Phosphatidate phosphatase Lipin1 involves in diabetic encephalopathy pathogenesis via regulating synaptic mitochondrial dynamics

Deciphering the NLRP3 inflammasome in diabetic encephalopathy: Molecular insights and emerging therapeutic targets

Diabetic encephalopathy (DE) is a neurological complication characterized by neuroinflammation, cognitive impairment, and memory decline, with its pathogenesis closely linked to the activation of the NLRP3 inflammasome. As a central regulator of the innate immune system, the NLRP3 inflammasome plays a pivotal role in DE progression by mediating neuroinflammation, pyroptosis, mitochondrial dysfunction, oxidative stress, endoplasmic reticulum (ER) stress, and microglial polarization. This review systematically explores the molecular mechanisms by which the NLRP3 inflammasome contributes to DE, focusing on its role in neuroinflammatory cascades and neuronal damage, as well as the diabetes-associated physiological changes that exacerbate DE pathogenesis. Furthermore, we summarize emerging therapeutic strategies targeting the NLRP3 inflammasome, including small-molecule inhibitors and bioactive compounds derived from traditional herbal medicine, highlighting their potential for DE treatment. These findings not only advance our understanding of DE but also provide a foundation for developing NLRP3-targeted pharmacological interventions.

Contributions of synaptic energetic dysfunction by microtubule dynamics and microtubule-based mitochondrial transport disorder to morphine tolerance

BACKGROUND AND PURPOSE

Morphine is among the most powerful analgesic, but its long-term use can cause tolerance. Synaptic ATP supply is critical for maintaining synaptic transmission. Microtubule-based mitochondrial transport ensures synaptic energy supply. How synaptic energy changes with morphine and the role of microtubule tracks in synaptic mitochondrial energy supply remain elusive. Chronic morphine treatment can destroy microtubule cytoskeletons. We investigated the effect of the microtubule cytoskeleton on synaptic mitochondrial energy supply and the mechanism of microtubule dynamics after morphine exposure.

EXPERIMENTAL APPROACH

Rats were treated with long-term morphine and the effect on thermal pain thresholds was evaluated by the tail-flick latency test. Various antagonists and agonists were used elucidated the role and mechanism of synaptic mitochondrial energy supply and microtubules in morphine tolerance in vivo and in SH-SY5Y cells.

KEY RESULTS

Chronic morphine treatment reduced synaptic mitochondrial ATP production. Improving mitochondrial oxidative phosphorylation (OXPHOS) alleviated the downregulation of synaptic ATP levels. Microtubule-stabilizing agents prevented microtubule disruption and ameliorated synaptic energy deficit via microtubule-based microtubule transport. In SH-SY5Y cells, morphine exposure reduced microtubule expression. And re-opening the synaptic Ca2+ channel by agonist alleviated microtubule decrease by calcium/calmodulin-dependent protein kinase 2 (CAMKK2)/AMP-activated protein kinase (AMPK) pathway.

CONCLUSION AND IMPLICATIONS

This study demonstrates that the microtubule cytoskeleton regulated by the Ca2+-CAMKK2-AMPK axis is critical for synaptic mitochondrial transport and ATP production, explaining an interplay between chronic morphine-induced abnormal neuroadaptation and synaptic energetic dysfunction. These findings implicated a potential clinical strategy for prolonging the opioid antinociceptive effect during long-term pain control.

Senegenin ameliorates diabetic encephalopathy via promoting mitophagy and repressing NLRP3 inflammasome activation

RATIONALE

Diabetic encephalopathy (DE) remains a severe complication of diabetes in central nervous system with limited effective therapy.

OBJECTIVES

This study investigated the beneficial effect of senegenin on DE and its possible mechanisms.

METHODS

Type 2 diabetes mellitus mouse model and high-glucose (HG)-stimulated PC-12 cells were used as the in vivo and in vitro DE models. Learning and memory ability was evaluated by MWM test. Pathological changes in the brain tissues were determined by HE staining. Cell viability was detected by CCK-8. Mitochondrial membrane potential was measured by JC-1 probe. Target protein levels were assessed by Western blotting. Nucleotide-binding domain-like receptor protein 3 (NLRP3) expression was observed by immunofluorescent staining.

