RESUMO
With over 575,000 deaths and about 13.3 million cases globally, the COVID-19 pandemic has had a terrible impact globally during the 6 months since cases were first detected in China. Conscious of the many challenges presented in settings with abundance of resources and with robust health systems, where mortality has been significant and transmission difficult to control, there was a logical concern to see how the virus could impact African countries, and their fragile and weak health systems. Such an anticipated "tsunami", with potentially devastating consequences, seems however to not have yet arrived, and African countries, albeit witnessing an increasing degree of autochthonous transmission, seem to this day relatively unaffected by the pandemic. In this article we review the current situation of the pandemic in the African continent, trying to understand the determinants of its slow progress.
Con más de 575.000 muertes y cerca de 13.3 millones de casos a nivel global, la pandemia por COVID-19 ha causado un terrible impacto en apenas medio año de evolución desde que por primera vez fuesen detectados casos en China. Conscientes de las dificultades planteadas en entornos con sistemas de salud robustos, donde la mortalidad ha sido significativa, y la transmisión difícilmente controlable, había una lógica preocupación por ver cómo el virus podría afectar a los países africanos, donde sus frágiles sistemas de salud auguraban un impacto aún mayor. Este "tsunami" anunciado, de potenciales consecuencias devastadoras, parece sin embargo no haber llegado todavía, y los países africanos, donde ya se ha evidenciado una creciente transmisión, no están viendo el impacto en la salud de sus habitantes que muchos habían predicho. En este artículo repasamos la situación actual de la pandemia en el continente Africano, intentando entender los determinantes de su lenta progresión.
RESUMO
With over 575,000 deaths and about 13.3 million cases globally, the COVID-19 pandemic has had a terrible impact globally during the 6 months since cases were first detected in China. Conscious of the many challenges presented in settings with abundance of resources and with robust health systems, where mortality has been significant and transmission difficult to control, there was a logical concern to see how the virus could impact African countries, and their fragile and weak health systems. Such an anticipated "tsunami", with potentially devastating consequences, seems however to not have yet arrived, and African countries, albeit witnessing an increasing degree of autochthonous transmission, seem to this day relatively unaffected by the pandemic. In this article we review the current situation of the pandemic in the African continent, trying to understand the determinants of its slow progress.
Assuntos
COVID-19/epidemiologia , Atenção à Saúde/organização & administração , África/epidemiologia , COVID-19/mortalidade , COVID-19/transmissão , Países em Desenvolvimento , Recursos em Saúde/estatística & dados numéricos , HumanosRESUMO
Periodontal disease is a highly prevalent chronic inflammatory disease and is associated with complex microbial infection in the subgingival cavity. Recently, American Heart Association supported a century old association between periodontal disease and atherosclerotic vascular disease. We have recently shown that polybacterial periodontal infection led to aortic atherosclerosis and modulation of lipid profiles; however the underlying mechanism(s) has not been yet demonstrated. Altered nitric oxide (NO) synthesis and tetrahydrobiopterin (BH4), a cofactor for nitric oxide synthases (NOS) has long been shown to be associated with vascular dysfunction and gastrointestinal motility disorders. We sought to examine the mechanism of periodontal infection leading to altered vascular and gastrointestinal smooth muscle relaxation, focusing on the BH4/nNOS pathways. In addition, we also have investigated how the antioxidant system (NRF2-Phase II enzyme expression) in vascular and GI specimens is altered by oral infection. Eight week old male ApoEnull mice were either sham-infected or infected orally for 16 weeks with a mixture of major periodontal bacteria Porphyromonas gingivalis, Treponema denticola and Tannerella forsythia to induce experimental periodontitis. Serum, vascular (mesenteric), stomach, and colon specimens were collected at the end of periodontal pathogen infection. Bacterial infection induced significant (p<0.05) reductions in the levels of BH4,in ratio of BH4:BH2+B and also in nitric oxide levels compared to sham-infected controls. In addition, we identified a significant (p<0.05) reduction in eNOS dimerization, nNOS dimerization and protein expression of BH4 biosynthesis enzymes; GCH-1, DHFR and NRF2 & Phase II enzymes in infected mice versus controls in both mesenteric artery and colon tissues. However, we found no differences in nNOS/BH4 protein expression in stomach tissues of infected and sham-infected mice. This suggests that a polybacterial infection can cause significant changes in the vascular and colonic BH4/nNOS/NRF2 pathways which might lead to impaired vascular relaxation and colonic motility.
