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We investigated the effects of the calmodulin inhibitor CGS 9343B on voltage-dependent K + (Kv) channels using whole-cell patch clamp technique in freshly isolated rabbit coronary arterial smooth muscle cells. CGS 9343B inhibited Kv currents in a concentration-dependent manner, with a half-maximal inhibitory concentration (IC 50 ) value of 0.81 μM. The decay rate of Kv channel inactivation was accelerated by CGS 9343B. The rate constants of association and dissociation for CGS 9343B were 2.77 ± 0.04 μM − 1 s − 1 and 2.55 ± 1.50 s − 1 , respectively. CGS 9343B did not affect the steady-state activation curve, but shifted the inactivation curve toward to a more negative potential. Train pulses (1 or 2 Hz) application progressively increased the CGS 9343B-induced Kv channel inhibition. In addition, the inactivation recovery time constant was increased in the presence of CGS 9343B, suggesting that CGS 9343B-induced inhibition of Kv channel was use-dependent. Another calmodulin inhibitor, W-13, did not affect Kv currents, and did not change the inhibitory effect of CGS 9343B on Kv current. Our results demonstrated that CGS 9343B inhibited Kv currents in a state-, time-, and use-dependent manner, independent of calmodulin inhibition. [ABSTRACT FROM AUTHOR]

The present study investigated the vasorelaxant effects of sitagliptin, which is a dipeptidyl peptidase-4 (DPP-4) inhibitor in aortic rings pre-contracted with phenylephrine (Phe). Sitagliptin induced vasorelaxation in a concentration-dependent manner but the inhibition of voltage-dependent K+ (Kv) channels by pretreatment with 4-aminopyridine (4-AP) effectively reduced this effect. By contrast, the inhibition of inward rectifier K+ (Kir) channels by pretreatment with barium (Ba2+), large-conductance calcium (Ca2+)-activated K+ (BK Ca) channels with paxilline, and adenosine triphosphate (ATP)-sensitive K+ (K ATP) channels with glibenclamide did not change this effect. Although the application of SQ 22536, which is an adenylyl cyclase inhibitor, also did not change this effect, treatment with KT 5720, a protein kinase A (PKA) inhibitor, effectively reduced the vasorelaxant effects of sitagliptin. ODQ, which is a guanylyl cyclase inhibitor, and KT 5823, a protein kinase G (PKG) inhibitor, did not impact the effect. Furthermore, neither the inhibition of Ca2+ channels by pretreatment with nifedipine nor the inhibition of sarcoplasmic/endoplasmic reticulum Ca2+-ATPase (SERCA) pumps by pretreatment with thapsigargin changed the effect. Similarly, the effects of sitagliptin were not altered by eliminating the endothelium, by pretreatment with a nitric oxide (NO) synthase inhibitor (L-NAME), or by inhibition of small- and intermediate-conductance Ca2+-activated K+ channels (SK Ca and IK Ca) using apamin and TRAM-34. Taken together, these results suggest that sitagliptin induces vasorelaxation by inhibiting both membrane potential (Em)-dependent and -independent vasoconstriction and activating PKA and Kv channels independently of PKG signaling pathways, other K+ channels, SERCA pumps, and the endothelium. Unlabelled Image • We investigated the vasorelaxant effects of sitagliptin and its related mechanisms. • Sitagliptin induced vasorelaxation via the activation of the Kv channel and PKA. • Tight control of sitagliptin dosing is needed, especially in hypotensive patients. [ABSTRACT FROM AUTHOR]

