RESUMEN
ABSTRACT: Acromegaly represents a rare endocrine condition characterized by an excessive secretion of the growth hormone (GH) and the insulin-like growth factor-1 (IGF-1), mostly subsequent to a pituitary adenoma. Acromegaly affects 40-60 people per million without significant dif-ference between men and women, with an average age of onset of 44. The slow progression of the disease leads to a delay in diagnosis of 4 to 10 years from the onset of the hormonal imbalance. The increase of the GH and IFG-1 levels is associated with cardiac, respiratory, metabolic and rheumatic disorders. The cardiac involvement, also called acromegalic cardiomyopathy, causes a serious deterioration of the prognosis quoad vitam. An early diagnosis and a targeted treatment at the initial stage of the myocardial damage can enable the revers-ibility of the structural alterations.
Asunto(s)
Acromegalia , Adenoma , Cardiomiopatías , Hormona de Crecimiento Humana , Acromegalia/complicaciones , Cardiomiopatías/diagnóstico , Cardiomiopatías/etiología , Femenino , Humanos , Factor I del Crecimiento Similar a la Insulina , Masculino , PronósticoRESUMEN
The skeletal muscle is an immunologically unique tissue. Leukocytes, virtually absent in physiological conditions, are quickly recruited into the tissue upon injury and persist during regeneration. Apoptosis, necrosis and autophagy coexist in the injured/regenerating muscles, including those of patients with neuromuscular disorders, such as inflammatory myopathies, dystrophies, metabolic and mitochondrial myopathies and drug-induced myopathies. Macrophages are able to alter their function in response to microenvironment conditions and as a consequence coordinate changes within the tissue from the early injury throughout regeneration and eventual healing, and regulate the activation and the function of stem cells. Early after injury, classically activated macrophages ('M1') dominate the picture. Alternatively activated M2 macrophages predominate during resolution phases and regulate the termination of the inflammatory responses. The dynamic M1/M2 transition is increasingly felt to be the key to the homeostasis of the muscle. Recognition and clearance of debris originating from damaged myofibers and from dying stem/progenitor cells, stromal cells and leukocytes are fundamental actions of macrophages. Clearance of apoptotic cells and M1/M2 transition are causally connected and represent limiting steps for muscle healing. The accumulation of apoptotic cells, which reflects their defective clearance, has been demonstrated in various tissues to prompt autoimmunity against intracellular autoantigens. In the muscle, in the presence of type I interferon, apoptotic myoblasts indeed cause the production of autoantibodies, lymphocyte infiltration and continuous cycles of muscle injury and regeneration, mimicking human inflammatory myopathies. The clearance of apoptotic cells thus modulates the homeostatic response of the skeletal muscle to injury. Conversely, defects in the process may have deleterious local effects, guiding maladaptive tissue remodeling with collagen and fat accumulation and promoting autoimmunity itself. There is strong promise for novel treatments based on new knowledge of cell death, clearance and immunity in the muscle.
Asunto(s)
Apoptosis , Músculo Esquelético/fisiología , Animales , Autoantígenos/inmunología , Autoantígenos/metabolismo , Autoinmunidad , Humanos , Inflamación , Macrófagos/inmunología , Macrófagos/metabolismo , Músculo Esquelético/inmunología , Músculo Esquelético/lesiones , Regeneración/fisiología , Linfocitos T/inmunología , Linfocitos T/metabolismoRESUMEN
Lecithin:cholesterol acyltransferase (LCAT) deficiency is associated with hypoalphalipoproteinemia, generally a predisposing factor for premature coronary heart disease. The evidence of accelerated atherosclerosis in LCAT-deficient subjects is however controversial. In this study, the effect of LCAT deficiency on vascular tone and endothelial function was investigated in LCAT knockout mice, which reproduce the human lipoprotein phenotype. Aortas from wild-type (Lcat(wt)) and LCAT knockout (Lcat(KO)) mice exposed to noradrenaline showed reduced contractility in Lcat(KO) mice (P<0.005), whereas acetylcholine exposure showed a lower NO-dependent relaxation in Lcat(KO) mice (P<0.05). Quantitative PCR and Western blotting analyses suggested an adequate eNOS expression in Lcat(KO) mouse aortas. Real-time PCR analysis indicated increased expression of ß2-adrenergic receptors vs wild-type mice. Aorta stimulation with noradrenaline in the presence of propranolol, to abolish the ß-mediated relaxation, showed the same contractile response in the two mouse lines. Furthermore, propranolol pretreatment of mouse aortas exposed to L-NAME prevented the difference in responses between Lcat(wt) and Lcat(KO) mice. The results indicate that LCAT deficiency leads to increased ß2-adrenergic relaxation and to a consequently decreased NO-mediated vasodilation that can be reversed to guarantee a correct vascular tone. The present study suggests that LCAT deficiency is not associated with an impaired vascular reactivity.
