Leucovorin and maximum tolerated dose toxicity of methotrexate in rats

Exploring the role of ATP-sensitive potassium channel, eNOS, and P-glycoprotein in mediating the hepatoprotective activity of nicorandil in methotrexate-induced liver injury in rats

BACKGROUND

Methotrexate (MTX) is a commonly used chemotherapeutic agent; however, its clinical use is challenged by various types of injuries, including hepatotoxic side effects. Therefore, finding new protective drugs against MTX-induced toxicities is a critical need. Moreover, the different mechanisms mediating such effects are still not clear. The current study aimed to evaluate the possible ameliorative action of nicorandil (NIC) in MTX-induced hepatotoxicity and examine the roles of the ATP-sensitive potassium channel (KATP), endothelial nitric oxide synthase (eNOS), and P-glycoprotein (P-gp).

MATERIALS AND METHODS

Thirty-six male Wistar albino rats were used. NIC (3 mg/kg/day) was given orally for 2 weeks, and hepatotoxicity was induced by a single intraperitoneal injection of MTX (20 mg/kg) on the 11th day of the experiment. We confirmed the role of KATP by co-administering glimepiride (GP) (10 mg/kg/day) 30 min before NIC. The measured serum biomarkers were [alanine transaminase (ALT) and aspartate transaminase (AST)], total antioxidant capacity (TAC), malondialdehyde (MDA), nitric oxide (NOx), tumor necrosis factor-alpha (TNFα), superoxide dismutase (SOD), and P-gp. Histopathology, eNOS, and caspase-3 immunoexpression were evaluated.

RESULTS

The MTX group displayed hepatotoxicity in the form of elevations of ALT, AST, MDA, NOx, and caspase-3 immunoexpression. Furthermore, the histopathological examination showed marked liver injury. TAC, SOD, P-gp, and eNOS immunoexpression showed significant inhibition. In the protective group, all parameters improved (P value < 0.05).

CONCLUSION

NIC has an ameliorative action against MTX-induced hepatotoxicity, most probably via its antioxidant, anti-inflammatory, and anti-apoptotic functions together with the modulation of the KATP channel, eNOS, and P-glycoprotein.

Paeonol Attenuates Methotrexate-Induced Cardiac Toxicity in Rats by Inhibiting Oxidative Stress and Suppressing TLR4-Induced NF-κB Inflammatory Pathway

Methotrexate (MTX) is a commonly used chemotherapeutic agent. Oxidative stress and inflammation have been proved in the development of MTX toxicity. Paeonol is a natural phenolic compound with various pharmacological activities including antioxidant and anti-inflammatory properties. The aim of the present study was to evaluate the protective effect of paeonol against MTX-induced cardiac toxicity in rats and to evaluate the various mechanisms that underlie this effect. Paeonol (100 mg/kg) was administered orally for 10 days. MTX cardiac toxicity was induced at the end of the fifth day of the experiment, with or without paeonol pretreatment. MTX-induced cardiac damage is evidenced by a distortion in the normal cardiac histological structure, with significant oxidative and nitrosative stress shown as a significant increase in NADPH oxidase-2, malondialdehyde, and nitric oxide levels along with a decrease in reduced glutathione concentration and superoxide dismutase activity compared to the control group. MTX-induced inflammatory effects are evidenced by the increased cardiac toll-like receptor 4 (TLR4) mRNA expression and protein level as well as increased cardiac tumor necrosis factor- (TNF-) α and interleukin- (IL-) 6 levels along with increased nuclear factor- (NF-) κB/p65 immunostaining. MTX increased apoptosis as shown by the upregulation of cardiac caspase 3 immunostaining. Paeonol was able to correct the oxidative and nitrosative stress as well as the inflammatory and apoptotic parameters and restore the normal histological structure compared to MTX alone. In conclusion, paeonol has a protective effect against MTX-induced cardiac toxicity through inhibiting oxidative and nitrosative stress and suppressing the TLR4/NF-κB/TNF-α/IL-6 inflammatory pathway, as well as causing an associated reduction in the proapoptotic marker, caspase 3.