Assuntos
Infecções por Bacteroidaceae/microbiologia , Biopterinas/análogos & derivados , Trato Gastrointestinal/microbiologia , Artérias Mesentéricas/microbiologia , Fator 2 Relacionado a NF-E2/metabolismo , Óxido Nítrico Sintase Tipo I/metabolismo , Doenças Periodontais/microbiologia , Animais , Apolipoproteínas E/genética , Apolipoproteínas E/metabolismo , Infecções por Bacteroidaceae/metabolismo , Biopterinas/metabolismo , Trato Gastrointestinal/metabolismo , Masculino , Artérias Mesentéricas/metabolismo , Camundongos , Camundongos Knockout , Doenças Periodontais/metabolismo , Porphyromonas gingivalis , Treponema denticolaRESUMO
Periodontal disease is a polymicrobial inflammatory disease that leads to chronic systemic inflammation and direct infiltration of bacteria/bacterial components, which may contribute to the development of Alzheimer's disease. ApoE-/- mice were orally infected (n = 12) with Porphyromonas gingivalis, Treponema denticola, Tannerella forsythia, and Fusobacterium nucleatum as mono- and polymicrobial infections. ApoE-/- mice were sacrificed following 12 and 24 weeks of chronic infection. Bacterial genomic DNA was isolated from all brain tissues except for the F. nucleatum mono-infected group. Polymerase chain reaction was performed using universal 16 s rDNA primers and species-specific primer sets for each organism to determine whether the infecting pathogens accessed the brain. Sequencing amplification products confirmed the invasion of bacteria into the brain during infection. The innate immune responses were detected using antibodies against complement activation products of C3 convertase stage and the membrane attack complex. Molecular methods demonstrated that 6 out of 12 ApoE-/- mice brains contained P. gingivalis genomic DNA at 12 weeks (p = 0.006), and 9 out of 12 at 24 weeks of infection (p = 0.0001). Microglia in both infected and control groups demonstrated strong intracellular labeling with C3 and C9, due to on-going biosynthesis. The pyramidal neurons of the hippocampus in 4 out of 12 infected mice brains demonstrated characteristic opsonization with C3 activation fragments (p = 0.032). These results show that the oral pathogen P. gingivalis was able to access the ApoE-/- mice brain and thereby contributed to complement activation with bystander neuronal injury.
Assuntos
Apolipoproteínas E/deficiência , Infecções por Bacteroidaceae/imunologia , Encéfalo/imunologia , Ativação do Complemento , Doenças Periodontais/imunologia , Porphyromonas gingivalis/patogenicidade , Animais , Apolipoproteínas E/genética , Infecções por Bacteroidaceae/microbiologia , Infecções por Bacteroidaceae/patologia , Encéfalo/microbiologia , Encéfalo/patologia , Doença Crônica , DNA Bacteriano/metabolismo , Modelos Animais de Doenças , Infecções por Fusobacterium/imunologia , Infecções por Fusobacterium/patologia , Fusobacterium nucleatum/genética , Masculino , Camundongos Knockout , Microglia/patologia , Microglia/fisiologia , Doenças Periodontais/microbiologia , Doenças Periodontais/patologia , Porphyromonas gingivalis/genética , Porphyromonas gingivalis/isolamento & purificação , Células Piramidais/imunologia , Células Piramidais/patologia , Treponema denticola/genética , Infecções por Treponema/imunologia , Infecções por Treponema/patologiaRESUMO
Thrombotic occlusion of inflammatory plaque in coronary arteries causes myocardial infarction. Treatment with emergent balloon angioplasty (BA) and stent implant improves survival, but restenosis (regrowth) can occur. Periodontal bacteremia is closely associated with inflammation and native arterial atherosclerosis, with potential to increase restenosis. Two virus-derived anti-inflammatory proteins, M-T7 and Serp-1, reduce inflammation and plaque growth after BA and transplant in animal models through separate pathways. M-T7 is a broad spectrum C, CC and CXC chemokine-binding protein. Serp-1 is a serine protease inhibitor (serpin) inhibiting thrombotic and thrombolytic pathways. Serp-1 also reduces arterial inflammation and improves survival in a mouse herpes virus (MHV68) model of lethal vasculitis. In addition, Serp-1 demonstrated safety and efficacy in patients with unstable coronary disease and stent implant, reducing markers of myocardial damage. We investigate here the effects of Porphyromonas gingivalis, a periodontal pathogen, on restenosis after BA and the effects of blocking chemokine and protease pathways with M-T7 and Serp-1. ApoE-/- mice had aortic BA and oral P. gingivalis infection. Arterial plaque growth was examined at 24 weeks with and without anti-inflammatory protein treatment. Dental plaques from mice infected with P. gingivalis tested positive for infection. Neither Serp-1 nor M-T7 treatment reduced infection, but IgG antibody levels in mice treated with Serp-1 and M-T7 were reduced. P. gingivalis significantly increased monocyte invasion and arterial plaque growth after BA (P<0.025). Monocyte invasion and plaque growth were blocked by M-T7 treatment (P<0.023), whereas Serp-1 produced only a trend toward reductions. Both proteins modified expression of TLR4 and MyD88. In conclusion, aortic plaque growth in ApoE-/- mice increased after angioplasty in mice with chronic oral P. gingivalis infection. Blockade of chemokines, but not serine proteases significantly reduced arterial plaque growth, suggesting a central role for chemokine-mediated inflammation after BA in P. gingivalis infected mice.
