Objective: Astrocytes play a key role in hypoxic brain injury. The aim of our research was to determine the effects of menaquinone-7 (MK-7), a subtype of vitamin K2 (VK2), on astrocytes during hypoxia and its potential mechanisms.
Materials and methods: Astrocytes from the palliums of newborn Sprague Dawley rats were cultured. An astrocyte-hypoxia model was established using a hypoxia workstation. Cell Counting Kit-8 (CCK-8) and BrdU assays were used to determine the effects of MK-7 on hypoxic astrocytes. 2',7'-Dichlorodihydrofluorescein diacetate (DCFDA) or dihydroethidium (DHE) assays were conducted to detect the levels of reactive oxygen species (ROS). An ATP assay was used to measure intracellular ATP production. The levels of proinflammatory cytokines and chemokines containing interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), CC-chemokine ligand 2 (CCL2), and CXC-chemokine ligand 10 (CXCL10), as well as vitamin K-dependent protein growth arrest-specific 6 (Gas6), were determined in hypoxia-induced astrocytes, in the presence or absence of MK-7 pretreatment. Small interfering RNA (siRNA) was used to knockdown Gas6 expression to determine its role in hypoxic astrocytes pretreated with MK-7.
Results: Hypoxia reduced astrocyte viability and proliferation significantly; however, when pretreated with MK-7, these conditions remarkably increased. MK-7 also inhibited hypoxia-induced ROS production and enhanced ATP generation of hypoxic astrocytes. Pretreatment with MK-7 effectively reduced the expression of IL-6, TNF-α, CCL2, and CXCL10 but enhanced the expression of Gas6 in hypoxic astrocytes. Gas6 inhibition markedly attenuated the decline in MK-7-induced ROS generation and IL-6 expression, and weakened MK-7-induced cell viability and ATP production in hypoxic astrocytes.
Conclusions: Our study is the first to confirm that MK-7 can protect astrocytes from hypoxia-induced cytotoxicity, possibly by inhibiting mitochondrial dysfunction and the expression of proinflammatory cytokines. Gas6 may also participate in these protective effects.