Environmental Enrichment Attenuated Sevoflurane-Induced Neurotoxicity through the PPAR-γ Signaling Pathway

The Impact of Hormesis, Neuronal Stress Response, and Reproduction, upon Clinical Aging: A Narrative Review

INTRODUCTION

The primary objective of researchers in the biology of aging is to gain a comprehensive understanding of the aging process while developing practical solutions that can enhance the quality of life for older individuals. This involves a continuous effort to bridge the gap between fundamental biological research and its real-world applications.

PURPOSE

In this narrative review, we attempt to link research findings concerning the hormetic relationship between neurons and germ cells, and translate these findings into clinically relevant concepts.

METHODS

We conducted a literature search using PubMed, Embase, PLOS, Digital Commons Network, Google Scholar and Cochrane Library from 2000 to 2023, analyzing studies dealing with the relationship between hormetic, cognitive, and reproductive aspects of human aging.

RESULTS

The process of hormesis serves as a bridge between the biology of neuron-germ cell interactions on one hand, and the clinical relevance of these interactions on the other. Details concerning these processes are discussed here, emphasizing new research which strengthens the overall concept.

CONCLUSIONS

This review presents a scientifically and clinically relevant argument, claiming that maintaining a cognitively active lifestyle may decrease age-related degeneration, and improve overall health in aging. This is a totally novel approach which reflects current developments in several relevant aspects of our biology, technology, and society.

Neonatal exposure to sevoflurane impairs preference for social novelty in C57BL/6 female mice at early-adulthood

Social interaction deficit is core symptom of children with autism, owing to interaction of genetic predisposition and environmental toxins. Sevoflurane could induce neurotoxicity in developing brain in rodent models. This study aims to investigate whether sevoflurane anesthesia in neonatal period could impair social behaviors in male and female mice. Twenty-eight male and thirty-one female mice were randomly assigned to receive 3.0% sevoflurane or 60% oxygen on postnatal day 6. They were tested for social interaction behaviors at one- and two-month-old. In addition, the cortex and hippocampus of neonatal mice undergoing sevoflurane anesthesia were harvested for immunoblotting analysis. As a result, both male and female mice undergoing sevoflurane anesthesia showed strong sociability and weak preference for social novelty at juvenile age. In addition, the male mice developed normal preference for social novelty at early-adulthood; However, the female mice remained weak preference for social novelty. Furthurmore, sevoflurane anesthesia could decrease the levels of PSD95 but not Neuroligin-1 in the hippocampus but not cortex of neonatal mice. In conclusion, sevoflurane anesthesia in neonatal period could disturb development of social memory and impair preference for social novelty in female mice at early-adulthood, with the potential mechanism of decreasing PSD95 expression in the hippocampus of C57BL/6 mice.

Docosahexaenoic acid supplementation alleviates behavioral memory impairment caused via repeated administration of sevoflurane in aged rats

Elderly patients often need repeated surgical intervention, so it is important to determine the impact of repeated exposure to anesthetics on learning and memory. Docosahexaenoic acid (DHA) is considered to be an essential nutrient for maintaining brain health. The aim of the present study was to explore the potential effects of DHA on memory impairment induced by repeated sevoflurane anesthesia in aged rats. A total of 54 Sprague Dawley aged rats (18 months) were randomly divided into the following six groups: i) Control group; ii) sevoflurane group (Sev, 2.5% for 5 min); iii) DHA group (3 g/kg); iv) Sev + DHA (0.3 g/kg) group; v) Sev + DHA (1 g/kg) group; and vi) Sev + DHA (3 g/kg) group. Morris water maze experiment was performed to evaluate the learning and memory ability of the rats following treatment. H&E staining was used to observe any histological changes. Superoxide dismutase, malondialdehyde and glutathione peroxidase levels were detected using ELISA. Immunohistochemistry and western blotting were used to determine nuclear factor erythroid-2-related factor 2 (Nrf2) and heme oxygenase 1 (HO-1) protein expression levels. Following repeated sevoflurane anesthesia, rats exhibited a prolonged escape latency. The number of times rats crossed the platform and the time spent in the target quadrant were also significantly reduced by repeated sevoflurane anesthesia. However, rats treated with Sev + DHA exhibited a reduced escape latency, whilst the number of times they crossed the platform and the time spent in the target quadrant increased compared with Sev treatment alone. Histopathological examination revealed that DHA treatment ameliorated the disordered neuron arrangement, deep staining of the neuronal nucleus pyknosis and cell edema observed in the brain tissue induced by repeated sevoflurane anesthesia. Furthermore, the protein expression levels of Nrf2 and HO-1 were demonstrated to be significantly increased in rats treated with DHA and exposed to repeated sevoflurane anesthesia compared with those in untreated rats that underwent repeated sevoflurane anesthesia. In conclusion, the present study revealed that DHA exerted protective effects against impairments in learning and memory induced by repeated sevoflurane anesthesia in aged rats, which may be associated with the Nrf2/HO-1 signaling pathway.

