Production Of Inhibitory Factors Research Articles

Alleviating tumor hypoxia and immunosuppression via sononeoperfusion: A new Ally for potentiating anti-PD-L1 blockade of solid tumor

The hypoxic and immunosuppressive tumor microenvironment (TME) remains a major obstacle to impede cancer immunotherapy. Here, we found that sononeoperfusion—a new effect of tumor perfusion enhancement induced by low mechanical index ultrasound stimulated microbubble cavitation (USMC)—ameliorated tumor tissue oxygenation and induced tumor vascular normalization (TVN). This TVN might be associated with the down-regulation of hypoxia-inducible factor 1-alpha (HIF-1α) and vascular endothelial growth factor (VEGF) within tumors. Moreover, the sononeoperfusion effect reduced the accumulation of immunosuppressive cells, such as regulatory T cells (Tregs), myeloid-derived suppressor cells (MDSCs) and M2-like tumor-associated macrophages (M2-TAMs), and decreased the production of immune inhibitory factors like transforming growth factor-β1 (TGF-β1), interleukin 10 (IL-10), chemoattractant chemokines CC-chemokine ligand 22 (CCL22), CCL28, adenosine and lactate within tumors. Notably, flow cytometry analysis revealed that sononeoperfusion not only increased the percentage of tumor infiltrating-CD8+ T cells, but also promoted the generation of interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α) by these cells. Furthermore, the improved immune TME by sononeoperfusion effect sensitized anti-PD-L1 treatment both in MC38 colon cancer and Lewis lung carcinoma mice, resulting in tumor regression and prolonged survival. Mechanically, the enhanced efficacy of combination therapy was mainly based on promoting the infiltration and function of CD8+ T cells within tumors. Together, sononeoperfusion could ameliorate hypoxia and immunosuppression in the TME, thereby potentiating anti-PD-L1 therapy for solid tumors. This novel method of USMC generating sononeoperfusion effect may provide a new therapeutic modality for facilitating cancer immunotherapy.

STING activation in alveolar macrophages and group 2 innate lymphoid cells suppresses IL-33-driven type 2 immunopathology.

2′3′-cGAMP is known as a nonclassical second messenger and small immune modulator that possesses potent antitumor and antiviral activities via inducing the stimulator of IFN genes–mediated (STING-mediated) signaling pathway. However, its function in regulating type 2 immune responses remains unknown. Therefore, we sought to determine a role of STING activation by 2′3′-cGAMP in type 2 inflammatory reactions in multiple mouse models of eosinophilic asthma. We discovered that 2′3′-cGAMP administration strongly attenuated type 2 lung immunopathology and airway hyperreactivity induced by IL-33 and a fungal allergen, Aspergillus flavus. Mechanistically, upon the respiratory delivery, 2′3′-cGAMP was mainly internalized by alveolar macrophages, in which it activated the STING/IFN regulatory factor 3/type I IFN signaling axis to induce the production of inhibitory factors containing IFN-α, which blocked the IL-33–mediated activation of group 2 innate lymphoid (ILC2) cells in vivo. We further demonstrated that 2′3′-cGAMP directly suppressed the proliferation and function of both human and mouse ILC2 cells in vitro. Taken together, our findings suggest that STING activation by 2′3′-cGAMP in alveolar macrophages and ILC2 cells can negatively regulate type 2 immune responses, implying that the respiratory delivery of 2′3′-cGAMP might be further developed as an alternative strategy for treating type 2 immunopathologic diseases such as eosinophilic asthma.

Stromal-like Wilms tumor cells induce human Natural Killer cell degranulation and display immunomodulatory properties towards NK cells

ABSTRACT The similarity of stromal-like Wilms tumor (str-WT) cells with mesenchymal stem cells (MSC), suggests their relevant role in the interplay with immune cells in the tumor microenvironment. We investigated the interaction between str-WT cells and NK cells. We observed that str-WT cells expressed some major ligands for activating and inhibitory NK cell receptors. Moreover, they expressed inhibitory checkpoint molecules involved in the negative regulation of anti-tumor immune response. The analysis of the interaction between str-WT cells and NK lymphocytes revealed that activated NK cells could efficiently degranulate upon interaction with str-WT cells. On the other hand, str-WT cells could exert potent inhibitory effects on cytokine-induced activation of NK cell proliferation and phenotype, which were mediated by the production of IDO and PGE2 inhibitory factors. Our data provide insight into the molecular interactions between str-WT cells and NK lymphocytes that may result in different outcomes possibly occurring in the WT microenvironment.

