Identification of Correlative Shifts in Indices of Brain Cholesterol Metabolism in the C57BL6/Mecp2tm1.1Bird Mouse,a Model for Rett Syndrome

Rett syndrome (RS) is a pervasive neurodevelopmental disorder resulting from loss‐of‐function mutations in the X‐linked gene methyl‐Cpg‐binding protein 2 (MECP2). Using a well‐defined model for RS, the C57BL6/Mecp2^tm1.1Bird mouse, we have previously found a moderate but persistently lower rate of cholesterol synthesis, measured in vivo, in the brains of Mecp2^?/y mice, starting from about the third week after birth. There was no genotypic difference in the total cholesterol concentration throughout the brain at any age. This raised the question of whether the lower rate of cholesterol synthesis in the mutants was balanced by a fall in the rate at which cholesterol was converted via cholesterol 24‐hydroxylase (Cyp46A1) to 24S‐hydroxycholesterol (24S‐OHC), the principal route through which cholesterol is ordinarily removed from the brain. Here, we show that while there were no genotypic differences in the concentrations in plasma and liver of three cholesterol precursors (lanosterol, lathosterol, and desmosterol), two plant sterols (sitosterol and campesterol), and two oxysterols (27‐hydroxycholesterol [27‐OHC] and 24S‐OHC), the brains of the Mecp2 ^?/y mice had significantly lower concentrations of all three cholesterol precursors, campesterol, and both oxysterols, with the level of 24S‐OHC being ~20% less than in their Mecp2 ^+/y controls. Together, these data suggest that coordinated regulation of cholesterol synthesis and catabolism in the central nervous system is maintained in this model for RS. Furthermore, we speculate that the adaptive changes in these two pathways conceivably resulted from a shift in the permeability of the blood–brain barrier as implied by the significantly lower campesterol and 27‐OHC concentrations in the brains of the Mecp2^?/y mice.     

Binding of squalene,lanosterol, desmosterol,and cholesterol to proteins in brain and liver 105,000 g supernatant fractions: Evidence for specific binding sites

The binding of squalene, lanosterol, desmosterol, and cholesterol to proteins in 105,000 g supernatant fraction (S₁₀₅) from brain and liver of rats was investigated. The S₁₀₅ fractions from both tissues contain specific binding sites for sterols, which are sensitive to trypsin. The dissociation constants for squalene and sterol protein complexes were in the range of 10⁻⁶ M and were not appreciably different for proteins in brain and liver S₁₀₅. Competition studies revealed that both brain and liver S₁₀₅ contain one receptor protein which binds lanosterol and is specific for methyl sterols, and a second receptor which binds both desmosterol and cholesterol. Binding of 7-dehydrocholesterol reported by others must occur at a third independent site since this compound does not interfere with the binding of lanosterol, desmosterol, or cholesterol. Although binding of squalene to proteins in brain and liver S₁₀₅ does occur, we were unable to show the specificity of squalene binding. The concentration of desmosterol and cholesterol binding sites, which ranged from 6 to 10 nmol/mg protein, was 3- to 5-fold higher than the concentration of squalene and lanosterol binding sites (1.6–2.3 nmol/mg protein). The brain S₁₀₅ from suckling rats contained fewer binding sites for desmosterol and cholesterol than the brain S₁₀₅ from weaned rats. However, the concentration of lanosterol binding sites in brain S₁₀₅ did not show an age-dependent change. The receptor proteins in brain and liver appear to be identical.     

Effects of ketoconazole on cholesterol synthesis and precursor concentrations in the rat liver

Ketoconazole, an antimycotic agent, given to rats for a week as 0.05% food addition had no effect on the hepatic concentrations of free and esterified cholesterol or on the activity of acyl coenzyme A: cholesterol-acyltransferase (ACAT). However, the levels of free methylated cholesterol precursors, especially lanosterols, less markedly Δ^8,24 and Δ⁸-dimethyl sterols and monomethyl sterols, were increased after only one day's treatment, while those of esterified methyl sterols were increased inconsistently, and those of free and esterified Δ⁸-lathosterol, lathosterol and desmosterol were not affected at all. Cholestyramine treatment had no significant effect on ACAT in spite of a decrease in the hepatic content of esterified cholesterol and caused a marked increase in the free cholesterol precursor levels, especially in those of lathosterols. Cholestyramine given to ketoconazole-treated rats increased the hepatic levels of Δ⁸ and Δ⁷-lathosterols but not desmosterol or methylated cholesterol precursors. Ketoconazole increased and cholestyramine markedly decreased plantssterols, sitosterol and campesterol in the liver. In serum, the contents of both lanosterols and lathosterol were increased but that of cholesterol tended to be decreased by ketoconazole (−19%). The results indicate that ketoconazole impairs demethylation processes at C-14 and to some extent at C-4 in the rat liver, resulting in lowered serum cholesterol level.     

