Plasmodium berghei-infection induces volume-regulated anion channel-like activity in human hepatoma cells

Abstract

Parasite infection can lead to alterations in the permeability of host plasma membranes. Presented here is the first demonstration that this phenomenon occurs in Plasmodium-infected liver cells. Using the whole-cell patch-clamp technique, volume-regulated anion channel (VRAC) activity was characterized in Huh-7 cells (a human hepatoma cell line) before and after infection with Plasmodium berghei. Consistent with the presence of VRACs, hypotonic bath solution induced large ion currents in Huh-7 cells that rectified outwardly, reversed close to the equilibrium potential for Cl- and were inhibited by tamoxifen, clomiphene, mefloquine and 5-nitro-2, 3-(phenylpropylamino)-benzoic acid (NPPB), with IC50 values of 4 ± 1, 4 ± 2, 2 ± 1 and 52 ± 12 μM respectively. In isotonic conditions, initial current recordings measured in uninfected and immature (24 h post invasion) parasite-infected Huh-7 cells were similar (with conductances of 14 ± 3 versus 19 ± 5 pS/pF). However, in mature (48–72 h post invasion) parasite-infected Huh-7 cells there was a sevenfold increase in currents (with a conductance of 98 ± 16 pS/pF). The elevated currents observed in the latter are consistent with VRAC-like activity and the possible reasons for their activation are discussed.

Targeting Channels and Transporters in Protozoan Parasite Infections

“…There is evidence that in the liver-stage, Plasmodium berghei infection leads to a sevenfold increase in chloride conductance of the host's volume-regulated anion channel, VRAC, as found using a human hepatoma cell line (Figure 1 ; Prudêncio et al, 2009 ). Conductivity was inhibited by tamoxifen, and mefloquine at single-digit micromolar concentrations (Table 1 ).…”

Repurposing Estrogen Receptor Antagonists for the Treatment of Infectious Disease

“…The antimalaria activity of TAM, CLM, and a TAM analog has also been investigated (66 – 69). In vitro studies in Plasmodium falciparum showed CLM inhibited parasite growth by 80% at 10 µM with IC 50 values of 6 µM (69).…”

“…In an ex vivo infection model using P. berghei and Huh-7 (human hepatoma) cell lines, TAM and CLM inhibited volume-regulated anion channels (VRAC) with IC 50 values of 4 µM (67). In a red blood cell model, 10 µM TAM or 10 µM CLM inhibited parasite growth in a time-dependent manner and was more effective within the first 24 h than at 25 to 48 h. The time dependency indicates that mechanisms other than VRAC inhibition are likely to be operative (67).…”

“…TAM and CLM also inhibit intracellular development of malarial parasites in the liver during the first 48 h of infection, when drug is given prophylactically before introduction of sporozoites (67). In contrast, treatment at 24 h postinfection had less of an effect (67).…”

Transmembrane solute transport in the apicomplexan parasite Plasmodium

“…[78,79]) and liver stages of Plasmodium development (e.g. [80][81][82]) and further studies are warranted. In addition, there remains the open question of the involvement of host transporters in the altered permeability of host erythrocytes, following Plasmodium infection.…”