Lactobacillus johnsonii L531 Ameliorates Escherichia coli-Induced Cell Damage via Inhibiting NLRP3 Inflammasome Activity and Promoting ATG5/ATG16L1-Mediated Autophagy in Porcine Mammary Epithelial Cells

Escherichia coli (E. coli), a main mastitis-causing pathogen in sows, leads to mammary tissue damage. Here, we explored the effects of Lactobacillus johnsonii L531 on attenuating E. coli-induced inflammatory damage in porcine mammary epithelial cells (PMECs). L. johnsonii L531 pretreatment reduced E. coli adhesion to PMECs by competitive exclusion and the production of inhibitory factors and decreased E. coli-induced destruction of cellular morphology and ultrastructure. E. coli induced activation of NLRP3 inflammasome associated with increased expression of NLRP3, ASC, and cleaved caspase-1, however, L. johnsonii L531 inhibited E. coli-induced activation of NLRP3 inflammasome. Up-regulation of interleukin (Il)-1β, Il-6, Il-8, Il-18, tumor necrosis factor alpha, and chemokine Cxcl2 expression after E. coli infection was attenuated by L. johnsonii L531. E. coli infection inhibited autophagy, whereas L. johnsonii L531 reversed the inhibitory effect of E. coli on autophagy by decreasing the expression of autophagic receptor SQSTM1/p62 and increasing the expression of autophagy-related proteins ATG5, ATG16L1, and light chain 3 protein by Western blotting analysis. Our findings suggest that L. johnsonii L531 pretreatment restricts NLRP3 inflammasome activity and induces autophagy through promoting ATG5/ATG16L1-mediated autophagy, thereby protecting against E. coli-induced inflammation and cell damage in PMECs.

Neuregulin‑1: An underlying protective force of cardiac dysfunction in sepsis (Review).

Neuregulin-1 (NRG-1) is a type of epidermal growth factor-like protein primarily distributed in the nervous and cardiovascular systems. When sepsis occurs, the incidence of cardiac dysfunction in myocardial injury is high and the mechanism is complicated. It directly causes myocardial cell damage, whilst also causing damage to the structure and function of myocardial cells, weakening of endothelial function and coronary microcirculation, autonomic dysfunction, and activation of myocardial inhibitory factors. Studies investigating NRG-1 have been performed using a variety of methods, including in vitro models, and animal and human clinical trials; however, the results are not consistent. NRG-1/ErbBs signaling is involved in a variety of cardiac processes, from the development of the myocardium and cardiac conduction systems to the promotion of angiogenesis in cardiomyocytes, and in cardio-protective effects during injury. NRG-1 may exert a multifaceted cardiovascular protective effect by activating NRG-1/ErbBs signaling and regulating multiple downstream signaling pathways, thereby improving myocardial cell dysfunction in sepsis, and protecting cardiomyocytes and endothelial cells. It may alleviate myocardial microvascular endothelial injury in sepsis; its anti-inflammatory effects inhibit the production of myocardial inhibitory factors in sepsis, improve myocardial ischemia, decrease oxidative stress, regulate the disruption to the homeostasis of the autonomic nervous system, improve diastolic function, and offer protective effects at multiple target sites. As the mechanism of action of NRG-1 intersects with the pathways involved in the pathogenesis of sepsis, it may be applicable as a treatment strategy to numerous pathological processes in sepsis.

Leydig cells contribute to the inhibition of spermatogonial differentiation after irradiation of the rat.

Irradiation with 6Gy produces a complete block of spermatogonial differentiation in LBNF1 rats that would be permanent without treatment. Subsequent suppression of gonadotropins and testosterone (T) restores differentiation to the spermatocyte stage; however, this process requires 6weeks. We evaluated the role of Leydig cells (LCs) in maintenance of the block in spermatogonial differentiation after exposure to radiation by specifically eliminating functional LCs with ethane dimethane sulfonate (EDS). EDS (but not another alkylating agent), given at 10weeks after irradiation, induced spermatogonial differentiation in 24% of seminiferous tubules 2weeks later. However, differentiation became blocked again at 4weeks as LCs recovered. When EDS was followed by treatment with GnRH antagonist and flutamide, sustained spermatogonial differentiation was induced in >70% of tubules within 2weeks. When EDS was followed by GnRH antagonist plus exogenous T, which also inhibits LC recovery but restores follicle stimulating hormone (FSH) levels, the spermatogonial differentiation was again rapid but transient. These results confirm that the factors that block spermatogonial differentiation are indirectly regulated by T, and probably FSH, and that adult and possibly immature LCs contribute to the production of such inhibitory factors. We tested whether insulin-like 3 (INSL3), a LC-produced protein whose expression correlated with the block in spermatogonial differentiation, was indeed responsible for the block by injecting synthetic INSL3 into the testes and knocking down its expression invivo with siRNA. Neither treatment had any effect on spermatogonial differentiation. The Leydig cell products that contribute to the inhibition of spermatogonial differentiation in irradiated rats remain to be elucidated.