RESULTS

Cognitive impairment and obvious pathological changes were found in DE mice, which were effectively attenuated by senegenin treatment. In addition, senegenin induced mitophagy and maintained homeostasis of mitochondrial dynamics to relieve mitochondrial dysfunction. Moreover, NLRP3 inflammation activation induced by DE was inhibited by senegenin. Finally, inhibition of mitophagy counteracted senegenin-mediated inactivation of NLRP3 inflammation and neuroprotection.

CONCLUSIONS

Senegenin relieved diabetic encephalopathy via inducing mitophagy to inactivate NLRP3 inflammasome. Senegenin might be an effective therapy for treating DE.

Phosphatidate phosphatase Lipin1 alters mitochondria-associated endoplasmic reticulum membranes (MAMs) homeostasis: effects which contribute to the development of diabetic encephalopathy

Diabetic encephalopathy (DE) is a common, chronic central nervous system complication of diabetes mellitus, and represents a condition without a clear pathogenesis or effective therapy. Findings from recent studies have indicated that a dyshomeostasis of mitochondria-associated endoplasmic reticulum membranes (MAMs) may be involved in the development of neurodegenerative diseases such as DE. MAMs represent a dynamic contact site between mitochondrial and endoplasmic reticulum (ER) membranes, where phospholipid components are exchanged with each other. Previous work within our laboratory has revealed that Lipin1, a critical enzyme related to phospholipid synthesis, is involved in the pathogenesis of DE. Here, we show that Lipin1 is downregulated within the hippocampus of a DE mouse model, an effect which was accompanied with a decrease in MAMs. Knockdown of Lipin1 in the hippocampus of normal mice resulted in a reduction of MAMs, ER stress, abnormal mitochondrial function, as well as impaired synaptic plasticity and cognitive function. These same phenomena were observed in the DE model, while an upregulation of Lipin1 within the hippocampus of DE mice improved these symptoms. Low levels of Lipin1 in DE mice were also associated with neuroinflammation, while an overexpression of Lipin1 significantly ameliorated the neuroinflammation observed in DE mice. In conclusion, Lipin1 ameliorates pathological changes associated with DE in a mouse model via prevention of dyshomeostasis in MAMs. Such findings suggest that Lipin1 may be serve as a new potential target for the treatment of DE.

Lipin1 ameliorates cognitive ability of diabetic encephalopathy via regulating Ca2+ transfer through mitochondria-associated endoplasmic reticulum membranes

Diabetic encephalopathy (DE) is a common central nervous system complication resulting from diabetes mellitus (DM). While the exact pathogenesis remains unclear, a homeostatic imbalance of mitochondria-associated endoplasmic reticulum (ER) membranes (MAMs) within neurons has been shown to be closely associated with the dysfunctional cognitive pathology of this condition. Our previous work has revealed that phosphatidate phosphatase Lipin1 plays a critical role in the cognitive processes of DE via regulating mitochondrial function. In this study, we reported that the integrity of neuronal MAMs was disrupted in DE mice, which was accompanied by a decrease in the expression of hippocampal Lipin1. With a knock-down of hippocampal Lipin1 in normal mice, ER stress was induced, MAMs structures were impaired and Ca2+ transfer was suppressed. Such effects resulted in mitochondrial dysfunction, synaptic plasticity impairments, and finally cognitive dysfunctions. In contrast, an up-regulation of hippocampal Lipin1 in the DE model partially alleviated these dysfunctions. These results suggest that Lipin1 may ameliorate the cognitive dysfunctions associated with DE via regulating Ca2+ transfers through MAMs. Therefore, targeting Lipin1 may serve as a therapeutic strategy for the clinical treatment of DE.

Sodium butyrate improves cognitive dysfunction in high-fat diet/ streptozotocin-induced type 2 diabetic mice by ameliorating hippocampal mitochondrial damage through regulating AMPK/PGC-1α pathway

