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Microglial activation is believed to play a role in many psychiatric and neurodegenerative diseases. Based largely on evidence from other cell types, it is widely thought that MAP kinase (ERK, JNK and p38) signalling pathways contribute strongly to microglial activation following immune stimuli acting on toll-like receptor (TLR) 3 or TLR4. We report here that exposure of SimA9 mouse microglial cell line to immune mimetics stimulating TLR4 (lipopolysaccharide-LPS) or TLR7/8 (resiquimod/R848), results in marked MAP kinase activation, followed by induction of nitric oxide synthase, and various cytokines/chemokines. However, in contrast to TLR4 or TLR7/8 stimulation, very few effects of TLR3 stimulation by poly-inosine/cytidine (polyI:C) were detected. Induction of chemokines/cytokines at the mRNA level by LPS and resiquimod were, in general, only marginally affected by MAP kinase inhibition, and expression of TNF, Ccl2 and Ccl5 mRNAs, along with nitrite production, were enhanced by p38 inhibition in a stimulus-specific manner. Selective JNK inhibition enhanced Ccl2 and Ccl5 release. Many distinct responses to stimulation of TLR4 and TLR7 were observed, with JNK mediating TNF protein induction by the latter but not the former, and suppressing Ccl5 release by the former but not the latter. These data reveal complex modulation by MAP kinases of microglial responses to immune challenge, including a dampening of some responses. They demonstrate that abnormal levels of JNK or p38 signalling in microglial cells will perturb their profile of cytokine and chemokine release, potentially contributing to abnormal inflammatory patterns in CNS disease states., (© 2021. The Author(s).)

The study of epigenetics has improved our understanding of mechanisms underpinning gene-environment interactions and is providing new insights in the pathophysiology of respiratory allergic diseases. We reviewed the literature on DNA methylation patterns across different tissues in asthma and/or rhinitis and attempted to elucidate differentially methylated loci that could be used to characterize asthma or rhinitis. Although nasal and bronchial epithelia are similar in their histological structure and cellular composition, genetic and epigenetic regulation may differ across tissues. Advanced methods have enabled comprehensive, high-throughput methylation profiling of different tissues (bronchial or nasal epithelial cells, whole blood or isolated mononuclear cells), in subjects with respiratory conditions, aiming to elucidate gene regulation mechanisms and identify new biomarkers. Several genes and CpGs have been suggested as asthma biomarkers, though research on allergic rhinitis is still lacking. The most common differentially methylated loci presented in both blood and nasal samples are ACOT7, EPX, KCNH2, SIGLEC8, TNIK, FOXP1, ATPAF2, ZNF862, ADORA3, ARID3A, IL5RA, METRNL and ZFPM1. Overall, there is substantial variation among studies, (i.e. sample sizes, age groups and disease phenotype). Greater variability of analysis method detailed phenotypic characterization and age stratification should be taken into account in future studies., (© 2022 The Authors. Clinical and Translational Allergy published by John Wiley & Sons Ltd on behalf of European Academy of Allergy and Clinical Immunology.)

Matrix remodeling plays a prominent role in growth plate calcification. Since interleukin-1 (IL-1) has been implicated in stimulating proteinase production and inhibiting matrix synthesis in articular cartilage, we examined whether IL-1 was present in growth plate and whether the vitamin D metabolites, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3; 1,25) and 24,25(OH)2D3 (24,25), regulate the level of IL-1 found in this tissue. Sprague-Dawley rats were placed on normal (Normal rats) or rachitogenic diet (-VDP rats). The -VDP rats were either left untreated, injected 24 h prior to euthanasia with 24,25 (-VDP+24,25 rats) or 1,25 (-VDP+1,25 rats), or were given ergocalciferol (Ergo rats) orally, 48 h prior to euthanasia. Growth plates were harvested and extracted in buffer containing 1 M guanidine. IL-1 activity was measured by adding authentic cytokine or growth plate extracts to cultures of lapine articular cartilage and assaying release of glycosaminoglycans (GAGs) and changes in collagenase and neutral metalloproteinase activity. Neutralization of activity in the extracts was performed using polyclonal antisera to IL-1alpha or IL-1beta. An ELISA was used to determine levels of IL-1alpha and beta in the extracts. All extracts contained IL-1alpha and beta, as determined by ELISA. Levels of IL-1beta, but not IL-1alpha, were affected by the vitamin D status of the animal. Extracts from -VDP+24,25 animals contained significantly more IL-1beta than any of the other treatment groups, with the level found in these animals being 3-fold higher than normal and 2-fold higher than -VDP. Extracts were also tested in the bioassay to determine the level of active cytokine present. All growth plate extracts contained activity which altered GAG and proteinase release by lapine articular cartilage. Extracts from -VDP-, -VDP+1,25-, and -VDP+Ergo-treated rats stimulated a 40% increase in glycosaminoglycan release compared with extracts from normal rats. In contrast, extracts from -VDP+24,25-treated rats stimulated a 300% increase in glycosaminoglycan release. Both collagenase and neutral metalloproteinase activity of lapine cartilage were increased after incubation with the growth plate extracts. Collagenase activity was significantly increased 8- to 13-fold by the addition of extracts from -VDP-, -VDP+24,25-, or -VDP+1,25-treated animals. Neutral metalloproteinase activity was similarly increased by 4- to 10-fold. To characterize this activity further, growth plate extracts were incubated with neutralizing antibody to IL-1alpha or beta prior to addition to the lapine articular cartilage cultures. When antibodies were used separately, only partial inhibition was observed; incubation with both antibodies blocked 25% of the glycosaminoglycan release observed without antibody and greater than 80% of the enzyme activity released by the articular cartilage cultures. The results of this study show that growth plate cartilage contains both IL-1alpha and beta and indicate that vitamin D regulates the level of IL-1 in this tissue.