Mesenchymal stem cells derived from low risk acute lymphoblastic leukemia patients promote NK cell antitumor activity

Mesenchymal stem cells (MSCs) are key components of the bone marrow microenvironment which contribute to the maintenance of the hematopoietic stem cell niche and exert immunoregulatory functions in innate and adaptive immunity. We analyze the immunobiology of MSCs derived from acute lymphoblastic leukemia (ALL) patients and their impact on NK cell function. In contrast to the inhibitory effects on the immune response exerted by MSCs from healthy donors (Healthy-MSCs), we demonstrate that MSCs derived from low/intermediate risk ALL patients at diagnosis (ALL-MSCs) promote an efficient NK cell response including cytokine production, phenotypic activation and most importantly, cytotoxicity. Longitudinal studies indicate that these immunostimulatory effects of ALL-MSCs are progressively attenuated. Healthy-MSCs adopt ALL-MSC-like immunomodulatory features when exposed to leukemia cells, acquiring the ability to stimulate NK cell antitumor function. The mechanisms underlying to these functional changes of ALL-MSCs include reduced production of soluble inhibitory factors, differential expression of costimulatory and coinhibitory molecules, increased expression of specific TLRs and Notch pathway activation. Collectively our findings indicate that, in response to leukemia cells, ALL-MSCs could mediate a host beneficial immunomodulatory effect by stimulating the antitumor innate immune response.

Evaluation of the effects of probiotics in controlling bacterial necrosis symptoms in larvae of the mud crab Scylla serrata during mass seed production

We aimed to evaluate the practicability of probiotics in controlling larval necrosis symptoms and mass mortality occurred during seed production of the mud crab Scylla serrata. We targeted a bacterium in the family Flavobacteriaceae that causes necrosis symptoms of mud crab larvae. Five candidate probiotic bacterial strains, which showed inhibitory effects against the causative bacterium but were innocuous to larvae, were screened from the seed production environment. Sterile culture medium supernatants of the candidate strains inhibited the causative bacterium through the secretion of extracellular factors. These inhibitory effects were largely reduced when the strains were inoculated into sea water, suggesting medium-dependent production of inhibitory factors. The strain that exhibited the highest inhibitory effect on larval necrosis in 7-day larval rearing experiments was selected as a probiotic strain. In large-scale larval rearing experiments, the probiotic treatment significantly suppressed larval necrosis symptoms and improved larval survival in the early rearing period until the fourth zoeal stage. However, the effect disappeared after the fifth (last) zoeal stage, corresponding to a decrease in inoculated probiotic bacterial counts in the larval rearing water. Almost all larvae had died by the first crab stage. The effectiveness of probiotics developed in vitro has not yet proved practical in commercial-scale seed production. The continuous proliferation of probiotic bacteria and extracellular production as inhibitory factors in larval rearing water are the key factors in developing probiotics for commercial-scale seed production.

Does plerixafor destroy the hematopoietic progenitor cell/mesenchymal stromal cell niche?