Propofol and Sevoflurane Anesthesia in Early Childhood Do Not Influence Seizure Threshold in Adult Rats

Experimental studies have demonstrated that general anesthetics administered during the period of synaptogenesis may induce widespread neurodegeneration, which results in permanent cognitive and behavioral deficits. What remains to be elucidated is the extent of the potential influence of the commonly used hypnotics on comorbidities including epilepsy, which may have resulted from increased neurodegeneration during synaptogenesis. This study aimed to test the hypothesis that neuropathological changes induced by anesthetics during synaptogenesis may lead to changes in the seizure threshold during adulthood. Wistar rat pups were treated with propofol, sevoflurane, or saline on the sixth postnatal day. The long-term effects of prolonged propofol and sevoflurane anesthesia on epileptogenesis were assessed using corneal kindling, pilocarpine-, and pentylenetetrazole-induced seizure models in adult animals. Body weight gain was measured throughout the experiment. No changes in the seizure threshold were observed in the three models. A significant weight gain after exposure to anesthetics during synaptogenesis was observed in the propofol group but not in the sevoflurane group. The results suggest that single prolonged exposure to sevoflurane or propofol during synaptogenesis may have no undesirable effects on epileptogenesis in adulthood.

Quantitative behavioural phenotyping to investigate anaesthesia induced neurobehavioural impairment

Anaesthesia exposure to the developing nervous system causes neuroapoptosis and behavioural impairment in vertebrate models. Mechanistic understanding is limited, and target-based approaches are challenging. High-throughput methods may be an important parallel approach to drug-discovery and mechanistic research. The nematode worm Caenorhabditis elegans is an ideal candidate model. A rich subset of its behaviour can be studied, and hundreds of behavioural features can be quantified, then aggregated to yield a 'signature'. Perturbation of this behavioural signature may provide a tool that can be used to quantify the effects of anaesthetic regimes, and act as an outcome marker for drug screening and molecular target research. Larval C. elegans were exposed to: isoflurane, ketamine, morphine, dexmedetomidine, and lithium (and combinations). Behaviour was recorded, and videos analysed with automated algorithms to extract behavioural features. Anaesthetic exposure during early development leads to persisting behavioural variation (in total, 125 features across exposure combinations). Higher concentrations, and combinations of isoflurane with ketamine, lead to persistent change in a greater number of features. Morphine and dexmedetomidine do not appear to lead to behavioural impairment. Lithium rescues the neurotoxic phenotype produced by isoflurane. Findings correlate well with vertebrate research: impairment is dependent on agent, is concentration-specific, is more likely with combination therapies, and can potentially be rescued by lithium. These results suggest that C. elegans may be an appropriate model with which to pursue phenotypic screens for drugs that mitigate the neurobehavioural impairment. Some possibilities are suggested for how high-throughput platforms might be organised in service of this field.

Depletion of SENP1-mediated PPARγ SUMOylation exaggerates intermittent hypoxia-induced cognitive decline by aggravating microglia-mediated neuroinflammation

Intermittent hypoxia (IH)-associated cognition decline is related to the neuroinflammation of microglia. SUMOylation is a post-translational modification related to multiple human diseases, which can be reversed by SENP1. Studies showed that SENP1 and PPARγ play essential roles in restricting inflammation by blocking NF-κB activation. However, the mechanism remains unclear. Herein, we investigated the precise mechanism underlying SENP1 and PPARγ in cognitive decline after IH insult. Biochemical analysis results revealed that IH triggered the inflammatory response and neuronal apoptosis, increased the SUMOylation of PPARγ, and decreased the level of PPARγ compared to that in the normoxia group. After SENP1 downregulation, the inflammatory response, neuronal apoptosis and the SUMOylation of PPARγ were enhanced, and the level of PPARγ was further decreased in vitro and in vivo. However, the application of PPARγ agonist, GW1929, abolished the enhancement of inflammation and neuronal apoptosis in vitro. The Morris Water Maze results showed that both IH groups mice exhibited longer latency and shorter dwell-time in the goal quadrant than normoxia groups. Notably, SENP1 downregulation aggravated these alterations. Overall, these results showed that SENP1 played an essential role in IH-associated cognitive dysfunction. SENP1 depletion aggravated neuroinflammation and neuronal apoptosis via promoting the SUMOylation of PPARγ, reducing the level of PPARγ, thus exaggerating IH-induced cognitive decline.