Simultaneous quantification of serum phytosterols and cholesterol precursors using a simple gas chromatographic method

Determination of the main phytosterols (Ps, β‐sitosterol and campesterol) and cholesterol precursors (desmosterol and lathosterol) in human serum using a simple GC‐FID method has been validated. Direct saponification, without lipid extraction, sterols extraction, and further derivatization was applied to samples prior to GC analysis. To evaluate the method, a pool of serum samples from eight healthy women was used. Good linearity (r>0.99) was found in the assay range: β‐sitosterol (0.99–17.82 µg/mL), campesterol (0.14–10.8 µg/mL), desmosterol (0.17–2.6 µg/mL), and lathosterol (0.6–5.97 µg/mL). Limits of detection (ng/mL) were: 86 (β‐sitosterol), 42 (campesterol), 4 (desmosterol), and 44 (lathosterol). Accuracy, estimated by recovery assays (%), were: 113 (β‐sitosterol), 114 (campesterol), 111 (desmosterol), and 102 (lathosterol). Within and between precision values (%), expressed as the relative SD (RSD), were: 2.6 and 8.1 (β‐sitosterol), 1.6 and 7.2 (campesterol), 2.1 and 7.9 (desmosterol), and 4.1 and 5.8 (lathosterol), respectively. The developed methodology allowed fast (1‐day analysis) and reliable quantification of sterols in serum, required a small volume of sample and reduced use of solvents. It therefore could be used in clinical assays for the determination of serum sterols, as in evaluating the pharmacological response to lipid‐lowering agents, and in assessing biological responses to Ps‐enriched diets. Practical applications : This methodology allows fast and reliable quantification of sterols in serum, requiring a small volume of sample and reduced use of solvents. It can be used as a routine method for the quantification of phytosterols and cholesterol precursors in clinical assays, and it is also suitable for monitoring biological responses to health‐promoting phytosterol‐enriched diets.     

Deuterium uptake and plasma cholesterol precursor levels correspond as methods for measurement of endogenous cholesterol synthesis in hypercholesterolemic women

To assess the validity of two techniques used to measure human cholesterol synthesis, the rate of uptake of deuterium (D) into plasma free cholesterol (FC), and plasma cholesterol precursor (squalene, lanosterol, desmosterol and lathosterol) levels were compared in 14 women [65–71 yr with low density lipoprotein-cholesterol (LDL-C)≥3.36 mmol·l ⁻¹]. Subjects consumed each of six diets for 5-wk periods according to a randomized crossover design. The experimental diets included a baseline diet (39% energy as fat, 164 mg chol·4.2 MJ⁻¹) and five reduced-fat diets (30% of energy as fat), where two-thirds of the fat was either soybean oil; squeeze, tub or stick margarines; or butter. Fractional and absolute synthesis rates (FSR and ASR) of FC were determined using the deuterium incorporation (DI) method, while cholesterol precursor levels were measured using gas-liquid chromatography. Data were pooled across diets for each variable and correlation coefficients were calculated to determine if associations were present. There was good agreement among levels of the various cholesterol precursors. In addition, FSR in pools/d (p·d⁻¹) and ASR in grams/d (g·d⁻¹) were strongly associated with lathosterol (r=0.72 and 0.71, P=0.0001), desmosterol (r=0.75 and 0.75, P=0.0001), lanosterol (r=0.67 and 0.67), and squalene (r=0.69 and 0.68) when levels of the precursors were expressed as μmol·mmol⁻¹C. Significant but lower correlations were observed between the D uptake and plasma cholesterol precursor levels when the latter were expressed in absolute amounts (μmol·L⁻¹). The wide range of fatty acid profiles of the experimental diets did not influence the degree of association between methods. In conclusion, the DI method and levels of some cholesterol precursors correspond as methods for shortterm measurement of cholesterol synthesis.     

