Context-dependent transcriptional regulation of microglial proliferation

Microglia proliferate during brain development and brain lesions, but how this is coordinated at the transcriptional level is not well understood. Here, we investigated fundamental aspects of the transcriptional process associated with proliferation of mouse microglia during postnatal development and in adults in a model of induced microglial depletion-repopulation. While each proliferative subset displayed globally a distinct signature of gene expression, they also co-expressed a subgroup of 1370 genes at higher levels than quiescent microglia. Expression of these may be coordinated by one of two mechanisms of regulation with distinct properties. A first mechanism augments expression of genes already expressed in quiescent microglia and is subject to regulation by Klf/Sp, Nfy, and Ets transcription factors. Alternatively, a second mechanism enables de novo transcription of cell cycle genes and requires additional regulatory input from Lin54 and E2f transcription factors. Of note, transcriptional upregulation of E2f1 and E2f2 family members may represent a critical regulatory checkpoint to enable microglia to achieve efficient cell cycling. Furthermore, analysis of the activity profile of the repertoire of promoter-distal genomic regulatory elements suggests a relatively restricted role for these elements in coordinating cell cycle gene expression in microglia. Overall, proliferating microglia integrates regulation of cell cycle gene expression with their broader, context-dependent, transcriptional landscape.

Essential contributions of enhancer genomic regulatory elements to microglial cell identity and functions

Microglia are the specialized macrophages of the brain and play essential roles in ensuring its proper functioning. Accumulating evidence suggests that these cells coordinate the inflammatory response that accompanies various clinical brain conditions, including neurodegenerative diseases and psychiatric disorders. Therefore, investigating the functions of these cells and how these are regulated have become important areas of research in neuroscience over the past decade. In this regards, recent efforts to characterize the epigenomic mechanisms underlying microglial gene transcription have provided significant insights into the mechanisms that control the ontogeny and the cellular competences of microglia. In particular, these studies have established that a substantial proportion of the microglial repertoire of promoter-distal genomic regulatory elements, or enhancers, is relatively specific to these cells compared to other tissue-resident macrophages. Notably, this specificity is under the regulation of factors present in the brain that modulate activity of target axes of signaling pathways-transcription factors in microglia. Thus, the microglial enhancer repertoire is highly responsive to perturbations in the cerebral tissue microenvironment and this responsiveness has profound implications on the activity of these cells in brain diseases. This article is categorized under: Physiology > Mammalian Physiology in Health and Disease Models of Systems Properties and Processes > Mechanistic Models Biological Mechanisms > Cell Fates Developmental Biology > Lineages.

A new function for Prokineticin 2: Recruitment of SVZ-derived neuroblasts to the injured cortex in a mouse model of traumatic brain injury

Traumatic brain injury is an important cause of global morbidity and mortality. After an initial injury, there is a cascade of cellular and molecular events that ultimately lead to cell death. Therapies aim to both counteract these mechanisms and replenish the lost cell population in order to improve recovery. The adult mammal brain has at least two neurogenic regions that maintain physiological functions: the subgranular zone of the dentate gyrus in the hippocampus, which produces neurons that integrate locally, and the subventricular zone (SVZ) adjacent to the lateral ventricles, which produces neuroblasts that migrate through the rostral migratory stream (RMS) to the olfactory bulbs. Brain injuries, as well as neurodegenerative diseases, induce the SVZ to respond by increasing cell proliferation and migration to the injured areas. Here we report that cells migrate from the SVZ and RMS to the injured cortex after traumatic brain injury in mice, and that the physiological RMS migration is not impaired. We also show that Prokineticin 2 (PROK2), a chemokine important for the olfactory bulb neurogenesis, expressed exclusively by cortical microglia in the cortex as early as 24 h after injury. We then show that administration of a PROK2 receptor antagonist decreases the number of SVZ cells that reach the injured cortex, while injection of recombinant PROK2 into the cortex of uninjured mice attracts SVZ cells. We also demonstrate that cells expressing PROK2 in vitro directionally attract SVZ cells. These data suggest that PROK2 could be utilized in regeneration efforts for the acutely injured mammalian cortex.

