Potential of short chain fatty acids to modulate the induction of DNA damage and changes in the intracellular calcium concentration by oxidative stress in isolated rat distal colon cells
Sl. Abrahamse et al., Potential of short chain fatty acids to modulate the induction of DNA damage and changes in the intracellular calcium concentration by oxidative stress in isolated rat distal colon cells, CARCINOGENE, 20(4), 1999, pp. 629-634
Short chain fatty acids (SCFA) are considered to be beneficial fermentation
products in the gut by exerting trophic effects in non-transformed colon c
ells and by slowing proliferation and enhancing differentiation in colonic
tumour cells. We have studied the further effects of SCFA on cellular event
s of early carcinogenesis, genotoxicity and cytotoxicity in rat distal colo
n cells. Cytotoxicity was assessed by measuring trypan blue exclusion and b
y determining the H2O2-induced changes in intracellular calcium concentrati
on ([Ca2+](i)) using a fluorospectrophotometer and the calcium-sensitive fl
uorescent dye Fura-2, The microgel electrophoresis technique (COMET assay)
was used to assess oxidative DNA damage. Individual SCFA and physiological
SCFA mixtures were investigated for their potential to prevent DNA and cell
damage induced by H2O2, For this, freshly isolated colon cells were treate
d with H2O2 (100-500 mu M) and 6.25 mM SCFA, We have found 100-500 mu M H2O
2 to cause a fast initial increase in [Ca2+](i), whereafter the levels grad
ually further increased, Addition of SCFA did not affect [Ca2+](i) nor did
it reduce the H2O2-induced increase in [Ca2+](i), Butyrate and acetate were
able to reduce the induction of DNA damage by 100, 200 and 500 mu M H2O2,
respectively. In contrast, i-butyrate and propionate were ineffective. The
degree of reduction of DNA damage for the two protective SCFA was similar,
Physiological mixtures containing acetate, propionate and butyrate in ratio
s of 41:21:38 or 75:15:10 that are expected to arise in the colon after fer
mentation of resistant starches and pectin, respectively, did not show sign
ificant antigenotoxic effects. The major difference between butyrate and ac
etate, on one hand, and i-butyrate and propionate, on the other hand, is th
at the former compounds are utilized best as energy sources by the colon ce
lls. Therefore, our results on antigenotoxicity coupled with the findings o
n [Ca2+](i) homeostasis indicate that molecular effects on the energy syste
m render these non-transformed, freshly isolated colon cells to be less sus
ceptible to H2O2.