Background: Voltage-gated sodium channels generate action potentials in excitable cells, but they have also been attributed noncanonical roles in nonexcitable cells. We hypothesize that voltage-gated sodium channels play a functional role during extravasation of neutrophils. Methods: Expression of voltage-gated sodium channels was analyzed by polymerase chain reaction. Distribution of Nav1.3 was determined by immunofluorescence and flow cytometry in mouse models of ischemic heart and kidney injury. Adhesion, transmigration, and chemotaxis of neutrophils to endothelial cells and collagen were investigated with voltage-gated sodium channel inhibitors and lidocaine in vitro. Sodium currents were examined with a whole cell patch clamp. Results: Mouse and human neutrophils express multiple voltage-gated sodium channels. Only Nav1.3 was detected in neutrophils recruited to ischemic mouse heart (25 ± 7%, n = 14) and kidney (19 ± 2%, n = 6) in vivo. Endothelial adhesion of mouse neutrophils was reduced by tetrodotoxin (56 ± 9%, unselective Nav-inhibitor), ICA121431 (53 ± 10%), and Pterinotoxin-2 (55 ± 9%; preferential inhibitors of Nav1.3, n = 10). Tetrodotoxin (56 ± 19%), ICA121431 (62 ± 22%), and Pterinotoxin-2 (59 ± 22%) reduced transmigration of human neutrophils through endothelial cells, and also prevented chemotactic migration (n = 60, 3 × 20 cells). Lidocaine reduced neutrophil adhesion to 60 ± 9% (n = 10) and transmigration to 54 ± 8% (n = 9). The effect of lidocaine was not increased by ICA121431 or Pterinotoxin-2. Conclusions: Nav1.3 is expressed in neutrophils in vivo; regulates attachment, transmigration, and chemotaxis in vitro; and may serve as a relevant target for antiinflammatory effects of lidocaine.

Background: In the present study, the influence of bacterial infection, lipopolysacharides (LPS) and hydroxyethyl starch (HES) on platelet function in a parallel plate flow chamber were measured. Experiments were performed with non-activated and protease-activating-receptor (PAR) 4 agonist activated platelets. Comparative measurements were in vivo capillary bleeding time, platelet function analyzer and impedance aggregometry. Results: PAR 4 agonist did not increase platelet adhesion of platelets from dogs with bacterial inflammation in the flow chamber in contrast to platelets of healthy dogs. Except from impedance aggregometry with lower sensitivity and specificity, PFA did not detect platelet dysfunctions in dogs with infection. In vitro addition of LPS or HES significantly reduced platelet covered area after PAR-activation. Conclusions: The flow chamber detects platelet dysfunctions in dogs with inflammatory diseases. In vitro addition of LPS highlights the inhibiting effect of bacterial wall components on platelet function. Platelet dysfunction induced by infection could possibly also be diagnosed after treatment of sepsis with colloids has commenced. The flow chamber could be a useful tool to detect sepsis associated platelet dysfunction given that larger prospective trials confirm these findings from a proof of concept study.

Transient receptor potential vanilloid 2 (TRPV2) is relevant for diseases like cancer, cardiac dysfunction, and infection, warranting drug development targeting TRPV2. However, this has been complicated by the lack of good modulators targeting TRPV2 and questions about species selectivity, so more detailed molecular insights into channel function and pharmacology are required. Two recent studies identified distinct binding sites on rat (r) and mouse (m) TRPV2 for activation by 2-aminoethoxydiphenyl borate (2-APB). Here we aimed to determine whether the mechanisms for 2-APB sensitivity of TRPV2 indeed differ among these closely related orthologs. Patch clamp electrophysiology revealed that mTRPV2 and human TRPV2 display similar sensitivities to 2-APB when compared with a considerably higher sensitivity of rTRPV2. For both mTRPV2 and rTRPV2, we observed that the exchange of putative 2-APB binding residues within the vanilloid binding pocket alters overall channel sensitivity to 3 TRPV2 pharmacological activators that bind at different sites: 2-APB, cannabidiol, and probenecid. By contrast, the exchange of putative 2-APB binding residues at the S5 binding pocket in both channels resulted in strongly reduced 2-APB sensitivies without reducing sensitivity to cannabidiol and probenecid. rTRPV2 mutants lacking key residues of both binding sites were almost completely 2-APB insensitive. These functional data suggest that the mechanisms accounting for 2-APB sensitivity are similar across mammalian TRPV2 orthologs. Except for serving as a binding site for 2-APB, the vanilloid binding pocket plays a key role in the overall function of TRPV2. These findings are relevant for the emerging framework toward an improved understanding of TRPV2. SIGNIFICANCE STATEMENT: This study resolves the conflict regarding how 2-aminoethoxydiphenyl borate binds to transient receptor potential vanilloid 2 (TRPV2), showing a shared mechanism despite sensitivity differences. These findings enhance TRPV2 modulation insights and highlight species considerations in drug design, aiding the development of selective TRPV2-targeted therapies.

