共查询到20条相似文献,搜索用时 31 毫秒
1.
Isenberg JS Ridnour LA Dimitry J Frazier WA Wink DA Roberts DD 《The Journal of biological chemistry》2006,281(36):26069-26080
CD36 is necessary for inhibition of some angiogenic responses by the matricellular glycoprotein thrombospondin-1 and is therefore assumed to be the receptor that mediates its anti-angiogenic activities. Although ligation of CD36 by antibodies, recombinant type 1 repeats of thrombospondin-1, or CD36-binding peptides was sufficient to inhibit nitric oxide (NO)-stimulated responses in both endothelial and vascular smooth muscle cells, picomolar concentrations of native thrombospondin-1 similarly inhibited NO signaling in vascular cells from wild-type and CD36-null mice. Ligation of the thrombospondin-1 receptor CD47 by recombinant C-terminal regions of thrombospondin-1, thrombospondin-1 peptides, or CD47 antibodies was also sufficient to inhibit NO-stimulated phenotypic responses and cGMP signaling in vascular cells. Thrombospondin-1 did not inhibit NO signaling in CD47-null vascular cells or NO-stimulated vascular outgrowth from CD47-null muscle explants in three-dimensional cultures. Furthermore, the CD36-binding domain of thrombospondin-1 and anti-angiogenic peptides derived from this domain failed to inhibit NO signaling in CD47-null cells. Therefore, ligation of either CD36 or CD47 is sufficient to inhibit NO-stimulated vascular cell responses and cGMP signaling, but only CD47 is necessary for this activity of thrombospondin-1 at physiological concentrations. 相似文献
2.
Ploquin C Chabi B Fouret G Vernus B Feillet-Coudray C Coudray C Bonnieu A Ramonatxo C 《American journal of physiology. Endocrinology and metabolism》2012,302(8):E1000-E1008
Loss of myostatin (mstn) function leads to a decrease in mitochondrial content, a reduced expression of cytochrome c oxidase, and a lower citrate synthase activity in skeletal muscle. These data suggest functional or ultrastructural mitochondrial abnormalities that can impact on muscle endurance characteristics in such phenotype. To address this issue, we investigated subsarcolemmal and intermyofibrillar (IMF) mitochondrial activities, skeletal muscle redox homeostasis, and muscle fiber endurance quality in mstn-deficient mice [mstn knockout (KO)]. We report that lack of mstn induced a decrease in the coupling of IMF mitochondria respiration, with significantly higher basal oxygen consumption. No lysis of mitochondrial cristae or excessive swelling were observed in mstn KO mice compared with wild-type (WT) mice. Concerning redox status, mstn KO gastrocnemius exhibited a significant decrease in lipid peroxidation levels (-56%; P < 0.01 vs. WT) together with a significant upregulation of the antioxidant glutathione system. In contrast, superoxide dismutase and catalase activities were altered in mstn KO, gastrocnemius and soleus with a reduction of up to 80% compared with WT animals. The force production observed after contractile endurance test was significantly lower in extensor digitorum longus and soleus muscles of mstn KO mice compared with the controls (17 ± 3 and 36 ± 5% vs. 28 ± 4 and 56 ± 5%, respectively, P < 0.05). Together, these findings indicate that, besides an increased skeletal muscle mass, genetic mstn inhibition has differential effects on redox homeostasis and mitochondrial function that would have functional consequences on muscle response to endurance exercise. 相似文献
3.
