Deletions in the mitochondrial DNA and decrease in the oxidative phosphorylation activity of children with Fanconi syndrome secondary to antiblastic therapy

Conventional Chemotherapy Nephrotoxicity

Conventional chemotherapies remain the mainstay of treatment for many malignancies. Kidney complications of these therapies are not infrequent and may have serious implications for future kidney function, cancer treatment options, eligibility for clinical trials, and overall survival. Kidney adverse effects may include acute kidney injury (via tubular injury, tubulointerstitial nephritis, glomerular disease and thrombotic microangiopathy), long-term kidney function loss and CKD, and electrolyte disturbances. In this review, we summarize the kidney complications of conventional forms of chemotherapy and, where possible, provide estimates of incidence, and identify risk factors and strategies for kidney risk mitigation. In addition, we provide recommendations regarding kidney dose modifications, recognizing that these adjustments may be limited by available supporting pharmacokinetic and clinical outcomes data. We discuss management strategies for kidney adverse effects associated with these therapies with drug-specific recommendations. We focus on frequently used anticancer agents with established kidney complications, including platinum-based chemotherapies (cisplatin, carboplatin, oxaliplatin), cyclophosphamide, gemcitabine, ifosfamide, methotrexate and pemetrexed, among others.

The Role of Mitochondria in Drug-Induced Kidney Injury

The kidneys utilize roughly 10% of the body’s oxygen supply to produce the energy required for accomplishing their primary function: the regulation of body fluid composition through secreting, filtering, and reabsorbing metabolites and nutrients. To ensure an adequate ATP supply, the kidneys are particularly enriched in mitochondria, having the second highest mitochondrial content and thus oxygen consumption of our body. The bulk of the ATP generated in the kidneys is consumed to move solutes toward (reabsorption) or from (secretion) the peritubular capillaries through the concerted action of an array of ATP-binding cassette (ABC) pumps and transporters. ABC pumps function upon direct ATP hydrolysis. Transporters are driven by the ion electrochemical gradients and the membrane potential generated by the asymmetric transport of ions across the plasma membrane mediated by the ATPase pumps. Some of these transporters, namely the polyspecific organic anion transporters (OATs), the organic anion transporting polypeptides (OATPs), and the organic cation transporters (OCTs) are highly expressed on the proximal tubular cell membranes and happen to also transport drugs whose levels in the proximal tubular cells can rapidly rise, thereby damaging the mitochondria and resulting in cell death and kidney injury. Drug-induced kidney injury (DIKI) is a growing public health concern and a major cause of drug attrition in drug development and post-marketing approval. As part of the article collection “Mitochondria in Renal Health and Disease,” here, we provide a critical overview of the main molecular mechanisms underlying the mitochondrial damage caused by drugs inducing nephrotoxicity.

Triptorelin for Fertility Preservation in Adolescents Treated With Chemotherapy for Cancer

BACKGROUND

Triptorelin, a gonadotropin releasing hormone analogue, can be administered to postpubertal female individuals with cancer who receive chemotherapy to obtain menstrual suppression and decrease the risk of hemorrhage caused by thrombocytopenia. Our goal was to assess whether triptorelin also has a protective role against the gonadotoxicity of chemotherapy.

PATIENTS AND METHODS

This retrospective observational study includes all postmenarchal female patients who presented to our Unit from 2000 to 2015 and received chemotherapy for cancer. They were administered depot triptorelin. We evaluated long-term ovarian function in order to detect clinical signs of ovarian damage, miscarriages, and pregnancies. Laboratory follow-up consisted in dosing serum follicle stimulating hormone, luteinizing hormone, prolactin, estradiol, and progesterone. Ultrasound of the ovaries was performed as well.

RESULTS

Of 36 evaluable patients, 9 received hematopoietic stem cell transplantation (HSCT). The remaining 27 patients maintained normal ovarian function at clinical, laboratory, and ultrasound assessment. Five of them achieved spontaneous physiological pregnancy. Four of the 9 patients who underwent HSCT developed premature ovarian failure.

CONCLUSION

Our study suggests that gonadotropin releasing hormone-a administered during chemotherapy can prevent premature ovarian failure in patients treated without HSCT and that it is not enough to preserve the ovarian function during HSCT. Hence, a prospective randomized trial with a larger population would be recommended.