Asunto(s)
Adrenérgicos/farmacología , Deficiencia de la Lecitina Colesterol Aciltransferasa/tratamiento farmacológico , Deficiencia de la Lecitina Colesterol Aciltransferasa/metabolismo , Lecitinas/metabolismo , Fosfatidilcolina-Esterol O-Aciltransferasa/metabolismo , Animales , Aorta/efectos de los fármacos , Aorta/metabolismo , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Óxido Nítrico/metabolismo , Óxido Nítrico Sintasa de Tipo III/metabolismo , Receptores Adrenérgicos beta 2/metabolismo , Vasodilatación/efectos de los fármacosRESUMEN
Mitochondrial fission and fusion are essential processes in the maintenance of the skeletal muscle function. The contribution of these processes to muscle development has not been properly investigated in vivo because of the early lethality of the models generated so far. To define the role of mitochondrial fission in muscle development and repair, we have generated a transgenic mouse line that overexpresses the fission-inducing protein Drp1 specifically in skeletal muscle. These mice displayed a drastic impairment in postnatal muscle growth, with reorganisation of the mitochondrial network and reduction of mtDNA quantity, without the deficiency of mitochondrial bioenergetics. Importantly we found that Drp1 overexpression activates the stress-induced PKR/eIF2α/Fgf21 pathway thus leading to an attenuated protein synthesis and downregulation of the growth hormone pathway. These results reveal for the first time how mitochondrial network dynamics influence muscle growth and shed light on aspects of muscle physiology relevant in human muscle pathologies.
Asunto(s)
Dinaminas/metabolismo , Músculo Esquelético/metabolismo , Animales , Western Blotting , ADN Mitocondrial/metabolismo , Dinaminas/genética , Inmunoprecipitación , Potencial de la Membrana Mitocondrial/genética , Potencial de la Membrana Mitocondrial/fisiología , Ratones , Ratones Transgénicos , Consumo de Oxígeno/fisiologíaRESUMEN
Swift and regulated clearance of apoptotic cells prevents the accumulation of cell remnants in injured tissues and contributes to the shift of macrophages towards alternatively activated reparatory cells that sustain wound healing. Environmental signals, most of which are unknown, in turn control the efficiency of the clearance of apoptotic cells and as such determine whether tissues eventually heal. In this study we show that vessel-associated stem cells (mesoangioblasts) specifically modulate the expression of genes involved in the clearance of apoptotic cells and in macrophage alternative activation, including those of scavenger receptors and of molecules that bridge dying cells and phagocytes. Mesoangioblasts, but not immortalized myoblasts or neural precursor cells, enhance CD163 membrane expression in vitro as assessed by flow cytometry, indicating that the effect is specific. Mesoangioblasts transplanted in acutely or chronically injured skeletal muscles determine the expansion of the population of CD163(+) infiltrating macrophages and increase the extent of CD163 expression. Conversely, macrophages challenged with mesoangioblasts engulf significantly better apoptotic cells in vitro. Collectively, the data reveal a feed-forward loop between macrophages and vessel-associated stem cells, which has implications for the skeletal muscle homeostatic response to sterile injury and for diseases in which homeostasis is jeopardized, including muscle dystrophies and inflammatory myopathies.
