Lipid rafts regulate 2-arachidonoylglycerol metabolism and physiological activity in the striatum

Several G protein-associated receptors and synaptic proteins function within lipid rafts, which are subdomains of the plasma membranes that contain high concentrations of cholesterol. In this study we addressed the possible role of lipid rafts in the control of endocannabinoid system in striatal slices. Disruption of lipid rafts following cholesterol depletion with methyl-β-cyclodestrin (MCD) failed to affect synthesis and degradation of anandamide, while it caused a marked increase in the synthesis and concentration of 2-arachidonoylglycerol (2-AG), as well as in the binding activity of cannabinoid CB1 receptors. Surprisingly, endogenous 2-AG-mediated control of GABA transmission was not potentiated by MCD treatment and, in contrast, neither basal nor 3,5-Dihydroxyphenylglycine-stimulated 2-AG altered GABA synapses in cholesterol-depleted slices. Synaptic response to the cannabinoid CB1 receptor agonist HU210 was however intact in MCD-treated slices, indicating that reduced sensitivity of cannabinoid CB1 receptors does not explain why endogenous 2-AG is ineffective in inhibiting striatal GABA transmission after cholesterol depletion. Confocal microscopy analysis suggested that disruption of raft integrity by MCD might uncouple metabotropic glutamate 5-CB1 receptor interaction by altering the correct localization of both receptors in striatal neuron elements. In conclusion, our data indicate that disruption of raft integrity causes a complex alteration of the endocannabinoid signalling in the striatum.     

Acute neuronal injury,excitotoxicity, and the endocannabinoid system

The endocannabinoid system is a valuable target for drug discovery, because it is involved in the regulation of many cellular and physiological functions. The endocannabinoid system constitutes the endogenous lipids anandamide, 2-arachidonoylglycerol and noladin ether, and the cannabinoid CB₁ and CB₂ receptors as well as the proteins for their inactivation. It is thought that (endo)cannabinoid-based drugs may potentially be useful to reduce the effects of neurodegeneration. This paper reviews recent developments in the endocannabinoid system and its involvement in neuroprotection. Exogenous (endo)cannabinoids have been shown to exert neuroprotection in a variety of in vitro and in vivo models of neuronal injury via different mechanisms, such as prevention of excitotoxicity by CB₁-mediated inhibition of glutamatergic transmission, reduction of calcium influx, and subsequent inhibition of deleterious cascades, TNF-α formation, and anti-oxidant activity. It has been suggested that the release of endogenous endocannabinoids during neuronal injury might be a protective response. However, several observations indicate that the role of the endocannabinoid system as a general endogenous protection system is questionable. The data are critically reviewed and possible explanations are given.     

Changes in brain levels of N-acylethanolamines and 2-arachidonoylglycerol in focal cerebral ischemia in mice

The N -acylethanolamines (NAEs) and 2-arachidonoylglycerol (2-AG) are bioactive lipids that can modulate inflammatory responses and protect neurons against glutamatergic excitotoxicity. We have used a model of focal cerebral ischemia in young adult mice to investigate the relationship between focal cerebral ischemia and endogenous NAEs. Over the first 24 h after induction of permanent middle cerebral artery occlusion, we observed a time-dependent increase in all the investigated NAEs, except for anandamide. Moreover, we found an accumulation of 2-AG at 4 h that returned to basal level 12 h after induction of ischemia. Accumulation of NAEs did not depend on regulation of N -acylphosphatidylethanolamine-hydrolyzing phospholipase D or fatty acid amide hydrolase. Treatment with the fatty acid amide hydrolase inhibitor URB597 (cyclohexyl carbamic acid 3'-carbamoyl-biphenyl-3-yl ester; 1 mg/kg; i.p.) 1.5 h before arterial occlusion decreased the infarct volume in our model system. Our results suggest that NAEs and 2-AG may be involved in regulation of neuroprotection during focal cerebral ischemia in mice.     

