Effects of cAMP-dependent protein kinase and ATP on N1-oxidation of 9-benzyladenine by animal hepatic microsomes

Inhibitory Effect of Lactococcus lactis subsp. lactis HFY14 on Diphenoxylate-Induced Constipation in Mice by Regulating the VIP-cAMP-PKA-AQP3 Signaling Pathway

Aim

The naturally fermented yak yogurt of pastoralists in the Tibetan Plateau, China, because of its unique geographical environment and the unique lifestyle of Tibetan pastoralists, is very different from other kinds of sour milk, and the microorganisms it contains are special. Lactococcus lactis subsp. lactis HFY14 (LLSL-HFY14) is a new lactic acid bacterium isolated from naturally fermented yak yogurt. The purpose of this study was to study the inhibitory effect of the bacterium on constipation.

Methods

Constipation was induced in ICR mice with diphenoxylate, and the constipated mice were treated with LLSL-HFY14. The weight and feces of the mice were visually detected. Colonic tissues were observed on hematoxylin and eosin-stained sections. Serum indices were detected with kits. mRNA expression in the colon was determined by quantitative polymerase chain reaction assay.

Results

Constipation caused weight loss, the number of defecation granules, defecation weight, fecal water content decreased, and the first black stool excretion time increased. LLSL-HFY14 alleviated these symptoms, and the effects were similar to those of lactulose (drug). The pathological examination revealed that constipation caused pathological changes in the colon, and LLSL-HFY14 effectively alleviated the disease. LLSL-HFY14 increased serum levels of motilin, gastrin, endothelin, substance P, acetylcholinesterase, and vasoactive intestinal peptide (VIP) and decreased serum levels of somatostatin in constipated mice. In addition, LLSL-HFY14 upregulated VIP, cAMP, protein kinase A, and aquaporin 3 expression in colonic tissues of constipated mice in a dose-dependent manner.

Conclusion

LLSL-HFY14 inhibited constipation, similar to lactulose, and has the potential to become a biological agent.

Influence of Kupffer cells on hepatic signal transduction as demonstrated by second messengers and nuclear transcription factors

AIM: To understand the influence of Kupffer cell (KC) on signal transduction pathways in the liver.

METHODS: To decrease selectively the number and function of KC, Kunming mice were ip injected with a single dose of gadolinium chloride (GdCl₃, 20 mg•kg^-1), the time-effect relationship assessment was performed after 1 d, 3 d and 6 d. sALT, sGST, liver glycogen content, phagocytic index, and expression of CD68 were assessed as the indexes of hepatotoxicity and functions of KC respectively, and morphology of KC was observed with transmission electron microscopy. Furthermore, cAMP, PGE₂ level, nitric oxide (NO) content, and mRNA expression of NFkappaBp65, Erk1, STAT1 were examined.

RESULTS: GdCl₃ could selectively cause apoptosis of KC and obvious reduction of KC’s activity, but no hepatotoxicity was observed. One day after KC blockade, NO, PGE₂, cAMP contents in the liver were reduced 21.0%, 6.94-fold, 8.3%, respectively, and mRNA expression of NFkappaBp65 was decreased 3.0-fold. The change tendency of NO, PGE₂, and cAMP contents and mRNA expression of NFkappaBp65 were concomitant with recovery of the functions of KC. The contents of NO, PEG2, cAMP were increased when the functions of KC was recovered. However, all of the changes could not return to the normal level except NO content after 6 d Gdcl₃ treatment. No obvious changes were found in STAT1 and Erk1 mRNA expression in the present study.

CONCLUSION: Hepatic NO, PGE2, cAMP level and mRNA expression of NFkappaBp65 are closely related with the status of KC. It suggests that KC may play an important role in the cell to cell signal transduction in the liver.