Feline Uroepithelial Cell Culture as a Novel Model of Idiopathic Cystitis: Investigations on the Effects of Norepinephrine on Inflammatory Response, Oxidative Stress, and Barrier Function

SIMPLE SUMMARY: Feline idiopathic cystitis is a common disease in domestic cats. The pathogenesis of the illness is not completely understood, but the role of various stress factors and the concomitant release of stress hormones, such as norepinephrine, is strongly suggested. Therefore, the examination of this hormone is essential to gain a deeper knowledge of the development of the disease. In the present study, a novel cell culture of uroepithelial cells from a feline urinary bladder was established to serve as a proper model for studying the effects of a norepinephrine triggered stress reaction. Acute, 1 h norepinephrine exposure affected uroepithelial cells by increasing metabolic activity, inducing a proinflammatory response, triggering oxidative stress, and decreasing the barrier integrity of the cultured cells. The results of this study underline that stress-associated norepinephrine release has a direct molecular effect on the uroepithelial cells; the reaction of these cells may play an important mediatory role in the pathogenesis of the disease. The established cell culture model can be a good tool for further in vitro investigations related to urinary disorders of cats. ABSTRACT: Feline idiopathic cystitis (FIC) is one of the most common urinary tract disorders in domestic cats. As stress is suggested to play a key role in the pathogenesis of FIC, the effects of norepinephrine (NE) as a stress mediator were investigated on a novel feline primary uroepithelial cell culture, serving as an in vitro model of the disease. The uroepithelial cells gained from the mucosa of the bladder of a euthanized cat were cultured for 6 days and were acutely exposed to NE (10, 100, and 1000 µM) for 1 h. NE increased the metabolic activity of the cultured cells and elevated the extracellular concentrations of the pro-inflammatory mediators interleukin-6 (IL-6) and stromal cell derived factor 1 (SDF-1), confirming that NE can trigger an inflammatory response in the uroepithelium. Cellular protein carbonyl levels were increased by NE exposure, while malondialdehyde and glucose regulated protein 78 concentrations remained unchanged, indicating that NE may provoke the oxidative damage of proteins without inducing lipid peroxidation or endoplasmic reticulum stress. Further, it can be strongly suggested that an acute NE challenge might diminish the barrier function of uroepithelial cells, as reflected by the decreased glycosaminoglycan concentration, claudin-4 protein expression, and reduced TER values of the NE-treated cell cultures. Based on these results, short-term NE exposure mimicking acute stress can provoke an inflammatory response and decrease the barrier integrity of cultured feline uroepithelial cells. Hence, it is highly expected that stress-associated NE release may play an important mediatory role in the pathogenesis of FIC.