Apoptosis in Microencapsulated Juvenile Rabbit Chondrocytes Induced by Ofloxacin: Role Played by β₁-Integrin Receptor

Abstract

Quinolone(s) (QNs) is widely used in infection therapy due to its good antimicrobial characteristics. However, QNs-induced arthropathy of immature animals has led to restrictions on the therapeutic use of these antimicrobial agents. The exact mechanism(s) of QNs-induced chondrotoxicity remain unknown. In the present study, we investigated the possible mechanism of ofloxacin (one typical QNs)-induced injuries of chondrocytes. Juvenile rabbit joint chondrocytes cultured in alginate microspheres were incubated with ofloxacin at concentrations of 0, 2, 5, 10, 20, and 40 g/ml for up to 96 h. Concentration of 10 g/ml ofloxacin induced apoptosis of chondrocyte with visible apoptotic signs, including degradation of poly(ADP-ribose) polymerase, caspase-3 activation, and DNA ladder formation. Furthermore, extracellular signal-regulated kinase 1/2 (phospho-ERK1/2) and growth factor receptor-bound protein 2 (Grb2) were significantly reduced, and similar changes were also observed in the ␤ 1 -integrin receptor as assessed by immunoblotting. However, the mRNA level of ␤ 1 -integrin obtained from reverse transcription-polymerase chain reaction remained unchanged. Results of ␤ 1 -integrin immunoprecipitation have also shown that ␤ 1 -integrin did not interact with activated intracellular signaling proteins. In addition, ofloxacin did not induce apoptosis and decrease ␤ 1 -integrin expression in chondrocytes supplemented with Mg 2ϩ , and the ofloxacin-induced apoptosis was caspase-8-dependent, inhibition of which did not affect the expression mode of phospho-ERK1/2 and ␤ 1 -integrin. Our results demonstrate that ofloxacin affects ␤ 1 -integrin receptor functions and the ERK mitogen-activated protein kinase signaling pathway, causing caspase-8-dependent apoptosis after exposure of 48 h.

Gene expression profiles in the articular cartilage of juvenile rats receiving the quinolone antibacterial agent ofloxacin

“…Recently, OFLX has been demonstrated to induce apoptosis in microencapsulated juvenile rabbit chondrocytes in vitro (Sheng et al, 2007). However, as shown in our results, OFLX has a potential to induce some genes related to cytokines, chemokines and/or proteases productions in chondrocytes but not genes showing activated apoptosis pathway.…”

“…Dusp1 protein has been known to inactivate c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK) pathways (Theodosiou and Ashworth, 2002). Recently, OFLX has been reported to inactivate ERK/MAPK signaling pathway in microencapsulated juvenile rabbit chondrocytes (Sheng et al, 2007). Although it is unclear whether increased Dusp1 results from activation of MAPK pathways or causes inactivation, the present (Table 4).…”

Chondrotoxicity of Quinolone Antimicrobial Agents

“…Slightly reduced expression of αv integrin on chondrocytes is exhibited in juvenile dogs receiving difloxacin in vivo 42 , and the expression of other integrins are also decreased in ofloxacintre ated mouse chondrocytes in vitro 4 3 -4 5 . W hen chondrocytes from juvenile rabbit joint cartilage are cultured with ofloxacin in alginate microspheres, β 1 -integrin expression is primarily reduced, and this causes subsequent changes in the extracellular signal-regulated kinase 1/2 / mitogen-activated protein kinase signaling pathway, resulting in caspase-8-dependent apoptosis of chondrocytes; supplementation with Mg 2+ blocks the changes in integrin and apoptosis 46 . Oxidation and mitochondrial change-In an ex vivo study using the chondrocytes of rabbits treated with ofloxacin or pefloxacin, an increase in cellular respiratory burst was observed in young animal cells, but not in adult animal cells, followed by decreased mitochondrial activity (suggestive of an injured membrane) and an increased mitochondrial mass (increased membrane area) 47 .…”

Quinolone-induced arthropathy: an update focusing on new mechanistic and clinical data

“…In microencapsulated chondrocytes from juvenile rabbits, ofloxacin markedly causes apoptosis via the caspase-8-dependent mitochondrial pathway by affecting the levels of ␤ 1 integrins and extracellular signal-regulated kinase (ERK)/MAPK signalling pathway. Using specific caspase inhibitors it was demonstrated that ofloxacin increased the level of Bax, tBid and p53 in a concentration-and time-dependent manner [18,19].…”