Visualization of 2-arachidonoylglycerol accumulation and cannabinoid CB1 receptor activity in rat brain cryosections by functional autoradiography

In neuronal signalling mediated by the endocannabinoid 2-arachidonoylglycerol, both synthetic and inactivating enzymes operate within close proximity to the G(i/o)-coupled pre-synaptic CB(1) receptors, thus allowing for rapid onset and transient duration of this lipid modulator. In rat brain, 2-arachidonoylglycerol is inactivated mainly via hydrolysis by serine hydrolase inhibitor-sensitive monoacylglycerol lipase activity. We show in this study that comprehensive pharmacological elimination of this activity in brain cryosections by methyl arachidonylfluorophosphonate or hexadecylsulphonyl fluoride results in endocannabinoid-mediated CB(1) receptor activity, which can be visualized by functional autoradiography. URB597, a specific inhibitor of anandamide hydrolysis proved ineffective. TLC indicated that the bioactivity resided in 2-arachidonoylglycerol-containing fraction and gas chromatography-mass spectroscopy detected elevated levels of monoacylglycerols, including 2-arachidonoylglycerol in this fraction. Although two diacylglycerol lipase inhibitors, tetrahydrolipstatin (THL) and RHC80267, blocked the bulk of 2-arachidonoylglycerol accumulation in methyl arachidonylfluorophosphonate-treated sections, only THL reversed the endocannabinoid-dependent CB(1) receptor activity. Further studies indicated that at the used concentrations, THL rather specifically antagonized the CB(1) receptor. These findings confirm that in brain sections there is preservation of enzymatic pathways regulating the production of endogenous receptor ligands. Furthermore, the presently described methodology may serve as an elegant and intuitive approach to identify novel membrane-derived lipid modulators operating in the CNS.     

Ether-linked analogue of 2-arachidonoylglycerol (noladin ether) was not detected in the brains of various mammalian species

2-Eicosa-5',8',11',14'-tetraenylglycerol (2-AG ether, HU310, noladin ether) is a metabolically stable ether-linked analogue of 2-arachidonoylglycerol (2-AG), an endogenous cannabinoid receptor ligand. 2-AG ether has been used as a valuable experimental tool by a number of investigators. Recently, several groups reported that 2-AG ether is present in mammalian brains. We examined in detail whether 2-AG ether actually exists in the brains of various mammalian species. We found that 2-AG ether is not present, at least in an appreciable amount, in the rat brain by gas chromatography-mass spectrometry analysis and fluorometric high performance liquid chromatography analysis. The level of 2-AG ether in the rat brain was below 0.2 pmol/g brain, if at all present. Similar results were obtained for the mouse brain, hamster brain, guinea-pig brain and pig brain. The fact that 2-AG ether was not detected in the brains of various mammalian species is consistent with the fact that an ether bond is formed through enzymatic replacement of the fatty acyl moiety of 1-acyl dihydroxyacetone phosphate by a fatty alcohol, the resultant 1-O-alkyl dihydroxyacetone phosphate being a common intermediate of the biosynthesis of ether-linked lipids in mammalian tissues. It is rather questionable whether 2-AG ether is present in appreciable amounts in the brain and acts as an 'endogenous' cannabinoid receptor ligand.     

Postnatal ethanol exposure alters levels of 2‐arachidonylglycerol‐metabolizing enzymes and pharmacological inhibition of monoacylglycerol lipase does not cause neurodegeneration in neonatal mice

The consumption of ethanol by pregnant women may cause neurological abnormalities, affecting learning and memory processes in children, and are collectively described as fetal alcohol spectrum disorders. However, the molecular mechanisms underlying these changes are still poorly understood. In our previous studies, we found that ethanol treatment of postnatal day 7 (P7) mice significantly enhances the anandamide levels but not the 2‐arachidonylglycerol (2‐AG) levels and induces widespread neurodegeneration, but the reason for the lack of significant effects of ethanol on the 2‐AG level is unknown. In this study, we examined developmental changes in diacylglycerol lipase‐α, β (DAGL‐α and β) and monoacylglycerol lipase (MAGL). We found that the levels of these proteins were significantly higher in adult brains compared to those detected early in brain development. Next, we examined the influence of P7 ethanol treatment on these enzymes, finding that it differentially altered the DAGL‐α protein and mRNA levels but consistently enhanced those of the DAGL‐β. Interestingly, the ethanol treatment enhanced MAGL protein and mRNA levels. Inhibition of MAGL with KML29 failed to induce neurodegeneration in P7 mice. Collectively, these findings suggest that ethanol significantly activates DAGL‐β and MAGL in the neonatal brain, resulting in no net change in 2‐AG levels.