Age-related changes in the metabolism of cholesterol in rat liver microsomes

The effects of aging on the hepatic metabolism of cholesterol were studied in 1-, 6- and 24-month-old male Sprague-Dawley rats. Microsomal 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activity, which regulates cholesterol biosynthesis, decreased from 835±144 (SEM) pmol/min/mg protein in the youngest group to 219±34 and 205±53 pmol/min/mg protein (p<0.001) in the 6- and 24-month-old groups, respectively. Cholesterol 7α-hydroxylase activity, which governs bile acid synthesis, was gradually reduced from 70±14 pmol/min/mg protein in the 1-month-old group to 32±7 and 16±3 pmol/min/mg protein (p<0.05) in the 6- and 24-month-old groups, respectively. Acyl coenzyme A:cholesterol acyltransferase activity, which catalyzes the esterification of cholesterol, averaged 431±47 and 452 ±48 pmol/min/mg protein in the 1- and 6-month-old groups, respectively, and was increased to 585±55 pmol/min/mg protein (p<0.05) in the 24-month-old group. The level of total cholesterol showed an age-related increase from 1.56±0.16 mg/g liver in the 1-month-old group to 1.70±0.15 and 2.20±0.19 mg/g liver (p<0.05) in the 6- and 24-month-old groups, respectively. The increase was mainly caused by an accumulation of esterified cholesterol. We conclude that a marked decrease in HMG-CoA reductase occurs between 1 and 6 months of age; thereafter the enzyme activity stays unchanged. The activity of cholesterol 7α-hydroxylase decreases progressively and drastically with age, whereas the capacity for esterifying cholesterol increases slightly. We speculate that the reduced conversion of cholesterol to bile acids may be one explanation of the age-related increase of plasma cholesterol seen in rats.     

Sterol biosynthesis in the oyster,Crassostrea virginica

Sterol biosynthesis in the oyster,Crassostrea virginica, was examined by injection of [2-¹⁴C]acetate and [2,3-³H] lanosterol. The oyster incorporated [2-¹⁴C] acetate into squalene 4,4′-dimethylsterols, 4-monomethylsterols, cholesterol, desmosterol, isofucosterol, and 24-methylenecholesterol, and also converted [2-³H] lanosterol to cholesterol. Therefore, the oyster was concluded to synthesize cholesterol, desmosterol, isofucosterol, and 24-methylenecholesterol from acetate via squalene, probably using the lanosterol pathway.     

Reactivity of key metabolic sterols in standard colorimetric assays for cholesterol

The reaction of lanosterol, desmosterol and 7-dehydrocholesterol, key intermediates in cholesterol biosynthesis, were-compared with cholesterol in 3 standard colorimetric assays for cholesterol based on formation of chomogens with acetic anhydride, ferric chloride and ferrous sulfate. Marked differences in the reaction of the sterols in the different assays were due both to formation of chomogens with qualitatively similar spectral patterns but with greatly different extinctions and to formation of chromogens with clearly different absorption maxima. For example, in all assays, cholesterol and desmosterol formed chromogens with very similar absorption spectra but with varying extinctions, whereas the lanosterol chromogen in all assays was different from cholesterol's in both absorption maxima and in extinctions. The findings show that attempts to measure tissue sterol levels by colorimetric methods can result in great errors when cholesterol is not the sole sterol. Also, the unique spectral properties of the lanosterol chromogen formed in the Liebermann-Burchard reaction (a sharp absorption peak at 450 nm) suggests the possible use of this method as a qualitative test for lanosterol.     

Age-dependent accumulation of phosphatidylcholine hydroperoxide in the brain and liver of the rat

Age-related changes in phosphatidylcholine hydroperoxide (PCOOH) content as an index for oxidative membrane lipid damage were determined by high-performance liquid chromatography using chemiluminescence detection. Brain and liver PCOOH content increased significantly in male and female rats with age. The brain PCOOH content of male 18-month-old rats was 4.4 times that of 1-month-old rats, and that of female 18-month-old rats was 3.5 times that of 1-month-old females. The liver PCOOH content of the male 18-month-old rats was 9.3 times that of the 1-month-old; and of the famale 18-month-old rats was 4.7 times that of the 1-month-old. PCOOH levels in heart and lung did not show age dependency. In both brain and liver (but not in heart and lung), the phosphatidylcholine content significantly decreased upon aging. The results indicate that oxidative deterioration, such as phospholipid hydroperoxidation, is prevalent in the membrane lipids of brain and liver of the rat due to aging.     

