Structure of benzothiadiazine at zwitterionic phospholipid cell membranes

Abstract

The use of drugs derived from benzothiadiazine, which is a bicyclic heterocyclic benzene derivative, has become a widespread treatment for diseases such as hypertension (treated with diuretics such as bendroflumethiazide or chlorothiazide), low blood sugar (treated with non-diuretic diazoxide) or the human immunodeficiency virus, among others. In this work we have investigated the interactions of benzothiadiazine with the basic components of cell membranes and solvents such as phospholipids, cholesterol, ions and water. The analysis of the mutual microscopic interactions is of central importance to elucidate the local structure of benzothiadiazine as well as the mechanisms responsible for the access of benzothiadiazine to the interior of the cell. We have performed molecular dynamics simulations of benzothiadiazine embedded in three different model zwitterionic bilayer membranes made by dimyristoilphosphatidylcholine, dioleoylphosphatidylcholine, 1,2- dioleoyl-sn-glycero-3-phosphoserine and cholesterol inside aqueous sodium-chloride solution in order to systematically examine microscopic interactions of benzothiadiazine with the cell membrane at liquid-crystalline phase conditions. From data obtained through radial distribution functions, hydrogen-bonding lengths and potentials of mean force based on reversible work calculations, we have observed that benzothiadiazine has a strong affinity to stay at the cell membrane interface although it can be fully solvated by water in short periods of time. Furthermore, benzothiadiazine is able to bind lipids and cholesterol chains by means of single and double hydrogen-bonds of different characteristic lengths.

In silico drug design of benzothiadiazine derivatives interacting with bilayer cell membranes

“…Interestingly, in the case of DBD’s ‘H4’, HB lengths are within the range of 2-2.1 Å, significantly longer than those formed by H2 (range around 1.6 to 1.8 Å). This was already observed for the reference DBD1 in a previous work[26]. In this case, the strongest HB is observed when ‘H4’ of DBD3 is connected to DOPS’s ‘O11-12’ oxygens.…”

“…In our earlier work[26] we reported by the first time DBD-membrane related freeenergy barriers. For the sake of comparison with other similar systems, we can report that the PMF of tryptophan in a di-oleoyl-phosphatidyl-choline bilayer membrane shows a barrier of the order of 4 kcal/mol[68], whereas the barrier for the movement of tryptophan attached to a poly-leucine α -helix inside a DPPC membrane was reported to be of 3 kcal/mol[69].…”

“…We have considered five different setups, where only the benzothiadiazine derivative is different in each case. We considered a previously investigated[26] standard DBD species as the reference (DBD1) and four more DBD derivatives (DBD2, DBD3, DBD4 and DBD5), designed by ourselves using in silico techniques. The way how we designed the new DBD species is as follows: Medicinal chemists modify the chemical structure of the drug for the purpose of improving the therapeutic effect of the drug, reducing the toxic and side effects.…”

“…When the drug acts the binding methods of drug and receptor to form a reversible complex are generally by ionic bond, hydrogen bond or covalent bond. In our previous work[26] we observed that DBD can form hydrogen bonds (HB) and become absorbed by the cell membrane with DBD having strong affinity for DOPC. ‘H2’ and ‘H4’ sites of DBD are important for the formation of such HB with membrane components.…”

“…In addition to the above-mentioned biopharmacological activities, benzothiadiazine derivatives also has the bio-activity such as Factor Xa inhibition[22], anti-Mycobacterium[23,24], anti-benign prostatic hyperplasia[25]. 3,4-dihydro-1,2,4- benzothiadiazine-1,1-dioxide (DBD) being the main common structure of the benzothiadiazine family was investigated in a previous work[26] to elucidate the mechanisms responsible for the interactions of DBD with the basic components of cell membranes in all-atom level for the first time. The DBD has a strong affinity to the DOPC species of lipids, is also able to bind other membrane component by single and double hydrogenbonds.…”