Decreased Bax expression by mucosal T cells favours resistance to apoptosis in Crohn's disease

J Itoh, C de La Motte, S A Strong, A D Levine, C Fiocchi, J Itoh, C de La Motte, S A Strong, A D Levine, C Fiocchi

Abstract

Background: Activated T cells are more susceptible to apoptosis than resting T cells. As intestinal T cells normally exhibit a higher state of activation, increased apoptosis may be necessary to maintain immune homeostasis in the specialised microenvironment of the mucosa. On the other hand, in Crohn's disease (CD) mucosal T cells are resistant to apoptosis, suggesting abnormal regulation of cell death mechanisms.

Aims: To investigate differences in expression of anti- and proapoptotic Bcl-2 family proteins, key regulators of apoptosis, between circulating and mucosal T cells, and possible alterations in CD.

Patients and methods: Lamina propria T cells (LPT) were isolated from 10 control, seven CD, and eight ulcerative colitis (UC) patients, and peripheral blood T cells (PBT) from healthy volunteers. Purified T cells were stained intracellularly for Bcl-2, Bcl-x(L), and Bax, and mean fluorescence intensity measured by flow cytometry.

Results: Compared with PBT, the expression level of Bcl-2 and Bax, but not Bcl-x(L), was significantly greater in LPT, resulting in lower Bcl-x(L)/Bax ratios. In PBT, Bax expression was highly and significantly correlated with both Bcl-2 and Bcl-x(L), but correlation with Bcl-2 was absent in LPT. Bax expression in CD, but not UC, LPT was significantly lower than in control LPT, resulting in a significantly higher Bcl-x(L)/Bax ratio. The significant correlation of Bcl-x(L) to Bax was preserved in CD, but not UC, LPT.

Conclusions: Regulation of Bcl-2 family protein expression differs between circulating and mucosal T cells, probably underlying diverse survival potentials. In CD LPT, a low Bax expression and a high Bcl-x(L)/Bax ratio favour resistance to apoptosis and may contribute to the chronicity of inflammation.

Figures

Figure 1
Figure 1
Representative flow cytometric analysis of intracellular staining for Bcl-2, Bcl-xL, and Bax protein levels in normal peripheral blood T cells (PBT) and control lamina propria T cells (LPT).
Figure 2
Figure 2
Flow cytometric analysis of intracellular staining for Bcl-2, Bcl-xL, and Bax protein levels in normal peripheral blood T cells (PBT) and control lamina propria T cells (LPT). Results are mean (SEM) fluorescence intensity for eight PBT and 10 LPT isolates. **p<0.002, ***p<0.001.
Figure 3
Figure 3
Flow cytometric analysis of intracellular staining for Bcl-2, Bcl-xL, and Bax protein levels in normal unseparated and CD45RO enriched (+) peripheral blood T cells (PBT). Results are mean (SEM) fluorescence intensity for eight PBT isolates. No statistically significant differences were observed for Bcl-2, Bcl-xL, and Bax.
Figure 4
Figure 4
Correlation of anti- and proapoptotic Bcl-2 family protein levels in normal peripheral blood T cells (PBT) (top) and control lamina propria T cells (LPT) (bottom). Individual data points represent mean fluorescence intensity of intracellular staining measured by flow cytometric analysis.
Figure 5
Figure 5
Representative flow cytometric analysis of intracellular staining for Bcl-2, Bcl-xL, and Bax protein levels in control, Crohn's disease (CD) and ulcerative colitis (UC) lamina propria T cells (LPT).
Figure 6
Figure 6
Flow cytometric analysis of intracellular staining for Bcl-2, Bcl-xL, and Bax protein levels in control, Crohn's disease (CD), and ulcerative colitis (UC) lamina propria T cells (LPT). Results are mean (SEM) fluorescence intensity for 10 control, seven CD, and eight UC isolates. **p<0.003, CD versus control and UC.
Figure 7
Figure 7
Correlation of proapoptotic Bax and antiapoptotic Bcl-xL protein levels in Crohn's disease (CD) and ulcerative colitis (UC) lamina propria T cells (LPT). Individual data points represent mean fluorescence intensity of intracellular staining measured by flow cytometric analysis.
Figure 8
Figure 8
Comparative correlation of proapoptotic Bax and antiapoptotic Bcl-xL in control and Crohn's disease (CD) lamina propria T cells (LPT). Individual data points represent mean fluorescence intensity of intracellular staining measured by flow cytometric analysis.

References

    1. N Engl J Med. 1998 Feb 26;338(9):564-71
    1. Nat Med. 1997 Jun;3(6):614-20
    1. Ann Intern Med. 1998 Mar 1;128(5):363-9
    1. Science. 1998 Apr 10;280(5361):243-8
    1. Neuropathol Appl Neurobiol. 1998 Jun;24(3):202-8
    1. Science. 1998 Aug 28;281(5381):1322-6
    1. Gut. 1998 Jul;43(1):48-55
    1. Gastroenterology. 1999 Mar;116(3):557-65
    1. Immunol Today. 1999 Jun;20(6):267-77
    1. J Immunol. 1999 Jul 15;163(2):1081-90
    1. Br Med J. 1955 Oct 29;2(4947):1041-8
    1. J Immunol. 1998 Feb 15;160(4):1627-37
    1. Gut. 1974 Jun;15(6):435-43
    1. Dig Dis Sci. 1979 Sep;24(9):705-17
    1. Gastroenterology. 1991 Oct;101(4):1020-30
    1. Gastroenterology. 1991 Dec;101(6):1529-36
    1. J Immunol. 1992 Oct 15;149(8):2816-22
    1. Blood. 1993 Jul 15;82(2):521-7
    1. Immunol Today. 1993 Jul;14(7):338-9
    1. Arthritis Rheum. 1994 Oct;37(10):1415-20
    1. J Clin Invest. 1995 Jan;95(1):211-8
    1. J Immunol. 1995 Jan 15;154(2):664-75
    1. Immunol Today. 1994 Dec;15(12):582-8
    1. Science. 1995 Mar 10;267(5203):1449-56
    1. Science. 1995 Mar 10;267(5203):1456-62
    1. Science. 1995 Jun 2;268(5215):1347-9
    1. J Immunol. 1995 Sep 1;155(5):2311-7
    1. J Clin Invest. 1996 Jan 15;97(2):316-22
    1. Eur J Immunol. 1996 Feb;26(2):294-9
    1. Blood. 1996 Jul 15;88(2):386-401
    1. J Clin Invest. 1996 Dec 1;98(11):2616-22
    1. J Clin Invest. 1997 Feb 1;99(3):439-46
    1. Immunol Today. 1997 Feb;18(2):72-6

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