Anti-inflammatory effects of FS48, the first potassium channel inhibitor from the salivary glands of the flea Xenopsylla cheopis

Abstract

Edited by Mike ShipstonThe voltage-gated potassium (Kv) 1.3 channel plays a crucial role in the immune responsiveness of T-lymphocytes and macrophages, presenting a potential target for treatment of immune-and inflammation related-diseases. FS48, a protein from the rodent flea Xenopsylla cheopis, shares the three disulfide bond feature of scorpion toxins. However, its threedimensional structure and biological function are still unclear. In the present study, the structure of FS48 was evaluated by circular dichroism and homology modeling. We also described its in vitro ion channel activity using patch clamp recording and investigated its anti-inflammatory activity in LPS-induced Raw 264.7 macrophage cells and carrageenaninduced paw edema in mice. FS48 was found to adopt a common αββ structure and contain an atypical dyad motif. It dose-dependently exhibited the Kv1.3 channel in Raw 264.7 and HEK 293T cells, and its ability to block the channel pore was demonstrated by the kinetics of activation and competition binding with tetraethylammonium. FS48 also downregulated the secretion of proinflammatory molecules NO, IL-1β, TNF-α, and IL-6 by Raw 264.7 cells in a manner dependent on Kv1.3 channel blockage and the subsequent inactivation of the MAPK/NF-κB pathways. Finally, we observed that FS48 inhibited the paw edema formation, tissue myeloperoxidase activity, and inflammatory cell infiltrations in carrageenantreated mice. We therefore conclude that FS48 identified from the flea saliva is a novel potassium channel inhibitor displaying anti-inflammatory activity. This discovery will promote understanding of the bloodsucking mechanism of the flea and provide a new template molecule for the design of Kv1.3 channel blockers.Voltage-gated potassium (Kv) channels play an important role in Ca 2+ signaling, action potential repolarization, cellular proliferation, migration and secretion, and cell volume

Antimicrobial and Anti-inflammatory Effects of a Novel Peptide From the Skin of Frog Microhyla pulchra

“…The anti-inflammatory function of brevinin-2MP in vivo was measured with the carrageenan-induced mouse paws as reported previously by us ( Deng et al, 2021 ). Briefly, male and female Kunming mice (20–22 g) were randomly divided into four groups, with six mice in each group.…”

The toxin mimic FS48 from the salivary gland of Xenopsylla cheopis functions as a Kv1.3 channel-blocking immunomodulator of T cell activation

“…These results further demonstrate that the immunoregulatory properties of FS48 on MAPK signal cascades. Furtherly, considering that FS48 displays anti-inflammatory effect in vivo via Kv1.3 channel blockage and expression suppression as well as MAPK/NF-κB pathway inactivation of macrophage, which is one important cellular component of DTH ( 16 , 44 , 45 ), we can speculate that the effects of FS48 on DTH should be due to its combined effects on two or more kinds of cells expressing Kv1.3 channels on their membranes. Notably, despite the fact that FS48 is a weak blocker of Kv1.3 channel when compared with the above toxin peptides which are known of displaying DTH suppression effects in vitro , it shows anti-inflammatory and immunomodulatory effects in vivo , which are relatively stronger in comparison with MgTx, KTX, ShK-186, and BmKTX-D33H ( 8 , 9 , 13 , 22 , 41 , 42 , 43 ).…”

“…Real-time PCR was carried out with Hieff qPCR SYBR Green Master Mix (Yeasen) in Light Cycler 480 system. In all experiments, a total of 40 amplification cycles was performed as previously reported ( 16 ). The primers sequences were listed in Table 1 .…”

“…Jurkat T cells were transfected with siRNA to knockdown the expression of Kv1.3 channel as described in our previous study ( 16 ). Western blot analysis was carried out to determine the efficiency of siRNA knockdown rate.…”

“…Natural peptide toxins are gradually acknowledged as potential therapeutic option for many diseases, which is attributed to their antitumor, immunomodulation, analgesic, and antimicrobial properties ( 8 , 15 ). We previously identified and characterized FS48, a novel potassium channel inhibitor from the salivary gland of Xenopsylla cheopis ( 16 ). FS48 downregulates the secretion of proinflammatory NO, IL-1β, IL-6, and TNF-α by Raw 264.7 cells via Kv1.3 channel blockage and expression suppression as well as MAPK/NF-κB pathway inactivation.…”