Dimethly Sulfoxide, commonly known as DMSO, is a small molecule composed of two methyl groups attached to a Sulfur with an Oxygen (C2H6OS). It was the production of cheaper paper that led to the discovery of this colorless liquid in the 19th Century, but it was its characteristic of being able to dissolve a large number of polar and non polar small molecules that made this a great solvent in the research world. When it was discovered that DMSO had the unusual chemical characteristic of carrying small molecules through membranes, the use of this solvent was expanded in the clinical and scientific. Due to its characteristics and chemistry, DMSO has three primary medical uses: 1) Penetration enhancing solvent, 2) Active pharmaceutical agent primarily as anti-inflammatory and 3) tissue/organ preservation (Capriotti et al, 2012).
In the 1960s Dr. Stanley Jacob, who worked with DMSO as a preserver of organs and tissues, rediscovered the ability of DMSO in penetrating the skin. This information spread and pharmaceuticals quickly started to push the use of DMSO as a solvent of their drugs. Other pharmaceuticals proposed the use of DMSO as a cure or treatment for a particular disease, getting all the way to clinical trials with this small molecule (Muir, http://www.dmso.org/articles/information/muir.htm) . However, after the death of a patient due to DMSO exposure, the FDA decided to end all the trials and rejected drugs that used DMSO as their solvent in drug formulations (however, in 1978 the FDA approved DMSO as a treatment for Interstitial Cystitis as an anti-inflammatory and antispasmodic, and currently it remains a treatment of this disease.
Nowadays, perhaps the most important role of DMSO in the drug discovery world as a small molecule/drug solvent and carrier of small molecules through the cell membrane. It dissolves a large variety of polar and non-polar small molecules, making it a universal small molecule/drug solvent. Like most labs, our current drug libraries are dissolved to 10μM in DMSO. Knowing the toxicity effects this solvent may have on our model organisms, we conduct studies to determine tolerance levels before we begin an investigation. For instance, our Niemann-Pick C (NPC) Drosophila loose tolerability to DMSO at ≥0.33% (Figure 1).
Figure 1: Our npc1 mutants showed a larval lethality phenotype in the absence of 7-dehydrocholesterol (7-d). Fly vials with different concentrations of DMSO (0% DMSO, 0.1% DMSO, 0.25% DMSO, 0.33% DMSO, 0.5% DMSO, and 1%DMSO) were prepared with food containing 5uM 7-d to get npc1 mutants larvae to pupae (a 33% pupae survival) and added npc1 mutant 1st instar larvae into each of the vials. We counted the number of pupae by Day 6 and observed how our npc1 mutants start to become sensitive after 0.33% DMSO while at 1% DMSO we get obvious developmental delay.
The sensitivity of NGLY1 larvae to DMSO is about 10 times more than NPC larvae’s. For our ngly1 flies, we conducted the same type of DMSO tolerance study and we observed that ngly1 flies are more sensitive to DMSO and loose tolerability to DMSO at ≥0.025% (Figure 2).
Figure 2: This graph shows how ngly1 mutants (ngly1 mutants have pupal lethal phenotype where larvae reach to pupae but don’t become adult flies) start to show significant development delay after 0.025% DMSO, suggesting that we have a range of 0% to 0.025% DMSO to conduct an ngly1 study before we start to introduce DMSO toxicity into our larvae.
A ≥0.33% DMSO tolerance on our NPC larvae allowed us to carry out a drug screen at 50uM using drugs from our library that are dissolved to 10μM in DMSO. A ≥0.025% DMSO tolerance on our NGLY1 larvae would allow us to carry out a drug screen at a maximum concentration of 2.5uM from our library before adding a DMSO challenge into the larvae. Interestingly, our NGLY1 larvae do not have the same level of sensitivity to Ethanol (another solvent used in the small drug discovery world) as they do for DMSO, where we observe that ngly1 larvae loose tolerability to Ethanol at ≥2.5% (Figure 3)
Figure 3: This graph shows how ngly1 mutants start to show significant development delay after 2.5% Ethanol.
Although ngly1 mutants tolerate Ethanol better than DMSO, Ethanol does not dissolve small molecules as well asDMSO does. Moreover, dissolving drugs in Ethanol has the disadvantage of being very volatile, which can lead to variable drug concentrations. Water is yet another solvent that can be used for small drugs dissolving; however, just like Ethanol, water does not dissolve small molecules as well as DMSO does.
DMSO is a great solvent for polar and non-polar small drugs molecules, but determining DMSO sensitivity to the mutant model organism is critical when discovering drugs to know the restrictions on small molecule dose that can be given to the flies/larvae. However, we are unaware of systematic small molecule studies in flies where the ideal average dose was identified. This is something we would like to conduct with a small library of bioactive compounds. Any reader that has a small molecule that works in Drosophila, we’d be very interested to know 1. name of the compound, 2. effective dose or IC50, 3. fly phenotype. We’re compiling a list such compounds and will share them with the community through this blog.
-Capriotti, Kara, and Joseph A. Capriotti. “Dimethyl Sulfoxide: History,Chemistry, and Clinical Utility in Dermatology.”The Journal of Clinical and Aesthetic Dermatology. Matrix Medical Communications, Sept.-Oct. 2012. Web. 16 Mar. 2016.
-Fintel, Bara, Athena T. Samaras, and Edson Carias. “Helix Magazine.” The Thalidomide Tragedy: Lessons for Drug Safety and Regulation. Helix Magazine, 28 July 2009. Web. 16 Mar. 2016.
-Hanna, Jacob, and Allison Hubel. “Preservation of Stem Cells.”Organogenesis. Landes Bioscience, 9 July 2009. Web. 28 Mar 2016.
-Muir, Maya. “DMSO: Many Uses, Much Controversy.” DMSO: Many Uses, Much Controversy. DMSO, 1996. Web. 16 Mar. 2016. OZ, Ece, Esra Aydemir, and Kayahan Fiskin. “DMSO Exhibits Similar Cytotoxicity Effects to Thalidomide in Mouse Breast Cancer Cells.” Oncology Letters. NCBI, 9 Jan. 2012. Web. 16 Mar. 2016.