The energy sensor AMP-activated protein kinase directly regulates the mammalian FOXO3 transcription factor.

The maintenance of homeostasis throughout an organism's life span requires constant adaptation to changes in energy levels. The AMP-activated protein kinase (AMPK) plays a critical role in the cellular responses to low energy levels by switching off energy-consuming pathways and switching on energy-producing pathways. However, the transcriptional mechanisms by which AMPK acts to adjust cellular energy levels are not entirely characterized. Here, we find that AMPK directly regulates mammalian FOXO3, a member of the FOXO family of Forkhead transcription factors known to promote resistance to oxidative stress, tumor suppression, and longevity. We show that AMPK phosphorylates human FOXO3 at six previously unidentified regulatory sites. Phosphorylation by AMPK leads to the activation of FOXO3 transcriptional activity without affecting FOXO3 subcellular localization. Using a genome-wide microarray analysis, we identify a set of target genes that are regulated by FOXO3 when phosphorylated at these six regulatory sites in mammalian cells. The regulation of FOXO3 by AMPK may play a crucial role in fine tuning gene expression programs that control energy balance and stress resistance in cells throughout life.

Alteration of skin temperature during low-level laser irradiation at 830 nm in a mouse model.

OBJECTIVE: This study investigated the change in local skin temperature in black and white mice during irradiation at 830 nm. BACKGROUND DATA: The photostimulation effect low-level laser therapy (LLLT) (700-900 nm) is widely accepted and used. However, the exact biological mechanisms of biostimulation are not yet established. MATERIALS AND METHODS: Groups of C57BL/6J and BALB/cJ mice (n = 12 in each group) were lightly anesthetized with 50% carbon dioxide and 50% oxygen. The dorsum was shaved and a 1.0 x 0.5 cm spot was marked in the same location on each subject. Animals were photo-irradiated with a diode laser (CW, 830 nm, 36 mW output at 5 cm distance). Fluences of 0.0-5.0 J/cm(2) were delivered. Skin surface temperature was monitored by a thermal camera. Two thermocouples were placed 1 mm below the skin surface at the site of light exposure. RESULTS: Temperature increased with increasing fluences of exposure. The surface temperature change at 5.0 J/cm(2) was 6.25 x 10(-2) +/- 2.0 x 10(-3) vs. 1.2 x 10(-2) +/- 3.0 x 10(-3) degrees C/mW for black and white mice, respectively. The temperature change at 1.0 mm depth was 4.51 x 10(-2) +/- 3.0 x 10(-3) vs. 0.83 x 10(-2) +/- 1.0 x 10(-3), respectively. CONCLUSION: CW irradiation at 830 nm and 5.0 J/cm(2) fluence induces a small temperature increase at the surface and at 1 mm in depth. The smaller effects seen in white mice might be due in part to reflection. This suggests that the thermal effects of irradiation at 830 nm are unlikely to explain the LLLT effect. However skin color should be considered, particularly at higher fluences. Further investigations are warranted to correlate the melanin content of the skin with observed LLLT effects.

Temperature-controlled 830-nm low-level laser therapy of experimental pressure ulcers.

OBJECTIVE: This study was performed to evaluate the effectiveness of near-infrared low-level laser therapy (LLLT) treatment of pressure ulcers under temperature-controlled conditions. BACKGROUND DATA: Little information is available regarding the potential thermal effects of near-infrared photo-radiation during LLLT. METHODS: Pressure ulcers were created in C57BL mice by placing the dorsal skin between two round ceramic magnetic plates (12.0 x 5.0 mm, 2.4 g, 1 K Gauss) for three 12-h cycles. Animals were divided into three groups (n = 9) for daily light therapy (830 nm, CW, 5.0 J/cm(2)) on days 3-13 post ulceration in both groups A and B. A special heat-exchange device was applied in Group B to maintain a constant temperature at the skin surface (30 degrees C). Group C served as controls, with irradiation at 5.0 J/cm(2) using an incandescent light source. Temperature of the skin surface, and temperature alterations during treatment were monitored. The wound area was measured and the rate and time to complete healing were noted. RESULTS: The maximum temperature change during therapy was 2.0 +/- 0.64 degrees C in Group A, 0.2 +/- 0.2 degrees C in Group B and 3.54 degrees C +/- 0.72 in Group C. Complete wound closure occurred at 18 +/- 4 days in Groups A and B and 25 +/- 6 days in Group C (p

A preliminary study of laser tissue soldering as arterial wall reinforcement in an acute experimental aneurysm model.

BACKGROUND AND OBJECTIVES: Aneurysm formation results from destruction of structural arterial wall connective tissue, leading to wall weakening and rupture. The purpose of this study was to demonstrate that reinforcement of the arterial wall using laser tissue soldering contributes to arterial wall stabilization and rupture prevention in an acute experimental model. STUDY DESIGN/MATERIALS AND METHODS: Elastase (10 U/mg protein, Sigma-Aldrich Co., St. Louis, MO) was applied with a fine paint brush on femoral artery segments to cause fusiform aneurysm formation. After aneurysms formed (approximately 45 minutes after treatment), elastase was rinsed out and indocyanine green (ICG) and albumin soldering mixture (2.5 mg/ml ICG in 50% albumin) was delivered to the arterial segment, followed by laser irradiation at 830 nm, (15mW output for 20 minutes). In situ pressure burst measurements were then performed. RESULTS: In situ burst pressures were > 503 mmHg for normal arteries and 181 +/- 26.0 mmHg, for Elastase treated segments. (P < 0.0001) Treatment of experimental aneurysms laser tissue soldering returned burst strengths to > 503 mmHg. CONCLUSIONS: These results indicate laser tissue soldering reinforcement of weak arterial walls, is possible and may reduce the likelihood of acute rupture. Further development of this technique for aneurysm management is warranted.