Antibiotics induce apoptosis of human peritoneal mesothelial cells

The peritoneal mesothelial cell is a critical component of the peritoneal membrane. The intraperitoneal use of several antibiotics to treat bacterial peritonitis is current clinical practice. Our previous study showed that cephalothin (CPL) and cefotaxime (CFT) have cytotoxic effects on human peritoneal mesothelial cells (HPMC), however, the exact mechanism of cytotoxicity has not been elucidated. In the present study, flow cytometry, TdT-mediated dUTP nick-end labelling (TUNEL) staining and electron microscopy were used to detect the apoptosis of HPMCs. Immunofluorescent staining was used to evaluate the cytochrome c distribution pattern. Western blotting was used to assess apoptotic signalling proteins. We found that CPL (0.5 mg/mL) and CFT (1 mg/mL) induced apoptosis of HPMCs, whereas cefazolin (0.5 mg/mL) and ceftriaxone (0.5 mg/mL) failed to induce apoptosis of HPMCs. While the DNA content of CFT- or CPL-treated cells was reduced, as determined by flow cytometry, cefazolin and ceftriaxone had no such effect. The CFT- or CPL-treated cells displayed the features of apoptosis both under the electron microscope and by using TUNEL staining. However, cefazolin and ceftriaxone produced the same result as the medium controls. Furthermore, CFT and CPL increased the expression of Bax and p53, and caused the translocation of cytochrome c from the mitochondria to the cytoplasm. The HPMC treated by CFT but not by CPL induced the cleavage of procaspase-3 to form active caspase-3. In conclusion, cefotaxime and cephalothin induce apoptosis of HPMCs in vitro. Signal transduction may be through the mitochondrial pathway.