NMDAR-independent, cAMP-dependent antidepressant actions of ketamine

Abstract

Ketamine produces rapid and robust antidepressant effects in depressed patients within hours of administration, often when traditional antidepressant compounds have failed to alleviate symptoms. We hypothesized that ketamine would translocate Gα from lipid rafts to non-raft microdomains, similarly to other antidepressants but with a distinct, abbreviated treatment duration. C6 glioma cells were treated with 10 µM ketamine for 15 min, which translocated Gα from lipid raft domains to non-raft domains. Other NMDA antagonist did not translocate Gα from lipid raft to non-raft domains. The ketamine-induced Gα plasma membrane redistribution allows increased functional coupling of Gα and adenylyl cyclase to increase intracellular cyclic adenosine monophosphate (cAMP). Moreover, increased intracellular cAMP increased phosphorylation of cAMP response element-binding protein (CREB), which, in turn, increased BDNF expression. The ketamine-induced increase in intracellular cAMP persisted after knocking out the NMDA receptor indicating an NMDA receptor-independent effect. Furthermore, 10 µM of the ketamine metabolite (2R,6R)-hydroxynorketamine (HNK) also induced Gα redistribution and increased cAMP. These results reveal a novel antidepressant mechanism mediated by acute ketamine treatment that may contribute to ketamine's powerful antidepressant effect. They also suggest that the translocation of Gα from lipid rafts is a reliable hallmark of antidepressant action that might be exploited for diagnosis or drug development.

Potential depression and antidepressant-response biomarkers in human lymphoblast cell lines from treatment-responsive and treatment-resistant subjects: roles of SSRIs and omega-3 polyunsaturated fatty acids

“…However, the redistribution of membrane proteins is different in LCLs relative to neuronal or glial cell populations. This is not observed after treatment with other antidepressants, including ketamine (Supplementary figure 3e-3h), in contrast with studies on C6 cells and primary astrocytes [34,47], suggesting the cell type-specific effects of antidepressant treatment.…”

“…effects of these compounds showed on cAMP accumulation in LCLs relative to neurons and glia [50,51], we further tested effects of MBCD and ketamine on cAMP accumulation [15,47]. We found that the MBCD-induced translocation of G s α from membrane domians reduced cAMP accumulation in LCLs while ketamine treatment had no effect on G s α translocation of cAMP accumulation (Supplementary figure 4a and 4b).…”

N-3 polyunsaturated fatty acids promote astrocyte differentiation and neurotrophin production independent of cAMP in patient-derived neural stem cells

“…With RP-cAMP treatment, DHA and EPA still elevated the BDNF and GDNF production (Supplemental figure 3). Antidepressants including ketamine, translocate Gα s from lipid rafts, which increases association of Gα s with adenylyl cyclase, increasing cellular cAMP production [31, 47]. To test if n-3 PUFAs have similar effect, we measured the cAMP with a fluorescent sensor in astrocytes from SSRI-sensitive and -resistant subjects.…”

“…Every 5 min, the average fluorescent density from each cell selected from the visual field was collected. The effect of n-3 PUFAs treatment on the potential of Gαs-stimulated cAMP production was determined as previous reported [31]. Astrocytes derived from the SSRI-sensitive patient were treated for 3 days, The average fluorescent density of selected cells (5-12 cell in each dish) were first recorded, then cells were challenged with forskolin (2μM), and recording was continued.…”

Altered GABAergic inhibition in CA1 pyramidal neurons modifies despair-like behavior in mice

“…However, the ketamine metabolite (2R,6R)-hydroxynorketamine (HNK), which exhibits acute and long-lasting antidepressant activity, elevates BDNF levels in the hippocampus through a NMDAR-independent mechanism (Zanos et al, 2016). A recent study reports that ketamine and (2R,6R)-HNK, but not the NMDAR antagonist MK-801, increases cyclic adenosine monophosphate (cAMP) -protein kinase A (PKA) signaling in astrocytes, leading to increased phosphorylation of cAMP response element-binding protein (CREB) and BDNF expression (Wray et al, 2018). Although the mechanisms underlying antidepressantinduced BDNF elevation are not fully understood, our results suggest that enhanced E/I ratio, either by disinhibition or by BDNF-induced synaptic modification, is critical for antidepressant responses.…”