Antisense pharmacologic activity

There are other complex issues with regard to the assessment of safety pharmacology studies. With the oligonucleotide therapeutics that modulate the translation of mRNA to proteins, like antisense/siRNA, there is a lag between administration of the drug and the pharmacologic activity that is mediated by reduction in protein levels. This lag is related to the mechanism of action and how long it takes for a reduction in protein synthesis to be reflected in reduced protein levels. Because of this lag it is probably better to... 

In addition to pharmacological approach, HO expression can also be downregulated by HO antisense treatment. Once the antisense is tagged to a specific cell type, cell type-specific local production of CO can be inhibited, which is more advantageous than general inhibition of HO activity by pharmacological compounds. 

For ASOs injected or infused directly into the CNS, the situation is quite different Neurons are known to take up PS ODNs, and antisense activity in CNS can be shown after local injections or intraventricular infusions. For PS ODNs that are administered locally to the CNS, safety pharmacology studies should be performed. For systemically administered PS ODNs, the scientific rationale is weak. 

In conclusion, phosphorothioate oligonucleotides may interact with a wide range of proteins through several types of mechanisms. These interactions may influence the pharmacokinetic, pharmacologic, and toxicologic properties of these molecules. They may also complicate studies on the mechanism of action of these drugs, and may obscure an antisense activity. For example, phosphorothio-... 

Changes in intracellular calcium levels are known to activate the mitochondrial pathway of apoptosis. A key regulator of Ca -dependent proteins is calmodulin. SM has been shown to cause a time-dependent induction of calmodulin in keratinocytes (Simbulan-Rosenthal et al., 2006). Moreover, depletion of calmodulin using antisense probes attenuated SM-induced activation of caspases involved in the mitochondrial pathway of apoptosis. Both antisense and pharmacological inhibition of calmodulin prevented SM-induced nuclear fragmentation in the keratinocytes. Bad, a proapoptotic Bcl-2 family member present in an inactive phosphorylated form in viable cells, was also activated by SM. Furthermore, cyclosporine A, a selective inhibitor of calcineurin, a Bad phosphatase, inhibited SM-induced keratinocyte apoptosis. These results suggest that calcium-dependent activation of Bad may be a mechanism by which SM induces apoptosis in keratinocytes. 

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