Fatal hyperammonemia and carbamoyl phosphate synthetase 1 (CPS1) deficiency following high-dose chemotherapy and autologous hematopoietic stem cell transplantation

Fatal hyperammonemia secondary to chemotherapy for hematological malignancies or following bone marrow transplantation has been described in few patients so far. In these, the pathogenesis of hyperammonemia remained unclear and was suggested to be multifactorial. We observed severe hyperammonemia (maximum 475 μmol/L) in a 2-year-old male patient, who underwent high-dose chemotherapy with carboplatin, etoposide and melphalan, and autologous hematopoietic stem cell transplantation for a neuroblastoma stage IV. Despite intensive care treatment, hyperammonemia persisted and the patient died due to cerebral edema. The biochemical profile with elevations of ammonia and glutamine (maximum 1757 μmol/L) suggested urea cycle dysfunction. In liver homogenates, enzymatic activity and protein expression of the urea cycle enzyme carbamoyl phosphate synthetase 1 (CPS1) were virtually absent. However, no mutation was found in CPS1 cDNA from liver and CPS1 mRNA expression was only slightly decreased. We therefore hypothesized that the acute onset of hyperammonemia was due to an acquired, chemotherapy-induced (posttranscriptional) CPS1 deficiency. This was further supported by in vitro experiments in HepG2 cells treated with carboplatin and etoposide showing a dose-dependent decrease in CPS1 protein expression. Due to severe hyperlactatemia, we analysed oxidative phosphorylation complexes in liver tissue and found reduced activities of complexes I and V, which suggested a more general mitochondrial dysfunction. This study adds to the understanding of chemotherapy-induced hyperammonemia as drug-induced CPS1 deficiency is suggested. Moreover, we highlight the need for urgent diagnostic and therapeutic strategies addressing a possible secondary urea cycle failure in future patients with hyperammonemia during chemotherapy and stem cell transplantation.

The Not So ‘Mighty Chondrion’: Emergence of Renal Diseases due to Mitochondrial Dysfunction

Mitochondria are intracellular organelles with a variety of vital functions, including the provision of energy in the form of adenosine 5'-triphosphate. Increasingly, we are becoming more aware of the importance of mitochondrial dysfunction in a number of common medical conditions. In this review and overview, we focus on the growing evidence that mitochondrial dysfunction is involved in either the etiology or underlying pathophysiology of a broad spectrum of renal diseases, including acute renal injury due to ischemia-reperfusion injury, renal Fanconi syndrome, and glomerular disorders such as focal segmental glomerulosclerosis. In addition, mitochondrial dysfunction may also contribute to the growing burden of chronic kidney disease seen in our aging population, which is still largely unexplained. Unfortunately, at present, our ability to diagnose and treat renal disorders related to mitochondrial dysfunction is limited, and further work in this field is needed.

Polyphenotypic Expression of Mitochondrial Toxicity Caused by Nucleoside Reverse Transcriptase Inhibitors

An HIV-infected man taking long-term zidovudine and didanosine presented with a polyphenotypic expression of nucleoside reverse transcriptase inhibitor (NRTI)-induced mitochondrial toxicity. Clinical features included lactic acidosis, myopathy, Fanconi-type proximal tubulopathy, pancreatic dysfunction, pseudo-obstruction, mega-oesophagus, peripheral sensory neuropathy and osteoporosis. A muscle biopsy showed morphologically abnormal mitochondria and respiratory chain biochemistry revealed marked reductions in the activity of respiratory chain enzymes containing mitochondrial DNA-encoded subunits. Southern blotting showed no mitochondrial DNA depletion and long PCR revealed only minor deletions. Following withdrawal of NRTI therapy, the lactic acidosis, pancreatic dysfunction and Fanconi's tubulopathy rapidly improved. Over the next 6 months there was marked improvement in osteoporosis, myopathy and neuropathy. At this stage, dual protease inhibitors and nevirapine were started. A repeat muscle biopsy 14 months after presentation showed normal morphology and respiratory chain biochemistry was almost normal.

Renal manifestations of congenital lactic acidosis

Congenital lactic acidoses (CLAs) constitute a group of rare inborn errors of mitochondrial metabolism in which cellular energy failure is the defining biochemical abnormality. We report the principal manifestations of renal dysfunction in 35 children with CLA caused by defects in either the pyruvate dehydrogenase multienzyme complex or one or more components of the respiratory chain. The most prominent renal abnormalities included bicarbonaturia, phosphaturia, hypercalciuria, complete Fanconi's syndrome, proteinuria, and decreased glomerular filtration rate. These data were compared with those from 79 previously published cases. Clinical manifestations of renal dysfunction in CLA are common and may be the first presenting sign of the disease. The glomerulus and proximal renal tubule appear to be the anatomic sites most vulnerable to abnormal mitochondrial energy transduction. We propose that the primary defect in mitochondrial energy metabolism, together with the consequent intracellular accumulation of lactate and hydrogen ions, precipitates a state of tissue injury that, unless interrupted, becomes self-perpetuating and ultimately leads to renal cell death.