The molecular pharmacology of doxorubicin in vivo

Doxorubicin (Dox), a powerful chemotherapeutic agent, has been shown to cause cardiotoxicity and neurotoxicity. Ranolazine, a drug that is commonly used to treat patients with chronic angina, has been shown to reduce toxicity from Dox therapy. Therefore, the present study aims to investigate the mechanisms behind the protective effects of ranolazine on the heart and brain in Dox-treatment. Twenty-four male Wistar rats received 6 doses of either 0.9% normal saline (0.9% NSS, i.p., n = 8) or Dox (3 mg/kg, i.p., n = 16). All Dox-treated rats were assigned into 2 groups to receive vehicle (0.9% NSS, orally; n = 8) or ranolazine (305 mg/kg/day, orally; n = 8) for 30 consecutive days. Following the treatments, left ventricular (LV) function and cognition were determined. Animals were euthanized, then the heart and brain were collected for further analysis. Dox induced systemic oxidative stress/inflammation, and cardiac injury evidenced by mitochondrial dysfunction, mitochondrial dynamic imbalance, and apoptosis, resulting in LV dysfunction. Ranolazine significantly improved LV function via attenuating cardiac injury. Dox also caused brain pathologies as indicated by increased brain inflammation, impaired blood-brain barrier integrity, brain mitochondrial dysfunction, microglial dysmorphology, hippocampal dysplasticity, and increased apoptosis, resulting in cognitive decline. Ranolazine exerted neuroprotective effects by suppressing brain pathologies and restoring cognitive function. These findings suggest that ranolazine has a potential role in cardio- and neuro-protection against chemotherapy.

Chemotherapy is an important component of cancer treatment, which has side effects like vomiting, peripheral neuropathy, and numerous organ toxicity but the most significant outcomes of chemotherapy are cognitive impairment, which is mainly referred to as chemobrain or CICI (chemotherapy-induced cognitive impairment). It is characterized by difficulty with language, concentrating, processing speed, learning, and memory, as it affects the hippocampus areas of the brain. Mitochondrial dysfunction and oxidative stress are one of the major mechanisms causing chemobrain. The generation of reactive oxygen species (byproducts of oxidative phosphorylation) mainly occurs in mitochondria that play a prominent role in the induction of oxidative stress. The homeostasis of ROS in the mitochondria is maintained by mitochondrial antioxidant mechanism via enzymes like catalase, glutathione, and superoxide dismutase. Lungs and breast cancer are the two most common types of cancer, which are the most leading cancers in the world with about 4.18 million cases. In this review we exposed the current knowledge regarding chemotherapy-induced oxidative stress and mitochondrial dysfunction to cause cognitive impairment.We especially focused on the antineoplastic agent (ADRIAMYCIN, CYCLOPHOSPHAMIDE), platinum group agent CISPLATIN, antimetabolite agents (METHOTREXATE), and nitrogen mustard agent (CARMUSTINE) which increase oxidative stress and inflammatory markers in the PNS (peripheral nervous system) as well as the central nervous system. We also highlight the behavioural and functional changes in the brain.

The development of efficient drug delivery and imaging approaches is of great importance for both diagnostic and therapeutic purposes. This is especially important for the triple-negative breast cancers for which chemotherapy is often the mainstay of treatment. Metal-organic frameworks (MOFs) have recently attracted tremendous attention as nanocarriers that can be loaded with a wide variety of therapeutic as well as bioimaging agents. Herein, the Fe₃O₄ core UiO-66-NH₂ MOF shell nanostructures, Fe₃O₄@MOF, were loaded with the anticancer drug doxorubicin (DOX), and the loaded nanostructures were conjugated to highly fluorescent carbon dots (CDs) and then capped with the nucleolin-binding aptamer, AS1411. The Fe₃O₄@MOF-DOX-CDs-Apt nanocarriers were specifically unlocked in the presence of the nucleolin-overexpressing cancer cells, resulted in the release of the loads. The drug delivery process rendered more efficient by pH-dependent controlled release kinetics that provides an enhanced therapeutic outcome. The stimuli-responsive drug delivery system reveals a rather selective permeation of the Fe₃O₄@MOF-DOX-CDs-Apt nanocarriers into the triple-negative MDA-MB-231 human breast cancer cells, compared to the normal HUVEC cells. Cytotoxicity experiments revealed that the nanocarriers inhibit cell proliferation and induce selective apoptosis towards the MDA-MB-231 cancer cells (>77% at 24 ​h); whereas, less than 10% apoptosis was induced in the normal HUVEC cells. In addition, we encapsulated CDs into the nanocarriers, thereby, the nanocarriers exhibit fluorescence imaging functionality, thus can effectively contribute to monitoring biodistribution of the nanocarriers in vitro. Based on these findings, the Fe₃O₄@MOF-DOX-CDs-Apt nanocarriers can serve as a promising multifunctional material for cancer therapy and cellular bioimaging.