Tissue homeostasis is dependent on replacement of damaged and aged cells, and stem cells are the primary source of new cell generation. Most tissue and organs of the body contain stromal cells that are part of the stem cell niche and are essential for the maintenance, proliferation and differentiation of stem cells. Hematopoiesis is a well-characterized tissue system in which interactions between hematopoietic stem cells (HSCs) and stromal cells in the bone marrow (BM) have been clearly established (1e3). The BM environment is subject to complex regulation that is critical for hematopoiesis. Many studies have demonstrated the production of both stimulating and inhibitory factors by BM stromal cells (mesenchymal stromal cells, MSCs) (4e6). However, the full potential of MSCs and their role in control of the HSC proliferation and differentiation remains unclear. Critical to sustained hematopoiesis is themaintenance of stem cell quiescence. Without a niche in which a stem cell pool can reside unstimulated by proliferative and differentiation signals, hematopoiesis cannot be sustained life-long. There is evidence that HSC quiescence is at least in part regulated by direct contact between HSCs and MSCs. This contact is mediated through chemokine receptor 4 (CXCR4) on HSCs engaging stromal cellederived factor (SDF)-1 on MSCs (7). With the advent of plerixafor—a CXCR4 antagonist used to mobilize HSCs for stem cell transplantation—it is pertinent to ask how this agent interferes with HSC/MSC interactions. In this issue of Cytotherapy, Ludwig et al. (8) cocultured HSCs and MSCs with and without plerixafor, studying cell division kinetics and stem cell surface marker changes to explore the relationship between HSCs and MSCs and the role of the CXCR4/SDF-1 axis. They found that co-culture of

Targeted Deletion of FGL2 Leads to Increased Early Viral Replication and Enhanced Adaptive Immunity in a Murine Model of Acute Viral Hepatitis Caused by LCMV WE

Mounting effective innate and adaptive immune responses are critical for viral clearance and the generation of long lasting immunity. It is known that production of inhibitory factors may result in the inability of the host to clear viruses, resulting in chronic viral persistence. Fibrinogen-like protein 2 (FGL2) has been identified as a novel effector molecule of CD4+CD25+ Foxp3+ regulatory T (Treg) cells that inhibits immune activity by binding to FCγRIIB expressed primarily on antigen presenting cells (APC). In this study, we show that infection of mice with Lymphocytic Choriomeningitis Virus WE (LCMV WE) leads to increased plasma levels of FGL2, which were detected as early as 2 days post-infection (pi) and persisted until day 50 pi. Mice deficient in FGL2 (fgl2−/−) had increased viral titers of LCMV WE in the liver early p.i but cleared the virus by day 12 similar to wild type mice. Dendritic cells (DC) isolated from the spleens of LCMV WE infected fgl2−/− had increased expression of the DC maturation markers CD80 and MHC Class II compared to wild type (fgl2+/+). Frequencies of CD8+ and CD4+ T cells producing IFNγ in response to ex vivo peptide re-stimulation isolated from the spleen and lymph nodes were also increased in LCMV WE infected fgl2 −/− mice. Increased frequencies of CD8+ T cells specific for LCMV tetramers GP33 and NP396 were detected within the liver of fgl2−/− mice. Plasma from fgl2−/− mice contained higher titers of total and neutralizing anti-LCMV antibody. Enhanced anti-viral immunity in fgl2−/− mice was associated with increased levels of serum alanine transaminase (ALT), hepatic necrosis and inflammation following LCMV WE infection. These data demonstrate that targeting FGL2 leads to early increased viral replication but enhanced anti-viral adaptive T & B cell responses. Targeting FGL2 may enhance the efficacy of current anti-viral therapies for hepatotropic viruses.

Abstract B60: Exploitation of a common food/traditional medicine of South America, yacon, in breast cancer prevention in the U.S. using preclinical rat model