Maternal anesthesia with sevoflurane during the mid-gestation induces social interaction deficits in offspring C57BL/6 mice

Sevoflurane anesthesia in pregnant mice could induce neurotoxicity in the developing brain and disturb learning and memory in the offspring mice. Whether it could impair social behaviors in the offspring mice is uncertain. Therefore, we assessed the neurobehavioral effect of in-utero exposure to sevoflurane on social interaction behaviors in C57BL/6 mice. The pregnant mice were anesthetized with 2.5% sevoflurane in 100% oxygen for 2 h, and their offspring mice were tested in three-chambered social paradigm, which includes three 10-min sessions of habituation, sociability, and preference for social novelty. At the juvenile age, the offspring mice showed abnormal sociability, as proved by not taking more time sniffing at the stranger 1 mouse compared with the empty enclosure (108.5 ± 25.4 vs. 108.2 ± 44.0 s, P = 0.9876). Meanwhile, these mice showed impaired preference for social novelty, as evidenced by not taking more time sniffing at the stranger 2 compared with the stranger 1 mouse (92.1 ± 52.2 vs. 126.7 ± 50.8 s, P = 0.1502). At the early adulthood, the offspring mice retrieved the normal sociability (145.6 ± 33.2 vs. 76.0 ± 31.8 s, P = 0.0001), but remained the impaired preference for social novelty (100.6 ± 29.3 vs. 118.0 ± 47.9 s, P = 0.3269). Collectively, these results suggested maternal anesthesia with sevoflurane could induce social interaction deficits in their offspring mice. Although the disturbance of sociability could be recoverable, the impairment of preference for social novelty could be long-lasting.

Dexmedetomidine attenuates sevoflurane‑induced neurocognitive impairment through α2‑adrenoceptors

It has been reported that sevoflurane induces neurotoxicity in the developing brain. Dexmedetomidine is an α2 adrenoceptor agonist used for the prevention of sevoflurane‑induced agitation in children in clinical practice. The aim of the present study was to determine whether dexmedetomidine could prevent sevoflurane‑induced neuroapoptosis, neuroinflammation, oxidative stress and neurocognitive impairment. Additionally, the involvement of α2 adrenoceptors in the neuroprotective effect of dexmedetomidine was assessed. Postnatal day (P)6 C57BL/6 male mice were randomly divided into four groups (n=6 in each group). Mice were pretreated with dexmedetomidine, either alone or together with yohimbine, an α2 adrenoceptor inhibitor, then exposed to 3% sevoflurane in 25% oxygen. Control mice either received normal saline alone or with sevoflurane exposure. Following sevoflurane exposure, the expression of cleaved caspase‑3 was detected by immunohistochemistry in hippocampal tissue sections. In addition, the levels of tumor necrosis factor‑α (TNF‑α), interleukin (IL)‑1β, IL‑6 and malondialdehyde, as well as superoxide dismutase (SOD) activity in the hippocampus were measured. At P35, the learning and memory abilities were assessed in each mouse using a Morris water maze test. Dexmedetomidine significantly decreased the expression of activated caspase‑3 following sevoflurane exposure. Moreover, dexmedetomidine significantly decreased the levels of TNF‑α, IL‑1β and IL‑6 in the hippocampus. SOD activity also increased in a dose‑dependent manner in dexmedetomidine‑treated mice. MDA decreased in a dose‑dependent manner in dexmedetomidine‑treated mice. Lastly, sevoflurane‑induced learning and memory impairment was reversed by dexmedetomidine treatment. By contrast, co‑administration of yohimbine significantly attenuated the neuroprotective effects of dexmedetomidine. These findings suggested that dexmedetomidine exerted a neuroprotective effect against sevoflurane‑induced apoptosis, inflammation, oxidative stress and neurocognitive impairment, which was mediated, at least in part, by α2 adrenoceptors.