Asunto(s)
Apoptosis/fisiología , Activación de Macrófagos/fisiología , Macrófagos/inmunología , Mioblastos/metabolismo , Animales , Femenino , Perfilación de la Expresión Génica , Regulación de la Expresión Génica , Inmunofenotipificación , Macrófagos/metabolismo , Ratones , Mioblastos/trasplante , Fagocitosis/fisiología , FenotipoRESUMEN
The damage of the skeletal muscle prompts a complex and coordinated response that involves the interactions of many different cell populations and promotes inflammation, vascular remodeling and finally muscle regeneration. Muscle disorders exist in which the irreversible loss of tissue integrity and function is linked to defective neo-angiogenesis with persistence of tissue necrosis and inflammation. Here we show that macrophages (MPs) are necessary for efficient vascular remodeling in the injured muscle. In particular, MPs sustain the differentiation of endothelial-derived progenitors to contribute to neo-capillary formation, by secreting pro-angiogenic growth factors. When phagocyte infiltration is compromised endothelial-derived progenitors undergo a significant endothelial to mesenchymal transition (EndoMT), possibly triggered by the activation of transforming growth factor-ß/bone morphogenetic protein signaling, collagen accumulates and the muscle is replaced by fibrotic tissue. Our findings provide new insights in EndoMT in the adult skeletal muscle, and suggest that endothelial cells in the skeletal muscle may represent a new target for therapeutic intervention in fibrotic diseases.
Asunto(s)
Células Endoteliales/citología , Endotelio Vascular/citología , Transición Epitelial-Mesenquimal , Macrófagos/metabolismo , Músculo Esquelético/fisiopatología , Neovascularización Patológica/fisiopatología , Células Madre/citología , Animales , Proteínas Morfogenéticas Óseas/metabolismo , Diferenciación Celular , Colágeno/metabolismo , Células Endoteliales/metabolismo , Endotelio Vascular/metabolismo , Humanos , Macrófagos/citología , Ratones Transgénicos , Músculo Esquelético/irrigación sanguínea , Músculo Esquelético/lesiones , Músculo Esquelético/metabolismo , Neovascularización Patológica/metabolismo , Regeneración , Células Madre/metabolismo , Factor de Crecimiento Transformador beta/metabolismoRESUMEN
AIMS/HYPOTHESIS: Human adipose tissue macrophages (ATMs) display an alternatively activated (M2) phenotype, but are still able to produce excessive inflammatory mediators. However, the processes driving this particular ATM phenotype are not understood. Genome-wide association studies associated the CDKN2A locus, encoding the tumour suppressor p16(INK4A), with the development of type 2 diabetes. In the present study, p16(INK4A) levels in human ATMs and the role of p16(INK4A) in acquiring the ATM phenotype were assessed. METHODS: Gene expression of p16 ( INK4A ) in ATMs was analysed and compared with that in monocyte-derived macrophages (MDMs) from obese patients or with macrophages from human atherosclerotic plaques (AMs). Additionally, p16(INK4A) levels were studied during macrophage differentiation and polarisation of monocytes isolated from healthy donors. The role of p16(INK4A) in MDMs from healthy donors was investigated by small interfering (si)RNA-mediated silencing or adenovirus-mediated overproduction of p16(INK4A). RESULTS: Compared with MDMs and AMs, ATMs from obese patients expressed lower levels of p16 ( INK4A ). In vitro, IL-4-induced M2 polarisation resulted in lower p16(INK4A) protein levels after differentiation of monocytes from healthy donors in macrophages. Silencing of p16(INK4A) in MDMs mediated by siRNA increased the expression of M2 marker genes and enhanced the response to lipopolysaccharide (LPS), to give a phenotype resembling that of ATM. By contrast, adenovirus-mediated overproduction of p16(INK4A) in MDMs diminished M2 marker gene expression and the response to LPS. Western blot analysis revealed that p16(INK4A) overproduction inhibits LPS- and palmitate-induced Toll-like receptor 4 (TLR4)-nuclear factor of κ light polypeptide gene enhancer in B cells (NF-κB) signalling. CONCLUSIONS/INTERPRETATION: These results show that p16(INK4A) inhibits the acquisition of the ATM phenotype. The age-related increase in p16(INK4A) level may thus influence normal ATM function and contribute to type 2 diabetes risk.