Abstract Background: Yacon has recently been introduced into farmer's markets and natural food stores in the U.S., but its preventive activity for breast cancer has rarely been evaluated. Yacon contains a large amount of non-digestible oligosaccharide called inulin that belongs to a class of carbohydrates known as fructans. Inulin-type fructans (ITF) decreases the rate of aberrant crypt foci (ACF), a pre-neoplastic lesion found in colon. The mechanism by which ITF inhibits ACF is associated with butyrate produced by the anaerobic bacterial fermentation of ITF in the colon. Butyrate can also be absorbed through the colonic epithelial cells into the portal blood and exert its effects within the body. Butyrate modulates gene transcription by inhibiting HDAC. Cancer cells appear to be more sensitive than non-transformed cells to HDAC inhibitory compounds. In addition, the yacon ITF promotes satiety and retard the absorption of food-derived energy via reducing a gastrointestinal peptide-ghrelin that is a growth hormone secretagogue. Reduction of serum ghrelin results in decreases of IGF-1. Subsequently, the PI3K/Akt-mTOR signaling pathway will be inactivated via increasing AMPK activity and its downstream events, inhibition of cell proliferation and induction of cell apoptosis. However, few studies have been shown the effect of the ITF on breast cancer. Objective: 1) To determine mammary carcinogenic responses to yacon in experimental animals; 2) To evaluate the association of the circulating growth factors and cytokines with the carcinogenic responses; 3) To determine the HDAC and identify AMPK/PI3K/Akt-mTOR cell signaling pathway. Methods: Mammary carcinogenesis was initiated by injection of female Sprague Dawley rats with 50 mg of 1-methyl-1-nitrosourea/kg body weight (i.p.) at 21 days of age. One week later, the rats were fed diets containing yacon powder at 0%, 15%, 30% or 60% (30 rats/group) for 8 weeks, respectively. Effects of yacon on mammary carcinomas, circulating growth factors and cytokines and molecular biological assessments in carcinomas, including HDAC and regulators that are associated with AMPK/PI3K/Akt-mTOR pathway, were evaluated. Difference between among different dietary groups was statistically analyzed by ANOVA and Chi-square test. Results/Relevance: Dietary yacon reduced the promotion and progression of MNU-induced mammary carcinogenesis in rat, which is associated with downregulation of IGF-1/HDAC/Akt/mTOR signaling pathway and anti-inflammation, i.e. reduction of plasma IL-6, TNFα, and C-reactive protein. Future work will focus on the effect of yacon on obesity and antiinflammation. The study provides crucial biological information to complement the knowledge of natural functional foods that is relevant to a number of foods rich in non-digestible, fermentable oligosaccharides. This could lead the way to develop a new type of functional whole food with a low calorie density and the ability to promote the intra-intestinal production of cancer inhibitory factors. Consequently, the new type of functional food will significantly contribute to the goal of preventing initiation of breast cancer and reduce survivor recurring because it is natural, tolerant and acceptable for the clinic patients. Supported by W81XWH-09-1-0428 from the Department of Defense-Army. Citation Information: Cancer Prev Res 2010;3(12 Suppl):B60.

Early bone marrow hematopoietic defect in simian/human immunodeficiency virus C2/1-infected macaques and relevance to advance of disease.

To clarify hematological abnormalities following infection with human immunodeficiency virus (HIV), we examined the hematopoietic capability of bone marrow by using cynomolgus monkeys infected with pathogenic simian/human immunodeficiency virus (SHIV) strain C2/1, an animal model of HIV infection. The relationship between the progress of the infection and the CD4/CD8 ratio of T lymphocytes or the amount of SHIV C2/1 viral load in the peripheral blood was also investigated. A colony assay was performed to assess the hematopoietic capability of bone marrow stem cells during the early and advanced phases of the infection. Colonies of granulocytes-macrophages (GM) were examined by PCR for the presence of the SIVmac239 gag region to reveal direct viral infection. There was a remarkable decrease in the CFU-GM growth on days 1 and 3 postinoculation, followed by recovery on day 56. During the more advanced stage, the CFU-GM growth decreased again. There was minimal evidence of direct viral infection of pooled cultured CFU-GM despite the continuously low CD4/CD8 ratios. These results indicate that the decrease in colony formation by bone marrow stem cells is reversible and fluctuates with the advance of the disease. This decrease was not due to direct viral infection of CFU-GM. Our data may support the concept that, in the early phase, production of inhibitory factors or deficiency of a stimulatory cytokine is responsible for some of the bone marrow defects described in the SHIV C2/1 model.

Modulation of VE-cadherin and PECAM-1 mediated cell-cell adhesions by mitogen-activated protein kinases.

Endothelial cell transition from a differentiated, quiescent phenotype to a migratory, proliferative phenotype is essential during angiogenesis. This transition is dependent on alterations in the balanced production of stimulatory and inhibitory factors, which normally keep angiogenesis in check. Activation of MAPK/ERKs is essential for endothelial cell migration and proliferation. However, its role in regulation of endothelial cell adhesive mechanisms requires further delineation. Here, we show that sustained activation of MAPK/ERKs results in disruption of cadherin-mediated cell-cell adhesion, down-regulation of PECAM-1 expression, and enhanced cell migration in microvascular endothelial cells. Expression of a constitutively active MEK-1 in mouse brain endothelial (bEND) cells resulted in down-regulation of VE-cadherin and catenins expression concomitant with down-regulation of PECAM-1 expression. In contrast, inhibition of MEK-1 restored parental morphology, cadherin/catenins expression and localization. These data are further supported by our observation that sustained activation of MAPK/ERKs in phorbol myristate acetate incubated HUVEC lead to disruption of cadherin-mediate cell-cell interactions and enhanced capillary formation on Matrigel. Thus, sustained activation of MAPK/ERKs plays an important role in disruption of cell-cell adhesion and migration of endothelial cells.