Humans are exposed to disinfection by-products through oral, inhalation, and dermal routes, during bathing and swimming, potentially causing skin lesions, asthma, and bladder cancer. Nuclear factor E2-related factor 2 (NRF2) is a master regulator of the adaptive antioxidant response via the antioxidant reaction elements (ARE) orchestrating the transcription of a large group of antioxidant and detoxification genes. Here we used an immortalized human keratinocyte model HaCaT cells to investigate NRF2-ARE as a responder and protector in the acute cytotoxicity of seven haloacetonitriles (HANs), including chloroacetonitrile (CAN), bromoacetonitrile (BAN), iodoacetonitrile (IAN), bromochloroacetonitrile (BCAN), dichloroacetonitrile (DCAN), dibromoacetonitrile (DBAN), and trichloroacetonitrile (TCAN) found in drinking water and swimming pools. The rank order of cytotoxicity among the HANs tested was IAN ≈ BAN ˃ DBAN ˃ BCAN ˃ CAN ˃ TCAN ˃ DCAN based on their LC 50. The HANs induced intracellular reactive oxygen species accumulation and activated cellular antioxidant responses in concentration- and time-dependent fashions, showing elevated NRF2 protein levels and ARE activity, induction of antioxidant genes, and increased glutathione levels. Additionally, knockdown of NRF2 by lentiviral shRNAs sensitized the HaCaT cells to HANs-induced cytotoxicity, emphasizing a protective role of NRF2 against the cytotoxicity of HANs. These results indicate that HANs cause oxidative stress and activate NRF2-ARE-mediated antioxidant response, which in turn protects the cells from HANs-induced cytotoxicity, highlighting that NRF2-ARE activity could be a sensitive indicator to identify and characterize the oxidative stress induced by HANs and other environmental pollutants. [Display omitted] • Haloacetonitriles cause acute cytotoxicity and oxidative stress in HaCaT cells. • Haloacetonitriles induce NRF2-ARE-mediated antioxidant response in HaCaT cells. • NRF2 protects human keratinocytes from HANs-induced acute cell damage. • NRF2-ARE activity is an indicator for the oxidative stress caused by haloacetonitriles. [ABSTRACT FROM AUTHOR]

We investigated the vasodilatory effects of empagliflozin (a sodium-glucose co-transporter 2 inhibitor) and the underlying mechanisms using rabbit aorta. Empagliflozin induced vasodilation in a concentration-dependent manner independently of the endothelium. Likewise, pretreatment with the nitric oxide synthase inhibitor L-NAME or the SKca inhibitor apamin together with the IKca inhibitor TRAM-34 did not impact the vasodilatory effects of empagliflozin. Pretreatment with the adenylyl cyclase inhibitor SQ22536 or a guanylyl cyclase inhibitor ODQ or a protein kinase A (PKA) inhibitor KT5720 also did not alter the vasodilatory response of empagliflozin. However, the vasodilatory effects of empagliflozin were significantly reduced by pretreatment with the protein kinase G (PKG) inhibitor KT5823. Although application of the ATP-sensitive K+ (K ATP) channel inhibitor glibenclamide, large-conductance Ca2+-activated K+ (BK Ca) channel inhibitor paxilline, or inwardly rectifying K+ (Kir) channel inhibitor Ba2+ did not impact the vasodilatory effects of empagliflozin, pretreatment with the voltage-dependent K+ (Kv) channel inhibitor 4-AP reduced the vasodilatory effects of empagliflozin. Pretreatment with DPO-1 (Kv1.5 channel inhibitor), guangxitoxin (Kv2.1 channel inhibitor), or linopirdine (Kv7 channel inhibitor) had little effect on empagliflozin-induced vasodilation. Application of nifedipine (L -type Ca2+ channel inhibitor) or thapsigargin (sarco-endoplasmic reticulum Ca2+-ATPase pump inhibitor) did not impact empagliflozin-induced vasodilation. Therefore, empagliflozin induces vasodilation by activating PKG and Kv channels. Unlabelled Image • We investigated the vasodilatory effects of empagliflozin and its related mechanisms. • Empagliflozin induced vasorelaxation via the activation of the Kv channel and PKG. • Tight control of empaliflozin dosing is needed, especially in hypotensive patients. [ABSTRACT FROM AUTHOR]