DNA damage in intact cells induced by bacterial metabolites of chloramphenicol

Abstract

Four chloramphenicol (CAP) metabolites known to be produced by intestinal bacteria were examined with respect to their capacity to induce DNA damage in intact cells. The induction of DNA single-strand breaks in Raji cells, activated human lymphocytes, and human marrow cells was assayed by the alkaline elution technique. One of the four compounds tested, dehydro-CAP, was capable of inducing DNA single-strand breaks in all three cell systems at concentrations of 10(-4) M. This effect is comparable to that observed previously with nitroso-CAP, the nitroreduction intermediate of CAP. The nitroreduction of dehydro-CAP by human bone marrow cell homogenate was detected by the production of the corresponding amino derivative amounting to 5.6 X 10(-5) M from 2 X 10(-3) M substrate under aerobic conditions. In sharp contrast, nitroreduction of CAP by bone marrow could not be demonstrated. The genotoxicity of dehydro-CAP, its relative stability compared to the nitroso-CAP, and its nitroreducibility by bone marrow suggest that this bacterial metabolite of CAP may play a key role as a mediator of aplastic anemia in the predisposed host.

Scientific Opinion on Chloramphenicol in food and feed

“…from tissue or gastro-enteric bacteria), are still a matter of debate or are simply not known. Compared with other metabolites, nitroso-chloramphenicol, dehydro-chloramphenicol and, to a lesser extent, dehydrochloramphenicol base and NPAP are characterised by higher cyto-and genotoxic potency (LafargeFraissinet et al, 1994, Jimenez et al, 1987Isildar et al, 1988b;Robbana-Barnat et al, 1997). The presence of all such metabolites except dehydro-chloramphenicol base has been demonstrated in kidney, liver and muscle samples from broiler chickens orally administered 50 mg chloramphenicol/kg b.w.…”

“…Four chloramphenicol metabolites known to be produced by intestinal bacteria were examined with respect to their capacity to induce DNA damage in cells in culture by Isildar et al (1988b). The induction of DNA single-strand breaks in Raji cells, activated human lymphocytes, and human bone marrow cells was assayed by the alkaline elution technique.…”

“…As discussed in Section 7.1, chloramphenicol can be metabolised into a number of metabolites, like the glucuronide, chloramphenicol base, an alcoholic derivative, dehydro-chloramphenicol, dehydrochloramphenicol base, referred to as NPAP and amino-chloramphenicol, some of them thought to be formed by enterobacteria in the large bowel (Smith and Worrel, 1950). Another potential metabolite is nitroso-chloramphenicol, but this metabolite is very reactive and as such difficult to detect in tissues and blood of treated humans or animals (Isildar et al 1988b). The ability of these metabolites to induce DNA damage in human cells was tested in human peripheral blood lymphocytes and in a lymphoma cell line (Raji) (See Table 8).…”

“…Bacterial biotransformations are reported to generate further metabolites other than nitroso-chloramphenicol, including dehydro-chloramphenicol and dehydrochloramphenicol base (Figure 3). Some authors referred to dehydro-chloramphenicol base as 2-amino-3-hydroxy-p-nitropropiophenone (NPAP) (Isildar et al, 1988b, Lafarge-Frayssinet et al, 1994Robbana-Barnat et al, 1997). However, two papers mention a different structure for NPAP (nitrophenylaminopropanedione and p-nitrophenyl-2-amino-3-hydroxypropanone HCl; Anadón et al, 1994;Jimenez et al, 1987;respectively).…”

“…The CONTAM Panel noted that these two papers reported a structure suggesting that HCl is covalently bound to the aminogroup of dehydro-CAP base. These metabolites have been implicated in the haematotoxicity of the antibiotic (Jimenez et al, 1987;Robbana-Barnat et al, 1997) and have been tested for their effects on DNA using the alkaline elution assay (Isildar et al, 1988b;Lafarge-Frayssinet et al, 1994) (see Section 7.2.7).…”