Asunto(s)
Tejido Adiposo/metabolismo , Polaridad Celular , Inhibidor p16 de la Quinasa Dependiente de Ciclina/biosíntesis , Macrófagos/metabolismo , Inhibidor p16 de la Quinasa Dependiente de Ciclina/genética , Diabetes Mellitus Tipo 2/metabolismo , Regulación hacia Abajo , Femenino , Silenciador del Gen , Humanos , Masculino , FN-kappa B/metabolismo , Obesidad/metabolismo , Placa Aterosclerótica/metabolismo , ARN Interferente Pequeño/metabolismo , Receptor Toll-Like 4/metabolismoRESUMEN
Liver X receptors (LXRs) are nuclear receptors that regulate macrophage cholesterol efflux by inducing ATP-binding cassette transporter A1 (ABCA1) and ABCG1/ABCG4 gene expression. The Niemann-Pick C (NPC) proteins NPC1 and NPC2 are located in the late endosome, where they control cholesterol trafficking to the plasma membrane. The mobilization of cholesterol from intracellular pools to the plasma membrane is a determinant governing its availability for efflux to extracellular acceptors. Here we investigated the influence of LXR activation on intracellular cholesterol trafficking in primary human macrophages. Synthetic LXR activators increase the amount of free cholesterol in the plasma membrane by inducing NPC1 and NPC2 gene expression. Moreover, ABCA1-dependent cholesterol efflux induced by LXR activators was drastically decreased in the presence of progesterone, which blocks postlysosomal cholesterol trafficking, and reduced when NPC1 and NPC2 mRNA expression was depleted using small interfering RNA. The stimulation of cholesterol mobilization to the plasma membrane by LXRs led to a decrease in cholesteryl ester formation and Acyl-coenzyme A cholesterol acyltransferase-1 activity. These data indicate that LXR activation enhances cholesterol trafficking to the plasma membrane, where it becomes available for efflux, at the expense of esterification, thus contributing to the overall effects of LXR agonists in the control of macrophage cholesterol homeostasis.
Asunto(s)
Ésteres del Colesterol/metabolismo , Colesterol/metabolismo , Proteínas de Unión al ADN/fisiología , Macrófagos/metabolismo , Receptores Citoplasmáticos y Nucleares/fisiología , Transportador 1 de Casete de Unión a ATP , Transportadoras de Casetes de Unión a ATP/fisiología , Animales , Transporte Biológico , Proteínas Portadoras/fisiología , Membrana Celular/metabolismo , Células Cultivadas , Ésteres del Colesterol/análisis , Células Espumosas/metabolismo , Glicoproteínas/fisiología , Humanos , Péptidos y Proteínas de Señalización Intracelular , Receptores X del Hígado , Glicoproteínas de Membrana/fisiología , Ratones , Ratones Endogámicos C57BL , Proteína Niemann-Pick C1 , Receptores Nucleares Huérfanos , Progesterona/farmacología , ARN Interferente Pequeño/farmacología , Proteínas de Transporte VesicularRESUMEN
The mobilization of cholesterol from intracellular pools to the plasma membrane is a determinant that governs its availability for efflux to extracellular acceptors. NPC1 and NPC2 are proteins localized in the late endosome and control cholesterol transport from the lysosome to the plasma membrane. Here, we report that NPC1 and NPC2 gene expression is induced by oxidized LDL (OxLDL) in human macrophages. Because OxLDLs contain natural activators of peroxisome proliferator-activated receptor alpha (PPARalpha), a fatty acid-activated nuclear receptor, the regulation of NPC1 and NPC2 by PPARalpha and the consequences on cholesterol trafficking were further studied. NPC1 and NPC2 expression is induced by synthetic PPARalpha ligands in human macrophages. Furthermore, PPARalpha activation leads to an enrichment of cholesterol in the plasma membrane. By contrast, incubation with progesterone, which blocks postlysosomal cholesterol trafficking, as well as NPC1 and NPC2 mRNA depletion using small interfering RNA, abolished ABCA1-dependent cholesterol efflux induced by PPARalpha activators. These observations identify a novel regulatory role for PPARalpha in the control of cholesterol availability for efflux that, associated with its ability to inhibit cholesterol esterification and to stimulate ABCA1 and scavenger receptor class B type I expression, may contribute to the stimulation of reverse cholesterol transport.