Noncholesterol Sterols as Surrogate Markers in Patients with Severe Alcoholic Hepatitis

Severe alcoholic hepatitis (AH) is a life‐threatening condition lacking good serologic markers to tailor treatment and predict recovery. We examined the cholesterol metabolism in severe AH to explore prognostic markers and evaluate the profile of cholesterol precursors, cholestanol and phytosterols, in this context. We assessed serum cholesterol, cholesterol precursors, cholestanol, phytosterols, and biochemical markers in 24 patients with severe AH treated with prednisolone and randomized to ciprofloxacin in the ratio 1:1. Response to prednisolone was assessed with the Lille model. Evaluations were made between responders and nonresponders to corticosteroid treatment and during follow‐up for 180 days. The findings were compared with those from patients with primary sclerosing cholangitis (PSC) (n = 156) and healthy individuals (n = 124). Responders to prednisolone had ~56–60% higher (p‐value 0.032–0.044) serum ratios to cholesterol of phytosterols, while the lathosterol/campesterol ratio was ~76% (p = 0.031) lower compared to nonresponders. Stigmasterol/cholesterol predicted response to corticosteroid therapy. Surrogate markers of cholesterol synthesis (lathosterol and desmosterol) inversely reflected those of absorption (cholestanol and phytosterols) in PSC and controls (r‐range ?0.247 to ?0.559, p < 0.01 for all), contrary to AH patients, among whom this reciprocal regulation was partially recovered on day 90 (lathosterol: r‐range ?0.733 to ?0.952, p < 0.05 for all). AH patients had ~26% lower lathosterol/cholesterol, but 1.13–3.87‐fold higher cholestanol/cholesterol and sitosterol/cholesterol compared to control groups (p < 0.05 for all). Median ferritin concentration at baseline was ~37% lower (p = 0.011) among the responders. Cholesterol precursors and phytosterols have a disease‐specific profile in AH. Phytosterols and ferritin may serve as surrogate markers for short‐term response.     

Fatty acid and sterol specificity of cholesterol esterifying enzyme in developing rat brain

The properties and fatty acid and sterol specificity of cholesterol-esterifying enzyme (EC 3.1.1.13) in rat brain were studied. The enzyme utilized free fatty acid for esterification, and activity was maximal at pH 5.6. Exogenous ATP and CoA did not stimulate the incorporation of free fatty acids into sterol esters. Substrates dispersed in Tween 20 or Triton X-100 were just as effective as the substrates dissolved in acetone solution, while dispersion in propylene glycol or sodium taurocholate was not as effective. Snake venom phospholipase A₂ (EC 3.1.1.4) increased the esterification of cholesterol in the absence of added fatty acid. The fatty acid specificity data indicated that oleic and palmitic acids were the preferred fatty acids. Little or no esterification occurred in the presence of long chain fatty acids (C₂₀–C₂₄). Esterification of cholesterol with palmitate or stearate was not affected by the presence of oleic acid in the mixture. Thus, the nonrequirement of the brain-esterifying enzyme for a bile acid or for an amphiphile such as an unsaturated fatty acid suggests that micellar solubilization of the substrate is not essential for activity. Although the brain enzyme catalyzed the esterification of desmosterol, cholesterol was the preferred substrate. Neither lanosterol (C₂₉ sterols) nor Δ7-dehydrocholesterol was esterified to any significant extent. The presence of low concentrations of desmosterol increased cholesterol esterification slightly, while there was a concentration-dependent inhibition of demosterol esterification by cholesterol. These data on fatty acid and sterol specificity of the esterifying enzyme correlate well with the composition of sterol esters present in developing rat brain.     

Agents affecting lipid metabolism. XXVI. Specificity of some inhibitors of the late stages of cholesterol biosynthesis

The capacity of 22,25-DAC, AY-9944 and triparanol to inhibit cholesterol biosynthesis from three precursors, mevalonate, 7-dehydrocholesterol and desmosterol, has been studied in rat liver homogenates.Evidence is presented that, in vitro, 22,25-DAC, a potent inhibitor of the sterol Delta(24)-reductase, also inhibits the 7-dehydrocholesterol-Delta(7)-reductase system.     