Jeff S. Isenberg Yan Qin Justin B. Maxhimer John M. Sipes Daryl Despres Jurgen Schnermann William A. Frazier David D. Roberts 《Matrix biology》2009,28(2):110-119
Nitric oxide (NO) locally regulates vascular resistance and blood pressure by modulating blood vessel tone. Thrombospondin-1 signaling via its receptor CD47 locally limits the ability of NO to relax vascular smooth muscle cells and increase regional blood flow in ischemic tissues. To determine whether thrombospondin-1 plays a broader role in central cardiovascular physiology, we examined vasoactive stress responses in mice lacking thrombospondin-1 or CD47. Mice lacking thrombospondin-1 exhibit activity-associated increases in heart rate, central diastolic and mean arterial blood pressure and a constant decrease in pulse pressure. CD47-deficient mice have normal central pulse pressure but elevated resting peripheral blood pressure. Both null mice show exaggerated decreases in peripheral blood pressure and increased cardiac output and ejection fraction in response to NO. Autonomic blockade also induces exaggerated hypotensive responses in awake thrombospondin-1 null and CD47 null mice. Both null mice exhibit a greater hypotensive response to isoflurane, and autonomic blockage under isoflurane anesthesia leads to premature death of thrombospondin-1 null mice. Conversely, the hypertensive response to epinephrine is attenuated in thrombospondin-1 null mice. Thus, the matricellular protein thrombospondin-1 and its receptor CD47 serve as acute physiological regulators of blood pressure and exert a vasopressor activity to maintain global hemodynamics under stress. 相似文献
4.
Jeff S. Isenberg Douglas S. Annis Michael L. Pendrak Malgorzata Ptaszynska William A. Frazier Deane F. Mosher David D. Roberts 《The Journal of biological chemistry》2009,284(2):1116-1125
Thrombospondin-1 regulates nitric oxide (NO) signaling in vascular cells
via CD47. Because CD47 binding motifs are conserved in the C-terminal
signature domains of all five thrombospondins and indirect evidence has
implied CD47 interactions with other family members, we compared activities of
recombinant signature domains of thrombospondin-1, -2, and -4 to interact with
CD47 and modulate cGMP signaling. Signature domains of thrombospondin-2 and -4
were less active than that of thrombospondin-1 for inhibiting binding of
radiolabeled signature domain of thrombospondin-1 or SIRPα
(signal-regulatory protein) to cells expressing CD47. Consistent with this
binding selectivity, the signature domain of thrombospondin-1 was more potent
than those of thrombospondin-2 or -4 for inhibiting NO-stimulated cGMP
synthesis in vascular smooth muscle cells and downstream effects on cell
adhesion. In contrast to thrombospondin-1- and CD47-null cells, primary
vascular cells from thrombospondin-2-null mice lack enhanced basal and
NO-stimulated cGMP signaling. Effects of endogenous thrombospondin-2 on
NO/cGMP signaling could be detected only in thrombospondin-1-null cells.
Furthermore, tissue survival of ischemic injury and acute recovery of blood
flow in thrombospondin-2-nulls resembles that of wild type mice. Therefore,
thrombospondin-1 is the dominant regulator of NO/cGMP signaling via CD47, and
its limiting role in acute ischemic injury responses is not shared by
thrombospondin-2.Nitric oxide (NO) is a major mediator of intracellular and paracellular
signal transduction. NO preserves vascular health by minimizing the adhesion
of inflammatory cells to the vessel wall, limiting platelet activation, and
increasing blood vessel diameter and blood flow by relaxing vascular smooth
muscle cells (VSMC).3
These actions of NO are mediated by activating soluble isoforms of guanylate
cyclase (sGC) to increase cGMP levels, resulting in downstream activation of
cGMP-dependent protein kinases and ion channels
(1).Physiological NO/cGMP signaling is limited by several phosphodiesterases
that degrade cGMP and by thrombospondin-1 (TSP). TSP1 is a secreted protein
that is produced by vascular and inflammatory cells that regulates cellular
behavior by engaging several cell surface receptors. Recently we reported that
TSP1 potently blocks NO-stimulated prosurvival responses in endothelial and
VSMC (2,
3). TSP1 also plays a role in
promoting platelet thrombus formation and hemostasis by antagonizing the
antithrombotic activity of NO
(4). In all of these vascular
cells, picomolar concentrations of TSP1 are sufficient to block NO-stimulated
fluxes in cGMP by engaging its receptor CD47
(5). Nanomolar concentrations
of TSP1 further inhibit the same signaling pathway by inhibiting CD36-mediated
uptake of myristate into vascular cells
(6). In vivo, mice
lacking TSP1 demonstrate elevated basal tissue cGMP levels and greater
increases in regional blood flow in response to a NO challenge than wild type
controls (4). After an ischemic
insult, the absence of TSP1 or CD47 in transgenic mice is associated with
better maintenance of tissue perfusion and enhanced tissue survival.