Anesthesia plus surgery in neonatal period impairs preference for social novelty in mice at the juvenile age

Anesthetic sevoflurane could induce neurotoxicity in developing brain and cause adverse neurobehavioral outcomes in mice, including inattention, social interaction deficit, and learning and memory impairment. However, there is less data on the effect of anesthesia plus surgery on social interaction behavior. Therefore, we investigated whether the combination of anesthesia and surgical stimulation could induce behavioral and biochemical changes in mice. Firstly, the six-day-old mice were received either 3% sevoflurane anesthesia or abdominal surgery under sevoflurane anesthesia. Then, these mice were scheduled to social interaction test in three-chambered social paradigm at one-month-old. In addition, the brain tissues of neonatal mice were harvested at 24 h after treatment, for measuring the levels of OXTR and NMDAR1 in Western blot analysis. We found that neonatal anesthesia with sevoflurane in a clinically-relevant dosage could not induce social interaction deficit. Nevertheless, anesthesia plus surgery was able to impair preference for social novelty in mice. Moreover, anesthesia plus surgery decreased the levels of OXTR in hippocampus and cortex of mice, as well as NMDAR1 in hippocampus. Collectively, these results suggested that anesthesia plus surgery could impair social novelty preference, but not sociability in mice, and that social memory might be more vulnerable than social affiliation in biological property. Furthermore, reduction in the levels of cortex OXTR and hippocampus NMDAR1 could be associated with social recognition memory in mice.

Ageing Throughout History: The Evolution of Human Lifespan

It is not surprising that one of the most complex phenomena in nature is that of ageing. It does not only bear biological interest, but it is also associated with cultural, psychological, social and even philosophical issues. It is therefore to be expected that a great deal of research is being performed in order to study the evolution of ageing and, more specifically, the evolution of human ageing. Historical aspects of this evolution will be discussed. Evidence from a variety of sources shows that the human lifespan is increasing, and may well continue to increase to levels that are difficult to predict. In addition, the most important theories about ageing based on evolutionary principles will be examined. Examples are mutation accumulation, antagonistic pleiotropy and the disposable soma theory. Finally, a section about future evolution of human ageing, based upon newly emerging research, will shed some light and provide speculative-provocative ideas about the future of ageing in humans.

Sevoflurane Exacerbates Cognitive Impairment Induced by Aβ 1-40 in Rats through Initiating Neurotoxicity, Neuroinflammation, and Neuronal Apoptosis in Rat Hippocampus

Objective

This study was aimed at investigating whether sevoflurane inhalation induced cognitive impairment in rats with a possible mechanism involved in the event.

Methods

Thirty-two rats were randomly divided into four groups of normal saline (NS) + O₂, NS + sevoflurane (sevo), amyloid-β peptide (Aβ) + O₂, and Aβ + sevo. The rats in the four groups received bilateral intrahippocampus injections of NS or Aβ. The treated hippocampus was harvested after inhaling 30% O₂ or 2.5% sevoflurane. Evaluation of cognitive function was performed by Morris water maze (MWZ) and an Aβ_1–42 level was determined by ELISA. Protein and mRNA expressions were executed by immunohistochemical (IHC) staining, Western blotting, and qRT-PCR.

Results

Compared with the NS-treated group, sevoflurane only caused cognitive impairment and increased the level of Aβ_1–42 of the brain in the Aβ-treated group. Sevoflurane inhalation but not O₂ significantly increased glial fibrillary acidic protein (GFAP) and ionized calcium-binding adaptor molecule (IBA)1 expression in Aβ-treated hippocampus of rats. Expression levels for Bcl-xL, caspase-9, receptor for advanced glycation end products (RAGE) and brain-derived neurotrophic factor (BDNF) were significantly different in quantification of band intensity between the rats that inhaled O₂ and sevoflurane in Aβ-treated groups (all P < 0.05). Interleukin- (IL-) 1β, nuclear factor-κB (NF-κB), and inducible nitric oxide synthase (iNOS) mRNA expression increased after the rats inhaled sevoflurane in the Aβ-treated group (both P < 0.01). There were no significant differences in the change of GFAP, IBA1, Bcl-xL, caspase-9, RAGE, BDNF, IL-1β, NF-κB, and iNOS in the NS + O₂ and NS + sevo group (all P > 0.05).

Conclusion

Sevoflurane exacerbates cognitive impairment induced by Aβ_1–40 in rats through initiating neurotoxicity, neuroinflammation, and neuronal apoptosis in rat hippocampus.