TRPV1 mediates pain occurring during sickling episodes in sickle cell disease (SCD). We examined if hemin, a porphyrin released during intravascular hemolysis modulates TRPV1. Calcium imaging and patch clamp were employed to examine effects of hemin on mouse dorsal root ganglion (DRG) neurons and HEK293t cells expressing TRPV1 and TRPA1. Hemin induced a concentration-dependent calcium influx in DRG neurons which was abolished by the unspecific TRP-channel inhibitor ruthenium red. The selective TRPV1-inhibitor BCTC or genetic deletion of TRPV1 only marginally impaired hemin-induced calcium influx in DRG neurons. While hTRPV1 expressed in HEK293 cells mediated a hemin-induced calcium influx which was blocked by BCTC, patch clamp recordings only showed potentiated proton- and heat-evoked currents. This effect was abolished by the PKC-inhibitor chelerythrine chloride and in protein kinase C (PKC)-insensitive TRPV1-mutants. Hemin-induced calcium influx through TRPV1 was only partly PKC-sensitive, but it was abolished by the reducing agent dithiothreitol (DTT). In contrast, hemin-induced potentiation of inward currents was not reduced by DTT. Hemin also induced a redox-dependent calcium influx, but not inward currents on hTRPA1. Our data suggest that hemin induces a PKC-mediated sensitization of TRPV1. However, it also acts as a photosensitizer when exposed to UVA-light used for calcium imaging. The resulting activation of redox-sensitive ion channels such as TRPV1 and TRPA1 may be an in vitro artifact with limited physiological relevance.

An important part of the biosynthesis of proteoglycans is the epimerization of glycosaminoglycan chains. As a consequence of the conversion of chondroitin sulfate (CS) to dermatan sulfate (DS), the glycosaminoglycans become more flexible and enable DS to perform more sophisticated signaling functions. In a recent study, we generated a chimera (S222A) composed of a truncated form of a DS (decorin) and CS (CSF-1) containing proteoglycan and analyzed the influence of the core protein on the extent of epimerization. C-terminal truncation constructs from S222A enabled us to identify an amino acid segment that lies within the CSF-1 part which prevents DS synthesis. Co-localization experiments using S222A-HA and DCN-Flag showed different intracellular localizations for the proteoglycans during biosynthesis. A data base search revealed a sequence motif (TNWVP) within the CSF-1 moiety that is found to be important in other proteoglycans. A single substitution of tryptophan-216 to leucine (W216L) in the chimera S222A increased the amount of L-IdoA to 12–16%. Co-localization with an ER-marker demonstrated that the biosynthesis of recombinant decorin is similar to the chimera S222A and S222A^W216L in HEK293 cells. Co-staining of S222A-HA and S222A^W216L-Flag showed different intracellular localizations for the proteoglycans. A more detailed analysis of the glycosaminoglycans reflects a similar total sulfate content for S222A and S222A^W216L. The 4/6 sulfation ratio was similar for decorin and S222A, but altered for S222A^W216L. However, the binding of fibroblasts growth factor-1 to CS/DS was only partially dependent on epimerization. These results are consistent with the model in which the core protein, via the amino acid tryptophan, is responsible for routing to subcellular compartments with or without sufficient access to chondroitin-glucuronate 5-epimerase.