Bacterial endotoxin lipopolysaccharide enhances synaptic transmission at low-output glutamatergic synapses

Acute lipopolysaccharide (LPS)-induced cell membrane hyperpolarization is independent of voltage gated and calcium activated potassium channels

The gram-negative toxin lipopolysaccharides (LPS) are known to trigger inflammatory cytokines in mammals, which can result in pathological responses. Upon treatment of bacterial sepsis with antibiotics, the lysing bacteria can present a surge in LPS, inducing a cytokine storm. However, LPS can also have direct cellular effects, including transient rapid hyperpolarizing of the membrane potential, blocking glutamate receptors and even promoting release of glutamate. The detailed mechanism of action for these immediate responses is still unresolved. In addressing the membrane hyperpolarization, voltage gated K+ channel blockers 4-aminopyridine (4-AP, 3 mM), quinidine hydrochloride monohydrate (0.1 mM) and tetraethylammonium (TEA, 20 mM) were examined along with RNAi knockdowns of potential calcium activated K+ channels. The immediate responses of LPS were not blocked. Even in the presence of glutamate, the membrane still hyperpolarizes with LPS. When the driving gradient for the ionotropic glutamate receptors is enhanced during hyperpolarization, spontaneous quantal responses are dampened in amplitude. Thus, glutamate receptors are blocked, and the mechanism of hyperpolarization remains unresolved. The larval Drosophila glutamatergic neuromuscular junction is used as a model synaptic preparation to address the direct rapid actions by LPS.

Ultrasonic-assisted activated carbon separation removing bacterial endotoxin from salvia miltiorrhizae injection

Ultrasonic-assisted activated carbon separation (UACS) was first employed to improve product quality by regulating adsorption rate and removing bacterial endotoxin from salvia miltiorrhizae injection. The adsorption rate was related to three variables: activated carbon dosage, ultrasonic power, and pH. With the increase of activated carbon dosage from 0.05 % to 1.0 %, the adsorption rates of salvianolic acids and bacterial endotoxin increased simultaneously. The adsorption rates at which bacteria endotoxins increased from 52.52 % to 97.16 % were much higher than salvianolic acids. As the ultrasonic power increased from 0 to 700 W, the adsorption rates of salvianolic acids on activated carbon declined to less than 10 %, but bacterial endotoxin increased to more than 87 %. As the pH increased from 2.00 to 8.00, the adsorption rate of salvianolic acid dropped whereas bacterial endotoxin remained relatively stable. On the basis of response surface methodology (RSM), the optimal separation conditions were established to be activated carbon dose of 0.70 %, ultrasonic power of 600 W, and pH of 7.90. The experimental adsorption rates of bacterial endotoxin were 94.15 %, which satisfied the salvia miltiorrhizae injection quality criterion. Meanwhile, salvianolic acids' adsorption rates were 1.92 % for tanshinol, 4.05 % for protocatechualdehyde, 2.21 % for rosmarinic acid, and 3.77 % for salvianolic acid B, all of which were much lower than conventional activated carbon adsorption (CACA). Salvianolic acids' adsorption mechanism on activated carbon is dependent on the component's molecular state. Under ideal separation conditions, the molecular states of the four salvianolic acids fall between 1.13 % and 6.60 %. The quality of salvia miltiorrhizae injection can be improved while maintaining injection safety by reducing the adsorption rates of salvianolic acids to less than 5 % by the use of ultrasound to accelerate the desorption mass transfer rate on the activated carbon surface. When activated carbon adsorption was used in the process of producing salvia miltiorrhizae injection, the pH of the solution was around 5.00, and the proportion of each component's molecular state was tanshinol 7.05 %, protocatechualdehyde 48.93 %, rosmarinic acid 13.79 %, and salvianolic acid B 10.28 %, respectively. The loss of useful components was evident, and the corresponding activated carbon adsorption rate ranged from 20.74 % to 41.05 %. The average variation rate in plasma His and IgE was significant (P < 0.05) following injection of 0.01 % activated carbon, however the average variation rate of salvia miltiorrhizae injection was dramatically decreased with the use of UACS and CACA (P > 0.05). The ultrasonic at a power intensity of 60 W/L and the power density of 1.20 W/cm2 may resolve the separation contradiction between salvianolic acids and bacterial endotoxin, according to experiments conducted with UACS at different power intensities. According to this study, UACS has a lot of potential applications in the pharmaceutical manufacturing industry and may represent a breakthrough in the field of ultrasonic separation.

