Formaldehyde-induced changes in microRNA signaling [Agilent]. Rattus norvegicus

MicroRNAs (miRNAs) are critical regulators of gene expression, yet much remains unknown regarding miRNA changes resulting from environmental exposures and whether they influence pathway signaling across various tissues and time. To gain knowledge on these novel topics, we set out to investigate in vivo miRNA responses to inhaled formaldehyde, an important air pollutant known to disrupt miRNA expression profiles. Rats were exposed by inhalation to either 0 or 2 ppm formaldehyde (6 hours/day) for 7 days, 28 days, or 28 days followed by a 7 day recovery. Genome-wide miRNA expression profiles and associated signaling pathways were assessed within the nasal respiratory mucosa, circulating mononuclear white blood cells (WBC), and bone marrow (BM). Overall design: Male Fischer rats received nose-only inhalation exposures of 2 ppm formaldehyde. Three exposure durations were investigated: (1) 2 ppm formaldehyde exposure, 6 hours/day, for 7 days (7-day group), (2) 2 ppm formaldehyde exposure, 6 hours/day, for 28 days (28-day group), and (3) 2 ppm formaldehyde exposure, 6 hours/day, for 28 days, with a 7 day recovery period following the last exposure (28-day plus recovery group). Control (unexposed) rats were placed in nose-only exposure tubes containing room air for the same duration. After the last exposure period (or the last recovery period for the 28-day plus recovery group), animals were euthanized. RNA were assessed from sampes collected from the nasal epithelium, circulating white blood cells, and bone marrow cells. Genome-wide miRNA expression profiles were evaluated using microarrays.