Assuntos
Angioplastia com Balão/efeitos adversos , Aorta/cirurgia , Placa Aterosclerótica/tratamento farmacológico , Receptores de Interferon/uso terapêutico , Proteínas Virais/uso terapêutico , alfa 1-Antitripsina/uso terapêutico , Animais , Aorta/efeitos dos fármacos , Infecções por Bacteroidaceae/complicações , Infecções por Bacteroidaceae/tratamento farmacológico , Placa Dentária/tratamento farmacológico , Placa Dentária/microbiologia , Camundongos , Placa Aterosclerótica/microbiologia , Porphyromonas gingivalis/patogenicidade , Proteínas Virais/farmacologia , alfa 1-Antitripsina/farmacologiaRESUMO
Atherosclerotic vascular disease is a leading cause of myocardial infarction and cerebrovascular accident, and independent associations with periodontal disease (PD) are reported. PD is caused by polymicrobial infections and aggressive immune responses. Genomic DNA of Porphyromonas gingivalis, the best-studied bacterial pathogen associated with severe PD, is detected within atherosclerotic plaque. We examined causal relationships between chronic P. gingivalis oral infection, PD, and atherosclerosis in hyperlipidemic ApoEnull mice. ApoEnull mice (nâ=â24) were orally infected with P. gingivalis for 12 and 24 weeks. PD was assessed by standard clinical measurements while the aorta was examined for atherosclerotic lesions and inflammatory markers by array. Systemic inflammatory markers serum amyloid A, nitric oxide, and oxidized low-density lipoprotein were analyzed. P. gingivalis infection elicited specific antibodies and alveolar bone loss. Fluorescent in situ hybridization detected viable P. gingivalis within oral epithelium and aorta, and genomic DNA was detected within systemic organs. Aortic plaque area was significantly increased in P. gingivalis-infected mice at 24 weeks (P<0.01). Aortic RNA and protein arrays indicated a strong Th2 response. Chronic oral infection with P. gingivalis results in a specific immune response, significant increases in oral bone resorption, aortic inflammation, viable bacteria in oral epithelium and aorta, and plaque development.
Assuntos
Aorta/microbiologia , Aterosclerose/etiologia , Infecções por Bacteroidaceae/complicações , Boca/microbiologia , Periodontite/complicações , Porphyromonas gingivalis , Animais , Aterosclerose/imunologia , Aterosclerose/microbiologia , Infecções por Bacteroidaceae/imunologia , Doença Crônica , Masculino , Camundongos , Periodontite/imunologia , Periodontite/microbiologia , Porphyromonas gingivalis/imunologia , Fatores de Risco , TranscriptomaRESUMO
Periodontal diseases are multifactorial, caused by polymicrobial subgingival pathogens, including Porphyromonas gingivalis, Treponema denticola, and Tannerella forsythia. Chronic periodontal infection results in inflammation, destruction of connective tissues, periodontal ligament, and alveolar bone resorption, and ultimately tooth loss. Enoxacin and a bisphosphonate derivative of enoxacin (bis-enoxacin) inhibit osteoclast formation and bone resorption and also contain antibiotic properties. Our study proposes that enoxacin and/or bis-enoxacin may be useful in reducing alveolar bone resorption and possibly bacterial colonization. Rats were infected with 10(9) cells of polymicrobial inoculum consisting of P. gingivalis, T. denticola, and T. forsythia, as an oral lavage every other week for twelve weeks. Daily subcutaneous injections of enoxacin (5 mg/kg/day), bis-enoxacin (5, 25 mg/kg/day), alendronate (1, 10 mg/kg/day), or doxycycline (5 mg/day) were administered after 6 weeks of polymicrobial infection. Periodontal disease parameters, including bacterial colonization/infection, immune response, inflammation, alveolar bone resorption, and systemic spread, were assessed post-euthanasia. All three periodontal pathogens colonized the rat oral cavity during polymicrobial infection. Polymicrobial infection induced an increase in total alveolar bone resorption, intrabony defects, and gingival inflammation. Treatment with bis-enoxacin significantly decreased alveolar bone resorption more effectively than either alendronate or doxycycline. Histologic examination revealed that treatment with bis-enoxacin and enoxacin reduced gingival inflammation and decreased apical migration of junctional epithelium. These data support the hypothesis that bis-enoxacin and enoxacin may be useful for the treatment of periodontal disease.
