl peptides of the protective response of interferon-alpha/beta against encephalomyocarditis virus infection.

The use of interferon-alpha (IFN-alpha) in the treatment of infectious diseases has shown limited efficacy and dose-limiting toxicity. We have selected safe immunomodulators of the muramyl peptide family with the potential of enhancing the efficacy of IFN-alpha without resulting in increased toxicity. One of these synthetic muramyl dipeptide (MDP) derivatives, namely murabutide which is in a clinical stage of development, has been recently found to synergize with IFN-alpha 2a in the selective induction of anti-inflammatory mediators and to enhance the biological activities of the therapeutic cytokine. The present study was performed to assess the antiviral activity of such muramyl peptides and a possible potentiation of the antiviral activity of IFN-alpha/beta by associated therapy using the classical assay of Encephalomyocarditis virus (EMCV) infection. In vitro, pretreatment of Moloney Sarcoma virus (MSV)-transformed cell line with MDP derivatives followed by treatment with IFN-alpha/beta showed a synergistic protection against the cytopathogenic effect of a subsequent EMCV infection. None of the MSV cultures could be protected by stimulation with muramyl peptides alone. In vivo, all of the muramyl peptide derivatives tested were found to be more potent than the parent molecule MDP in inducing protection against death or in the prolongation of the mean survival time of infected mice. Sequential administration of suboptimal doses of exogenous IFN-alpha/beta and muramyl peptides established a strong antiviral state and considerably improved the protective effect of the cytokine, frequently leading to an abortive infection. Our findings suggest that combination therapy with safe muramyl peptides and IFN-alpha/beta could constitute a highly effective and new regimen for the treatment of viral infections in humans.

Synergistic effects between recombinant interleukin-2 and the synthetic immunomodulator murabutide: selective enhancement of cytokine release and potentiation of antitumor activity.

The use of interleukin-2 (IL-2) in the treatment of cancer has shown limited efficacy and dose-limiting toxicity. Combination therapy with other cytokines and/or chemotherapeutic agents has been attempted to enhance the antitumor activity and to reduce the effective therapeutic dose of IL-2. We recently showed, in vitro and in vivo, a synergistic activity between the synthetic immunomodulator murabutide, which is in clinical stage of development, and another therapeutic cytokine, interferon-alpha (IFN-alpha). The present study was performed to assess a possible potentiation of the biologic activities of IL-2 by its association with murabutide. Human PBMC stimulated in vitro with IL-2 and murabutide showed synergistic levels of induced mRNA accumulation and protein secretion for IFN-gamma, IL-12, and colony-stimulating factors (CSFs). No such effects were obtained on the induction of most inflammatory cytokines, including IL-6, IL-8, and tumor necrosis factor alpha (TNF-alpha). Furthermore, the combined administration of murabutide with IL-2 into Meth-A sarcoma-bearing mice resulted in a very significant tumor inhibition as well as in complete tumor regression in nearly 70% of the treated mice. Under the same conditions, treatment with either compound separately had little or no antitumor effect. These preclinical findings will be pursued by the evaluation of the clinical tolerance and biologic activity of the murabutide/IL-2 combination therapy in cancer patients.