Methotrexate (MTX) induces the formation of reactive oxygen species (ROS) and leads to neurotoxicity. The drug also negatively impacts neurogenesis and memory. Hesperidin (Hsd) is a major flavanoid with multiple beneficial pharmacological effects such as anti-oxidation, anti-inflammation, and neuroprotective effects. The aim of our study was to investigate the neuroprotective effects of Hsd against MTX-induced alterations in oxidative stress and neurogenesis. Sprague Dawley rats were divided into four groups: 1) a vehicle group, which received saline and propylene glycol, 2) an Hsd group, which was orally administered with Hsd (100 mg/kg) for 21 days, 3) an MTX group, which received MTX (75 mg/kg) by intravenous injection on days 8 and 15, and 4) an MTX + Hsd group, which received both MTX and Hsd. After treatment with MTX, p21-positive cells had increased significantly and doublecortin (DCX) expression in the hippocampus had decreased significantly. Treatment with MTX also increased malondialdehyde (MDA) in both the hippocampus and prefrontal cortex and decreased levels of brain-derived neurotropic factor (BDNF) and nuclear factor erythroid 2-related factor 2 (Nrf2) in the hippocampus and prefrontal cortex. Additionally, there were significant decreases in superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT) in the hippocampus and prefrontal cortex in the MTX group. However, co-treatment with Hsd ameliorated the negative effects of MTX on neurogenesis, oxidative stress, and antioxidant enzymes. These findings suggest that Hsd may be able to prevent neurotoxic effects of MTX by reducing oxidative stress and enhancing hippocampal neurogenesis.

Cancer treatments are developing fast and the number of cancer survivors could arise to 20 million in United State by 2025. However, a large fraction of cancer survivors demonstrate cognitive dysfunction and associated decreased quality of life both shortly, and often long-term, after chemotherapy treatment. The etiologies of chemotherapy induced cognitive impairment (CICI) are complicated, made more so by the fact that many anti-cancer drugs cannot cross the blood-brain barrier (BBB). Multiple related factors and confounders lead to difficulties in determining the underlying mechanisms. Chemotherapy induced, oxidative stress-mediated tumor necrosis factor-alpha (TNF-α) elevation was considered as one of the main candidate mechanisms underlying CICI. Doxorubicin (Dox) is a prototypical reactive oxygen species (ROS)-generating chemotherapeutic agent used to treat solid tumors and lymphomas as part of multi-drug chemotherapeutic regimens. We previously reported that peripheral Dox-administration leads to plasma protein damage and elevation of TNF-α in plasma and brain of mice. In the present study, we used TNF-α null (TNFKO) mice to investigate the role of TNF-α in Dox-induced, oxidative stress-mediated alterations in brain. We report that Dox-induced oxidative stress in brain is ameliorated and brain mitochondrial function assessed by the Seahorse-determined oxygen consumption rate (OCR) is preserved in brains of TNFKO mice. Further, we show that Dox-decreased the level of hippocampal choline-containing compounds and brain phospholipases activity are partially protected in TNFKO group in MRS study. Our results provide strong evidence that Dox-targeted mitochondrial damage and levels of brain choline-containing metabolites, as well as phospholipases changes decreased in the CNS are associated with oxidative stress mediated by TNF-α. These results are consistent with the notion that oxidative stress and elevated TNF-α in brain underlie the damage to mitochondria and other pathological changes that lead to CICI. The results are discussed with reference to our identifying a potential therapeutic target to protect against cognitive problems after chemotherapy.

Protein phosphatase 5 (PP5), a serine/threonine phosphatase, has a wide range of biological functions and exhibits elevated expression in tumor cells. We previously reported that pp5-deficient mice have altered ataxia-telangiectasia mutated (ATM)-mediated signaling and function. However, this regulation was likely indirect, as ATM is not a known PP5 substrate. In the current study, we found that pp5-deficient mice are hypersensitive to genotoxic stress. This hypersensitivity was associated with the marked up-regulation of the tumor suppressor tumor protein p53 and its downstream targets cyclin-dependent kinase inhibitor 1A (p21), MDM2 proto-oncogene (MDM2), and phosphatase and tensin homolog (PTEN) in pp5-deficient tissues and cells. These observations suggested that PP5 plays a role in regulating p53 stability and function. Experiments conducted with p53^+/−pp5^+/− or p53^+/−pp5^−/− mice revealed that complete loss of PP5 reduces tumorigenesis in the p53^+/− mice. Biochemical analyses further revealed that PP5 directly interacts with and dephosphorylates p53 at multiple serine/threonine residues, resulting in inhibition of p53-mediated transcriptional activity. Interestingly, PP5 expression was significantly up-regulated in p53-deficient cells, and further analysis of pp5 promoter activity revealed that p53 strongly represses PP5 transcription. Our results suggest a reciprocal regulatory interplay between PP5 and p53, providing an important feedback mechanism for the cellular response to genotoxic stress.