Dantrolene Prevents the Lymphostasis Caused by Doxorubicin in the Rat Mesenteric Circulation

Background and Purpose: Doxorubicin (DOX) is a risk factor for arm lymphedema in breast cancer patients. We reported that DOX opens ryanodine receptors (RYRs) to enact “calcium leak,” which disrupts the rhythmic contractions of lymph vessels (LVs) to attenuate lymph flow. Here, we evaluated whether dantrolene, a clinically available RYR1 subtype antagonist, prevents the detrimental effects of DOX on lymphatic function.Experimental Approach: Isolated rat mesenteric LVs were cannulated, pressurized (4–5 mm Hg) and equilibrated in physiological salt solution and Fura-2AM. Video microscopy recorded changes in diameter and Fura-2AM fluorescence tracked cytosolic free calcium ([Ca2+i]). High-speed in vivo microscopy assessed mesenteric lymph flow in anesthetized rats. Flow cytometry evaluated RYR1 expression in freshly isolated mesenteric lymphatic muscle cells (LMCs).Key Results: DOX (10 μmol/L) increased resting [Ca2+i] by 17.5 ± 3.7% in isolated LVs (n = 11). The rise in [Ca2+i] was prevented by dantrolene (3 μmol/L; n = 10). A single rapid infusion of DOX (10 mg/kg i.v.) reduced positive volumetric lymph flow to 29.7 ± 10.8% (n = 7) of baseline in mesenteric LVs in vivo. In contrast, flow in LVs superfused with dantrolene (10 μmol/L) only decreased to 76.3 ± 14.0% (n = 7) of baseline in response to DOX infusion. Subsequently, expression of the RYR1 subtype protein as the presumed dantrolene binding site was confirm in isolated mesenteric LMCs by flow cytometry.Conclusion and Implications: We conclude that dantrolene attenuates the acute impairment of lymph flow by DOX and suggest that its prophylactic use in patients subjected to DOX chemotherapy may lower lymphedema risk.

Prostanoid receptors in GtoPdb v.2021.2

Prostanoid receptors (nomenclature as agreed by the NC-IUPHAR Subcommittee on Prostanoid Receptors [694]) are activated by the endogenous ligands prostaglandins PGD2, PGE1, PGE2 , PGF2α, PGH2, prostacyclin [PGI2] and thromboxane A2. Differences and similarities between human and rodent prostanoid receptor orthologues, and their specific roles in pathophysiologic conditions are reviewed in [448]. Measurement of the potency of PGI2 and thromboxane A2 is hampered by their instability in physiological salt solution; they are often replaced by cicaprost and U46619, respectively, in receptor characterization studies.

Effects of Green Alga, Chaetomorpha aerea Extract on Non-Specific Immune Responses and Disease Resistance against Edwardsiella tarda Infection in Labeo rohita

The current study evaluated the effects of a methanol extract from Chaetomorpha aerea (a green alga) on non-specific immune responses and resistance against Edwardsiella tarda infection in Labeo rohita. Different doses of the extract (5, 50 and 500 mg/kg of body weight) were injected into the fish intraperitoneally while a control group was injected with 0.2 mL of sterile physiological salt solution. Variations in several immunostimulatory parameters (i.e., neutrophil, serum lysozyme, myeloperoxidase, serum antiprotease, and ceruloplasmin activity), reactive oxygen species (ROS) and reactive nitrogen species (RNS) were assessed after 7, 14, 21, and 28 days of post stimulation. E. tarda culture was injected into the fish after 28 days of post stimulation to induce infection to monitor fish mortality within 14 days. Interestingly, all doses of methanolic extract enhanced neutrophil, lysozyme, and myeloperoxidase activity, ROS and RNS, while a dose of 50 mg/kg was the most effective. Fish injected with this optimal dose were also protected against infection with virulent strain of E. tarda. The results of the study suggest that C. aerea extract is a potential prophylactic agent against bacterial infections in finfish.

