Transcription factor Phox2 upregulates expression of norepinephrine transporter and dopamine β-hydroxylase in adult rat brains

Abstract

Degeneration of the noradrenergic locus coeruleus (LC) in aging and neurodegenerative diseases is well documented. Slowing or reversing this effect may have therapeutic implications. Phox2a and Phox2b are homeodomain transcriptional factors that function as determinants of the noradrenergic phenotype during embryogenesis. In the present study, recombinant lentiviral eGFP-Phox2a and -Phox2b (vPhox2a and vPhox2b) were constructed to study the effects of Phox2a/2b over-expression on dopamine β-hydroxylase (DBH) and norepinephrine transporter (NET) levels in central noradrenergic neurons. Microinjection of vPhox2 into the LC of adult rats significantly increased Phox2 mRNA levels in the LC region. Over-expression of either Phox2a or Phox2b in the LC was paralleled by significant increases in mRNA and protein levels of DBH and NET in the LC. Similar increases in DBH and NET protein levels were observed in the hippocampus following vPhox2 microinjection. In the frontal cortex, only NET protein levels were significantly increased by vPhox2 microinjection. Over-expression of Phox2 genes resulted in a significant increase in BrdU-positive cells in the hippocampal dentate gyrus. The present study demonstrates an upregulatory effect of Phox2a and Phox2b on the expression of DBH and NET in noradrenergic neurons of rat brains, an effect not previously shown in adult animals. Phox2 genes may play an important role in maintaining the function of the noradrenergic neurons after birth, and regulation of Phox2 gene expression may have therapeutic utility in aging or disorders involving degeneration of noradrenergic neurons.

Altered Expression of Phox2 Transcription Factors in the Locus Coeruleus in Major Depressive Disorder Mimicked by Chronic Stress and Corticosterone Treatment In Vivo and In Vitro

“…Such divergent expression of Phox2a and Phox2b may indicate differences in their functions, and leads to the notion that expression of Phox2b is not necessary for the maintenance of the noradrenergic phenotype in the adult brainstem (Card et al 2010). However, our previous study (Fan et al 2011) and the current work showed that Phox2b is expressed in the LC of adult Fischer 344 rats. More importantly, gene expression and proteins of Phox2a and Phox2b are found in the LC of humans at ages ranging from 18–77 years (Table 1).…”

“…Protein levels of Phox2a and Phox2b from rat LC and cultured cells were determined by western blotting as reported previously (Fan et al 2011). Briefly, these samples were prepared by homogenization, centrifugation and measurement of protein concentrations.…”

Effects of chronic social defeat on expression of dopamine β‐hydroxylase in rat brains

“…For the immunofluorescence staining experiments, the immunofluorescence staining method is similar to that described previously (Fan et al, ). Briefly, brain sections were pre‐incubated in 5% bovine serum albumin in phosphate‐buffered saline supplemented with 0.2% Triton‐X 100 for 1 h at room temperature, followed by incubation with the primary polyclonal antibody against DBH raised from rabbit (1:500; Protos Biotech Corp, New York, NY) overnight at 4°C.…”

Desogestrel down-regulates PHOX2B and its target genes in progesterone responsive neuroblastoma cells

“…Phox2b gene expression persists in various structures in adult rats and human [21,40], and various findings indicate that it plays a role in maintaining the function of noradrenergic neurons in the adult [41]. Recent studies have also shown residual cardiorespiratory responses in prevalently younger CCHS patients, thus suggesting age-dependent mechanisms such as the developmental reconfiguration of respiratory circuits or the continuing loss of vulnerable cell populations within them due to the expression of an altered PHOX2B transcription factor [42].…”