Similarly, targeting TSP1 or CD47 using function blocking antibodies enhances
ischemic tissue perfusion and survival in wild type mice and pigs
(7,
8).TSP1 belongs to a family of five secreted glycoproteins that share an
evolutionarily conserved C-terminal signature domain
(9). TSP1 and TSP2 form a
distinct subfamily of trimeric proteins that exhibit similar anti-angiogenic
activities for endothelial cells in vitro and activities in
vivo to block tumor growth. Despite their similarities in structure, TSP1
and TSP2 have markedly different expression patterns after tissue injury, with
TSP1 being immediately expressed and maximal at day 3, whereas TSP2 was not
expressed until day 7 and was maximal 10 days after injury
(10). In addition, large
amounts of TSP1 but not TSP2 are stored in platelet α-granules and
released into the wound environment. Polymorphisms in TSP1 and TSP2 have been
linked to altered risk of premature myocardial infarction
(11,
12). A 3′-untranslated
region polymorphism in TSP2 is also associated with type 2 diabetes in men
(13). The molecular basis for
these associations is unclear.Less is known about the roles of the pentameric TSP3–5 in vascular
cells. TSP3 and TSP5 (also known as cartilage oligomeric matrix protein)
appear to serve their primary functions in bone development
(14,
15). However, a polymorphism
in TSP4 is associated with premature myocardial infarcts in certain
populations (11,
16,
17). A proatherogenic activity
for the A387P variant of TSP4 was proposed based on its differential ability
to modulate proliferation of endothelial and VSMC
(18). Cardiovascular functions
of TSP4 may also be linked to the high expression of TSP4 in heart
(19) and its altered
expression in that tissue during hypertensive heart failure
(20).The C-terminal domain of TSP1 is sufficient to mediate CD47-dependent
inhibition of cGMP signaling
(5). Of the two CD47 binding
VVM motifs identified in this domain of TSP1, the first is conserved among all
five TSPs, suggesting that CD47 binding could be a universal attribute of this
family (21). Based on
structural evidence that the VVM motifs may not be accessible
(22,
23), however, conservation of
VVM motifs may not be sufficient to predict CD47 binding. Uncertainty
regarding the location of the CD47 binding site in the G domain of TSP1
therefore limits interpretation of the known sequence homology to predict CD47
binding to other TSP family members.Although CD47 recognition of other TSPs has not been demonstrated
experimentally, a local deficiency of inflammation-associated T cell apoptosis
shared by TSP1-, CD47-, and TSP2-null mice is consistent with this hypothesis
(24). Furthermore, a
21-residue peptide from the C-terminal domain of TSP4 was found to decrease
human umbilical vein endothelial cell proliferation similar to the CD47
binding peptides from TSP1, although it lacks the VVM motif and no interaction
with CD47 was demonstrated
(25).To directly address whether other TSP family members can inhibit NO
responses and signaling in vascular cells, we now compare binding of
recombinant signature domains of TSP1, TSP2, and TSP4 to cell surface CD47 and
inhibition of NO-stimulated cell responses and cGMP signaling by these
domains. We also compared acute tissue blood flow and perfusion responses to
ischemic challenge in TSP1 and TSP2-null mice and cGMP responses in primary
cultures of vascular cells isolated from these mice. These studies clearly
demonstrate that CD47 selectively interacts with TSP1 and that the signature
domains of TSP2 and TSP4 are less potent inhibitors of NO signaling in
vascular cells in vitro. Furthermore, we show that the role of TSP1
to acutely limit recovery from ischemic injury in vivo is not shared
by TSP2. 相似文献
5.