     

WIN-55,212-2 and SR-141716A alter nicotine-induced changes in locomotor activity, but do not alter nicotine-evoked [3H]dopamine release

Nicotine, the main psychoactive ingredient in tobacco, plays a key role in the development of cigarette smoking addiction. The endocannabinoid system has been demonstrated to have an important role in the motivational and reinforcing effects of drugs. The present study used behavioral and neurochemical techniques to study the interaction of cannabinoid receptors and nicotine pharmacology. In a locomotor activity experiment in rats, the CB(1)/CB(2) cannabinoid receptor agonist WIN-55,212-2 (0.28-2.8 mg/kg) attenuated nicotine (0.4 mg/kg)-induced hyperactivity, but did not alter nicotine (1.0 mg/kg)-induced hypoactivity. In contrast, the selective CB(1) cannabinoid receptor antagonist SR-141716A (1.0 mg/kg) diminished nicotine-induced hypoactivity, but did not alter nicotine-induced hyperactivity. In a neurochemical experiment, rat striatal slices preloaded with [(3)H]dopamine were superfused with WIN-55,212-2 or SR-141716A. A high concentration (100 microM) of WIN-55,212-2 evoked [(3)H]overflow, but this effect was not blocked by the cannabinoid receptor antagonist AM-251. SR-141716A did not evoke [(3)H]overflow, and neither WIN-55,212-2 nor SR-141716A altered nicotine-evoked [(3)H]overflow. Overall, these results indicate a behavioral interaction between cannabinoid receptors and nicotine pharmacology. Likely, WIN-55,212-2 and SR-141716A block nicotine-induced changes in behavior through an indirect mechanism, such as alteration in endocannabinoid regulation of motor circuits, rather than directly through blockade of nicotinic acetylcholine receptors.     

Anandamide inhibits Cdk2 and activates Chk1 leading to cell cycle arrest in human breast cancer cells

This study was designed to determine the molecular mechanisms underlying the anti-proliferative effect of the endocannabinoid anandamide on highly invasive human breast cancer cells, MDA-MB-231. We show that a metabolically stable analogue of anandamide, Met-F-AEA, induces an S phase growth arrest correlated with Chk1 activation, Cdc25A degradation and suppression of Cdk2 activity. These findings demonstrate that Met-F-AEA induced cell cycle blockade relies on modulated expression and activity of key S phase regulatory proteins. The observed mechanism of action, already reported for well-known chemotherapeutic drugs, provides strong evidence for a direct role of anandamide related compounds in the activation of cell cycle checkpoints.     

Serotonin 5-HT(2A) receptor activation induces 2-arachidonoylglycerol release through a phospholipase c-dependent mechanism

To date, several studies have demonstrated that phospholipase C-coupled receptors stimulate the production of endocannabinoids, particularly 2-arachidonoylglycerol. There is now evidence that endocannabinoids are involved in phospholipase C-coupled serotonin 5-HT(2A) receptor-mediated behavioral effects in both rats and mice. The main objective of this study was to determine whether activation of the 5-HT(2A) receptor leads to the production and release of the endocannabinoid 2-arachidonoylglycerol. NIH3T3 cells stably expressing the rat 5-HT(2A) receptor were first incubated with [(3)H]-arachidonic acid for 24 h. Following stimulation with 10 mum serotonin, lipids were extracted from the assay medium, separated by thin layer chromatography, and analyzed by liquid scintillation counting. Our results indicate that 5-HT(2A) receptor activation stimulates the formation and release of 2-arachidonoylglycerol. The 5-HT(2A) receptor-dependent release of 2-arachidonoylglycerol was partially dependent on phosphatidylinositol-specific phospholipase C activation. Diacylglycerol produced downstream of 5-HT(2A) receptor-mediated phospholipase D or phosphatidylcholine-specific phospholipase C activation did not appear to contribute to 2-arachidonoylglycerol formation in NIH3T3-5HT(2A) cells. In conclusion, our results support a functional model where neuromodulatory neurotransmitters such as serotonin may act as regulators of endocannabinoid tone at excitatory synapses through the activation of phospholipase C-coupled G-protein coupled receptors.     

