IL-22 in tissue-protective therapy

IL-22, a member of the IL-10 cytokine family, has recently gained significant attention as a protective agent in murine models of diseases driven by epithelial injury. Like its biochemical and functional sibling IL-10, IL-22 elicits cellular activation primarily by engaging the STAT3 signalling pathway. Exclusively produced by leukocytes, but targeting mostly cells of epithelial origin, IL-22 has been proposed as a specialized cytokine messenger acting between leukocytic and non-leukocytic cell compartments. A lack of response in leukocytes to IL-22 mirrors tightly controlled IL-22 receptor expression and probably explains the apparent lack of instant adverse effects after systemic IL-22 administration to mice. Anti-apoptotic, pro-proliferative and pro-regenerative characteristics the major biological properties of this cytokine. Specifically, application of IL-22 is associated with tissue protection and/or regeneration in murine models of infection/microbe-driven inflammation at host/environment interfaces, ventilator-induced lung injury, pancreatitis and liver damage. Overall, preclinical studies would support therapeutic administration of seemingly well-tolerated recombinant IL-22 for treatment of an array of acute diseases manifested in epithelial tissues. However, the feasibility of prolonged administration of this cytokine is expected to be restricted by the tumourigenic potential of the IL-22/STAT3 axis. IL-22, moreover, apparently displays an inherent context-specific capacity to amplify distinct aspects of autoimmune inflammation. Here, the prospects, expectations and restrictions of IL-22 administration in tissue-protective therapy are discussed.

Universal cloning and direct sequencing of rearranged antibody V genes using C region primers, biotin-captured cDNA and one-side PCR

Polymerase chain reaction (PCR) cloning has greatly facilitated the cloning of heavy and light chain genes from B cells and hybridomas and has been critical for the generation of natural antibody gene libraries for expression in bacteria and on filamentous phages. There remain difficulties, however, in cloning VH and VL genes from a number of mouse and rat hybridoma lines and from B cells from several other species due to insufficient sequence information. Here we describe a rapid and 'universal' strategy for cloning rearranged antibody genes from any species for which the sequence of the C segment(s) are known. First strand synthesis is primed with a biotinylated C region primer and full length cDNA is captured on streptavidin-coated magnetic beads for tailing with dGTP and terminal deoxynucleotidyl transferase. After tailing, the cDNA is captured again, amplified using polyC primers and used for direct sequencing or cloning. The use of C region primers and cDNA capture ensures that this one-side PCR procedure is efficient and rapid as well as being entirely independent of the sequence of the V segment. We demonstrate its application to the direct sequencing or cloning of the H and L chain genes from six mouse and rat hybridomas and propose that the method described will find applications in three areas: (i) cloning rearranged antibody genes in all cases in which cloning with V-J primers is not possible; (ii) repertoire studies in which an unbiased cloning procedure is required for accurate estimate of gene usage; and (iii) generation of VH and VL gene libraries from immunised animals.

Constitutive transcription of the osteocalcin gene in osteosarcoma cells is reflected by altered protein-DNA interactions at promoter regulatory elements

The bone-specific osteocalcin (OC) gene is transcribed only after completion of proliferation in normal diploid calvarial-derived osteoblasts during extracellular matrix mineralization. In contrast, the OC gene is expressed constitutively in both proliferating and nonproliferating ROS 17/2.8 osteosarcoma cells. To address molecular mechanisms associated with these tumor-related modifications in transcriptional control, we examined sequence-specific interactions of transactivation factors at key basal and hormone-responsive elements in the OC gene promoter. In ROS 17/2.8 cells compared to normal diploid osteoblasts, the absence of a stringent requirement for cessation of proliferation to support both induction of OC transcription and steroid hormone-mediated transcriptional modulation is reflected by modifications in transcription factor binding at (i) the two primary basal regulatory elements, the OC box (which contains a CCAAT motif as a central core) and the TATA/glucocorticoid-responsive element domain, and (ii) the vitamin D-responsive element. Particularly striking are two forms of the vitamin D receptor complex that are present in proliferating osteoblasts and osteosarcoma cells. Both forms of the complex are sensitive to vitamin D receptor antibody and retinoic X receptor antibody. After the down-regulation of proliferation, only the lower molecular weight complex is found in normal diploid osteoblasts. Both forms of the complex are present in nonproliferating ROS 17/2.8 cells with increased representation of the complex exhibiting reduced electrophoretic mobility that is phosphorylation-dependent.

