Mononuclear Phagocyte Proliferation, Maturation and Function

Retinoid-related orphan nuclear receptor alpha (RORα)-deficient mice display morphological testicular defects

The role of retinoid-related orphan receptor, one of the transcription factors reported in testis, in testicular function is unclear, so this study was performed to evaluate the qualitative and quantitative changes in the testicular structure of RORα-deficient mice using light-, electron-microscopy, and immunohistochemistry. Among the most striking alterations observed in the testis of the mutant mice were hypospermatogenesis, marked reduction in volume proportions of interstitial tissues and number of Leydig cells, significant decrease in the diameter of seminiferous tubules and height of their epithelium, vacuolation in the epithelium of the seminiferous tubules with occurrence of mast cells, appearance of delay spermiation signs, and changes in sperm morphology. Moreover, the testis of mutant mice showed symplasts, in addition to appearance of multinucleated giant bromophenol-positive cells. ATPase activity was limited to spermatogonia and some primary spermatocytes, with higher alkaline phosphatase expression. Stronger vimentin reaction was immunolocalized to spermatogonia, spermatids, Leydig cells, and Sertoli cells. The expression of CD117 (C-kit, stem cell growth factor receptor) was limited to spermatogonia, primary spermatocytes, and Leydig cells. Seminiferous tubules showed overexpression of vascular endothelial growth factor (VEGF). Transmission electron microscopy examination of the mutant mice revealed abnormal Sertoli cells, hypertrophied spermatogonia, spermatocytes with degenerated mitochondria, and incompletely developed sperms. In conclusion, RORα is one of the essential proteins that regulate testicular structure.

NF-κB inhibition attenuates LPS-induced TLR4 activation in monocyte cells

Toll-like receptor (TLR) family are receptors for extracellular or intracellular signaling, such as lipopolysaccharide (LPS), or 12-O-tetradecanoylphorbol-13-acetate. TLR induces the differentiation of human myeloid monocytic‑leukemia cells (THP-1) to macrophages. However, the relationship between extracellular or intracellular signaling and the TLR protein level remain to be determined. Using RT-PCR and western blot analysis, the aim of the present study was to determine whether TLR4, a major TLR family member, could be moderately upregulated by high concentration of LPS and whether it promoted the maturation of THP1 cells. The results showed that, upregulated TLR4 at the protein level and mRNA level enriched the TLR4 modulation style. In addition, TLR4 expression was blocked by nuclear factor (NF)-κB inhibitor, and LPS stimulated NF-κB binding in the TLR4 gene promoter. Therefore, the increased expression of TLR4 in the responsiveness of LPS-treated THP1 cells occurred in response to the upregulation of their respective receptors, as well as a tight binding of NF-κB in the TLR4 gene promoter.

Upregulation of TLR1, TLR2, TLR4, and IRAK-2 Expression During ML-1 Cell Differentiation to Macrophages: Role in the Potentiation of Cellular Responses to LPS and LTA

12-O-tetradecanoylphorbol 13-acetate (TPA) induces the differentiation of human myeloid ML-1 cells to macrophages. In the current study, the expression, responsiveness, and regulation of toll-like receptors (TLRs) in TPA-induced ML-1-derived macrophages were investigated. We have found that TPA-induced differentiation of ML-1 cells was accompanied by the upregulation of TLR1, TLR2, TLR4, and CD14 expression at both the mRNA and protein levels. Interestingly, TLR1 and TLR4 protein expression on ML-1 cells could be blocked by pretreatment with U0126, suggesting the role of an Erk1/2-induced differentiation signal in this process. In addition, the expression of IRAK-2, a key member of the TLR/IRAK-2/NF-κB-dependent signaling cascade was also induced in response to TPA. Accordingly, we demonstrated an increased cellular release of inflammatory cytokines (TNF-α and various interleukins) upon stimulation with LPS and LTA ligands for TLR4 and TLR2, respectively. Furthermore, using luminol-dependent chemiluminescence, addition of LPS and LTA induces a sustained DPI-inhibitable generation of reactive oxygen species (ROS) by the differentiated ML-1 cells. Together, these data suggest that the increase in the responsiveness of TPA-treated ML-1 cells to LPS and LTA occurs in response to the upregulation of their respective receptors as well as an induction of the IRAK-2 gene expression.

