On the inhibitory affect of some dementia drugs on DNA polymerase Beta activity

In silico study of thymohydroquinone interaction with blood-brain barrier disrupting proteins

Aim:

To evaluate the inhibitory interaction of thymohydroquinone against blood–brain barrier (BBB)-associated neuropsychiatric and neurodegenerative disorders.

Materials & methods:

An elaborated in silico study was designed to evaluate the interaction of thymohydroquinone with BBB-disrupting proteins and to highlight its pharmacokinetic and safety attributes.

Results:

Thymohydroquinone demonstrated stable interaction with BBB-disrupting protein active site with Ki (inhibition constant) ranges of (2.71 mM–736.15 μM), binding energy (-4.3 to 5.6 Kcal/mol), ligand efficiency (-0.36 to 0.42 Kcal/mol) and root mean square deviation value of (0.80–2.59 Å).

Conclusion:

Further pharmacokinetic analysis revealed that thymohydroquinone is BBB and central nervous system (CNS) permeant with high acute toxicity and could be a candidate drug for the treatment of these neurological conditions.

The blood–brain barrier (BBB) is a complex neurological barrier whose disruption is associated with the development and exacerbation of different neurodegenerative and neuropsychiatric diseases. There are several drug candidates available that provide symptomatic treatment but have low BBB and central nervous system (CNS) permeability. Thymohydroquinone, a renowned medicinal compound has demonstrated a promising role in inhibiting BBB-disrupting proteins by forming hydrogen bonds with the active subunits with great stability and efficiency, thus, outcompeting its natural substrate. Through pharmacokinetic investigation, it was proven that thymohydroquinone has high BBB and CNS permeability with appropriate acute toxicity and adverse effects profiles.

Dietary Calorie Restriction from Adulthood Through Old Age in Rats: Improved DNA Polymerase β and DNA Gap Repair Activity in Cortical Neurons

It is well established now that dietary calorie restriction (CR) leads to extension of life span in many species, although the exact mechanism of this effect is still eluding. In the present study, we examined the effect of 40 % CR imposed during a prolonged period of life span (from 6 to 30 months) of rats on the activity of DNA polymerase β (pol β) in view of its role in short gap base excision DNA repair and template driven primer extension. DNA pol β activity is very low at this late age. However, cortical neuronal extracts prepared from CR rats of 30 months age showed significantly higher pol β protein levels and activity when compared to control 30 month old rats. Yet, one-nucleotide gap repair in old control neurons and an improved efficiency in CR neurons could be visualized only after supplementation of the extracts with T4 DNA ligase indicating the lack of CR affect on ligase activity. No impressive primer extension activity is seen either in the CR or old control neurons. These results are taken to convey that extended CR through adult life leads to improved pol β activity and therefore, pol β dependent DNA gap repair activity.