Chronic ethanol treatment potentiates ethanol-induced increases in interstitial nucleus accumbens endocannabinoid levels in rats

We employed in vivo microdialysis to characterize the effect of an ethanol challenge injection on endocannabinoid levels in the nucleus accumbens of ethanol-naïve and chronic ethanol-treated rats. Ethanol (0.75 and 2 g/kg, i.p.) dose-dependently increased dialysate 2-arachidonoylglycerol (to a maximum 157 ± 20% of baseline) and decreased anandamide (to a minimum 52 ± 9% of baseline) in ethanol-naïve rats. The endocannabinoid clearance inhibitor N -(4-hydrophenyl) arachidonoylamide (AM404; 3 mg/kg) potentiated ethanol effects on 2-arachidonoylglycerol levels but did not alter ethanol-induced decreases in anandamide. AM404 alone did not alter dialysate levels of either endocannabinoid. Then, we characterized the effect of ethanol challenge on nucleus accumbens endocannabinoid levels in rats previously maintained on an ethanol-containing liquid diet. Ethanol challenge produced a greater and more prolonged increase in 2-arachidonoylglycerol (to a maximum 394 ± 135% of baseline) in ethanol-experienced than in ethanol-naïve rats. The profile in ethanol-experienced rats was similar to that produced by AM404 pre-treatment in ethanol-naïve rats. AM404 in ethanol-experienced rats led to a further enhancement in the 2-arachidonoylglycerol response to ethanol challenge (to a maximum 704 ± 174% of baseline). Our findings demonstrate that ethanol-induced increases in nucleus accumbens 2-arachidonoylglycerol are potentiated in animals with a history of ethanol consumption.     

Gas chromatography-mass spectrometry analysis of endogenous cannabinoids in healthy and tumoral human brain and human cells in culture

Endocannabinoids are lipid mediators thought to modulate central and peripheral neural functions. We report here gas chromatography-electron impact mass spectrometry analysis of human brain, showing that lipid extracts contain anandamide and 2-arachidonoylglycerol (2-AG), the most active endocannabinoids known to date. Human brain also contained the endocannabinoid-like compounds N-oleoylethanolamine, N-palmitoylethanolamine and N-stearoylethanolamine. Anandamide and 2-AG (0.16 +/- 0.05 and 0.10 +/- 0.05 nmol/mg protein, respectively) represented 7.7% and 4.8% of total endocannabinoid-like compounds, respectively. N-Palmitoyethanolamine was the most abundant (50%), followed by N-oleoyl (23.6%) and N-stearoyl (13.9%) ethanolamines. A similar composition in endocannabinoid-like compounds was found in human neuroblastoma CHP100 and lymphoma U937 cells, and also in rat brain. Remarkably, human meningioma specimens showed an approximately six-fold smaller content of all N-acylethanolamines, but not of 2-AG, and a similar decrease was observed in a human glioblastoma. These ex vivo results fully support the purported roles of endocannabinoids in the nervous system.     

Imidazopyridine CB2 agonists: optimization of CB2/CB1 selectivity and implications for in vivo analgesic efficacy

A new series of imidazopyridine CB2 agonists is described. Structural optimization improved CB2/CB1 selectivity in this series and conferred physical properties that facilitated high in vivo exposure, both centrally and peripherally. Administration of a highly selective CB2 agonist in a rat model of analgesia was ineffective despite substantial CNS exposure, while administration of a moderately selective CB2/CB1 agonist exhibited significant analgesic effects.     

Elevation of GM2 ganglioside during ethanol-induced apoptotic neurodegeneration in the developing mouse brain

GM2 ganglioside in the brain increased during ethanol-induced acute apoptotic neurodegeneration in 7-day-old mice. A small but a significant increase observed 2 h after ethanol exposure was followed by a marked increase around 24 h. Subcellular fractionation of the brain 24 h after ethanol treatment indicated that GM2 increased in synaptic and non-synaptic mitochondrial fractions as well as in a lysosome-enriched fraction characteristic to the ethanol-exposed brain. Immunohistochemical staining of GM2 in the ethanol-treated brain showed strong punctate staining mainly in activated microglia, in which it partially overlapped with staining for LAMP1, a late endosomal/lysosomal marker. Also, there was weaker neuronal staining, which partially co-localized with complex IV, a mitochondrial marker, and was augmented in cleaved caspase 3-positive neurons. In contrast, the control brain showed only faint and diffuse GM2 staining in neurons. Incubation of isolated brain mitochondria with GM2 in vitro induced cytochrome c release in a manner similar to that of GD3 ganglioside. Because ethanol is known to trigger mitochondria-mediated apoptosis with cytochrome c release and caspase 3 activation in the 7-day-old mouse brain, the GM2 elevation in mitochondria may be relevant to neuroapoptosis. Subsequently, activated microglia accumulated GM2, indicating a close relationship between GM2 and ethanol-induced neurodegeneration.     