Androgen-independent prostate cancer DU145 cells suppress androgen-dependent growth of prostate stromal cells through production of inhibitory factors for androgen responsiveness

Imbalances in the epithelial–stromal interactions are important in the pathogenesis of prostate cancer. However, we know little about androgenic regulation in the stroma of prostate cancer. We examined the cancer–stromal interaction paying attention to androgen responsiveness of stromal side. In co-culture, PC3 and LNCaP cells did not affect dihydrotestosterone (DHT)-dependent growth of prostate stromal cells (PrSCs), but DU145 cells significantly reduced it. Conditioned medium from DU145 cells (DU145-CM) also inhibited DHT-dependent PrSCs growth, androgen receptor (AR) expression, and prostate specific antigen transcription. Although the inhibitory effect of DU145-CM was not affected by neutralizing antibody against EGF, FGF-2, or TNF-α, pretreatment with testosterone–Sepharose partially reduced the inhibitory ability of DU145-CM. These results suggest that DU145 cells produce inhibitory factors for androgen responsiveness, including steroid-binding protein(s), and these may participate in crosstalk between DU145 cells and PrSCs as modulators of androgen.

Differential taurine effect on outgrowth from goldfish retinal ganglion cells after optic crush or axotomy. Influence of the optic tectum

The interaction between innervated tissues, targets and nerves is crucial in the maintenance of physiological conditions, and the disturbance of this harmony causes the production of morphological and biochemical changes. After lesion of the optic nerve, several modifications take place in the retina, the optic tectum and the optic nerve. The influence of the tectum on the outgrowth from the goldfish retina and the possible role of taurine was studied. Ganglion retinal cells were identified by retrolabeling with Dil. Crushing the optic nerve 10 days prior to plating retinal cells, as compared with optic axotomy, did not affect the survival of cultured retinal cells, as well as the length of the neurites. However, the number of neurites per cell and the branching of the longest fiber were higher after axotomy than after crushing. The addition of taurine to the medium did not modify this response at 5 days in culture. At early periods in culture, the stimulatory effect on isolated ganglion cell outgrowth produced by taurine was enhanced after axotomy respecting crushing of the optic nerve, but was not affected in retinal explants. The addition of medium from cultured optic tectum several days post-crush of the optic nerve to retinal explants from intact retinas or coming from post-crush retina modified the outgrowth, being inhibitory or stimulatory in a time-dependent manner. The co-culture of optic tectum and retina also affected the outgrowth from the retina with a byphasic shape. The results support the differential response of the retina facing partial or complete interruption with the target and limit the effect of taurine to early periods in culture. In addition, the production of inhibitory factors from the tectum, plus the stimulatory ones, are strongly supported by this work.

On the TRAIL of lymphocyte death in measles

Measles virus (MV) infection is still a major cause of childhood mortality in developing countries. MV causes severe immunosuppression, which allows secondary infection of the host and it is these secondary infections that can cause death. Several mechanisms for MV-induced immunosuppression have been proposed, including inhibition of interleukin (IL)-12 production by monocytes/macrophages and dendritic cells by crosslinking of the MV cellular receptor, CD46; the production of soluble inhibitory factors; negative signalling to T cells by antigen-presenting cells; retardation of lymphocytes in specific stages of the cell cycle; and lymphocyte apoptosis. A recent paper by Vidalain et al.1xMeasles virus induces functional TRAIL production by human dendritic cells. Vidalain, P-O. et al. J. Virol. 2000; 74: 556–559Crossref | PubMedSee all References1, further pursuing the mechanisms of lymphocyte apoptosis, has shown that tumour necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) expression is upregulated in human dendritic cells upon MV infection, and this mediates apoptosis of cells that interact with these dendritic cells. Surprisingly, TRAIL is not readily detectable on the surface of MV-infected dendritic cells, but appears to remain internalized after MV infection. However, apoptosis of MDA-231 cells induced by MV-infected dendritic cells and monocytes appears to be mediated by TRAIL, as a soluble TRAIL-receptor-2 construct inhibits the apoptotic-inducing activity of the accessory cells. Previously, TRAIL was thought to be important in apoptotic killing of transformed cells but the evidence here, and other data coming from HIV research, suggests that it could also be involved in lymphocyte apoptosis, especially after certain infections.

