Corallodiscus flabellata B.L. Burtt Extracts Stimulate Diuretic Activity and Regulate the Renal Expression of Aquaporins

Abstract

Corallodiscus flabellata B. L. Burtt is a traditional Chinese medicine. Previous studies in our laboratory showed that C. flabellata alleviated symptoms of Alzheimer's disease (AD) in a rat model of AD and increased healthy rats' urine volume. The aims of this study were to explore the diuretic activity of different extracts from C. flabellata and to identify the underlying mechanisms of action. Different doses of a C. flabellata extract (CF-L, CF-M, and CF-H) were administered orally to male KM mice in a single dose. In another procedure, C. flabellata (CF), water extract, and 20%, 30%, and 40% ethanol extracts of C. flabellata (CF-WE, CF-20, CF-30, and CF-40) were administered orally daily for 5 days. The urinary excretion rate, osmolality, and electrolyte levels in urine and serum, renal expression of aquaporins (AQPs), apoptosis-related protein, and MAPK-related protein were analyzed. The results showed that single doses of CF-M and CF-H increased urinary volume significantly, as well as daily administration of CF, CF-WE, CF-20, CF-30, and CF-40. Furthermore, CF-20 and CF-30 increased the concentration of Na⁺ in the urine. Treatment with CF-40 increased the urine osmolality and Na⁺ and Cl^- concentrations and decreased the concentration of Na⁺ in the serum. Also, CF, CF-WE, CF-20, CF-30, and CF-40 decreased the renal expression of AQPs, as well as the ratios of Bcl-2/Bax, p-ERK/ERK, p-JNK/JNK, and p-p38/p38. In sum, the medium and high doses of the C. flabellata extract and CF-WE, CF-20, CF-30, and CF-40 were found to have a diuretic activity. They may inhibit the renal expression of AQPs and apoptosis-related proteins by inhibiting the MAPK signaling pathway, thereby achieving diuretic effects.

Figure 1

The distribution of AQPs in the kidney as shown by immunofluorescence staining (40x). First column: AQP1 (green). Second column: AQP2 (green). Third column: AQP3 (green). Fourth column: AQP4 (green). Red arrowheads show the protein distribution (n = 3 per group).

Figure 2

The expression of AQPs in the kidney as shown by Western blotting. Thirty minutes before drug administration, all mice were administered 0.2 mL/10 g body weight (BW) of isotonic saline to impose uniform water and salt load by oral gavage. Values are expressed as mean ± SD of three mice in each group. ^∗P < 0.05 and ^∗∗P < 0.01 compared to controls using Dunnett's t-test.

Figure 3

The expression of apoptosis-related proteins in the kidney tested by the Western-blot method. Thirty minutes before drug administration, all mice were administered 0.2 mL/10 g body weight (BW) of isotonic saline to impose uniform water and salt load by oral gavage. Values are expressed as mean ± SD of three mice in each group. ^∗P < 0.05 and ^∗∗P < 0.01 compared to controls using Dunnett's t-test.

Figure 4

The expression of MAPK signaling pathway-related proteins in the kidney tested by the Western-blot method. Thirty minutes before drug administration, all mice were administered 0.2 mL/10 g body weight (BW) of isotonic saline to impose uniform water and salt load by oral gavage. Values are expressed as mean ± SD of three mice in each group. ^∗P < 0.05 and ^∗∗P < 0.01 compared to controls using Dunnett's t-test.