Low-voltage activated (LVA) inward current in murine antral smooth muscle cells is an artifact

We characterized the two types of voltage-dependent inward currents in murine antral SMC. The HVA and LVA inward currents were identified when cells were bathed in Ca2+-containing physiological salt solution. We examined whether the LVA inward current was due to: 1) T-type Ca2+ channels, 2) Ca2+-activated Cl- channels, 3) non-selective cation channels (NSCC) or 4) voltage-dependent K+ channels with internal Cs+-rich solution. Replacement of external Ca2+ (2 mM) with equimolar Ba2+ increased the amplitude of the HVA current but blocked the LVA current. Nicardipine blocked the HVA current, and in the presence of nicardipine, T-type Ca2+ blockers failed to block LVA. The Cl- channel antagonist had little effect on LVA. Cation-free external solution completely abolished both HVA and LVA. Addition of Ca2+ in cation-free solution restored only HVA currents. Addition of K+ (5 mM) to cation-free solution induced LVA current that reversed at -20 mV. These data suggest that LVA is not due to T-type Ca2+ channels, Ca2+-activated Cl- channels or NSCC. Antral SMC express A-type K+ currents (KA) and delayed rectifying K+ currents (KV) with dialysis of high K+ (140 mM) solution. When cells were exposed to high K+ external solution with dialysis of Cs+-rich solution in the presence of nicardipine, LVA was evoked and reversed at positive potentials. These HK-induced inward currents were blocked by K+ channel blockers, 4-aminopyridine and TEA. In conclusion, LVA inward currents can be generated by K+ influx via KA and KV channels in murine antral SMC when cells were dialyzed with Cs+-rich solution.

In Vitro Neurotoxicity of Chinese Krait (Bungarus multicinctus) Venom and Neutralization by Antivenoms

Bungarus multicinctus, the Chinese krait, is a highly venomous elapid snake which causes considerable morbidity and mortality in southern China. B. multicinctus venom contains pre-synaptic PLA2 neurotoxins (i.e., β-bungarotoxins) and post-synaptic neurotoxins (i.e., α-bungarotoxins). We examined the in vitro neurotoxicity of B. multicinctus venom, and the efficacy of specific monovalent Chinese B. multicinctus antivenom, and Australian polyvalent elapid snake antivenom, against venom-induced neurotoxicity. B. multicinctus venom (1–10 μg/mL) abolished indirect twitches in the chick biventer cervicis nerve-muscle preparation as well as attenuating contractile responses to exogenous ACh and CCh, but not KCl. This indicates a post-synaptic neurotoxic action but myotoxicity was not evident. Given that post-synaptic α-neurotoxins have a more rapid onset than pre-synaptic neurotoxins, the activity of the latter in the whole venom will be masked. The prior addition of Chinese B. multicinctus antivenom (12 U/mL) or Australian polyvalent snake antivenom (15 U/mL), markedly attenuated the neurotoxic actions of B. multicinctus venom (3 μg/mL) and prevented the inhibition of contractile responses to ACh and CCh. The addition of B. multicinctus antivenom (60 U/mL), or Australian polyvalent snake antivenom (50 U/mL), at the t90 time point after the addition of B. multicinctus venom (3 μg/mL), did not restore the twitch height over 180 min. The earlier addition of B. multicinctus antivenom (60 U/mL), at the t20 or t50 time points, also failed to prevent the neurotoxic effects of the venom but did delay the time to abolish twitches based on a comparison of t90 values. Repeated washing of the preparation with physiological salt solution, commencing at the t20 time point, failed to reverse the neurotoxic effects of venom or delay the time to abolish twitches. This study showed that B. multicinctus venom displays marked in vitro neurotoxicity in a skeletal muscle preparation which is not reversed by antivenom. This does not appear to be related to antivenom efficacy, but due to the irreversible/pseudo-irreversible nature of the neurotoxins.

Prostanoid receptors (version 2020.4) in the IUPHAR/BPS Guide to Pharmacology Database

Prostanoid receptors (nomenclature as agreed by the NC-IUPHAR Subcommittee on Prostanoid Receptors [661]) are activated by the endogenous ligands prostaglandins PGD2, PGE1, PGE2 , PGF2α, PGH2, prostacyclin [PGI2] and thromboxane A2. Differences and similarities between human and rodent prostanoid receptor orthologues, and their specific roles in pathophysiologic conditions are reviewed in [423]. Measurement of the potency of PGI2 and thromboxane A2 is hampered by their instability in physiological salt solution; they are often replaced by cicaprost and U46619, respectively, in receptor characterization studies.