Cognitive dysfunction is an important comorbidity of type 2 diabetes mellitus (T2DM). Sodium butyrate (NaB) is a short-chain fatty acid and has an effect improving T2DM-associated cognitive dysfunction. Using a high-fat diet (HFD)/streptozotocin (STZ)-induced T2DM mouse model, the present study investigated the mechanism involved in the beneficial effect of butyrate on diabetic cognitive dysfunction, with a focus on ameliorating mitochondrial damage through regulating the adenosine monophosphate-activated protein kinase/peroxisome proliferator-activated receptor gamma coactivator 1α (AMPK/PGC-1α) pathway considering the important role of mitochondrial impairments in the occurrence of T2DM-associated cognitive dysfunction. We found, based on reconfirmation of the improvement of NaB on cognitive impairment, that NaB treatment improved damaged synaptic structural plasticity including the decrease in dendritic spine density and downregulation in the expression of postsynaptic density protein 95 and synaptophysin in the hippocampus in the model mice. NaB treatment also ameliorated mitochondrial ultrastructural damage, increased mitochondrial membrane potential and adenosine 5'-triphosphate content, and improved mitochondrial biogenesis and dynamics in the model mice. Furthermore, the expression of phosphorylated AMPK and PGC-1α was upregulated after NaB treatment in the model mice. In particular, the above beneficial effects of NaB were blocked by the inhibition of either AMPK or PGC-1α. In conclusion, NaB treatment improved cognitive impairment and damaged synaptic structural plasticity in the hippocampus by ameliorating damage to mitochondrial morphology and function through regulating the AMPK/PGC-1α pathway in HFD/STZ-induced T2DM mice.

Chemokine CX3CL1 (Fractalkine) Signaling and Diabetic Encephalopathy

Diabetes mellitus (DM) is the most common metabolic disease in humans, and its prevalence is increasing worldwide in parallel with the obesity pandemic. A lack of insulin or insulin resistance, and consequently hyperglycemia, leads to many systemic disorders, among which diabetic encephalopathy (DE) is a long-term complication of the central nervous system (CNS), characterized by cognitive impairment and motor dysfunctions. The role of oxidative stress and neuroinflammation in the pathomechanism of DE has been proven. Fractalkine (CX3CL1) has unique properties as an adhesion molecule and chemoattractant, and by acting on its only receptor, CX3CR1, it regulates the activity of microglia in physiological states and neuroinflammation. Depending on the clinical context, CX3CL1-CX3CR1 signaling may have neuroprotective effects by inhibiting the inflammatory process in microglia or, conversely, maintaining/intensifying inflammation and neurotoxicity. This review discusses the evidence supporting that the CX3CL1-CX3CR1 pair is neuroprotective and other evidence that it is neurotoxic. Therefore, interrupting the vicious cycle within neuron-microglia interactions by promoting neuroprotective effects or inhibiting the neurotoxic effects of the CX3CL1-CX3CR1 signaling axis may be a therapeutic goal in DE by limiting the inflammatory response. However, the optimal approach to prevent DE is simply tight glycemic control, because the elimination of dysglycemic states in the CNS abolishes the fundamental mechanisms that induce this vicious cycle.

Iron/ROS/Itga3 mediated accelerated depletion of hippocampal neural stem cell pool contributes to cognitive impairment after hemorrhagic stroke

Hemorrhagic stroke, specifically intracerebral hemorrhage (ICH), has been implicated in the development of persistent cognitive impairment, significantly compromising the quality of life for affected individuals. Nevertheless, the precise underlying mechanism remains elusive. Here, we report for the first time that the accumulation of iron within the hippocampus, distal to the site of ICH in the striatum, is causally linked to the observed cognitive impairment with both clinical patient data and animal model. Both susceptibility-weighted imaging (SWI) and quantitative susceptibility mapping (QSM) demonstrated significant iron accumulation in the hippocampus of ICH patients, which is far from the actual hematoma. Logistical regression analysis and multiple linear regression analysis identified iron level as an independent risk factor with a negative correlation with post-ICH cognitive impairment. Using a mouse model of ICH, we demonstrated that iron accumulation triggers an excessive activation of neural stem cells (NSCs). This overactivation subsequently leads to the depletion of the NSC pool, diminished neurogenesis, and the onset of progressive cognitive dysfunction. Mechanistically, iron accumulation elevated the levels of reactive oxygen species (ROS), which downregulated the expression of Itga3. Notably, pharmacological chelation of iron accumulation or scavenger of aberrant ROS levels, as well as conditionally overexpressed Itga3 in NSCs, remarkably attenuated the exhaustion of NSC pool, abnormal neurogenesis and cognitive decline in the mouse model of ICH. Together, these results provide molecular insights into ICH-induced cognitive impairment, shedding light on the value of maintaining NSC pool in preventing cognitive dysfunction in patients with hemorrhagic stroke or related conditions.