6.
Adaptations of the kinetic properties of mitochondria in striated muscle lacking cytosolic (M) and/or mitochondrial (Mi) creatine kinase (CK) isoforms in comparison to wild-type (WT) were investigated in vitro. Intact mitochondria were isolated from heart and gastrocnemius muscle of WT and single- and double CK-knock-out mice strains (cytosolic (M-CK-/-), mitochondrial (Mi-CK-/-) and double knock-out (MiM-CK-/-), respectively). Maximal ADP-stimulated oxygen consumption flux (State3 Vmax; nmol O2 x mg mitochondrial protein(-1) x min(-1)) and ADP affinity (K50ADP; microM) were determined by respirometry. State 3 Vmax and of M-CK-/- and MiM-CK-/- gastrocnemius mitochondria were twofold higher than those of WT, but were unchanged for Mi-CK-/-. For mutant cardiac mitochondria, only the of mitochondria isolated from the MiM-CK-/- phenotype was different (i.e. twofold higher) than that of WT. The implications of these adaptations for striated muscle function were explored by constructing force-flow relations of skeletal muscle respiration. It was found that the identified shift in affinity towards higher ADP concentrations in MiM-CK-/- muscle genotypes may contribute to linear mitochondrial control of the reduced cytosolic ATP free energy potentials in these phenotypes. 相似文献
7.
8.
Momken I Lechêne P Ventura-Clapier R Veksler V 《American journal of physiology. Heart and circulatory physiology》2004,287(2):H914-H920
One of the main factors that control vasoreactivity and angiogenesis is nitric oxide produced by endothelial nitric oxide synthase (eNOS). We recently showed that knocking out eNOS induces an important reduction of mitochondrial oxidative capacity in slow-twitch skeletal muscle. Here we investigated eNOS's role in physical activity and contribution to adaptation of muscle energy metabolism to exercise conditions. Physical capacity of mice null for the eNOS isoform (eNOS-/-) was estimated for 8 wk with a voluntary wheel-running protocol. In parallel, we studied energy metabolism enzyme profiles and their response to voluntary exercise in cardiac and slow-twitch soleus (Sol) and fast-twitch gastrocnemius (Gast) skeletal muscles. Weekly averaged running distance was two times lower for eNOS-/- (4.09 +/- 0.42 km/day) than for wild-type (WT; 7.74 +/- 0.42 km/day; P < 0.01) mice. Average maximal speed of running was also lower in eNOS-/- (17.2 +/- 1.4 m/min) than WT (21.2 +/- 0.9 m/min; P < 0.01) mice. Voluntary exercise influenced adaptation to exercise specifically in Sol muscle. Physical activity significantly increased Sol weight by 22% (P < 0.05) in WT but not eNOS-/- mice. WT Sol muscle did not change its metabolic profile in response to exercise, in contrast to eNOS-/- muscle, in which physical activity decreased cytochrome-c oxidase (COX; -36%; P < 0.05), citrate synthase (-37%; P < 0.06), and creatine kinase (-24%, P < 0.01) activities. Voluntary exercise did not change energy enzyme profile in heart (except for 39% increase in COX activity in WT) or Gast muscle. These results suggest that eNOS is necessary for maintaining a suitable physical capacity and that when eNOS is downregulated, even moderate exercise could worsen energy metabolism specifically in oxidative skeletal muscle. 相似文献
9.
