In vitro activity: Chloroquine is a chemotherapeutic agent for the clinical treatment of malaria. Chloroquine is able to bind to DNA, and inhibit DNA replication and RNA synthesis which in turn results in cell death. The effect of Chloroquine may also be related to the formation of a toxic heme-Chloroquine complex. Chloroquine inhibits trophozoite hemoglobin degradation through increasing vacuolar pH and inhibiting the activity of vacuolar phospholipase, vacuolar proteases, and heme polymerase. Chloroquine possesses definite antirheumatic properties. Chloroquine has immuno-modulatory effects, suppressing the production/release of tumour necrosis factor and interleukin 6. Moreover, Chloroquine exerts direct antiviral effects, inhibiting pH-dependent steps of the replication of several viruses including members of the flaviviruses, retroviruses, and coronaviruses. Its best-studied effects are those against HIV replication. Chloroquine can accumulate inside the macrophage phagolysosome by ion trapping where it exerts potent antifungal activity against Histoplasma capsulatum and Cryptococcus neoformans by distinct mechanisms. Chloroquine inhibits growth of H. capsulatum by pH-dependent iron deprivation, whereas it is directly toxic to C. neoformans.

Cell Assay: The cells are cultured in 6-well plates with normal culture medium in the presence of vehicle or 25 or 50 μM chloroquine, until near confluency, after which they are rinsed with sterile phosphate-buffered saline (PBS) and cultured further for the indicated times in serum-free culture medium. At the desired time-points, the culture medium is discarded and the cells are quickly harvested in lysis buffer and clarified by centrifugation. Subsequent to boiling the supernatants in reducing sodium dodecyl sulphate (SDS) sample buffer, equal amounts of protein (100 μg) are loaded per lane and the samples are electrophoresed into 10 or 4-20% gradient polyacrylamide SDS gels, then transferred to a nitrocellulose membrane. To detect TLR9, the blots are incubated overnight at 4°C with anti-TLR9 antibodies, diluted 1:500 in Tris-buffered saline with 0.1% (v/v) Tween-20 (TBST). Equal loading is confirmed with polyclonal rabbit anti-actin. Secondary detection is performed with horseradish peroxidase-linked secondary antibodies. The protein bands are visualized by chemiluminescence using an ECL kit.