The effect of 5-aminoimidazole-4-carboxamide-ribonucleoside was mediated by p38 mitogen activated protein kinase signaling pathway in FRO thyroid cancer cells

BACKGROUND/AIMS: 5'-Adenosine monophosphate (AMP)-activated protein kinase (AMPK) is a cellular energy sensor that monitors intracellular AMP/adenosine triphosphate (ATP) ratios and is a key regulator of the proliferation and survival of diverse malignant cell types. In the present study, we investigated the effect of activating AMPK by 5-aminoimidazole-4-carboxamide-ribonucleotide (AICAR) in thyroid cancer cells. METHODS: We used FRO thyroid cancer cells harboring the BRAF(V600E) mutation to examine the effect of AICAR on cell proliferation and cell survival. We also evaluated the involvement of mitogen-activated protein kinase (MAPK) pathways in this effect. RESULTS: We found that AICAR treatment promoted AMPK activation and suppressed cell proliferation and survival by inducing p21 accumulation and activating caspase-3. AICAR significantly induced activation of p38 MAPK, and pretreatment with SB203580, a specific inhibitor of the p38 MAPK pathway, partially but significantly rescued cell survival. Furthermore, small interfering RNA targeting AMPK-alpha1 abolished AICAR-induced activation of p38 MAPK, p21 accumulation, and activation of caspase-3. CONCLUSIONS: Our findings demonstrate that AMPK activation using AICAR inhibited cell proliferation and survival by activating p38 MAPK and proapoptotic molecules in FRO thyroid cancer cells. These results suggest that the AMPK and p38 MAPK signaling pathways may be useful therapeutic targets to treat thyroid cancer.

Activation of AMP-activated protein kinase stimulates the nuclear localization of glyceraldehyde 3-phosphate dehydrogenase in human diploid fibroblasts

In addition to its well-known glycolytic activity, GAPDH displays multiple functions, such as nuclear RNA export, DNA replication and repair, and apoptotic cell death. This functional diversity depends on its intracellular localization. In this study, we explored the signal transduction pathways involved in the nuclear translocation of GAPDH using confocal laser scanning microscopy of immunostained human diploid fibroblasts (HDFs). GAPDH was present mainly in the cytoplasm when cultured with 10% FBS. Serum depletion by culturing cells in a serum-free medium (SFM) led to a gradual accumulation of GAPDH in the nucleus, and this nuclear accumulation was reversed by the re-addition of serum or growth factors, such as PDGF and lysophosphatidic acid. The nuclear export induced by the re-addition of serum or growth factors was prevented by LY 294002 and SH-5, inhibitors of phosphoinositide 3-kinase (PI3K) and Akt/protein kinase B, respectively, suggesting an involvement of the PI3K signaling pathway in the nuclear export of GAPDH. In addition, 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR), an activator of AMP-activated protein kinase (AMPK), stimulated the nuclear translocation of GAPDH and prevented serum- and growth factor-induced GAPDH export. AMPK inhibition by compound C or AMPK depletion by siRNA treatment partially prevented SFM- and AICAR-induced nuclear translocation of GAPDH. Our data suggest that the nuclear translocation of GAPDH might be regulated by the PI3K signaling pathway acting mainly as a nuclear export signal and the AMPK signaling pathway acting as a nuclear import signal.

The Preconditioning with AICAR Protects Against Subsequent Renal Ischemia Reperfusion Injury / 대한신장학회지

PURPOSE:Preconditioning due to activation of AMPK might reduce ischemia-reperfusion (I/R) injury in the kidney, based on the key role of AMPK in preserving ATP. To evaluate this possibility, the effect of preconditioning with 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR), AMPK activator, before sustained ischemia was investigated. METHODS:Adult male Sprague-Dawley rats weighing approximately 220-250 g were used. To induce renal ischemia, a laparotomy was performed under ketamine and xylazine hydrochloride, and the blood supply to both kidneys was interrupted by placement of vessel clamps at the level of the renal pedicles. Reflow was initiated by removing the clamps. The following experimental groups were defined 1. Acute renal ischemia 0 sec, 10 min, 15 min, 2. AICAR treatment, 3. Sham group (S), 4. Ischemia/ Reperfusion group (I/R), 5. AICAR+I/R group (A+I/R), 6. AraA (Adenine-9-b-D-arabinofuranoside, an AMPK) inhibitor+AICAR+I/R group (AraA+A+I/R) RESULTS:There was only faint AMPK phosphorylation in the sham group. After 10 minutes of ischemia, or AICAR preconditioning however, Thr172 phosphorylation of AMPK was increased (p<0.05). The serum levels of BUN and creatinine were significantly decreased in AICAR preconditioning group (A+I/R). (128.0+/-7.33 mg/dL, 4.18+/-0.27 mg/dL vs. 90.2+/-11.13 mg/dL, 2.58+/-0.7 mg/dL, p<0.05), but these effects were attenuated by AMPK inhibitor, AraA (AraA+A+I/R group). In quantitative analysis of tubular injury, tubular injury score in AICAR preconditioning group significantly decreased (p<0.05). CONCLUSION:The AMPK activator AICAR has a protective effect against renal I/R injury.