L-carnitine halts apoptosis and myelosuppression induced by carboplatin in rat bone marrow cell cultures (BMC)

Carboplatin (CP), a second generation platinum compound, is effective against various types of cancers, producing less nephrotoxicity and ototoxicity but more myelotoxicity than cisplatinum. CP-myelosuppression is the rate-limiting step of its clinical use. Prevention of CP-myelosuppression is a major target in the field of chemotherapy. Therefore, the present study investigates the use of L-carnitine (LCR)-an antioxidant, cardioprotective, neuroprotective, and immunostimulant nontoxic natural compound-to protect against CP-induced myelosuppression. The viability of BMC was studied using a trypan blue exclusion technique following incubation with CP and/or LCR as a function of time and concentration. Apoptosis was tested for by detecting the amount of DNA fragmentation and the visualization of DNA ladders upon gel electrophoresis. Bone marrow progenitor cell function was examined by colony forming unit assay. Cellular contents of glutathione (GSH) and malondialdehyde (MDA) were also estimated. Results revealed that LC50 of CP is 4.7 mM and the highest safe concentration of LCR is 5 mM. Co-exposure of LCR+CP rescued BMC viability by 37% compared to the CP-treated cultures. The LCR halts CP-induced apoptosis and it significantly improves the function of the bone marrow progenitors by increasing the number of colony-forming units as a response to granulocyte/macrophage colony stimulating factors. Finally, LCR restores CP-induced GSH depletion and prevents MDA elevation in BMC. In summary, the results suggest that LCR is able to protect against CP-induced myelosuppression, which suggests its use as an adjuvant therapy. This finding merits further investigation into the mechanism(s) of such protection as well as its interaction with CP antitumor activity.