Hydropenia may accelerates the progression of orthotopic bladder cancer induced by N-methyl-N-nitrosourea by increasing the expression levels of AQP1, AQP3, and AQP4

BACKGROUND: Increasing evidence has demonstrated aquaporins (AQPs) to be critical players in carcinogenesis. Here, we aimed to explore the role of hydropenia in the progression of bladder cancer (BCa), as well as to assess the expression of AQP1, AQP3, and AQP4 in bladder tissues from hydropenic and N-methyl-N-nitrosourea (MNU)-treated rats. METHODS: An orthotopic BCa model was induced by administering Sprague Dawley rats with MNU. A hydropenic rat model was established by administrating rats with 2/3 of the amount of water given to the control group. At week 8, the rats were sacrificed and their bladder tissues were collected. Then, pathological alterations in the rat bladders were assessed by hematoxylin and eosin staining. The RNA and protein expression levels of AQP1, AQP3, and AQP4 were determined by using qRT-PCR and western blot assays. RESULTS: All of the rats (100%) administrated with MNU developed tumors, of which 5 were large (diameter, 0.5–1.0 cm), 10 were medium (diameter, 0.2–0.5 cm), and 5 were small (diameter, <0.2 cm) in size. The tumors were nodular and cauliflower shaped, with multiple satellite focus, and were accompanied by bleeding, ulcers, stones, and residual urine. Hematoxylin and eosin staining revealed that the bladder mucosa was incomplete, with a large amount of necrotic tissue and obvious leukocytic infiltration. The tumor volume in the MNU + hydropenia group was significantly larger than that in the MNU group. Noticeably, hydropenia exacerbated pathological changes induced by MNU administration. QRT-PCR and western blot analysis revealed that the MNU group, hydropenia group, and MNU + hydropenia group had significantly increased levels of AQP1, AQP3, and AQP4 compared to the control group, with the most dramatic increase seen in the MNU + hydropenia group. CONCLUSIONS: Hydropenia exacerbates pathological alterations induced by MNU in rats with orthotopic BCa by increasing the expression levels of AQP1, AQP3, and AQP4. This study reveals a possible mechanism of the occurrence of BCa.