Dietary antioxidants may attenuate oxidative damage from strenuous exercise in various tissues. Beneficial effects of the antioxidant astaxanthin have been demonstrated in vitro, but not yet in vivo. We investigated the effect of dietary supplementation with astaxanthin on oxidative damage induced by strenuous exercise in mouse gastrocnemius and heart. C57BL/6 mice (7 weeks old) were divided into groups: rested control, intense exercise, and exercise with astaxanthin supplementation. After 3 weeks of exercise acclimation, both exercise groups ran on a treadmill at 28 m/min until exhaustion. Exercise-increased 4-hydroxy-2-nonenal-modified protein and 8-hydroxy-2'-deoxyguanosine in gastrocnemius and heart were blunted in the astaxanthin group. Increases in plasma creatine kinase activity, and in myeloperoxidase activity in gastrocnemius and heart, also were lessened by astaxanthin. Astaxanthin showed accumulation in gastrocnemius and heart from the 3 week supplementation. Astaxanthin can attenuate exercise-induced damage in mouse skeletal muscle and heart, including an associated neutrophil infiltration that induces further damage.

The ADO/FKF/LKP/ZTL family of proteins of Arabidopsis thaliana Heynh. have a LOV domain, an F-box motif, and a kelch repeat region. LKP2 is a member of this family and functions either within or very close to the circadian oscillator in Arabidopsis. Promoter-GUS fusion studies revealed that the LKP2 gene was highly active in rosette leaves. In CaMV 35S:LKP2-GFP plants, GFP-associated fluorescence was detected in nuclei, suggesting that LKP2 is a nuclear protein. Yeast two-hybrid analysis demonstrated that LKP2 interacted with some Arabidopsis Skp1-like proteins (ASK), as do other ADO/FKF/LKP/ZTL family proteins, suggesting that LKP2 can form an SCF (Skp1-Cullin-F-box protein) complex that functions as a ubiquitin E3 ligase. LKP2 interacted not only with itself but also with other members of the family, LKP1 and FKF1. The two-hybrid analysis also demonstrated that LKP2 interacted with TOC1, a clock component, but not with CCA1 or LHY, negative regulators of TOC1 gene expression. The LOV domain of LKP2 was shown to be necessary and sufficient for the interaction with TOC1. An interaction between LKP2 and APRR5, a paralogue of TOC1, was also observed, but LKP2 did not interact with APRR3, APRR7, or APRR9, other paralogues of TOC1.

No abstract

The molecular signaling pathways linking the atrophy of skeletal muscle during aging have not been identified. Using reverse transcription (RT)-PCR, Western blotting, and immunofluorescence microscopy, we investigated whether the amounts of RhoA, RhoGDI, SRF, MRTF-A, and MyoD in the triceps brachii and quadriceps muscles change with aging in mice. Young adult (3 mo) and aged (24 mo) C57BL/6J mice were used. Senescent mice possessed many fibers with central nuclei in the quadriceps muscle. Western blotting using a homogenate of whole muscle or the cytosolic fraction clearly showed that the amount of SRF protein was significantly decreased in the aged skeletal muscles. Immunofluorescence labeling indicated more SRF-positive muscle fibers in young mice. Both young and old mice possessed SRF immunoreactivity in some satellite cells expressing Pax7. MRTF-A and STARS mRNA levels significantly declined with aging in the triceps brachii and quadriceps muscles. The amount of MRTF-A protein was markedly reduced in the nuclear fraction of aged muscle of mice. The amounts of RhoA and RhoGDI in the crude homogenate or the cytosolic and membrane fractions were greater in the aged muscle. Senescent mice possessed significantly higher levels of MyoD protein in the cytosol and nucleus. Decreased SRF and MRTF expression may induce the atrophy of skeletal muscle with aging.

No abstract

These catecholaminergic changes may be caused by chronic hypoxia or ischemia, and also may underlie alterations in respiratory and cardiovascular control in sleep.

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LOV KELCH PROTEIN2 (LKP2) is an F-box protein that has been postulated to function centrally, or near to the circadian clock oscillator. As a first step to determine which proteins act as substrates of LKP2, yeast two-hybrid screening was performed using LKP2 as bait, and two interaction factors, Di19 and COL1, were isolated. The transiently expressed Di19-GUS fusion protein was localized in the nucleus of Arabidopsis petiole cells. COL1 and other CO/COL family proteins could also interact with LKP1/ZTL, LKP2 or FKF1. The LKP2-binding site in CO or COL1 was near the center of each protein. The CCT motif in CO or COL1 was not sufficient for interaction with LKP2. LKP2 recognized CO with F-box and kelch repeat-containing regions, while it recognized COL1 with an LOV domain. When LKP2 was fused with cyan fluorescent proein (CFP) and transiently expressed in onion epidermal cells, CFP-LKP2 signals were localized in the nucleus and cytosol. Both yellow fluorescent protein (YFP)-CO and YFP-COL1 were located in the nucleus, forming nuclear bodies when they were transiently expressed. However, co-expression of CFP-LKP2 with YFP fused to either CO or COL1 resulted in the recruitment of CFP-LKP2 in nuclear bodies. Furthermore, the CFP-LKP2 and YFP-CO signals co-localized with signals for pU2B''-mRFP, which is a marker for Cajal bodies. These results suggest the possibility that LKP2 functions with CO/COL family proteins in the nuclear bodies.