Thomas W. Miller Sukhbir Kaur Kelly Ivins-O'Keefe David D. Roberts 《Matrix biology》2013,32(6):316-324
Thrombospondin-1 is a potent suppressor of T cell activation via its receptor CD47. However, the precise mechanism for this inhibition remains unclear. Because H2S is an endogenous potentiator of T cell activation and is necessary for full T cell activation, we hypothesized that thrombospondin-1 signaling through CD47 inhibits T cell activation by antagonizing H2S signaling. Primary T cells from thrombospondin-1 null mice were more sensitive to H2S-dependent activation assessed by proliferation and induction of interleukin-2 and CD69 mRNAs. Exogenous thrombospondin-1 inhibited H2S responses in wild type and thrombospondin-1 null T cells but enhanced the same responses in CD47 null T cells. Fibronectin, which shares integrin and glycosaminoglycan binding properties with thrombospondin-1 but not CD47 binding, did not inhibit H2S signaling. A CD47-binding peptide derived from thrombospondin-1 inhibited H2S-induced activation, whereas two other functional sequences from thrombospondin-1 enhanced H2S signaling. Therefore, engaging CD47 is necessary and sufficient for thrombospondin-1 to inhibit H2S-dependent T cell activation. H2S stimulated T cell activation by potentiating MEK-dependent ERK phosphorylation, and thrombospondin-1 inhibited this signaling in a CD47-dependent manner. Thrombospondin-1 also limited activation-dependent T cell expression of the H2S biosynthetic enzymes cystathionine β-synthase and cystathionine γ-lyase, thereby limiting the autocrine role of H2S in T cell activation. Thus, thrombospondin-1 signaling through CD47 is the first identified endogenous inhibitor of H2S signaling and constitutes a novel mechanism that negatively regulates T cell activation. 相似文献
10.
Pearen MA Eriksson NA Fitzsimmons RL Goode JM Martel N Andrikopoulos S Muscat GE 《Molecular endocrinology (Baltimore, Md.)》2012,26(3):372-384
Nuclear hormone receptors (NR) have been implicated as regulators of lipid and carbohydrate metabolism. The orphan NR4A subgroup has emerged as regulators of metabolic function. Targeted silencing of neuron-derived orphan receptor 1 (Nor-1)/NR4A3 in skeletal muscle cells suggested that this NR was necessary for oxidative metabolism in vitro. To investigate the in vivo role of Nor-1, we have developed a mouse model with preferential expression of activated Nor-1 in skeletal muscle. In skeletal muscle, this resulted in a marked increase in: 1) myoglobin expression, 2) mitochondrial DNA and density, 3) oxidative enzyme staining, and 4) genes/proteins encoding subunits of electron transport chain complexes. This was associated with significantly increased type IIA and IIX myosin heavy chain mRNA and proteins and decreased type IIB myosin heavy chain mRNA and protein. The contractile protein/fiber type remodeling driving the acquisition of the oxidative type II phenotype was associated with 1) the significantly increased expression of myocyte-specific enhancer factor 2C, and phospho-histone deacetylase 5, and 2) predominantly cytoplasmic HDAC5 staining in the Tg-Nor-1 mice. Moreover, the Nor-1 transgenic line displayed significant improvements in glucose tolerance, oxygen consumption, and running endurance (in the absence of increased insulin sensitivity), consistent with increased oxidative capacity of skeletal muscle. We conclude that skeletal muscle fiber type is not only regulated by exercise-sensitive calcineurin-induced signaling cascade but also by NR signaling pathways that operate at the nexus that coordinates muscle performance and metabolic capacity in this major mass tissue. 相似文献
11.
12.