Assuntos
Perda do Osso Alveolar/tratamento farmacológico , Perda do Osso Alveolar/etiologia , Enoxacino/uso terapêutico , Periodontite/induzido quimicamente , Periodontite/complicações , Perda do Osso Alveolar/imunologia , Perda do Osso Alveolar/microbiologia , Animais , Contagem de Colônia Microbiana , DNA Bacteriano/genética , Placa Dentária/sangue , Placa Dentária/complicações , Placa Dentária/imunologia , Placa Dentária/microbiologia , Enoxacino/farmacologia , Ensaio de Imunoadsorção Enzimática , Feminino , Imunidade Humoral/efeitos dos fármacos , Imunidade Humoral/imunologia , Imunoglobulina G/sangue , Imunoglobulina M/sangue , Mandíbula/efeitos dos fármacos , Mandíbula/microbiologia , Mandíbula/patologia , Periodontite/imunologia , Periodontite/microbiologia , Periodonto/efeitos dos fármacos , Periodonto/microbiologia , Periodonto/patologia , Porphyromonas gingivalis/efeitos dos fármacos , Porphyromonas gingivalis/crescimento & desenvolvimento , Ratos , Ratos Sprague-Dawley , Treponema/efeitos dos fármacos , Treponema/crescimento & desenvolvimentoRESUMO
Treponema denticola is a predominantly subgingival oral spirochete closely associated with periodontal disease and has been detected in atherosclerosis. This study was designed to evaluate causative links between periodontal disease induced by chronic oral T. denticola infection and atherosclerosis in hyperlipidemic ApoE(-/-) mice. ApoE(-/-) mice (n = 24) were orally infected with T. denticola ATCC 35404 and were euthanized after 12 and 24 weeks. T. denticola genomic DNA was detected in oral plaque samples, indicating colonization of the oral cavity. Infection elicited significantly (P = 0.0172) higher IgG antibody levels and enhanced intrabony defects than sham infection. T. denticola-infected mice had higher levels of horizontal alveolar bone resorption than sham-infected mice and an associated significant increase in aortic plaque area (P ≤ 0.05). Increased atherosclerotic plaque correlated with reduced serum nitric oxide (NO) levels and increased serum-oxidized low-density lipoprotein (LDL) levels compared to those of sham-infected mice. T. denticola infection altered the expression of genes known to be involved in atherosclerotic development, including the leukocyte/endothelial cell adhesion gene (Thbs4), the connective tissue growth factor gene (Ctgf), and the selectin-E gene (Sele). Fluorescent in situ hybridization (FISH) revealed T. denticola clusters in both gingival and aortic tissue of infected mice. This is the first study examining the potential causative role of chronic T. denticola periodontal infection and vascular atherosclerosis in vivo in hyperlipidemic ApoE(-/-) mice. T. denticola is closely associated with periodontal disease and the rapid progression of atheroma in ApoE(-/-) mice. These studies confirm a causal link for active oral T. denticola infection with both atheroma and periodontal disease.