The Effects of Doxapram Blocking the Response of Gram-Negative Bacterial Toxin (LPS) at Glutamatergic Synapses

Lipopolysaccharides (LPS) associated with Gram-negative bacteria are one factor responsible for triggering the mammalian immune response. Blocking the action of LPS is key to reducing its downstream effects. However, the direct action of LPS on cells is not yet fully addressed. LPS can have rapid, direct effects on cells in the absence of a systemic immune response. Recent studies have shown that doxapram, a blocker of a subset of K2P channels, also blocks the acute actions of LPS. Doxapram was evaluated to determine if such action also occurs at glutamatergic synapses in which it is known that LPS can increase synaptic transmission. Doxapram at 5 mM first enhanced synaptic transmission, then reduced synaptic response, while 10 mM rapidly blocked transmission. Doxapram at 5 mM blocked the excitatory response induced by LPS. Enhancing synaptic transmission with LPS and then applying LPS combined with doxapram also resulted in retarding the response of LPS. It is possible doxapram and LPS are mediated via a similar receptor or cellular responses. The potential of designing pharmacological compounds with a similar structure to doxapram and determining the binding of such compounds can aid in addressing the acute, direct actions by LPS on cells.

The effects of Gram-positive and Gram-negative bacterial toxins (LTA & LPS) on cardiac function in Drosophila melanogaster larvae

The effects of Gram negative and positive bacterial sepsis depend on the type of toxins released, such as lipopolysaccharides (LPS) or lipoteichoic acid (LTA). Previous studies show LPS to rapidly hyperpolarize larval Drosophila skeletal muscle, followed by desensitization and return to baseline. In larvae, heart rate increased then decreased with exposure to LPS. However, responses to LTA, as well as the combination of LTA and LPS, on the larval Drosophila heart have not been previously examined. This study examined the effects of LTA and a cocktail of LTA and LPS on heart rate. The combined effects were examined by first treating with either LTA or LPS only, and then with the cocktail. The results showed a rapid increase in heart rate upon LTA application, followed by a gradual decline over time. When applying LTA followed by the cocktail, an increase in the rate occurred. However, if LPS was applied before the cocktail, the rate continued declining. These responses indicate the receptors or cellular cascades responsible for controlling heart rate within seconds and the rapid desensitization are affected by LTA or LPS and a combination of the two. The mechanisms for rapid changes which are not regulated by gene expression by exposure to LTA or LPS or associated bacterial peptidoglycans have yet to be identified in cardiac tissues of any organism.

Rapid and Direct Action of Lipopolysaccharide (LPS) on Skeletal Muscle of Larval Drosophila

The endotoxin lipopolysaccharide (LPS) from Gram-negative bacteria exerts a direct and rapid effect on tissues. While most attention is given to the downstream actions of the immune system in response to LPS, this study focuses on the direct actions of LPS on skeletal muscle in Drosophila melanogaster. It was noted in earlier studies that the membrane potential rapidly hyperpolarizes in a dose-dependent manner with exposure to LPS from Pseudomonas aeruginosa and Serratia marcescens. The response is transitory while exposed to LPS, and the effect does not appear to be due to calcium-activated potassium channels, activated nitric oxide synthase (NOS), or the opening of Cl- channels. The purpose of this study was to further investigate the mechanism of the hyperpolarization of the larval Drosophila muscle due to exposure of LPS using several different experimental paradigms. It appears this response is unlikely related to activation of the Na-K pump or Ca2+ influx. The unknown activation of a K+ efflux could be responsible. This will be an important factor to consider in treatments of bacterial septicemia and cellular energy demands.

The Effect of Bacterial Endotoxin LPS on Serotonergic Modulation of Glutamatergic Synaptic Transmission

The release of the endotoxin lipopolysaccharides (LPS) from gram-negative bacteria is key in the induction of the downstream cytokine release from cells targeting cells throughout the body. However, LPS itself has direct effects on cellular activity and can alter synaptic transmission. Animals experiencing septicemia are generally in a critical state and are often treated with various pharmacological agents. Since antidepressants related to the serotonergic system have been shown to have a positive outcome for septicemic conditions impacting the central nervous system, the actions of serotonin (5-HT) on neurons also exposed to LPS were investigated. At the model glutamatergic synapse of the crayfish neuromuscular junction (NMJ), 5-HT primarily acts through a 5-HT2A receptor subtype to enhance transmission to the motor neurons. LPS from Serratia marcescens also enhances transmission at the crayfish NMJ but by a currently unknown mechanism. LPS at 100 µg/mL had no significant effect on transmission or on altering the response to 5-HT. LPS at 500 µg/mL increased the amplitude of the evoked synaptic excitatory junction potential, and 5-HT in combination with 500 µg/mL LPS continued to promote enhanced transmission. The preparations maintained responsiveness to serotonin in the presence of low or high concentrations of LPS.