Blood vitronectin is a major activator of LIF and IL-6 in the brain through integrin–FAK and uPAR signaling

Abstract

We defined how blood-derived vitronectin (VTN) rapidly and potently activates leukemia inhibitory factor (LIF) and pro-inflammatory interleukin 6 (IL-6) and after vascular injury in the brain. Treatment with VTN (but not fibrinogen, fibronectin, laminin-111 or collagen-I) substantially increased LIF and IL-6 within 4 h in C6-astroglioma cells, while VTN mouse plasma was less effective than that from wild-type mice. LIF and IL-6 were induced by intracerebral injection of recombinant human (rh)VTN in mice, but induction seen upon intracerebral hemorrhage was less in VTN mice than in wild-type littermates. , VTN effects were inhibited by RGD, αvβ3 and αvβ5 integrin-blocking peptides and antibodies. VTN activated focal adhesion kinase (FAK; also known as PTK2), whereas pharmacological- or siRNA-mediated inhibition of FAK, but not PYK2, reduced the expression of LIF and IL-6 in C6 and endothelial cells and after traumatic cell injury. Dominant-negative FAK (Y397F) reduced the amount of injury-induced LIF and IL-6. Pharmacological inhibition or knockdown of uPAR (also known as PLAUR), which binds VTN, also reduced cytokine expression, possibly through a common target of uPAR and integrins. We propose that VTN leakage into tissues promotes inflammation. Integrin-FAK signaling is therefore a novel IL-6 and LIF regulation mechanism relevant to the inflammation and stem cell fields.

Inhibition of astrocyte FAK–JNK signaling promotes subventricular zone neurogenesis through CNTF

“…Intratriatal FAK inhibition with FAK14 increased CNTF expression in the SVZ, as previously seen with PF573228 (Keasey et al 2013), another specific FAK inhibitor (Keasey et al 2018). Intrastriatal FAK14 decreased JNK but increased P38 and ERK activation, suggesting some specificity of pathway regulation downstream of FAK.…”

“…(c) Intrastriatal injection of U0126 reduced CNTF and LIF, but not IL-6, expression in the periventricular region of the same mice at 4 h (Student's t test, *** p < .001). (d) Intrastriatal ERK inhibition reduced SVZ cell proliferation measured by Ki67 at 4 h (same extracts as in (c), Student's t test, * p < .05) another specific FAK inhibitor (Keasey et al, 2018). Intrastriatal FAK14 decreased JNK but increased P38 and ERK activation, suggesting some specificity of pathway regulation downstream of FAK.…”

“…Moreover, FAK inhibition also down-regulates IL-6 in C6 cells (Keasey et al 2018). This raises the possibility that there are major differences between proliferating and non-proliferating cells.…”

“…The finding that intrastriatal FAK inhibition increases IL-6 expression is in apparent disagreement with a previous report that FAK mediates TNFα-induced IL-6 expression in cultured cancer cells and fibroblasts (Schlaepfer et al, 2007). Moreover, FAK inhibition also down-regulates IL-6 in C6 cells (Keasey et al, 2018). This raises the possibility that there are major differences between proliferating and non-proliferating cells.…”

“…Identifying such intracellular signaling pathways may help to therapeutically modulate their expression in the CNS in disorders characterized by excessive inflammation. Our previous study showed that FAK inhibition reduced LIF and IL-6 expression in cultured C6 cells (Keasey et al 2018). Here, we determined whether JNK, P38 and ERK downstream from FAK might regulate LIF and IL-6.…”