Assuntos
Aorta/microbiologia , Apolipoproteínas E/metabolismo , Aterosclerose/etiologia , Infecções por Bactérias Gram-Negativas/complicações , Doenças Periodontais/etiologia , Treponema denticola/fisiologia , Animais , Anticorpos Antibacterianos/sangue , Apolipoproteínas E/genética , Aterosclerose/microbiologia , Reabsorção Óssea/microbiologia , Gengivite/complicações , Gengivite/microbiologia , Hibridização in Situ Fluorescente , Masculino , Camundongos , Camundongos Knockout , Doenças Periodontais/microbiologia , Fatores de RiscoRESUMO
Periodontal disease (PD) and atherosclerosis are both polymicrobial and multifactorial and although observational studies supported the association, the causative relationship between these two diseases is not yet established. Polymicrobial infection-induced periodontal disease is postulated to accelerate atherosclerotic plaque growth by enhancing atherosclerotic risk factors of orally infected Apolipoprotein E deficient (ApoE(null)) mice. At 16 weeks of infection, samples of blood, mandible, maxilla, aorta, heart, spleen, and liver were collected, analyzed for bacterial genomic DNA, immune response, inflammation, alveolar bone loss, serum inflammatory marker, atherosclerosis risk factors, and aortic atherosclerosis. PCR analysis of polymicrobial-infected (Porphyromonas gingivalis [P. gingivalis], Treponema denticola [T. denticola], and Tannerella forsythia [T. forsythia]) mice resulted in detection of bacterial genomic DNA in oral plaque samples indicating colonization of the oral cavity by all three species. Fluorescent in situ hybridization detected P. gingivalis and T. denticola within gingival tissues of infected mice and morphometric analysis showed an increase in palatal alveolar bone loss (p<0.0001) and intrabony defects suggesting development of periodontal disease in this model. Polymicrobial-infected mice also showed an increase in aortic plaque area (p<0.05) with macrophage accumulation, enhanced serum amyloid A, and increased serum cholesterol and triglycerides. A systemic infection was indicated by the detection of bacterial genomic DNA in the aorta and liver of infected mice and elevated levels of bacterial specific IgG antibodies (p<0.0001). This study was a unique effort to understand the effects of a polymicrobial infection with P. gingivalis, T. denticola and T. forsythia on periodontal disease and associated atherosclerosis in ApoE(null) mice.
Assuntos
Aorta/patologia , Apolipoproteínas E/genética , Aterosclerose/microbiologia , Infecções Bacterianas/microbiologia , Hiperlipidemias/microbiologia , Doenças Periodontais/microbiologia , Animais , Aterosclerose/complicações , Infecções Bacterianas/complicações , Sequência de Bases , Primers do DNA , DNA Bacteriano/análise , Placa Dentária/microbiologia , Hiperlipidemias/complicações , Hibridização in Situ Fluorescente , Camundongos , Camundongos Knockout , Doenças Periodontais/complicações , Reação em Cadeia da Polimerase , Porphyromonas gingivalis/genética , Porphyromonas gingivalis/isolamento & purificação , Treponema denticola/genética , Treponema denticola/isolamento & purificaçãoRESUMO
Porphyromonas gingivalis, Treponema denticola, and Tannerella forsythia are periodontal pathogens associated with the etiology of adult periodontitis as polymicrobial infections. Recent studies demonstrated that oral infection with P. gingivalis induces both periodontal disease and atherosclerosis in hyperlipidemic and proatherogenic ApoE(-/-) mice. In this study, we explored the expression of microRNAs (miRNAs) in maxillas (periodontium) and spleens isolated from ApoE(-/-) mice infected with P. gingivalis, T. denticola, and T. forsythia as a polymicrobial infection. miRNA expression levels, including miRNA miR-146a, and associated mRNA expression levels of the inflammatory cytokines tumor necrosis factor alpha (TNF-α) and interleukin-1ß (IL-1ß) were measured in the maxillas and spleens from mice infected with periodontal pathogens and compared to those in the maxillas and spleens from sham-infected controls. Furthermore, in response to these periodontal pathogens (as mono- and polymicrobial heat-killed and live bacteria), human THP-1 monocytes demonstrated similar miRNA expression patterns, including that of miR-146a, in vitro. Strikingly, miR-146a had a negative correlation with TNF-α secretion in vitro, reducing levels of the adaptor kinases IL-1 receptor-associated kinase 1 (IRAK-1) and TNF receptor-associated factor 6 (TRAF6). Thus, our studies revealed a persistent association of miR-146a expression with these periodontal pathogens, suggesting that miR-146a may directly or indirectly modulate or alter the chronic periodontal pathology induced by these microorganisms.