Simvastatin improves morphological and functional recovery of sciatic nerve injury in Wistar rats

AIM

The purpose of this work is to investigate the effects of simvastatin on sciatic nerve regeneration in male Wistar Rats.

MATERIALS AND METHODS

Forty animals were allocated into four groups: (1) control (C); (2) control+simvastatin (CS); (3) lesioned animals+sterile PBS (LC) and (4) lesioned animals+simvastatin (LS). Lesioned animals were submitted to crushing lesion of right sciatic nerve. Simvastatin (20mg/kg/day, i.p.) was administered for five days. Footprints were obtained weekly for evaluation of functional locomotor recovery by means of the Sciatic Function Index (SFI). Blood samples were obtained weekly for quantifying circulating leukocytes. Animals were sacrificed after 21 days for histological analyses of sciatic nerve and spleen.

RESULTS

LS Animals presented increased SFI scores, decreased areas of oedema and mononuclear cell infiltration during Wallerian degeneration and nerve regeneration (7,14 and 21 days; P<0.05). Spleen weight and white pulp areas was increased in LC animals after 21 days. Increased numbers of circulating neutrophils were observed in simvastatin treated animals (CS e LS) at seven, 14 and 21 days, compared to non-treated groups (C and LC).

CONCLUSION

The study suggests that simvastatin accelerates the morphological and functional recovery process of the peripheral nervous system interfering with innate and acquired immunity.

Recommendations for the use of extended criteria donors in lung transplantation

Selection criteria for lung donation were based on initial experiences with lung transplantation without further studies to improve them, thereby guaranteeing the best use of donated organs. A definition of an extended criteria donor is therefore required to obtain more lungs to meet the demands of patients awaiting transplantation. Studies have been reviewed for the impact on survival and morbidity of age ranges, oxygen fraction, cause of death, smoking habits, x-ray findings, infection, hepatitis serology and non-heart-beating status, seeking to support physicians to make decisions regarding the use of marginal organs.

Efeito do treinamento físico no pulmão de ratos submetidos à ingestão alcoólica

O alcoolismo crônico provoca alterações nos tecidos pulmonares caracterizadas por edema pulmonar e formação de extenso infiltrado inflamatório. O objetivo deste trabalho foi avaliar o efeito do exercício físico sobre as lesões pulmonares provocadas por ingestão crônica de álcool em ratos Wistar. MATERIAL E MÉTODOS: Trinta e dois ratos Wistar machos (261,1 ± 1,3 gramas) receberam aguardente de cana-de-açúcar diluída (30%, v/v, grupo alcoolizado) ou água potável (grupo controle) durante 120 dias. Após este período, cinco animais de cada grupo foram sacrificados. Os demais animais receberam apenas água potável até o final do experimento e foram divididos em quatro grupos: alcoolizados sedentários (AS), controle sedentários (CS), alcoolizados treinados (AT) e controles treinados (CT). Os animais AT e CT foram submetidos a protocolo de natação, aumentando gradativamente o tempo de exercício até 20 minutos por dia, cinco vezes por semana, durante um período total de cinco semanas. Neste mesmo período, os animais AS e CS foram mantidos em sedentarismo. RESULTADOS: Após o período de ingestão alcoólica, os animais do grupo alcoolizado apresentaram redução de peso (P < 0,05) e aumento da massa relativa do pulmão (P < 0,05). O pulmão do grupo alcoolizado apresentou edema pulmonar e extenso infiltrado inflamatório. Os animais dos grupos CS e CT não apresentaram diferenças morfológicas. Os animais do grupo AT apresentaram aumento do quadro de edema pulmonar e do número de macrófagos pigmentados em relação ao grupo AC (P < 0,05). CONCLUSÃO: O exercício físico pode acentuar o processo inflamatório pulmonar quando aplicado em animais com lesão pulmonar inflamatória provocada pelo consumo crônico de álcool.