MicroRNA-27a-3p suppression of peroxisome proliferator-activated receptor-γ contributes to cognitive impairments resulting from sevoflurane treatment

Sevoflurane is the most widely used anaesthetic administered by inhalation. Exposure to sevoflurane in neonatal mice can induce learning deficits and abnormal social behaviours. MicroRNA (miR)-27a-3p, a short, non-coding RNA that functions as a tumour suppressor, is up-regulated after inhalation of anaesthetic, and peroxisome proliferator-activated receptor γ (PPAR-γ) is one of its target genes. The objective of this study was to investigate how the miR-27a-3p-PPAR-γ interaction affects sevoflurane-induced neurotoxicity. A luciferase reporter assay was employed to identify the interaction between miR-27a-3p and PPAR-γ. Primary hippocampal neuron cultures prepared from embryonic day 0 C57BL/6 mice were treated with miR-27a-3p inhibitor or a PPAR-γ agonist to determine the effect of miR-27a-3p and PPAR-γ on sevoflurane-induced cellular damage. Cellular damage was assessed by a flow cytometry assay to detect apoptotic cells, immunofluorescence to detect reactive oxygen species, western blotting to detect NADPH oxidase 1/4 and ELISA to measure inflammatory cytokine levels. In vivo experiments were performed using a sevoflurane-induced anaesthetic mouse model to analyse the effects of miR-27a-3p on neurotoxicity by measuring the number of apoptotic neurons using the Terminal-deoxynucleoitidyl Transferase Mediated Nick End Labeling (TUNEL) method and learning and memory function by employing the Morris water maze test. Our results revealed that PPAR-γ expression was down-regulated by miR-27a-3p following sevoflurane treatment in hippocampal neurons. Down-regulation of miR-27a-3p expression decreased sevoflurane-induced hippocampal neuron apoptosis by decreasing inflammation and oxidative stress-related protein expression through the up-regulation of PPAR-γ. In vivo tests further confirmed that inhibition of miR-27a-3p expression attenuated sevoflurane-induced neuronal apoptosis and learning and memory impairment. Our findings suggest that down-regulation of miR-27a-3p expression ameliorated sevoflurane-induced neurotoxicity and learning and memory impairment through the PPAR-γ signalling pathway. MicroRNA-27a-3p may, therefore, be a potential therapeutic target for preventing or treating sevoflurane-induced neurotoxicity.

PPARγ activation ameliorates postoperative cognitive decline probably through suppressing hippocampal neuroinflammation in aged mice

Neuroinflammation plays a key role in many neurodegenerative disorders, including postoperative cognitive decline (POCD). Growing evidence has demonstrated that activation of the peroxisome proliferator-activated receptor-γ (PPARγ) attenuates the inflammatory response and improves cognitive dysfunction associated with many neuropsychiatric disorders. We hypothesize that down-regulation of PPARγ is linked to neuroinflammation and the subsequent cognitive deficits observed in an animal model of POCD. In the present study, the POCD animal model was established by performing an exploratory laparotomy under isoflurane anesthesia in 20-month-old male C57BL/6 mice. Behavioral tests, inflammatory biomarkers, including tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-1β, ionized calcium-binding adaptor molecule-1 (IBA1)-positive cells, as well as glial fibrillary acidic protein (GFAP)-positive cells and brain-derived neurotrophic factor (BDNF), were measured. Herein, we showed that surgery induced profound impairment in cognition that was associated with significant decreases in PPARγ and BDNF expression, and significant increases in IL-1β, IBA1-positive cells, and GFAP-positive cells in the hippocampus. As expected, the PPARγ agonist pioglitazone attenuated the surgery-induced inflammatory changes and rescued the associated cognitive impairment. However, these beneficial effects were abolished by the PPARγ specific antagonist GW9662, suggesting a pivotal role of the PPARγ pathway in the pathogenesis of POCD. Taken together, our results provide evidence that down-regulation of PPARγ may be involved in neuroinflammation and subsequent POCD, and suggest that activation of PPARγ by pioglitazone may represent a new way to prevent or treat POCD.