Assuntos
Infecções por Bactérias Gram-Negativas/genética , Infecções por Bactérias Gram-Negativas/microbiologia , MicroRNAs/biossíntese , Periodontite/genética , Periodontite/microbiologia , Animais , Apolipoproteínas E/deficiência , Apolipoproteínas E/imunologia , Bacteroides/imunologia , Western Blotting , Modelos Animais de Doenças , Infecções por Bactérias Gram-Negativas/imunologia , Humanos , Interleucina-1beta/biossíntese , Interleucina-1beta/imunologia , Masculino , Camundongos , Camundongos Knockout , MicroRNAs/genética , MicroRNAs/imunologia , Monócitos/imunologia , Monócitos/metabolismo , Periodontite/imunologia , Porphyromonas gingivalis/imunologia , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Baço/imunologia , Baço/metabolismo , Treponema denticola/imunologia , Fator de Necrose Tumoral alfa/biossíntese , Fator de Necrose Tumoral alfa/imunologiaRESUMO
Porphyromonas gingivalis secretes a serine phosphatase enzyme, SerB, upon contact with gingival epithelial cells in vitro. The SerB protein plays a critical role in internalization and survival of the organism in epithelial cells. SerB is also responsible for the inhibition of interleukin-8 (IL-8) secretion from gingival epithelial cells infected with P. gingivalis. This study examined the ability of a P. gingivalis SerB mutant to colonize the oral cavity and induce gingival inflammation, immune responses, and alveolar bone resorption in a rat model of periodontal disease. Both P. gingivalis ATCC 33277 and an isogenic ΔSerB mutant colonized the oral cavities of rats during the 12-week experimental period. Both of the strains induced significant (P < 0.05) systemic levels of immunoglobulin G (IgG) and isotypes IgG1, IgG2a, and IgG2b, indicating the involvement of both T helper type 1 (Th1) and Th2 responses to infection. Both strains induced significantly (P < 0.05) higher levels of alveolar bone resorption in infected rats than in sham-infected control rats. However, horizontal and interproximal alveolar bone resorption induced by the SerB mutant was significantly (P < 0.05) lower than that induced by the parental strain. Rats infected with the ΔSerB mutant exhibited significantly higher levels of apical migration of the junctional epithelium (P < 0.01) and polymorphonuclear neutrophil (PMN) recruitment (P < 0.001) into the gingival tissues than rats infected with the wild type. In conclusion, in a rat model of periodontal disease, the SerB phosphatase of P. gingivalis is required for maximal alveolar bone resorption, and in the absence of SerB, more PMNs are recruited into the gingival tissues.
Assuntos
Perda do Osso Alveolar/microbiologia , Infecções por Bacteroidaceae/microbiologia , Doenças Periodontais/microbiologia , Monoéster Fosfórico Hidrolases/metabolismo , Porphyromonas gingivalis/patogenicidade , Perda do Osso Alveolar/imunologia , Perda do Osso Alveolar/patologia , Animais , Anticorpos Antibacterianos/sangue , Infecções por Bacteroidaceae/imunologia , Infecções por Bacteroidaceae/patologia , Modelos Animais de Doenças , Feminino , Humanos , Imunoglobulina G/sangue , Inflamação/imunologia , Inflamação/microbiologia , Inflamação/patologia , Doenças Periodontais/imunologia , Doenças Periodontais/patologia , Monoéster Fosfórico Hidrolases/genética , Porphyromonas gingivalis/enzimologia , Porphyromonas gingivalis/genética , Porphyromonas gingivalis/imunologia , Ratos , Ratos Sprague-DawleyRESUMO
The mammalian skeleton adjusts bone structure and strength in response to changes in mechanical loading, however the molecular and cellular mechanisms governing this process in vivo are unknown. Terminally differentiated osteoblasts, the osteocytes, are presumptive mechanosensory cells for bone, and cell culture studies demonstrate that beta1 integrins participate in mechanical signaling. To determine the role of beta1 integrins in osteoblasts in vivo, we used the Cre-lox system to delete beta1 integrin from cells committed to the osteoblast lineage. While pCol2.3 Cre-mediated recombination was widespread in bones from Colalpha1(I)-Cre+/beta1fl/fl conditional knockout mice (cKO), beta1 integrin protein was depleted from cortical osteocytes, but not from cancellous osteocytes or cells lining bone surfaces in adults. Bones from cKO mice that were normally loaded were similar in structure to WT littermates. However, hindlimb unloading of adult cKO mice for one week intended to cause bone loss (disuse osteopenia), resulted in unexpected, rapid changes in the geometry of cortical bone; hindlimb unloading increased the cross-sectional area, marrow area, and moments of inertia in cKO, but not WT mice. Furthermore, these hindlimb unloading-induced geometric changes in cortical bone of cKO mice resulted in increased whole bone bending stiffness and strength of the femur. Together, these results confirmed the concept that osteocytes are mechanosensory cells and showed beta1 integrins in cortical osteocytes limited changes in cortical geometry in response to disuse, thus providing the first in vivo evidence that beta1 integrins on osteocytes mediate specific aspects of mechanotransduction.
