Ketamine treatment protects against oxidative damage and the immunological response induced by electroconvulsive therapy

The bidirectional roles of the cGAS-STING pathway in pain processing: Cellular and molecular mechanisms

Pain is a common clinical condition. However, the mechanisms underlying pain are not yet fully understood. It is known that the neuroimmune system plays a critical role in the pathogenesis of pain. Recent studies indicated that the cyclic-GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway can activate the innate immune system by sensing both extrinsic and intrinsic double-stranded DNA in the cytoplasm, which is involved in pain processing. In this review, we summarise (1) the roles of the cGAS-STING pathway in different pain models, (2) the effect of the cGAS-STING pathway in different cells during pain regulation, and (3) the downstream molecular mechanisms of the cGAS-STING pathway in pain regulation. This review provides evidence that the cGAS-STING pathway has pro- and anti-nociceptive effects in pain models. It has different functions in neuron, microglia, macrophage, and T cells. Its downstream molecules include IFN-I, NF-κB, NLRP3, and eIF2α. The bidirectional roles of the cGAS-STING pathway in pain processing are mediated by regulating nociceptive neuronal sensitivity and neuroinflammatory responses. However, their effects in special brain regions, activation of astrocytes, and the different phases of pain require further exploration.

Dexmedetomidine and Ketamine Attenuated Neuropathic Pain Related Behaviors via STING Pathway to Induce ER-Phagy

Our previous work indicated that ER-phagy level had altered in spinal nerve ligation (SNL) rats. In this study, we investigated whether dexmedetomidine or ketamine exhibits anti-anxiety or anti-nociceptive effects via modulation of the spinal STING/TBK pathway to alter ER-phagy in SNL rats. We evaluated the analgesic and anti-anxiety effects of ketamine and dexmedetomidine in SNL rats. 2’3’-cGAMP (a STING pathway agonist) was administrated to investigate whether enhanced spinal STING pathway activation could inhibit dexmedetomidine or ketamine treatment effects in SNL rats. Analgesic effects were assessed with the mechanical withdrawal threshold (MWT) and anti-anxiety effects were measured via an open field test (OFT). Protein expression levels were evaluated by immunoblotting. Distribution and cellular localization of Grp78 (ER stress marker) were evaluated by confocal immunofluorescence. SNL induced mechanical hypersensitivity and anxiety in rats; dexmedetomidine and ketamine both provided analgesia and anti-anxiety effects in SNL rats. Furthermore, the STING pathway was involved in the modulation of ER stress and ER-phagy in SNL rats and dexmedetomidine and ketamine alleviated ER stress by inhibiting STING pathway to enhance ER-phagy. Thus, both ketamine and dexmedetomidine provided anti-anxiety and anti-nociceptive effects by alleviating ER stress through the inhibition of the STING/TBK pathway to modulate spinal ER-phagy in SNL rats.

Effects of an intravenous ketamine infusion on inflammatory cytokine levels in male and female Sprague-Dawley rats

Background

Ketamine, a multimodal dissociative anesthetic drug, is widely used as an analgesic following traumatic injury. Although ketamine may produce anti-inflammatory effects when administered after injury, the immunomodulatory properties of intravenous (IV) ketamine in a non-inflammatory condition are unclear. In addition, most preclinical studies use an intraperitoneal (IP) injection of ketamine, which limits its clinical translation as patients usually receive an IV ketamine infusion after injury.

Methods

Here, we administered sub-anesthetic doses of a single IV ketamine infusion (0, 10, or 40 mg/kg) to male and female Sprague–Dawley rats over a 2-h period. We collected blood samples at 2- and 4-h post-ketamine infusion to determine plasma inflammatory cytokine levels using multiplex immunoassays.

Results

The 10 mg/kg ketamine infusion reduced spontaneous locomotor activity in male and female rats, while the 40 mg/kg infusion stimulated activity in female, but not male, rats. The IV ketamine infusion produced dose-dependent and sex-specific effects on plasma inflammatory cytokine levels. A ketamine infusion reduced KC/GRO and tumor necrosis factor alpha (TNF-α) levels in both male and female rats, interleukin-6 (IL-6) levels in female rats, and interleukin-10 (IL-10) levels in male rats. However, most cytokine levels returned to control levels at 4-h post-infusion, except for IL-6 levels in male rats and TNF-α levels in female rats, indicating a different trajectory of certain cytokine changes over time following ketamine administration.

Conclusions

The current findings suggest that sub-anesthetic doses of an IV ketamine infusion may produce sex-related differences in the effects on peripheral inflammatory markers in rodents, and further research is warranted to determine potential therapeutic effects of an IV ketamine infusion in an inflammatory condition.

Combination of electroconvulsive stimulation with ketamine or escitalopram protects the brain against inflammation and oxidative stress induced by maternal deprivation and is critical for associated behaviors in male and female rats

This study aimed at evaluating the treatment effects with ketamine, electroconvulsive stimulation (ECS), escitalopram, alone or in combination in adult rats of both sexes, subjected to the animal model of maternal deprivation (MD). All groups were subjected to the forced swimming test (FST), splash and open field tests. The prefrontal cortex (PFC), hippocampus and serum were collected to analyze oxidative stress and inflammatory parameters. MD induced depressive-like behavior in the FST test in males and reduced grooming time in male and female rats. The treatments alone or combined reversed depressive and anhedonic behavior in females. In males, all treatments increased grooming time, except for ECS + escitalopram + ketamine. MD increased lipid peroxidation and protein carbonylation, nitrite/nitrate concentration and myeloperoxidase activity in the PFC and hippocampus of males and females. However, the treatment's response was sex dependent. Catalase activity decreased in the PFC of males and the PFC and hippocampus of females, and most treatments were not able to reverse it. MD increased the inflammation biomarkers levels in the PFC and hippocampus of males and females, and most treatments were able to reverse this increase. In all groups, a reduction in the interleukin-10 levels in the PFC and hippocampus of female and male rats was observed. Our study shows different responses between the sexes in the patterns evaluated and reinforces the use of the gender variable as a biological factor in MDD related to early stress and in the response of the therapeutic strategies used.

Effect of ketamine on the physiological responses to combined hypoglycemic and psychophysical stress

There is evidence that hypoglycemic stress can interact with other stressors, and that ketamine can mitigate the impact of these stressors on behavior and physiology. The current study in male Sprague-Dawley rats investigated whether pre-treatment with 0, 10, or 20 mg/kg ketamine could modulate the interaction between hypoglycemia induced by 0 or 300 mg/kg 2-deoxy-D-glucose (2-DG) and the psychophysical stress of forced swimming (FSS; 6 sessions, 10 min/session) on serum concentrations of corticosterone (CORT) and the pro-inflammatory cytokine, tumor necrosis factor (TNF)-α. It was found that 2-DG enhanced the CORT response to an initial session of FSS, and this effect dissipated after multiple sessions. More importantly, animals displayed significantly higher levels of CORT and lower levels of TNF-α in response to a drug-free test swim conducted 1 week after exposure to the combined stressors, and these responses were not observed in rats that were pre-treated with ketamine. Overall, these findings indicate that ketamine has the potential to reduce the negative impact of interacting stressors on the biological reactivity of the hypothalamic-pituitary-adrenal axis and the immune system.