Articular hyaline cartilage, though a metabolically active tissue, has limited capacity for repair. Though the integrity of the cartilage is dependent upon a certain level of force placed upon it, excessive force leads to damage. It is when the breakdown of the cartilage exceeds the capacity of the cartilage for repair that osteoarthritis results. At present, pharmacologic treatment of osteoarthritis is focused toward the control of pain and stiffness. This treatment, however, masks the symptoms of the disease and effectively allows the patient to do further damage to the joint.

Articular hyaline cartilage is of interest to both the clinician and the basic scientist because of its unique physical and chemical properties which are a consequence of its biochemical composition. Although it is a tissue which is hypocellular, avascular, and also lacks nerves and lymphatics, it is active in synthesis and degradation. Articular cartilage responds to the forces to which it is subjected and, in this way, maintains its integrity as long as those forces do not exceed the tissue's capacity for repair or permanently change the biologic response of the cells.

The differentiation and calcification of fracture callus cartilage studied by light microscopy resembles that of the epiphyseal plate cartilage. In this study, a correlation between the ultrastructural cytology and the chemical composition of the various cartilage types found in fracture callus was attempted. Fibrocartilage cells were very active with profuse secretion of collagen into the matrix. Collagen fibres were observed in close proximity to the cell membrane. Cells from hypertrophic and calcifying cartilage showed progressive degeneration while their mitochondria contain dense osmiophilic granules. Mitochondria granules were occasionally seen in fibrocartilage cells. The intercellular matrix of hypertrophic and calcifying cartilage showed needle-shaped crystals quite often arranged as a cluster in a radiated pattern. Chemical analyses of the various types of cartilage found in fracture callus demonstrated the presence of a high molecular weight bound phosphate and an increase of sialic acid in the differentiated types of cartilage.

A sulphamidase activity present in rat spleen capable of hydrolysing N-[(35)S]sulphated heparin was studied. This activity was associated with the lysosomal fraction. Studies in vivo showed that the rat is capable of significantly desulphating heparin. Lysosomes in all the major tissues can effectively accumulate heparin. The heparin sulphamidase and arylsulphatase activities from rat spleen were separated by isoelectric focusing. Heparin sulphamidase was a distinct entity from all the arylsulphatase activities.

Unlabelled: We report here that an endogenous protein in cartilage is capable of inhibiting leukocyte elastase degradation of cartilage matrix. This inhibitor is specific for elastase. After 30 min of incubation, small amounts of the purified elastase are capable of releasing relatively large amounts of uronic acid positive material and relatively small amounts of collagenous and noncollagenous protein. The hydrolytic effectiveness of elastase is exemplified by its action on various natural substrates. This action, however, is inhibited by a specific natural elastase inhibitor purified from cartilage., Introduction: The extracellular matrix of cartilage is responsible for the resiliency, tensile strength plus ion and water binding ability of this tissue. Any modification in the arrangement or composition of proteoglycans, collagen and glycoproteins found in the cartilage matrix affects these properties. Such modification can be derived by the action of hydrolytic enzymes originating from chrondrocytes or from cells attracted in the cartilage area by chemotaxis.

Fibronectin content was determined in articular cartilage in a spontaneous dog model and in a meniscectomy rabbit model of osteoarthritis. Determination of the fibronectin content of urea extracts of articular cartilage by an enzyme linked immunosorbent assay (ELISA) disclosed that degenerated cartilage contained from 10- to 40-fold more fibronectin than normal cartilage. The finding that cartilage fibronectin content was increased in both animal models suggests that elevated cartilage fibronectin content is a general feature of the osteoarthritic process. Immunoperoxidase studies disclosed that fibronectin was distributed throughout the matrix in hyaluronidase treated normal and osteoarthritic cartilage from both animal models, but quantitative differences in fibronectin were not observed by these techniques.