Increase in macrophages in the testis of cathepsin a deficient mice suggests an important role for these cells in the interstitial space of this tissue

Cathepsin A (PPCA) is a lysosomal carboxypeptidase that functions as a protective protein for alpha-neuraminidase and beta-galactosidase in a multienzyme complex. In the present study, the testes of PPCA -/- mice from 2 to 10 months of age were compared with those of their wild type counterparts. While germ and Sertoli cells appeared comparable in appearance and distribution, the mean profile area of seminiferous tubules showed a significant decrease between wild type and PPCA -/- mice, suggesting changes to the seminiferous tubules and their contents. In addition, macrophages in the interstitial space (IS) of PPCA -/- mice were large, spherical, and filled with pale lysosomes, unlike those seen in wild type mice, and a quantitative analysis of their frequency per unit area of IS in PPCA -/- mice revealed a significant increase compared to that of wild type mice; this was also the case for their mean profile area. Absence of mitotic figures, cycling cells, or degenerating figures in the IS suggests that the major recruitment of macrophages appears to be from the circulation. In the IS, Leydig cells also showed an accumulation of large pale lysosomes in PPCA -/- mice, and their frequency also increased significantly as compared to wild type mice. In the electron microscope, a close association of Leydig cell microvilli with the surface of macrophages was pronounced in PPCA -/- mice. Since macrophages and Leydig cells interact by secreting various factors between each other, and considering the fact that Leydig cells show an accumulation of large pale lysosomes in PPCA -/- mice, it is suggested that macrophages accumulate as a result of abnormalities occurring in Leydig cells. Taken together, the data on increase in frequency of macrophages suggests important functions for these cells in both wild type and PPCA -/- mice.

Patterns of cellular activation after tendon injury

Mechanisms which lead to disabling adhesions following flexor tendon surgery of the hand were investigated in a rabbit model which was used to assess the relative response of the cells of the synovial sheath, epitenon and the endotenon to injury. A transverse laceration, cutting through 50% of the tendon, was made just outside the synovial sheath on the flexor aspect of the flexor digitorum profundus tendon. The synovial sheath was preserved intact. Using monoclonal antibodies for localizing specific inflammatory markers, we were able to follow the response and activity of the synovial sheath, epitenon and endotenon with respect to these markers at various times after surgery. Our findings suggest that the synovial sheath and the epitenon are relatively more reactive in the early period after injury, as judged by a range of inflammatory indices with the notable exception of the expression of the potent neovascularizing agent, basic fibroblast growth factor (bFGF).

Histiocytosis X and acute monocytic leukemia. Biologic illustration of the monocyte phagocytic system

The concept of a mononuclear phagocytic system consisting of a continuum of cells arising from the bone marrow monoblast and terminating in the mature tissue macrophage is being actively investigated. The presentation of documented acute monocytic leukemia 18 months following the confirmed diagnosis of histiocytosis X in a 39-year-old man strongly supports the concept of the mononuclear phagocytic system lineage.

The pathogenesis, diagnosis, and treatment of histiocytosis syndromes

The histiocytosis syndromes previously known, and often still referred to, as histiocytosis-X were originally categorized by many as malignant neoplasms. They have been treated as such with aggressive chemotherapy and radiation therapy. Although these modalities are still used, there are significant differences between the histiocytosis syndromes and the true malignant disease that suggest conservative management for many patients. The clinical course of malignant neoplasia is relentlessly progressive with virtually no survival in untreated patients. The histiocytosis syndromes are characterized by frequent spontaneous remissions and exacerbations, with varying morbidity and survival in untreated patients, depending on the extent of the disease. Pathologically, the lesions of histiocytosis appear as reactive infiltrates, possessing little of the cellular atypicality and homogeneity characteristic of malignancy. Although the etiology of these phenomena is unknown, histiocytosis syndromes appear to represents a reactive autoimmune disorder triggered by unknown stimuli.

Monocytes in inflammatory bowel disease: phagocytosis and intracellular killing

The ability of peripheral blood monocytes from patients with ulcerative colitis and Crohn's disease to phagocytose and kill a standard strain of Staphyloccus aureus has been studied. Using lysostaphin, a rapidly acting muralytic enzyme, phagocytosis could be accurately differentiated from intracellular killing. When compared with normal healthy individuals and patients with gastrointestinal diseases not thought to be immunologically mediated, monocytes from patients with inflammatory bowel disease showed a statistically significant increase in the number of bacteria phagocytosed in 2 hours. There was no difference, however, between patients with Crohn's disease and those with ulcerative colitis. For all groups studied, more than 95% of ingested organisms were killed, and there was no difference between groups. These results suggest that peripheral blood monocytes in patients with Crohn's disease and ulcerative colitis are activated. It is unlikely that the granulomata of Crohn's disease result from a defect in the microbicidal function of the monocyte/macrophage system.

Monocytes, macrophages, and their diseases in man

Mononuclear phagocytes are a widely distributed system of cells involved in host defense functions, immunologic reactions, disposal of unwanted organic and inorganic materials, and synthesis of biologically active compounds such as complement components and prostaglandins. The system includes early precursor cells in the bone marrow, blood monocytes, alveolar and peritoneal macrophages, sinusoidal lining cells in the spleen, and Kupffer cells in the liver. We have recently come to understand the biology of these interesting cells and the diseases they produce.