The sputtering of the MgO protective layer by energetic ions is one of the factors limiting the lifetime of the plasma display panels (PDPs). The sputtering profile of the MgO layer in a coplanar PDP cell has been studied using two-dimensional particle-in-cell Monte-Carlo Collision (PIC-MCC) simulations. The sputtering profile of the MgO layer for various gas conditions is obtained accounting for the energy and angle distributions of different ion species and their respective sputtering yields. Based on the simulation results, the MgO layer is more aggressively sputtered in Ne-based discharges than in He-based discharges. As a result, it is expected that the addition of He to the Ne-Xe mixture in PDPs will reduce the sputtering of the MgO layer and extend the lifetime of the PDP cells.