Do anesthetics harm the developing human brain? An integrative analysis of animal and human studies

Anesthetics that permit surgical procedures and stressful interventions have been found to cause structural brain abnormalities and functional impairment in immature animals, generating extensive concerns among clinicians, parents, and government regulators regarding the safe use of these drugs in young children. Critically important questions remain, such as the exact age at which the developing brain is most vulnerable to the effects of anesthetic exposure, whether a particular age exists beyond which anesthetics are devoid of long-term effects on the brain, and whether any specific exposure duration exists that does not lead to deleterious effects. Accordingly, the present analysis attempts to put the growing body of animal studies, which we identified to include >440 laboratory studies to date, into a translational context, by integrating the preclinical data on brain structure and function with clinical results attained from human neurocognitive studies, which currently exceed 30 studies. Our analysis demonstrated no clear exposure duration threshold below which no structural injury or subsequent cognitive abnormalities occurred. Animal data did not clearly identify a specific age beyond which anesthetic exposure did not cause any structural or functional abnormalities. Several potential mitigating strategies were found, however, no general anesthetic was identified that consistently lacked neurodegenerative properties and could be recommended over other anesthetics. It therefore is imperative, to expand efforts to devise safer anesthetic techniques and mitigating strategies, even before long-term alterations in brain development are unequivocally confirmed to occur in millions of young children undergoing anesthesia every year.

Amelioration of oxidative stress-induced phenotype loss of parvalbumin interneurons might contribute to the beneficial effects of environmental enrichment in a rat model of post-traumatic stress disorder

Post-traumatic stress disorder (PTSD) is a common psychiatric disease following exposure to a severe traumatic event or physiological stress, which is characterized by anxiety- and depression-like behaviors and cognitive impairment. However, the underlying mechanisms remain elusive. Parvalbumin (PV) interneurons that are susceptible to oxidative stress are a subset of inhibitory GABAergic neurons regulating the excitability of pyramidal neurons, while dysfunction of PV interneurons is casually linked to many mental disorders including PTSD. We therefore hypothesized that environmental enrichment (EE), a method of enhanced cognitive, sensory and motor stimulation, can reverse the behavioral impairments by normalizing PV interneurons in a rat model of PTSD induced by inescapable foot shocks (IFS). Behavioral changes were determined by the open field, elevated plus maze, fear conditioning, and Morris water maze tests. The levels of nicotinamide adenosine dinucleotide phosphate (NADPH) oxidase 2 (NOX2), NOX4, PV, glutamic acid decarboxylase 67 (GAD-67), and 8-hydroxy-2-deoxyguanosine (8-OH-dG) in the hippocampus and prefrontal cortex were determined. Our results showed that in this PTSD model, rats displayed the anxiety-like behavior, enhanced fear learning behavior, and hippocampus- dependent spatial memory deficit, which were accompanied by the up-regulation of NOX2, 8-OH-dG, and down-regulation of PV and GAD-67. Notably, EE reversed all these abnormalities. These results suggest that restoration of PV interneurons by inhibiting oxidative stress in the hippocampus and prefrontal cortex might represent a mechanism through which EE reverses the behavioral impairments in a rat model of PTSD induced by IFS.

Environmental Enrichment, Age, and PPARα Interact to Regulate Proliferation in Neurogenic Niches

Peroxisome proliferator-activated receptor alpha (PPARα) ligands have been shown to modulate recovery after brain insults such as ischemia and irradiation by enhancing neurogenesis. In the present study, we investigated the effect of the genetic deletion of PPARα receptors on the proliferative rate of neural precursor cells (NPC) in the adult brain. The study was performed in aged Pparα^−/− mice exposed to nutritional (treats) and environmental (games) enrichments for 20 days. We performed immunohistochemical analyses of cells containing the replicating cell DNA marker 5-bromo-2′-deoxyuridine (BrdU+) and the immature neuronal marker doublecortin (Dcx+) in the main neurogenic zones of the adult brain: subgranular zone of dentate gyrus (SGZ), subventricular zone of lateral ventricles (SVZ), and/or hypothalamus. Results indicated a reduction in the number of BrdU+ cells in the neurogenic zones analyzed as well as Dcx+ cells in the SGZ during aging (2, 6, and 18 months). Pparα deficiency alleviated the age-related reduction of NPC proliferation (BrdU+ cells) in the SVZ of the 18-months-old mice. While no genotype effect on NPC proliferation was detected in the SGZ during aging, an accentuated reduction in the number of Dcx+ cells was observed in the SGZ of the 6-months-old Pparα^−/− mice. Exposing the 18-months-old mice to nutritional and environmental enrichments reversed the Pparα^−/−-induced impairment of NPC proliferation in the neurogenic zones analyzed. The enriched environment did not modify the number of SGZ Dcx+ cells in the 18 months old Pparα^−/− mice. These results identify PPARα receptors as a potential target to counteract the naturally observed decline in adult NPC proliferation associated with aging and impoverished environments.