The Ameliorative Effect of Pioglitazone against Neuroinflammation Caused by Doxorubicin in Rats.

Doxorubicin (DOX) is a chemotherapeutic agent that is linked with complications such as cardiotoxicity and cognitive dysfunction, known as chemobrain. Chemobrain affects up to 75% of cancer survivors, and there are no known therapeutic options for its treatment. This study aimed to determine the protective effect of pioglitazone (PIO) against DOX-induced cognitive impairment. Forty Wistar female rats were equally divided into four groups: control, DOX-treated, PIO-treated, and DOX + PIO-treated. DOX was administered at a dose of 5 mg/kg, i.p., twice a week for two weeks (cumulative dose, 20 mg/kg). PIO was dissolved in drinking water at a concentration of 2 mg/kg in the PIO and DOX-PIO groups. The survival rates, change in body weight, and behavioral assessment were performed using Y-maze, novel object recognition (NOR), and elevated plus maze (EPM), followed by estimation of neuroinflammatory cytokines IL-6, IL-1ß, and TNF-α in brain homogenate and RT-PCR of a brain sample. Our results showed a survival rate of 40% and 65% in the DOX and DOX + PIO groups, respectively, compared with a 100% survival rate in the control and PIO treatment groups at the end of day 14. There was an insignificant increase in body weight in the PIO group and a significant reduction in the DOX and DOX + PIO groups as compared with the control groups. DOX-treated animals exhibited impairment of cognitive function, and the combination PIO showed reversal of DOX-induced cognitive impairment. This was evidenced by changes in IL-1ß, TNF-α, and IL-6 levels and also by mRNA expression of TNF- α, and IL-6. In conclusion, PIO treatment produced a reversal of DOX-induced memory impairment by alleviating neuronal inflammation by modulating the expression of inflammatory cytokines.

Protective Effects of Pioglitazone on Cognitive Impairment and the Underlying Mechanisms: A Review of Literature.

Pioglitazone, a peroxisome proliferator-activated receptor gamma (PPARγ) agonist, is known to have anti-inflammatory and anti-oxidant effects on the brain, and its clinical potential in the treatment of cognitive impairment in diseases such as Alzheimer's disease (AD) and Parkinson disease (PD) is currently being explored. This review focused on the reported beneficial effects of pioglitazone on cognitive dysfunction and summarized the associated mechanisms associated with pioglitazone-induced improvement in cognitive dysfunction. Our review of the relevant literature indicated that there is conclusive evidence of the effect of pioglitazone on improving cognitive impairment via its agonistic effect on PPAR-γ. Further, several mechanisms of action have been reported, and these include enhanced NF-kB and p38 activity; regulation of the pro-inflammatory cytokines IL-1, IL-6, and TNF-α; inhibition of Aß production; alterations in the levels of mitochondrial proteins such as mitoNEET; regulation of protein kinases such as CDK5 and JNK; regulation of ROS and MDA levels and the levels of the antioxidant proteins TRX1 and PON2; and increased expression of thyroid hormone receptors. Despite these promising findings, pioglitazone treatment is also associated with cardiovascular risks, such as weight gain and edema, which subsequently increase the risk of mortality. Further, it has been documented that pioglitazone may be unable to cross the blood-brain barrier when administered in certain forms, and it can also cause cell death when administered at high concentrations. Therefore, further research is required to explore the effects of acute and chronic pioglitazone treatment on memory function and the associated risks, in order to determine its clinical applicability in the treatment of cognitive disorders. Nonetheless, the current literature does demonstrate that pioglitazone promotes the function of PPAR receptors in ameliorating inflammation, oxidative stress, amyloidogenesis, and hypothyroidism, and enhancing neurogenesis, synaptic plasticity, and mitochondrial function. Therefore, these mechanisms of PPAR receptors warrant further investigation in order to establish the clinical applicability of pioglitazone in the treatment of cognitive disorders, such as PD and AD, and neuronal impairment in conditions such as diabetes.