HMOX1 and Parkinson disease: The intranasal LPS instillation strongly upregulated the expression of Nrf2 and HO-1 in young LPS-PD mice (Nrf2=0.51±0.03, p<0.01 and HO-1=0.28±0.01, p<0.001) (Fig. 4B and 4F), but did not influence the levels of Nrf2 and HO-1 in aged LPS-PD mice.