Neuronal pentraxin 1 expression is regulated by hypoxia inducible factor-1α

Neuronal pentraxins (NPs) are belong to sub family of long pentraxin proteins consist of neuronal pentraxin 1 (NP1), neuronal pentraxin 2 (NP2), and neuronal pentraxin receptor (NPR). Enhanced expression of NP1 in hypoxic conditions has shown to induce cell death in neuronal cells, however, the underlying mechanism of NP1 regulation by hypoxia remains elusive. To demonstrate that, we have cloned human NP1 gene promoter upstream of the luciferase gene and the activity of NP1 promoter was studied using HEK cell lines. Within the promoter region of the human NP1 gene, we identified six putative hypoxia inducible factor (HIF) responsive elements. By luciferase reporter assays we determined that the hypoxia inducible factor responsive element is located between -332 to -215 positions relative to the translation start site are essential for transcriptional activation of NP1 under hypoxic conditions. To further confirm the activity is solely due to hypoxia, we transiently transfected green fluorescent protein (EGFP) under transcriptional control of five copies of a hypoxia response element (HRE). The intensity of GFP was recorded at normal and hypoxic conditions. Taken together, our results demonstrate that NP1 gene is a target of as a hypoxia-inducible factor and it regulate NP1 expression by binding to hypoxia responsive elements (HREs) in its promoter region.