Manipulation of outer root sheath cell survival perturbs the hair-growth cycle.

Transgenic mice that overexpress the anti-apoptotic gene bcl-xL under the control of the keratin 14 promoter have significantly shorter hair than non-transgenic littermates. The deficit in hair length correlated with a decrease in the duration of anagen, the growth phase of the hair cycle. A prolongation in telogen, the resting phase of the hair cycle, was also observed in adult animals. In the developing hair bulb, bcl-xL transgene expression was observed exclusively in the outer root sheath (ORS) cells. Bcl-xL expression enhanced the survival of ORS cells treated with apoptotic stimuli. The results suggest that preventing the apoptotic death of ORS cells during anagen leads to a more rapid termination of progenitor cell commitment/proliferation, while the increased survival of ORS cells during telogen delays the initiation of a new hair cycle. ORS cells produce fibroblast growth factor-5 (FGF-5), which acts in a paracrine fashion to terminate precursor cell division during anagen. The short hair phenotype of bcl-xL transgenic mice was substantially reversed in FGF-5-deficient mice. Thus, the production of growth inhibitory factors by ORS cells may provide a mechanism through which the hair-growth cycle is regulated by cell survival.

The Role of Osteoblasts in the Hematopoietic Microenvironment

Hematopoietic stem cell differentiation occurs in direct proximity to osteoblasts within the bone marrow cavity. Despite this striking affiliation, surprisingly little is known about the precise cellular and molecular impact of osteoblasts on the bone marrow microenvironment. Recently, it has been proposed that human osteoblasts support the growth of primitive human hematopoietic cells in vitro and possibly in vivo. Evidence to support this hypothesis is reviewed as follows: the influence of osteoblasts on osteoclast development; the participation of osteoblasts in long-term bone marrow cultures; the production of positive hematopoietic regulatory molecules by osteoblasts; the production of cell-cycle inhibitory factors by osteoblasts, and cell-cell interactions between early hematopoietic cells and osteoblasts.

Imbalance in production of cytokines by bone marrow stromal cells following cytomegalovirus infection.

The effect of cytomegalovirus (CMV) infection on the production of growth factors and negative regulators in unstimulated or lipopolysaccharide-stimulated human bone marrow stromal cells was assessed. After 5 days, the constitutive and lipopolysaccharide-stimulated production of growth factors was significantly decreased in CMV-infected compared with uninfected stromal cells. This decrease was noted as early as 72 h after infection and appeared to be strictly related to viral replication. On the other hand, the production of inhibitory factors was increased after CMV infection, and this increased release was detectable as early as 24 h after infection. No modulation in the production of interleukin-10 was observed after CMV infection. These data suggest that CMV disturbs the balanced cytokine network, which controls proliferation and differentiation of hematopoietic progenitors. CMV-induced myelosuppression results from this lack of production of growth factors and excess production of inhibitory factors.

Inhibition of flowering of cucumber grafted on rooted squash stock

For the elucidation of the mechanisms of floral transition in indifferent plants, cucumber seedlings (Cucumis sativus cv. Rennsei or cv. Shimoshirazu‐jibai) were grafted onto squash seedlings (Cucurbita maxima Duchesne X C. moschata Duchesne cv. Shintosa‐ichigou) of which the meristems had been removed, and the effect on flower induction on the cucumber scion was examined. In both cultivars, the grafted cucumber bore no flowers, whereas control plants developed flowers above the second to fourth nodes. The inhibition of flower formation on the grafted cucumber scion occurred even when the root of cucumber was left with the squash root on the grafted plant, and flower formation occurred after removal of the squash stock. The inhibitory effect of the squash stock in the presence of the cucumber root was abolished by removal of the squash root. Neither the dry weight of stem plus leaf nor the chlorophyll content of the leaf, as indicators of vegetative growth, were correlated with flower formation on cucumber plants that had been grafted in the presence of cucumber roots on whole, cotyledon‐free or root‐free squash stock. These results indicate that flower formation in cucumber was inhibited by a factor produced by squash roots, an inhibition probably not involved in the modulation of vegetative growth. The root may control floral transition by the production of inhibitory factors in some day‐neutral Cucurbitaceae plants.