[Activation of nuclear factor kappaB (NF-kappaB), induction of proinflammatory cytokines in vitro and evaluation of biocompatibility of the carbonate ceramic in vivo].

Ceramic materials based on calcium carbonate have been prepared in response for the demand for resorbable materials for use in bone surgery. Calcium carbonate in the form of crystalline aragonite or calcite with various amount of lithium fluoride was the raw material. Material CC-1FA from crystalline aragonite (99% CaCO3 and 1% LiF), CC-5FA - from crystalline aragonite (95% CaCO3 and 5% LiF) and CC-1FK -material from crystalline calcite (99% CaCO3 and 1% LiF) was studied. To evaluate their biocompatibility and inflammatory effect we investigated the activity of nuclear factor kappaB (NF-kappaB) and proinflammatory cytokine concentrations: tumor necrosis factor TNF-alpha, interleukins 11-6 and IL-8 in peripheral human leukocytes (PBL) after stimulation in vitro with tested calcite materials. Evaluation of local soft tissue reaction after implantation was also the aim of our study. Proinflammatory cytokines take part in inflammatory reaction caused by biomaterials. Expression of these proteins is controlled by proinflammatory regulatory transcription factors including the commonly appearing NF-kappaB (Nuclear Factor kappaB). In a quiescent cell NF-kappaB resides in the cytosol in an inactive form which its activated under the influence of kinases. The activated NF-kappaB protein translocates from cytosol to nucleus of cell and binding to specific DNA sequence it initiates transcriptions. Thanks to the quick regulation of immunological response it ensures the survival of cells in unfavorable reactions of environmental factors. It regulates the expression of many genes mainly connected with the course of the inflammatory process (of some cytokines, proteins of acute phase, collagenasis, stromilozine other enzymes decomposing the elements of matrix) and with proliferation and differentiating of cells. However its excessive activity can lead to unfavorable reactions, for example uncontrollable division of cells, appearance of giant cells of foreign body type. In our study protein expression of NF-kappaB in PBL were assessed using anti-c-Rel-antibody (PBL expressing c-Rel in the nucleus = labelled NF-kappaB (+) cells). The NF-kappaB activation in PBL was expressed as: the percentage of NF-kappaB (+) cells. The level of cytokines: IL-6, IL-8 and TNF-alpha level in the supernatants from leukocytes culture with tested materials was determined by an enzyme-linked immunoabsorbent assay (ELISA) after 24 and 72 hours incubation. The local tissue reaction in vivo was evaluated 1 and 3 months after implantation calcite devices into dorsal muscles of rats. The achieved results showed that the tested calcite material incubated 24 and 72 hours with PBL culture didn't synthesized higher amounts of the cytokines IL-6 and IL-8 in comparison with the untreated cells. All tested materials stimulated after 24 and 72 hours PBL culture to produce a significant level of TNF-alpha (p < 0.05) (higher level after CC-5FA and CC-1FA materials and lower after CC-1FK). Activation of transcription factor nuclear factor NF-kappaB in leukocytes after 24 hours incubation with CC-5FA, CC-1FA was higher than CC-1FK but significantly was only after CC-5FA stimulating. The expression of NF-kappaB after 72 hours of incubation decreased and was on the level comparable with control group. Histological observation 1 month after implantation showed that the carbonate ceramic devices were surrounded with connective tissue surrounding implants capsule with presence of macrophages. Additionally after 3 month in the dense connective tissue cartilaginous and calcification focus was visible. Soft tissue reaction showed chronic inflammatory reaction connected with resorbtion of biomaterials, the most increased after implantation of CC-5FA, than CC-1FA and CC-1FK.

CONCLUSIONS

Transcription nuclear factor NF-kappaB was activated after in vitro stimulation in short time by the tested calcite material CC-5FA. This activity was correlated with induction in vitro of TNF-alpha in short and long time. The most increased soft tissue reaction 1 and 3 month after implantation of CC-5FA material was found. Our study showed that calcite materials can activate NF-kappaB and demonstrated differences in biocompatibility of tested materials.