Abstract P224: Cyclooxygenase-dependent Mechanisms Mediate In Part The Anti-dilatory Effects Of Uterine Perivascular Adipose Tissue In Rat Pregnancy

Introduction: Uterine perivascular adipose tissue (PVAT) contributes to uterine blood flow regulation in pregnancy, at least in part, due to its effects on uterine artery tone. We hypothesized that the anti-dilatory effects of uterine PVAT are mediated by vascular nitric oxide synthase (NOS)- and cyclooxygenase (COX)-dependent mechanisms. Methods: Main uterine arteries from pregnant and non-pregnant rats were mounted onto a wire myograph. Concentration-response curves to acetylcholine (ACh, 10 -9 - 3x10 -5 M) were performed on arteries exposed to physiological salt solution or PVAT-conditioned media (PVAT media ) in the presence of the following inhibitors: a) L-NAME (NOS inhibitor, 100 μM), b) indomethacin (COX inhibitor, 10 μM), c) SC560 (COX-1 inhibitor, 1 μM), d) NS398 (COX-2 inhibitor, 1 μM)]. Results: NOS inhibition abolished ACh-induced relaxation in uterine arteries from pregnant rats and exposure to PVAT media did not change this effect [AUC, (-)PVAT media : 244.6 ± 18.1 vs. (-)PVAT media /(+)L-NAME: 52.64 ± 7.4, p < 0.0001; (+)PVAT media : 202.4 ± 15.5 vs. (+)PVAT media /(+)L-NAME: 56.17 ± 11.3, p < 0.0001]. Indomethacin suppressed ACh-induced relaxation in uterine arteries from pregnant rats [AUC, (-)PVAT media : 243.6 ± 6.6 vs. (-)PVAT media /(+)Indomethacin: 123.6 ± 12.3, p < 0.0001] but not in non-pregnant rats (p>1.0). In arteries incubated with PVAT media , the presence of indomethacin increased ACh-induced relaxation [AUC, (+)PVAT media : 125.2 ± 11.4 vs. (+)PVAT media /(+)Indomethacin: 179.1 ± 14.7, p = 0.01]. COX-1 but not COX-2 inhibition suppressed relaxation responses to ACh [AUC, COX-1 inhibition, (-)PVAT media : 244.6 ± 12.0 vs. (-)PVAT media /(+)SC560: 142.4 ± 15.4, p = 0.02; COX-2 inhibition, (-)PVAT media vs. (-)PVAT media /(+)NS398, p=0.1). The anti-dilatory effects of PVAT were not observed in the presence of SC560 or NS398 (p>0.05). Exposure to PVAT media increased the protein content of COX-1 (p=0.05) and COX-2 (p=0.03) and the production of thromboxane B 2 (p=0.01) in uterine arteries from pregnant rats. Conclusion: The anti-dilatory effects of PVAT-derived factors on uterine arteries are mediated in part by COX-derived products and this mechanism is specific to pregnancy.

Extracellular Calcium and Induction of Uterine Muscle Contraction by Aqueous Ethanolic Leaf Extract of Mucuna pruriens

Calcium (Ca2+) serves as an essential signaling molecule in biological systems, regulating a wide range of cellular processes of which uterine smooth muscle contraction is among. The present study was designed to evaluate the involvement of Ca2+ on isolated uterine muscle contraction induced by aqueous ethanolic leaf extract of Mucuna pruriens (M. pruriens). Uterine muscle contraction induced by the extract was concentration-dependent and was completely abolished (100%; P<0.05) in nominally Ca2+ -free physiological salt solution and in solutions containing (EGTA 1.5 mmol), lanthanium chloride (1.5 and 3 mmol), caffeine (3and 4.4 mmol) and verapamil (0.007-0.14 μmol). It is concluded that the inability of the extract to produce contractions in Ca2+ -free media, indicates that it lacks the ability to mobilize calcium from intracellular storage sites. Hence, its uterine stimulatory property is therefore solely dependent on extracellular Ca2+. Keywords: Calcium, Mucuna pruriens, Uterus, Contraction.

Prostanoid receptors (version 2019.5) in the IUPHAR/BPS Guide to Pharmacology Database

Prostanoid receptors (nomenclature as agreed by the NC-IUPHAR Subcommittee on Prostanoid Receptors [659]) are activated by the endogenous ligands prostaglandins PGD2, PGE1, PGE2 , PGF2α, PGH2, prostacyclin [PGI2] and thromboxane A2. Measurement of the potency of PGI2 and thromboxane A2 is hampered by their instability in physiological salt solution; they are often replaced by cicaprost and U46619, respectively, in receptor characterization studies.