Ceramide inhibits the outward potassium current in rat pinealocytes

CD1 mice lacking the CB1 receptors (knockout, KO) were compared with wild-type littermates for their ability to degrade N-arachidonoylethanolamine (anandamide, AEA) through a membrane transporter (AMT) and a fatty acid amide hydrolase (FAAH). The regional distribution and age-dependence of AMT and FAAH activity were investigated. Anandamide membrane transporter and FAAH increased with age in knockout mice, whereas they showed minor changes in wild-type animals. Remarkably, they were higher in all brain areas of 6-month-old knockout versus wild-type mice, and even higher in 12-month-old animals. The molecular mass (approximately 67 kDa) and isoelectric point (approximately 7.6) of mouse brain FAAH were determined and the FAAH protein content was shown to parallel the enzyme activity. The kinetic constants of AMT and FAAH in the cortex of wild-type and knockout mice at different ages suggested that different amounts of the same proteins were expressed. The cortex and hippocampus of wild-type and knockout mice contained the following N-acylethanolamines: AEA (8% of total), 2-arachidonoylglycerol (5%), N-oleoylethanolamine (20%), N-palmitoylethanolamine (53%) and N-stearoylethanolamine (14%). These compounds were twice as abundant in the hippocampus as in the cortex. Minor differences were observed in AEA or 2-arachidonoylglycerol content in knockout versus wild-type mice, whereas the other compounds were lower in the hippocampus of knockout versus wild-type animals.     

Decahydroquinoline amides as highly selective CB2 agonists: role of selectivity on in vivo efficacy in a rodent model of analgesia

A novel series of decahydroquinoline CB2 agonists is described. Optimization of the amide substituent led to improvements in CB2/CB1 selectivity as well as physical properties. Two key compounds were examined in the rat CFA model of acute inflammatory pain. A moderately selective CB2 agonist was active in this model. A CB2 agonist lacking functional CB1 activity was inactive in this model despite high in vivo exposure both peripherally and centrally.     

Accumulation of the anandamide precursor and other N-acylethanolamine phospholipids in infant rat models of in vivo necrotic and apoptotic neuronal death

It has been demonstrated that the endogenous cannabinoid receptor ligand, anandamide, and other N-acylethanolamines (NAEs), accumulate during neuronal injury in vitro, a process that may be linked to the neuroprotective effects of NAEs. The crucial step for generation of NAEs is the synthesis of the corresponding precursors, N-acylethanolamine phospholipids (NAPEs). However, it is unknown whether this key event for NAE formation is regulated differently in the context of insults causing necrotic or apoptotic neuronal death. To address this question, we monitored a range of cortical NAPE species in three infant rat models of in vivo neurodegeneration: (i) necrosis caused by intrastriatal injection of NMDA (25 nmol); (ii) apoptosis induced by systemic administration of the NMDA-receptor antagonist (+)MK-801 (3 x 0.5 mg/kg, i.p.); and (iii) apoptosis following focal necrosis triggered by concussive head trauma. A marked increase of all NAPE species was observed in both hemispheres 4 and 24 h after NMDA-induced injury, with a relatively larger increase in N-stearoyl-containing NAPE species. Thus, the percentage of the anandamide precursor fell from 1.1 to 0.5 mol %. In contrast, administration of (+)MK-801 did not alter cortical NAPE levels. Concussion head trauma resulted in a similar but less pronounced upregulation of NAPE levels at both 4 and 24 h as compared to NMDA injections. Increased levels of NAPE 24 h post-trauma possibly reflect that necrosis is still ongoing at this time point. Consequently, our data suggest that excitotoxic necrotic mechanisms of neurodegeneration, as opposed to apoptotic neurodegeneration, have a profound effect on in vivo NAE precursor homeostasis.     

Lysosomal dysfunction in neurodegeneration: The role of ATP13A2/PARK9

Neuronal homeostasis and survival critically depend on an efficient autophagy-lysosomal degradation pathway, especially since neurons cannot reduce the concentration of misfolded proteins and damaged organelles by cell division. While increasing evidence implicates lysosomal dysfunction in the pathogenesis of neurodegenerative disorders, the molecular underpinnings of the role of lysosomes in neurodegeneration remain largely unknown. To this end, studies of neurodegenerative disorders caused by mutations in lysosomal proteins offer an opportunity to elucidate such mechanisms and potentially identify specific therapeutic targets. One of these disorders is Kufor-Rakeb syndrome, caused by mutations in the lysosomal protein ATP13A2/PARK9 and characterized by early-onset Parkinsonism, pyramidal degeneration and dementia. We found that loss of ATP13A2 function results in impaired lysosomal function and, consequently, accumulation of SNCA/α-synuclein and neurotoxicity. Our results suggest that targeting of ATP13A2 to lysosomes to enhance lysosomal function may result in neuroprotection in Kufor-Rakeb syndrome. From a broader perspective, these findings, together with other recent studies of lysosomal dysfunction in neurodegeneration, suggest that strategies to upregulate lysosomal function in neurons represent a promising therapeutic approach for neurodegenerative disorders.     