Assuntos
Integrina beta1/fisiologia , Osteócitos/metabolismo , Doença Aguda , Animais , Doenças Ósseas Metabólicas , Feminino , Deleção de Genes , Integrina beta1/genética , Integrina beta1/metabolismo , Camundongos , Camundongos Knockout , Modelos Biológicos , Modelos Genéticos , Osteoblastos/metabolismo , Transdução de Sinais , Resistência à Tração , Distribuição TecidualRESUMO
CcpA globally regulates transcription in response to carbohydrate availability in many gram-positive bacteria, but its role in Streptococcus mutans remains enigmatic. Using the fructan hydrolase (fruA) gene of S. mutans as a model, we demonstrated that CcpA plays a direct role in carbon catabolite repression (CCR). Subsequently, the expression of 170 genes was shown to be differently expressed (> or = 2-fold) in glucose-grown wild-type (UA159) and CcpA-deficient (TW1) strains (P < or = 0.001). However, there were differences in expression of only 96 genes between UA159 and TW1 when cells were cultivated with the poorly repressing substrate galactose. Interestingly, 90 genes were expressed differently in wild-type S. mutans when glucose- and galactose-grown cells were compared, but the expression of 515 genes was altered in the CcpA-deficient strain in a similar comparison. Overall, our results supported the hypothesis that CcpA has a major role in CCR and regulation of gene expression but revealed that in S. mutans there is a substantial CcpA-independent network that regulates gene expression in response to the carbohydrate source. Based on the genetic studies, biochemical and physiological experiments demonstrated that loss of CcpA impacts the ability of S. mutans to transport and grow on selected sugars. Also, the CcpA-deficient strain displayed an enhanced capacity to produce acid from intracellular stores of polysaccharides, could grow faster at pH 5.5, and could acidify the environment more rapidly and to a greater extent than the parental strain. Thus, CcpA directly modulates the pathogenic potential of S. mutans through global control of gene expression.
Assuntos
Proteínas de Bactérias/metabolismo , Proteínas de Ligação a DNA/metabolismo , Regulação Bacteriana da Expressão Gênica , Proteínas Repressoras/metabolismo , Streptococcus mutans/metabolismo , Proteínas de Bactérias/genética , Proteínas de Bactérias/fisiologia , Transporte Biológico , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/fisiologia , Ensaio de Desvio de Mobilidade Eletroforética , Galactose/metabolismo , Glucose/metabolismo , Glicosídeo Hidrolases/genética , Glicosídeo Hidrolases/metabolismo , Concentração de Íons de Hidrogênio , Análise de Sequência com Séries de Oligonucleotídeos , Polissacarídeos/metabolismo , Proteínas Repressoras/genética , Proteínas Repressoras/fisiologia , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Streptococcus mutans/genética , Streptococcus mutans/crescimento & desenvolvimento , Transcrição Gênica , Virulência/genéticaRESUMO
UNLABELLED: bFGF stimulates osteo- and adipogenesis concurrently at skeletal sites with red but not with fatty marrow, whereas a PGE2 receptor subtype 4 agonist has bone anabolic effects at both skeletal sites and decreases adipose tissue within red and fatty marrow. INTRODUCTION: Basic fibroblast growth factor (bFGF) stimulates osteogenesis at skeletal sites with hematopoietic but not with fatty marrow. The prostaglandin E2 (PGE2) receptor subtype 4 agonist (EP4A) stimulates osteogenesis at the former skeletal sites, but its effects at fatty marrow sites are unknown. In addition, both bFGF and PGE2 through the EP4 receptor have also been implicated in adipogenesis. However, their specific effects on bone marrow adipogenesis and the inter-relationship with osteogenesis have never been studied in vivo. MATERIALS AND METHODS: Female Sprague-Dawley rats were ovariectomized (OVX) or sham-operated and maintained for 1 yr after surgery. OVX rats were then injected daily with bFGF or with EP4A SC for 3 wk. The osteo- and adipogenic effects of these agents were assessed by histomorphometry and by determining changes in expression of genes associated with these events by real-time PCR in the lumbar and caudal vertebrae, bones with a predominance of hematopoietic and fatty marrow, respectively. Expression of FGFR1-4 and the EP4 receptor were also evaluated by real-time PCR and immunocytochemistry. RESULTS: bFGF and EP4A stimulated bone formation at skeletal sites with hematopoietic marrow, but only the later anabolic agent is also effective at fatty marrow sites. The diminished bone anabolic effect of bFGF at the fatty marrow site was not caused by a lack of cell surface receptors for the growth factor at this site. Interestingly, whereas EP4A decreased fatty marrow area and the number of adipocytes, bFGF increased osteogenesis and adipogenesis within the bone marrow. CONCLUSIONS: bFGF can stimulate osteogenesis and bone marrow adipogenesis concurrently at red marrow sites, but not at fatty marrow sites. In contrast, EP4A stimulates bone formation at skeletal sites with hematopoietic and fatty marrow and simultaneously decreased fatty marrow area and the number of adipocytes in the bone marrow, suggesting that osteogenesis occurs at the expense of adipogenesis.