Production of tumour necrosis factor alpha by primary cultured rat alveolar epithelial cells

Tumour necrosis factor alpha(TNF-alpha) is one of the most important pro-inflammatory cytokines, which plays an important role in host defense and acute inflammation related to tissue injury. The major source of TNF-alpha has been shown to be immune cells such as macrophages and neutrophils. In the present study, we demonstrated that LPS-treatment on alveolar epithelial cells isolated from adult rat lungs also induced a dose- and time-dependent release of TNF-alpha. The purity and identity of these cells were examined by immunofluorescent staining and confocal microscopy with antibodies for cytokeratin and pro-surfactant protein C, markers for epithelial cells and type II pneumocytes respectively. Positive staining of TNF-alpha was observed throughout the cell layer and localized intracellularly. LPS-induced TNF-alpha production from alveolar epithelial cells was blocked not only by cycloheximide, an inhibitor of protein translation, but also by actinomycin D, an inhibitor of gene transcription. The mRNA of TNF-alpha rapidly increased within 1 h of LPS stimulation. These data suggest that LPS-induced TNF-alpha production from alveolar epithelial cells is primarily regulated at the transcriptional level, which is different from that of macrophages and neutrophils. TNF-alpha produced by alveolar epithelial cells may function as an alert signal in host defense to induce production of other inflammatory mediators.

Cell death in human lung transplantation: apoptosis induction in human lungs during ischemia and after transplantation

OBJECTIVE

To examine the presence and extent of apoptosis as well as the affected cell types in human lung tissue before, during, and after transplantation.

SUMMARY BACKGROUND DATA

Apoptosis has been described in various human and animal models of ischemia-reperfusion injury, including heart, liver, and kidney, but not in lungs. Therefore, the presence of apoptosis and its role in human lungs after transplantation is not clear.

METHODS

Lung tissue biopsies were obtained from 20 consecutive human lungs for transplantation after cold ischemic preservation (1-5 hours), after warm ischemia time (during implantation), and 30, 60, and 120 minutes after graft reperfusion. To detect and quantify apoptosis, fluorescent in situ end labeling of DNA fragments (TUNEL assay) was used. Electron microscopy was performed to verify the morphologic changes consistent with apoptosis and to identify the cell types, which were lost by apoptosis.

RESULTS

Almost no evidence of apoptosis was found in specimens after immediate cold and warm ischemic periods. Significant increases in the numbers of cells undergoing apoptosis were observed after graft reperfusion in a time-dependent manner. The mean fraction of apoptotic cells at 30, 60, and 120 minutes after graft reperfusion were 16.6%, 22.1%, and 34.9% of total cells, respectively. Most of the apoptotic cells appeared to be alveolar type II pneumocytes, as confirmed by electron microscopy.

CONCLUSIONS

Programmed cell death (apoptosis) appears to be a significant type of cell loss in human lungs after transplantation, and this may contribute to ischemia-reperfusion injury during the early phase of graft reperfusion. This cell loss might be responsible for severe organ dysfunction, which is seen in 20% of patients after lung transplantation. Therefore, this work is of importance to surgeons for the future development of interventions to prevent cell death in transplantation.

Tumor necrosis factor-alpha mediates lipopolysaccharide-induced macrophage inflammatory protein-2 release from alveolar epithelial cells. Autoregulation in host defense

