It remains a considerable challenge to realize complete tumor suppression and avoid tumor regrowth by rational design of photosensitizers (PSs) to improve their photon utilization. In this Article, we provide a molecular design (Icy-NBF) based on the oxygen-content-regulated deactivation process of excited states. In the presence of overexpressed nitroreductase in hypoxic cancer cells, Icy-NBF is reduced and converted into a molecule with the same skeleton (Icy-NH 2 ), in which the deactivation of the PS under 808 nm light irradiation proceeds via a different pathway: the excited states deactivation pathway of Icy-NBF involves radiative transition and energy transfer between Icy-NBF and O2; as for Icy-NH 2 , the deactivation pathway is attributed to non-radiative relaxation. By varying the O2 concentration in tumor cells, the therapeutic mechanism of Icy-NBF under 808 nm light irradiation can be switched between photodynamic and photothermal therapies, which maximizes the advantages of phototherapies with no tumor regrowth. Our study provides help in designing of smart PSs with improvement of photon utilization for efficient tumor photoablation.

Neuronal death is known to trigger reactive microgliosis. However, little is known regarding the manner by which microglia are activated by injured neurons and how microgliosis participates in neurodegeneration. In this study we delineate the critical role of macrophage Ag complex-1 (MAC1), a member of the β2 integrin family, in mediating reactive microgliosis and promoting dopaminergic (DAergic) neurodegeneration in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) model of Parkinson’s disease. MAC1 deficiency greatly attenuated the DAergic neurodegeneration induced by MPTP or 1-methyl-4-phenyl-pyridium iodide (MPP+) exposure both in vivo and in vitro, respectively. Reconstituted experiments created by adding microglia from MAC1−/− or MAC1+/+ mice back to MAC1+/+ neuron-enriched cultures showed that microglia with functional MAC1 expression was mandatory for microglia-enhanced neurotoxicity. Both in vivo and in vitro morphological and Western blot studies demonstrated that MPTP/MPP+ produced less microglia activation in MAC1−/− mice than MAC1+/+ mice. Further mechanistic studies revealed that a MPP+-mediated increase in superoxide production was reduced in MAC1−/− neuron-glia cultures compared with MAC1+/+ cultures. The stunted production of superoxide in MAC1−/− microglia is likely linked to the lack of translocation of the cytosolic NADPH oxidase (PHOX) subunit (p47phox) to the membrane. In addition, the production of PGE2 markedly decreased in neuron plus MAC1−/− microglia cocultures vs neuron plus MAC1+/+ microglia cocultures. Taken together, these results demonstrate that MAC1 plays a critical role in MPTP/MPP+-induced reactive microgliosis and further support the hypothesis that reactive microgliosis is an essential step in the self-perpetuating cycle leading to progressive DAergic neurodegeneration observed in Parkinson’s disease.

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