We study the probability oscillations of mixed particles in the presence of self-gravitational interaction. We show a breaking of the CPT-symmetry due to the contemporary violation of the T-symmetry and the CP-symmetry preservation. This violation is directly associated to the rising of the entanglement among the elements of the system that can be seen as a pure many-body effect scaling with the number of the elements in the system. This effect could have played a relevant role in the first stages of the Universe or in core of very dense systems. Experiments based on Rydberg atoms confined in microtraps can simulate the mixing and the mutual interaction and could allow to test the mechanism here presented.