Our recent studies have demonstrated that in response to lipopolysaccharide (LPS) challenge, alveolar epithelial cells produced tumor necrosis factor (TNF)-alpha, an early response cytokine in the inflammatory process. To investigate whether LPS-induced TNF-alpha release is related to other inflammatory mediators from the same cell type, we examined effects of LPS stimulation on macrophage inflammatory protein (MIP)-2 production by alveolar epithelial cells, and then examined the relationship between TNF-alpha and MIP-2 production. LPS stimulation induced a dose- and time-dependent release of MIP-2. The steady-state messenger RNA level of MIP-2 was significantly increased, with the MIP-2 protein localized within alveolar epithelial cells, as determined by confocal microscopy. The LPS-induced MIP-2 production is regulated at both the transcriptional and post-transcriptional levels. TNF-alpha also induced MIP-2 production from alveolar epithelial cells. Preincubation with an antisense oligonucleotide against TNF-alpha inhibited LPS-induced TNF-alpha in a dose-dependent and sequence-specific manner. The same antisense also inhibited MIP-2 production. The inhibitory effects were highly correlated. Polyclonal and monoclonal antibodies against TNF-alpha also attenuated LPS-induced MIP-2. These results suggest that LPS-induced MIP-2 release from alveolar epithelial cells may be mediated in part by TNF-alpha from the same cell type. This autoregulatory mechanism may amplify LPS-induced signals involved in host defense as well as in acute inflammatory reactions.

LPS-induced depolymerization of cytoskeleton and its role in TNF-alpha production by rat pneumocytes

Lipopolysaccharide (LPS) polymerizes microfilaments and microtubules in macrophages and monocytes. Disrupting microfilaments or microtubules with cytochalasin D (CytoD) or colchicine can suppress LPS-induced tumor necrosis factor-alpha (TNF-alpha) gene expression and protein production from these cells. We have recently demonstrated that primary cultured rat alveolar epithelial cells can produce TNF-alpha on LPS stimulation. In the present study, we found that the LPS-induced increase in TNF-alpha mRNA level and protein production in alveolar epithelial cells was not inhibited by CytoD or colchicine (1 nM to 10 microM). In fact, LPS-induced TNF-alpha production was further enhanced by CytoD (1-10 microM) and inhibited by jasplakinolide, a polymerizing agent for microfilaments. Immunofluorescent staining and confocal microscopy showed that LPS (10 microg/ml) depolymerized microfilaments and microtubules within 15 min, which was prolonged until 24 h for microfilaments. These results suggest that the effects of LPS on the cytoskeleton and the role of the cytoskeleton in mediating TNF-alpha production in alveolar epithelial cells are opposite to those in immune cells. This disparity may reflect the different roles between nonimmune and immune cells in host defense.

Effect of complement inhibition with soluble complement receptor 1 on pig allotransplant lung function

BACKGROUND

Lung dysfunction after transplantation continues to be a significant clinical problem. Soluble complement receptor 1 (sCR1) is a potent inhibitor of complement activation. We evaluated the inhibitory effect of sCR1 on complement activation and reperfusion injury in pig lung allografts.

METHODS

In a randomized and blinded study, left lung transplantation was performed in 13 pigs. Donor lungs were flushed and then stored for 30 hr at 4 degrees C. Control pigs (n=7) received saline, and the treatment group (n=6) received 15 mg/kg sCR1 1 hr before reperfusion. One hour after reperfusion, the right pulmonary artery was clamped for 10 min to assess the function of the transplanted lung. Pulmonary function was assessed again on day 3.

RESULTS

Complement inhibition was 93% in the sCR1 group and returned to baseline (8% inhibition) after 3 days. There was a trend toward a higher partial pressure of oxygen at 1 hr in the sCR1 group compared with the control group (mean +/- SE: 408+/-42 mmHg vs. 288+/-69 mmHg, P = 0.19). Alveolar ventilation was better in the sCR1 group than in the control group (P = 0.01) at 1 hr. Mixed venous saturation was significantly lower in the control group at both 1 hr (P = 0.02) and 3 days (P = 0.001). The wet/dry weight of the lung tissue was lower in the sCR1 group compared with the control group on day 3 (P < 0.05). Chemiluminescence, an index of phagocyte priming, was lower in the sCR1 group when cells were stimulated with complement opsonized zymosan but not when stimulated with zymosan or phorbol myristate acetate.