Skeletal muscle adaptation in response to voluntary running in Ca2+/calmodulin-dependent protein kinase IV-deficient mice 总被引:6,自引:0,他引:6
Akimoto T Ribar TJ Williams RS Yan Z 《American journal of physiology. Cell physiology》2004,287(5):C1311-C1319
Mammalian skeletal muscles undergo adaptation in response to alteration in functional demands by means of a variety of cellular signaling events. Previous experiments in transgenic mice showed that an active form of Ca2+/calmodulin-dependent protein kinase IV (CaMKIV) is capable of stimulating peroxisome proliferator-activated receptor -coactivator 1 (PGC-1) gene expression, promoting fast-to-slow fiber type switching and augmenting mitochondrial biogenesis in skeletal muscle. However, a role for endogenous CaMKIV in skeletal muscle has not been investigated rigorously. We report that genetically modified mice devoid of CaMKIV have normal fiber type composition and mitochondrial enzyme expression in fast-twitch skeletal muscles and responded to long-term (4 wk) voluntary running with increased expression of myosin heavy chain type IIa, myoglobin, PGC-1, and cytochrome c oxidase IV proteins in plantaris muscle in a manner similar to that of wild-type mice. Short-term motor nerve stimulation (2 h at 10 Hz) likewise increased PGC-1 mRNA expression in tibialis anterior muscles in both Camk4/ and wild-type mice. In addition, we have confirmed that no detectable CaMKIV protein is expressed in murine skeletal muscle. Thus CaMKIV is not required for the maintenance of slow-twitch muscle phenotype and endurance training-induced mitochondrial biogenesis and IIb-to-IIa fiber type switching in murine skeletal muscle. Other protein kinases sharing substrates with constitutively active CaMKIV may function as endogenous mediators of activity-dependent changes in myofiber phenotype. cellular signaling; proliferator-activated receptor -coactivator 1; fiber type switching; mitochondrial biogenesis 相似文献
13.
K D Hankenson I E James S Apone G B Stroup S M Blake X Liang M W Lark P Bornstein 《Matrix biology》2005,24(5):362-370
Although bone is composed primarily of extracellular matrix (ECM), the dynamic role that the ECM plays in regulating bone remodeling secondary to estrogen loss is relatively unexplored. Previous studies have shown that mice deficient in the matricellular protein thrombospondin-2 (TSP2-null) form excess endocortical bone; thus, we postulated that enhanced bone formation in TSP2-null mice could protect against ovariectomy (OVX)-induced bone loss. Wild-type (WT) OVX mice showed a significant loss of both midfemoral endocortical and proximal tibial trabecular bone, but OVX did not significantly alter TSP2-null bone. TSP2-null mice showed an increase in bone formation, as indicated by a 70% increase in serum osteocalcin two weeks post OVX and a two-fold increase in bone formation rate (BFR) five weeks post OVX as measured by dynamic histomorphometry. WT animals showed only a 20% increase in serum osteocalcin at two weeks and no change in BFR at five weeks. This increase in bone formation in TSP2-null OVX mice was accompanied by a three-fold increase in osteoprogenitor number. Although these results provide a partial explanation for the maintenance of bone geometry post-OVX, TSP2-null mice five weeks post-OVX also showed a significantly lower level of bone resorption than OVX WT mice, as determined by serum levels of the amino-terminal telopeptide of type I collagen (NTx). We conclude that the absence of TSP2 protects against OVX-induced bone loss by two complementary processes: increased formation and decreased resorption. 相似文献
14.
Isenberg JS Jia Y Fukuyama J Switzer CH Wink DA Roberts DD 《The Journal of biological chemistry》2007,282(21):15404-15415
Although CD36 is generally recognized to be an inhibitory signaling receptor for thrombospondin-1 (TSP1), the molecular mechanism for transduction of this signal remains unclear. Based on evidence that myristic acid and TSP1 each modulate endothelial cell nitric oxide signaling in a CD36-dependent manner, we examined the ability of TSP1 to modulate the fatty acid translocase activity of CD36. TSP1 and a CD36 antibody that mimics the activity of TSP1 inhibited myristate uptake. Recombinant TSP1 type 1 repeats were weakly inhibitory, but an anti-angiogenic peptide derived from this domain potently inhibited myristate uptake. This peptide also inhibited membrane translocation of the myristoylated CD36 signaling target Fyn and activation of Src family kinases. Myristate uptake stimulated cGMP synthesis via endothelial nitric-oxide synthase and soluble guanylyl cyclase. CD36 ligands blocked myristate-stimulated cGMP accumulation in proportion to their ability to inhibit myristate uptake. TSP1 also inhibited myristate-stimulated cGMP synthesis by engaging its receptor CD47. Myristate stimulated endothelial and vascular smooth muscle cell adhesion on type I collagen via the NO/cGMP pathway, and CD36 ligands that inhibit myristate uptake blocked this response. Therefore, the fatty acid translocase activity of CD36 elicits proangiogenic signaling in vascular cells, and TSP1 inhibits this response by simultaneously inhibiting fatty acid uptake via CD36 and downstream cGMP signaling via CD47. 相似文献
15.