The invasive RBTCC-8 rat bladder carcinoma cell line (passage number, greater than 100) and its derivates, the RBTCC-8 tumor isografts and the 1-RBTCC-8 daughter cell line (fourth passage), express proteolytic activities of broad substrate specificity, which allow them to efficiently degrade extracellular (collagenous) matrices. Cell-associated, collagenolytic activity is evidenced by the release of hydroxyproline from collagen substrates of types I and IV, by visualizing the low-molecular-weight collagen breakdown products on sodium dodecyl sulfate-polyacrylamide gels, and by the depth of invasion into extracellular matrices in our bone invasion assays. Fractionated by diethylaminoethyl column chromatography, the major collagenolytic activities against collagens of types I and IV coelute in a relatively narrow peak within a NaCl gradient. The pooled collagenolytic diethylaminoethyl fractions contain: (a) two chymotrypsin-like, catheptic activities; (b) activity against a synthetic elastase substrate; (c) gelatinase activity; and (d) caseinolytic activity. Despite efficient collagenolysis, a vertebrate-type collagenase cannot be detected in any of our tumor samples, even after trypsin activation of the tumor cell extracts. The mechanism of action of these nonspecific proteinases is thought to be that of collagen "crosslinkases." The neutral proteinase activities are highest in RBTCC-8 tumor isografts, intermediate in the fourth passage 1-RBTCC-8 carcinoma cell line, and lowest in the RBTCC-8 carcinoma cell line of high passage number. The levels of these nonspecific enzyme activities are well correlated with the depth of invasion into bony matrices, as shown by our invasion assays.

An in vitro model has been devised to study the differentiation and calcification of fibrocartilage from fracture calluses. Morphological and biochemical studies substantiating cartilage metaplasia in vitro are presented. A role that such a model may play in the study of cartilage calcification is suggested.

Differentiation and calcification of cartilage of a fracture callus morphologically, ultrastructurally, and histochemically resembles cartilage of growing epiphyseal plate. The fracture callus includes the various cartilage cell types found in the epiphyseal plate. Proliferating and hypertrophic cartilage had higher activities of cytochrome oxidase, alkaline phosphatase and glutamate aspartate transaminase than fibrocartilage. Enzymes controlling glycogen synthesis and glycolysis had higher levels of activity in fibrocartilage than in hypertrophic cartilage. Lysosomal enzymes, catalase, 6-phospho-gluconic acid and glucose 6-phosphate dehydrogenase were uniformly distributed. Alkaline phosphatase was associated with extracellular vesicles found in hypertrophic cartilage. EM dense granules were found in mitochondria in hypertrophic cartilage. There was an increase of total lipids in hypertropic and calcified cartilage as compared to resting cartilage.

The morphologic and biochemical events during fracture callus cartilage differentiation and calcification are presented. 1. Histologic studies have demonstrated that unimmobilized fractures heal through endochondral ossification. 2. Biochemical studies have demonstrated an increase in the activities of alkaline phosphatase, enzymes involved with aerobic glucose metabolism, and lysosomal enzymes and a decrease in activities of enzymes involved with glycogen synthesis and anaerobic glycolysis. Hexosamines and hydroxyproline show a net decrease with cartilage differentiation. 3. Electron microscopic studies have demonstrated the intracellular origin and aggregation of collagen molecules, the cellular origin of matrix vesicles, and the early sites of calcification in the fracture callus.

The cartilage from a non-immobilized fracture undergoes a series of morphological and biochemical changes resembling the in vivo differentiation and calcification in the epiphyseal plate. The studies reported here demonstrate that a homogeneous population of chondrocytes isolated from fracture callus fibrocartilage undergoes the same changes in vitro. Chondrocyte primary cultures were grown for 28 days during which time the morphological, histological and histochemical properties of the cultures were studied. Demonstrated by various histological procedures, chondrocytes synthesized the characteristic cartilage matrix, and progressively calcified with increased culture age. This system can be used to elucidate the cellular and molecular mechanisms of calcification.

A purine nucleoside triphosphate phosphohydrolase (unspecified diphosphate phosphohydrolase, EC 3.6.1.15) was chromatographically separated from the bulk of alkaline phosphatase activity by gel filtration chromatography of butanol and EDTA extracts of fracture callus and bovine epiphyseal cartilage. The callus enzyme differed from alkaline phosphatase in a variety of characteristics. The purine nucleoside triphosphate phosphatase hydrolyzed a more specific group of substrates, required Ca2+ and Mg2+ for optimal activity, remained unaffected by a potent alkaline phosphatase inhibitor, and demonstrated a narrower range of optimal pH for catalytic activity. The enzyme was localized in the microsomal pellet following subcellular fractionation of callus chondrocytes. These characteristics indicate a role for the enzyme in Ca2+ transport.

Callus calcifying cartilage alkaline phosphatase was resolved by DEAE-cellulose column chromatography into two distinct phsophatase activities. The phosphatase activity which was eluted first from the column, (phosphatase I), was active towards a variety of phosphate esters, sodium pyrophosphatase and several linear polyphosphates, while the second phosphatase activity , (phosphatase II), was active toward simple phosphate esters but not towards sodium pyrophosphate and linear oligo or polyphosphates. All the phosphate esters, sodium pyrophosphate and polyphosphates at higher concentrations were inhibitory for phosphatase I. The modulating effects of magnesium, calcium, zinc and other phosphatase modulators have been investigated. Both phosphatases from callus calcifying cartilage were found to be substrates of neuraminidase with sialic acid as the product. Besides the difference in their specificity, the phosphatases were found to be immunologically different and to have different molecular weights, strong indication that they are different enzymes.