Assuntos
Adipogenia/efeitos dos fármacos , Fator 2 de Crescimento de Fibroblastos/farmacologia , Osteogênese/efeitos dos fármacos , Ovariectomia , Receptores de Prostaglandina E/agonistas , Compostos de Sulfidrila/farmacologia , Tiofenos/farmacologia , Animais , Peso Corporal/efeitos dos fármacos , Calcificação Fisiológica/efeitos dos fármacos , Colágeno Tipo I/genética , Subunidade alfa 1 de Fator de Ligação ao Core/genética , Feminino , Expressão Gênica/efeitos dos fármacos , Hematócrito , Vértebras Lombares/efeitos dos fármacos , Vértebras Lombares/metabolismo , Osteoblastos/citologia , Osteoblastos/efeitos dos fármacos , Osteoblastos/metabolismo , Osteocalcina/genética , PPAR gama/genética , Antagonistas de Prostaglandina/farmacologia , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Ratos , Ratos Sprague-Dawley , Receptores de Fatores de Crescimento de Fibroblastos/genética , Receptores de Prostaglandina E/antagonistas & inibidores , Receptores de Prostaglandina E/genética , Receptores de Prostaglandina E Subtipo EP4 , Coluna Vertebral/efeitos dos fármacos , Coluna Vertebral/metabolismoRESUMO
UNLABELLED: Lrp5 deficiency decreases bone formation and results in low bone mass. This study evaluated the bone anabolic response to intermittent PTH treatment in Lrp5-deficient mice. Our results indicate that Lrp5 is not essential for the stimulatory effect of PTH on cancellous and cortical bone formation. INTRODUCTION: Low-density lipoprotein receptor-related protein 5 (Lrp5), a co-receptor in canonical Wnt signaling, increases osteoblast proliferation, differentiation, and function. The purpose of this study was to use Lrp5-deficient mice to evaluate the potential role of this gene in mediating the bone anabolic effects of PTH. MATERIALS AND METHODS: Adult wildtype (WT, 23 male and 25 female) and Lrp5 knockout (KO, 27 male and 26 female) mice were treated subcutaneously with either vehicle or 80 microg/kg human PTH(1-34) on alternate days for 6 weeks. Femoral BMC and BMD were determined using DXA. Lumbar vertebrae were processed for quantitative bone histomorphometry. Bone architecture was evaluated by microCT. Data were analyzed using a multiway ANOVA. RESULTS: Cancellous and cortical bone mass were decreased with Lrp5 deficiency. Compared with WT mice, cancellous bone volume in the distal femur and the lumbar vertebra in Lrp5 KO mice was 54% and 38% lower, respectively (p<0.0001), whereas femoral cortical thickness was 11% lower in the KO mice (p<0.0001). The decrease in cancellous bone volume in the lumbar vertebrae was associated with a 45% decrease in osteoblast surface (p<0.0001) and a comparable decrease in bone formation rate (p<0.0001). Osteoclast surface, an index of bone resorption, was 24% lower in Lrp5 KO compared with WT mice (p<0.007). Treatment of mice with PTH for 6 weeks resulted in a 59% increase in osteoblast surface (p<0.0001) and a 19% increase in osteoclast surface (p=0.053) in both genotypes, but did not augment cancellous bone volume in either genotype. Femur cortical thickness was 11% higher in PTH-treated mice in comparison with vehicle-treated mice (p<0.0001), regardless of genotype. CONCLUSIONS: Whereas disruption of Lrp5 results in decreased bone mass because of decreased bone formation, Lrp5 does not seem to be essential for the stimulatory effects of PTH on cancellous and cortical bone formation.