Postproliferative transcription of the rat osteocalcin gene is reflected by vitamin D-responsive developmental modifications in protein-DNA interactions at basal and enhancer promoter elements

In the osteocalcin (OC) gene promoter, both independent positive and negative regulatory elements, as well as others with contiguous [TATA/glucocorticoid-responsive elements (GRE)] or overlapping [TATA/GRE, vitamin D-responsive enhancer elements (VDRE)/AP-1, and OC box/AP-1] domains, are sites for modifications in protein-DNA interactions. In the present studies, we have examined nuclear protein extracts from fetal rat calvarial cells that undergo a developmental sequence of bone cell differentiation. Our results demonstrate modifications in protein-DNA interactions that relate to the developmental stages of the osteoblast and support developmental regulation of OC gene transcription. Basal expression of the OC gene is associated with sequence-specific protein-DNA interactions at the OC box, VDRE, and TATA/GRE box. Distinct differences are observed in proliferating osteoblasts, where the OC gene is not transcribed compared to postproliferative, differentiated osteoblasts that transcribe the OC gene. Furthermore, the protein-DNA complexes that reflect hormonal control are also developmentally regulated, mediating both the transcriptionally active and repressed states of the OC gene. For example, in proliferating osteoblasts, a vitamin D receptor-antibody-sensitive complex is formed that is different from the DNA binding complex induced by vitamin D postproliferatively when the OC gene is transcribed. Mutational analysis of the steroid hormone binding domain and the overlapping AP-1 site at the VDRE supports mutually exclusive occupancy by Fos-Jun heterodimers and vitamin D receptor. Such protein-DNA interactions at the VDRE are consistent with repression of competency for vitamin D-mediated transcriptional enhancement in proliferating osteoblasts expressing high levels of Fos and Jun.

Effect of fluoride on aluminum-induced bone disease in rats with renal failure

Aluminum (Al) accumulation in renal failure is an etiological factor in the pathogenesis of low turnover bone disease. Aluminum-induced impairment of mineralization has been related to a reduced extent of active bone-forming surface. The present study investigated the effect of fluoride, a potent stimulator of osteoblast number, on the toxicity of aluminum in rats with renal failure (Nx). Following a large parenteral aluminum load (3.2 mg/kg x day) over a period of nine weeks, bone histomorphometry of vertebral cancellous bone revealed a severe low-turnover osteodystrophy as evidenced by a fall in osteoblastic osteoid surfaces and mineral apposition rates. Concurrent administration of fluoride [20 mg/liter (F20) or 40 mg/liter (F40) supplied with the drinking water] resulted in a significant increase in the number of osteoblasts (Nx+Al+F40 vs. Nx+Al, 33.75 +/- 2.83 vs. 1.81 +/- 0.43 mm-1, P less than 0.001) together with an overall reduced deposition of aluminum in bone (469.3 +/- 24.6 vs. 592.2 +/- 28.3 micrograms/g, P less than 0.01). However, there was an increase in the fraction of osteoid surface exhibiting stainable aluminum at the bone-osteoid interface (70.7 +/- 7.1 vs. 44.3 +/- 6.0%, P less than 0.005). Fluoride-exposed rats accumulated a significantly larger osteoid volume, suggesting an exacerbation of the osteomalacic lesion, and furthermore, dynamic histomorphometric parameters remained depressed. These results indicate that fluoride has a distinct effect on the pattern of aluminum deposition in bone. In addition, fluoride antagonizes the aluminum-induced reduction in osteoblast number but provides no amelioration of the impaired mineralization in aluminum-intoxicated rats. Thus, in this model a decrease in the extent of osteoblast surface does not account for the development of aluminum-related bone disease.(ABSTRACT TRUNCATED AT 250 WORDS)