Preventing and Managing Toxicities of High-Dose Methotrexate

: High-dose methotrexate (HDMTX), defined as a dose higher than 500 mg/m2, is used to treat a range of adult and childhood cancers. Although HDMTX is safely administered to most patients, it can cause significant toxicity, including acute kidney injury (AKI) in 2%-12% of patients. Nephrotoxicity results from crystallization of methotrexate in the renal tubular lumen, leading to tubular toxicity. AKI and other toxicities of high-dose methotrexate can lead to significant morbidity, treatment delays, and diminished renal function. Risk factors for methotrexate-associated toxicity include a history of renal dysfunction, volume depletion, acidic urine, and drug interactions. Renal toxicity leads to impaired methotrexate clearance and prolonged exposure to toxic concentrations, which further worsen renal function and exacerbate nonrenal adverse events, including myelosuppression, mucositis, dermatologic toxicity, and hepatotoxicity. Serum creatinine, urine output, and serum methotrexate concentration are monitored to assess renal clearance, with concurrent hydration, urinary alkalinization, and leucovorin rescue to prevent and mitigate AKI and subsequent toxicity. When delayed methotrexate excretion or AKI occurs despite preventive strategies, increased hydration, high-dose leucovorin, and glucarpidase are usually sufficient to allow renal recovery without the need for dialysis. Prompt recognition and effective treatment of AKI and associated toxicities mitigate further toxicity, facilitate renal recovery, and permit patients to receive other chemotherapy or resume HDMTX therapy when additional courses are indicated.

IMPLICATIONS FOR PRACTICE

High-dose methotrexate (HDMTX), defined as a dose higher than 500 mg/m2, is used for a range of cancers. Although HDMTX is safely administered to most patients, it can cause significant toxicity, including acute kidney injury (AKI), attributable to crystallization of methotrexate in the renal tubular lumen, leading to tubular toxicity. When AKI occurs despite preventive strategies, increased hydration, high-dose leucovorin, and glucarpidase allow renal recovery without the need for dialysis. This article, based on a review of the current associated literature, provides comprehensive recommendations for prevention of toxicity and, when necessary, detailed treatment guidance to mitigate AKI and subsequent toxicity.

Methotrexate induces cell swelling and necrosis in renal tubular cells

BACKGROUND

The present study was carried out to investigate if methotrexate (MTX) has a direct lethal effect in renal tubular cells, and if so, to further clarify the mechanisms of cell death.

MATERIALS AND METHODS

Renal tubular cells (LLC-PK(1) cells) were incubated with MTX (0.01 microM, 0.1 microM, and 1 microM), either alone or in combination with 0.1 microM amiloride (Na(+)/H(+) antiporter inhibitor) or 1 microM carbachol (M-cholinergic agonist). Cell viability was then determined by means of trypan blue (TB) exclusion tests and MTT assays.

RESULTS

After 4 hr incubation with 0.1 microM MTX the number of viable cells was decreased by 18% in comparison with control cells, and the proportion of dead cells was increased by 38%. Cell death induced by MTX was time-dependent and did not show apoptotic features. On the contrary, cell swelling was discovered. This cell death was prevented by co-incubating the cells with amiloride or carbachol.

CONCLUSIONS

MTX induces cell swelling and cell death in renal tubular LLC-PK(1) cells. The tubular cell death induced by MTX is time-dependent. Cell death can be prevented by co-incubating with amiloride, thus indicating that the Na(+)/H(+) antiporter and possibly other volume regulatory factors in renal tubular cells are involved in MTX-induced renal failure.

Acute Cardiac Toxicity Associated with High-Dose Intravenous Methotrexate Therapy: Case Report and Review of the Literature

A 36-year-old woman was hospitalized for preoperative chemotherapy for osteosarcoma. She received intravenous fluids for 12 hours for volume expansion, then methotrexate 24 g (12 g/m2) over 6 hours. This was followed by intravenous leucovorin 200 mg over 1 hour. Two hours after the methotrexate infusion the patient developed chest pain and bradycardia. An electrocardiogram revealed sinus pauses, and telemetry recordings indicated a 4-beat run of ventricular tachycardia. A cardiac work-up consisting of cardiac enzyme level determination, two-dimensional echocardiography, and an adenosine technetium-99m tetrofosmin stress test was negative for structural and ischemic heart disease. The patient recovered without treatment and, approximately 2 weeks later, received a second course of methotrexate at half the dose without complication. One month later the patient received treatment with doxorubicin and cisplatin; 2 days later she died unexpectedly at home. Clinicians should be aware that high-dose methotrexate can cause cardiac symptoms and arrhythmias in previously healthy adults. This complication warrants attention and needs additional clinical investigation.