《Matrix biology》2014
Cardiovascular homeostasis and health is maintained through the balanced interactions of cardiac generated blood flow and cross-talk between the cellular components that comprise blood vessels. Central to this cross-talk is endothelial generated nitric oxide (NO) that stimulates relaxation of the contractile vascular smooth muscle (VSMC) layer of blood vessels. In cardiovascular disease this balanced interaction is disrupted and NO signaling is lost. Work over the last several years indicates that regulation of NO is much more complex than previously believed. It is now apparent that the secreted protein thrombospondin-1 (TSP1), that is upregulated in cardiovascular disease and animal models of the same, on activating cell surface receptor CD47, redundantly inhibits NO production and NO signaling. This inhibitory event has implications for baseline and disease-related responses mediated by NO. Further work has identified that TSP1-CD47 signaling stimulates enzymatic reactive oxygen species (ROS) production to further limit blood flow and promote vascular disease. Herein consideration is given to the most recent discoveries in this regard which identify the TSP1-CD47 axis as a major proximate governor of cardiovascular health. 相似文献
16.
J Scott Isenberg Maria J Calzada Longen Zhou Nenghua Guo Jack Lawler Xue-Qing Wang William A Frazier David D Roberts 《Matrix biology》2005,24(2):110-123
We have reexamined the role of endogenous thrombospondin-1 (TSP1) in growth and motility of vascular smooth muscle cells (SMCs). Based on the ability of aortic-derived SMCs isolated from TSP1 null mice and grown in the absence of exogenous TSP1 to grow at comparable rates and to a slightly higher density than equivalent cells from wild-type mice, TSP1 is not necessary for their growth. Low concentrations of exogenous TSP1 stimulate growth of TSP1 null SMCs, but higher doses of TSP1 or its C-terminal domain are inhibitory. However, SMCs from TSP1 null mice are selectively deficient in chemotactic and proliferative responses to platelet-derived growth factor and in outgrowth in three-dimensional cultures. Recombinant portions of the N- and C-terminal domains of TSP1 stimulate SMC chemotaxis through different integrin receptors. Based on these data, the relative deficiency in SMC outgrowth during an ex vivo angiogenic response of muscle tissue from TSP1 null mice is probably due to restriction of platelet-derived growth factor dependent SMC migration and/or proliferation. 相似文献
17.
Jonas M. Kristensen Steen Larsen J?rn W. Helge Flemming Dela J?rgen F. P. Wojtaszewski 《PloS one》2013,8(1)
Metformin is used as an anti-diabetic drug. Metformin ameliorates insulin resistance by improving insulin sensitivity in liver and skeletal muscle. Reduced mitochondrial content has been reported in type 2 diabetic muscles and it may contribute to decreased insulin sensitivity characteristic for diabetic muscles. The molecular mechanism behind the effect of metformin is not fully clarified but inhibition of complex I in the mitochondria and also activation of the 5′AMP activated protein kinase (AMPK) has been reported in muscle. Furthermore, both AMPK activation and metformin treatment have been associated with stimulation of mitochondrial function and biogenesis. However, a causal relationship in skeletal muscle has not been investigated. We hypothesized that potential effects of in vivo metformin treatment on mitochondrial function and protein expressions in skeletal muscle are dependent upon AMPK signaling. We investigated this by two weeks of oral metformin treatment of muscle specific kinase dead α2 (KD) AMPK mice and wild type (WT) littermates. We measured mitochondrial respiration and protein activity and expressions of key enzymes involved in mitochondrial carbohydrate and fat metabolism and oxidative phosphorylation. Mitochondrial respiration, HAD and CS activity, PDH and complex I-V and cytochrome c protein expression were all reduced in AMPK KD compared to WT tibialis anterior muscles. Surprisingly, metformin treatment only enhanced respiration in AMPK KD mice and thereby rescued the respiration defect compared to the WT mice. Metformin did not influence protein activities or expressions in either WT or AMPK KD mice.We conclude that two weeks of in vivo metformin treatment enhances mitochondrial respiration in the mitochondrial deficient AMPK KD but not WT mice. The improvement seems to be unrelated to AMPK, and does not involve changes in key mitochondrial proteins. 相似文献
18.