Asunto(s)
Colesterol/metabolismo , Macrófagos/metabolismo , PPAR alfa/metabolismo , Transporte Biológico , Proteínas Portadoras/genética , Diferenciación Celular , Membrana Celular/efectos de los fármacos , Membrana Celular/metabolismo , Células Cultivadas , Regulación de la Expresión Génica , Glicoproteínas/genética , Humanos , Péptidos y Proteínas de Señalización Intracelular , Lipoproteínas LDL/farmacología , Macrófagos/citología , Glicoproteínas de Membrana/genética , Proteína Niemann-Pick C1 , PPAR alfa/genética , Progesterona/farmacología , ARN Mensajero/genética , ARN Interferente Pequeño/genética , Proteínas de Transporte VesicularRESUMEN
The intravascular ultrasound (IVUS) modality has rapidly gained acceptance for the measurement of arterial plaque thickness and for anatomical characterization. In view, however, of the growing interest in the direct assessment of plaque size after therapeutic modalities directly reducing plaque burden, a non-invasive method such as magnetic resonance imaging (MRI) may be of help for repeated evaluations. The two methods were compared directly on a focal plaque developed at the abdominal aortic level by a combination of local electric lesion followed by a hypercholesterolemic diet. The plaque was fully characterized histopathologically at intervals up to 120 days from lesion induction, and maximal plaque formation was detected at 90 days from electrical injury. Plaques could be well assessed by IVUS at each time point analyzed and data correlated very well to histopathologic findings (r = 0.969, P = 0.0014). The MRI technology provided reliable determinations only at 90 days after lesion induction, i.e. at maximal plaque formation, with excellent correspondence to IVUS determinations (r = 0.989, P = 0.0111). Altogether these findings indicate that the non-invasive MRI technology, when applied to the analysis of arterial plaques of adequate size, can be used successfully for plaque determination, with results comparable to the invasive IVUS technique.
Asunto(s)
Arteriosclerosis/diagnóstico por imagen , Arteriosclerosis/patología , Angiografía por Resonancia Magnética/métodos , Ultrasonografía Intervencional/métodos , Análisis de Varianza , Animales , Aorta/patología , Técnicas de Cultivo , Modelos Animales de Enfermedad , Inmunohistoquímica , Masculino , Probabilidad , Conejos , Sensibilidad y EspecificidadRESUMEN
Dipalmitoylphosphatidic acid (DPPA) was found to exert a strong inhibitory effect on Fe-induced peroxidation of arachidonic acid inserted into liposomal dipalmitoylphosphatidylcholine (DPPC) vesicles. This inhibition was quite effective both below and above the phase transition temperature of the liposomes. Moreover, we demonstrated the antiperoxidative activity of phosphatidic acid (PA) in synaptosomal membranes. PA enriched synaptosomes were prepared by the stimulation of the endogenous phospholipase D activity or by the incubation of the synaptosomes with Streptomyces chromofuscus phospholipase D. The possible contribution of PA to the in vivo defense mechanism against free radical-induced damage is discussed.