Neuropeptides, growth factors, and cytokines: a cohort of informational molecules whose expression is up-regulated by the stress-associated slow transmitter PACAP in chromaffin cells

Abstract

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a co-transmitter with acetylcholine at the adrenomedullary synapse, mediating sustained hormone secretion and regulation of cellular plasticity in response to stress at the level of gene transcription. Here we have extended our investigation of PACAP-regulated neuroendocrine cell-specific genes from PC12 cells to PC12 cells expressing physiological levels of the PAC1hop receptor found on chromaffin cells in vivo. PACAP induces in these PC12_bPAC1hop cells an additional cohort of genes, compared to PC12 cells, enriched in informational molecules including cytokines, neuropeptides, and growth factors. Using two newly developed microarray platforms for expressed bovine transcripts, we further examined PACAP-induced genes in bovine chromaffin cells during a period of exposure (6 h) corresponding to a period of prolonged metabolic or psychogenic stress in vivo during which PACAP is released from the splanchnic nerve onto chromaffin cells. As in PC12_bPAC1hop cells, PACAP induced in bovine chromaffin cells a cohort of genes encoding secretory proteins, identified by tiling for cellular localization using Ingenuity Pathway Analysis, which were highly enriched in informational molecules (secreted proteins acting at extracellular receptors). These included cytokines, growth factors and hormones, as well as converting enzymes, or protease inhibitors modulating converting enzyme function. Several neuropeptide prohormone transcripts not previously shown to be PACAP-regulated in chromaffin cells, such as thyrotropin-releasing hormone, and tachykinin precursor 1, were identified. Identification of this cohort of informational molecule-encoding transcripts suggests a wider, more integrative role for PACAP as a co-transmitter specific to stress transduction in the adrenal medulla.

Fig. 1

Effect of inhibiting MEK or PKA on PACAP induction of neuropeptide gene expression. Chromaffin cells were incubated for 6 h in control conditions or with 100 nM PACAP, in the absence or presence of 10 μM U0126 or 10 μM H89 (a, b) as described in “Materials and Methods”. TAC1 (a) and VIP (b) mRNA levels, determined by Q-RT-PCR, are expressed as fold increase over corresponding control values and represent means ± SEM of three or four determinations for each condition from one experiment representative of three different experiments. ** P < 0.05; *** P < 0.001 versus the corresponding control (one-way ANOVA test, Bonferroni posttest). NS not significant