19.
Thomas W. Miller David R. Soto-Pantoja Anthony L. Schwartz John M. Sipes William G. DeGraff Lisa A. Ridnour David A. Wink David D. Roberts 《The Journal of biological chemistry》2015,290(41):24858-24874
Modulating tissue responses to stress is an important therapeutic objective. Oxidative and genotoxic stresses caused by ionizing radiation are detrimental to healthy tissues but beneficial for treatment of cancer. CD47 is a signaling receptor for thrombospondin-1 and an attractive therapeutic target because blocking CD47 signaling protects normal tissues while sensitizing tumors to ionizing radiation. Here we utilized a metabolomic approach to define molecular mechanisms underlying this radioprotective activity. CD47-deficient cells and cd47-null mice exhibited global advantages in preserving metabolite levels after irradiation. Metabolic pathways required for controlling oxidative stress and mediating DNA repair were enhanced. Some cellular energetics pathways differed basally in CD47-deficient cells, and the global declines in the glycolytic and tricarboxylic acid cycle metabolites characteristic of normal cell and tissue responses to irradiation were prevented in the absence of CD47. Thus, CD47 mediates signaling from the extracellular matrix that coordinately regulates basal metabolism and cytoprotective responses to radiation injury. 相似文献
20.
Smith BK Jain SS Rimbaud S Dam A Quadrilatero J Ventura-Clapier R Bonen A Holloway GP 《The Biochemical journal》2011,437(1):125-134
FAT/CD36 (fatty acid translocase/Cluster of Differentiation 36), a plasma membrane fatty-acid transport protein, has been found on mitochondrial membranes; however, it remains unclear where FAT/CD36 resides on this organelle or its functional role within mitochondria. In the present study, we demonstrate, using several different approaches, that in skeletal muscle FAT/CD36 resides on the OMM (outer mitochondrial membrane). To determine the functional role of mitochondrial FAT/CD36 in this tissue, we determined oxygen consumption rates in permeabilized muscle fibres in WT (wild-type) and FAT/CD36-KO (knockout) mice using a variety of substrates. Despite comparable muscle mitochondrial content, as assessed by unaltered mtDNA (mitochondrial DNA), citrate synthase, β-hydroxyacyl-CoA dehydrogenase, cytochrome c oxidase complex IV and respiratory capacities [maximal OXPHOS (oxidative phosphorylation) respiration] in WT and KO mice, palmitate-supported respiration was 34% lower in KO animals. In contrast, palmitoyl-CoA-supported respiration was unchanged. These results indicate that FAT/CD36 is key for palmitate-supported respiration. Therefore we propose a working model of mitochondrial fatty-acid transport, in which FAT/CD36 is positioned on the OMM, upstream of long-chain acyl-CoA synthetase, thereby contributing to the regulation of mitochondrial fatty-acid transport. We further support this model by providing evidence that FAT/CD36 is not located in mitochondrial contact sites, and therefore does not directly interact with carnitine palmitoyltransferase-I as original proposed. 相似文献