Blockade of cannabinoid CB(1) receptor function protects against in vivo disseminating brain damage following NMDA-induced excitotoxicity

The ability of cannabinoid CB(1) receptors to influence glutamatergic excitatory neurotransmission has fueled interest in how these receptors and their endogenous ligands may interact in conditions of excitotoxic insults. The present study characterized the impact of stimulated and inhibited CB(1) receptor function on NMDA-induced excitotoxicity. Neonatal (6-day-old) rat pups received a systemic injection of a mixed CB(1) /CB(2) receptor agonist (WIN55,212-2) or their respective antagonists (SR141716A for CB(1) and SR144528 for CB(2) ) prior to an unilateral intrastriatal microinjection of NMDA. The NMDA-induced excitotoxic damage in the ipsilateral forebrain was not influenced by agonist-stimulated CB(1) receptor function. In contrast, blockade of CB(1), but not CB(2), receptor activity evoked a robust neuroprotective response by reducing the infarct area and the number of cortical degenerating neurons. These results suggest a critical involvement of CB(1) receptor tonus on neuronal survival following NMDA receptor-induced excitotoxicity in vivo.     

Lysosomal dysfunction in neurodegeneration

Neuronal homeostasis and survival critically depend on an efficient autophagy-lysosomal degradation pathway, especially since neurons cannot reduce the concentration of misfolded proteins and damaged organelles by cell division. While increasing evidence implicates lysosomal dysfunction in the pathogenesis of neurodegenerative disorders, the molecular underpinnings of the role of lysosomes in neurodegeneration remain largely unknown. To this end, studies of neurodegenerative disorders caused by mutations in lysosomal proteins offer an opportunity to elucidate such mechanisms and potentially identify specific therapeutic targets. One of these disorders is Kufor-Rakeb syndrome, caused by mutations in the lysosomal protein ATP13A2/PARK9 and characterized by early-onset Parkinsonism, pyramidal degeneration and dementia. We found that loss of ATP13A2 function results in impaired lysosomal function and, consequently, accumulation of SNCA/α-synuclein and neurotoxicity. Our results suggest that targeting of ATP13A2 to lysosomes to enhance lysosomal function may result in neuroprotection in Kufor-Rakeb syndrome. From a broader perspective, these findings, together with other recent studies of lysosomal dysfunction in neurodegeneration, suggest that strategies to upregulate lysosomal function in neurons represent a promising therapeutic approach for neurodegenerative disorders.     

Lipophagy prevents activity‐dependent neurodegeneration due to dihydroceramide accumulation in vivo

Dihydroceramide desaturases are evolutionarily conserved enzymes that convert dihydroceramide (dhCer) to ceramide (Cer). While elevated Cer levels cause neurodegenerative diseases, the neuronal activity of its direct precursor, dhCer, remains unclear. We show that knockout of the fly dhCer desaturase gene, infertile crescent (ifc), results in larval lethality with increased dhCer and decreased Cer levels. Light stimulation leads to ROS increase and apoptotic cell death in ifc‐KO photoreceptors, resulting in activity‐dependent neurodegeneration. Lipid‐containing Atg8/LC3‐positive puncta accumulate in ifc‐KO photoreceptors, suggesting lipophagy activation. Further enhancing lipophagy reduces lipid droplet accumulation and rescues ifc‐KO defects, indicating that lipophagy plays a protective role. Reducing dhCer synthesis prevents photoreceptor degeneration and rescues ifc‐KO lethality, while supplementing downstream sphingolipids does not. These results pinpoint that dhCer accumulation is responsible for ifc‐KO defects. Human dhCer desaturase rescues ifc‐KO larval lethality, and rapamycin reverses defects caused by dhCer accumulation in human neuroblastoma cells, suggesting evolutionarily conserved functions. This study demonstrates a novel requirement for dhCer desaturase in neuronal maintenance in vivo and shows that lipophagy activation prevents activity‐dependent degeneration caused by dhCer accumulation.