CONCLUSION

sCR1 improves ventilation, reduces pulmonary edema, and may be beneficial in improving posttransplant lung oxygenation.

Radiotherapy alone and chemoradiation for nonmetastatic esophageal carcinoma. A critical review of chemoradiation

Sixty-five patients with nonmetastatic (Stages I, II, and III) esophageal cancer (EC) were treated with radiotherapy (RT) alone (56.00 to 61.00 Gy in 6 to 7 weeks) or synchronous combinations of radiotherapy and chemotherapy (RT-CT). RT-CT consisted of 41.40 to 50.40 Gy in 4.5 to 8 weeks with continuous infusion 5-fluorouracil 5-FU (1000 mg/m2/d for 4 days in weeks 1, 4, and 8), mitomycin C (10 mg/m2 intravenously [IV] in weeks 1 and 8), cisplatin (75 mg/m2 IV in week 4). Maintenance CT consisted of methotrexate (200 mg/m2 IV), leucovorin (10 mg/m2 orally every 6 hours for 5 doses), and 5-FU (600 mg/m2 IV) in weeks 10, 12, and 14. Thirty-five patients treated by RT alone (Group A) were comparable in terms of age, sex, AJC staging, histologic condition, and location of primary with 30 patients treated by RT-CT (Group B). In Group A (range, 2- to 144+ months), two patients (42 and 144 months) are alive and well. In Group B (range, 2- to 59+ months), 12 patients (7 to 59 months) are alive and well. Median survival in Group A is 8 months, compared with 15 months for patients achieving a complete response (CR) in Group B. Patients in Group B achieved a 77% CR rate by endoscopy-biopsy, whereas 30% of the patients in Group A achieved a CR (P = 0.0001). The recurrence rates at the primary site/regional nodes were 77% and 27% in Groups A and B, respectively (P = 0.0001). The incidences of distant metastases were 29% and 20%, respectively (P = 0.423). In Group A, the 1-year and 2-year cumulative survival rates were 27% and 13%, respectively. In Group B, the cumulative survival rates were 53% at 1 year and 29% at 2 years (P = 0.023). Aside from reversible myelotoxicity, the incidences of pulmonary fibrosis, esophagitis, and fistulae formation were less frequent in the combined technique treatment group. A compilation of reported chemoradiation protocols for EC indicates consistently improved 1-year and 2-year survival rates, compared with surgical and RT series. The key to further improvement in the treatment of EC appears to lie in increasing the biologic response (RT fractionation and endocavitary RT) and optimal use of multiple effective CT agents with nonadditive toxicities.

Chronic anemia progressing to Auer rod-positive and TdT-positive acute leukemia with 5q- chromosomal anomaly

The 5q- syndrome is a recently described entity characterized by partial deletion of the long arm of chromosome No. 5 and by hematologic findings of chronic anemia with reticulocytopenia, nonlobulated megakaryocytes, and megathrombocytes. We report on a patient with the hematologic features of the 5q- syndrome who progressed to acute leukemia and whose uniqueness consisted of 1) lack of additional cytogenetic abnormalities, 2) presence of blasts with Auer rods, and 3) bone marrow cells positive for terminal deoxynucleotidyl transferase. His leukemia was refractory to conventional chemotherapy.

Combination chemotherapy with 5-fluorouracil, CCNU, and vincristine in metastatic colorectal carcinoma

Twenty-four patients with metastatic colorectal carcinoma were treated with a chemotherapeutic regimen consisting of 5-fluorouracil, CCNU, and vincristine (FCV). Twenty patients were evaluable for response and 22 were evaluable for drug toxicity. One patient (5%) showed partial response, eight patients (40%) had stabilization of disease, and the remaining 11 patients (55%) had progression of disease. There was no statistically significant difference between the median survivals of patients with stabilization and of those with progression of their disease (p greater than 0.01). We were unable to demonstrate objective efficacy of the FCV regimen in the schedule used.