Desmosterol in developing rat brain

The brain of the young rat contains appreciable amounts of desmosterol (24-dehydrocholesterol). The peak desmosterol concentration is seen during the first week of life and only traces of this sterol are found at 21 days. The spinal cord also contains some desmosterol. Rat brain desmosterol is distributed in the white matter, gray matter and cerebellum and occurs in the same proportion to cholesterol in each of these brain fractions. Rat brain contains a small amount of sterol ester but no appreciable amounts of desmosterol are present in this fraction. Studies carried out in intact animals injected either intraperitoneally or intracerebrally with mevalonic acid-2-¹⁴C or glucose-U-¹⁴C indicate the biosynthetic origin or brain desmosterol. Rat brain slices (1–20 day old) incubated in suitably fortified medium convert sodium acetate-2-¹⁴C and glucose-U-¹⁴C to desmosterol, whereas brain slices from adult rats yielded no radioactive desmosterol under similar conditions. When labeled desmosterol was incubated with young rat brain slices, it was converted to cholesterol. When pregnant rats were treated with triparanol (20 mg/kg/day) during the course of their pregnancy, they either resorbed the fetuses or gave birth to small, stillborn litters. The brains of the progeny of triparanol treated mothers contained large amounts of desmosterol as well as another sterol which may be Δ^7,24-cholestadiene-3β-ol.     

Steroids in bovine muscle and adipose tissue

Thin layer and gas liquid chromatography, (GLC) were employed as complementary techniques to investigate naturally-occurring steroids in the unsaponifiable matter of bovine muscle and adipose tissue. Three GLC liquid phases, differing in selective partition properties, were used to effectively identify unknown steroids. The results indicate that cholesterol and minor amounts of desmosterol, Δ⁷-cholestenol, lanosterol, dihydrolanosterol, dehydromethostenol, Δ⁸-methostenol, Δ⁷-methostenol, cholestanol and possibly ergosterol were present in the bovine tissues. The minor steroids, with the exception of cholestanol and ergosterol, are steroid precursors in cholesterol biosynthesis. Common hormonal steroids were not found in the unsaponifiables of the tissues.     

Comparative studies of metabolism of 4-desmethyl, 4-monomethyl and 4,4-dimethyl sterols inManduca sexta

To investigate the metabolism and possible deleterious effects of 4-methyl and 4,4-dimethyl steroids inManduca sexta, the 4,4-dimethyl sterols lanosterol and cycloartenol, the 4-methyl sterol obtusifoliol and the 4,4-dimethyl pentacyclic triterpenoid α-amyrin were fed in an artificial agar-based diet at various concentrations. Utilization and metabolism of these four compounds were compared with sitosterol, stigmasterol, brassicasterol, ergosterol and 24-methylenecholesterol, 24-alkyl sterols that are readily dealkylated and converted to cholesterol inManduca and in most phytophagous insects. None of the 4-methylated compounds significantly inhibited development except at very high dietary concentrations. The Δ²⁴-bonds of lanosterol and cycloartenol were effectively reduced by theManduca Δ²⁴-sterol reductase enzyme, as is the Δ²⁴-bond of desmosterol which, in most phytophagous insects, is an intermediate in the conversion of sitosterol, stigmasterol and other C₂₈ and C₂₉ phytosterols to cholesterol. On the other hand, the 24-methylene substituent of obtusifoliol was not dealkylated. Each of the 4-desmethyl C₂₈ and C₂₉ sterols was readily converted to cholesterol, and a significant amount of 7-dehydro-cholesterol was derived from ergosterol metabolism. The reason for the differences in substrate specificity of these sterols is not clear, but the information may be useful in the development of new, specific, mechanism-based inhibitors of sterol metabolism.     

Impact of Melatonin Deficit on Emotional Status and Oxidative Stress-Induced Changes in Sphingomyelin and Cholesterol Level in Young Adult,Mature, and Aged Rats

The pineal gland regulates the aging process via the hormone melatonin. The present report aims to evaluate the effect of pinealectomy (pin) on behavioral and oxidative stress-induced alterations in cholesterol and sphingomyelin (SM) levels in young adult, mature and aging rats. Sham and pin rats aged 3, 14 and 18 months were tested in behavioral tests for motor activity, anxiety, and depression. The ELISA test explored oxidative stress parameters and SM in the hippocampus, while total cholesterol was measured in serum via a commercial autoanalyzer. Mature and aged sham rats showed low motor activity and increased anxiety compared to the youngest rats. Pinealectomy affected emotional responses, induced depressive-like behavior, and elevated cholesterol levels in the youngest rats. However, removal of the pineal gland enhanced oxidative stress by diminishing antioxidant capacity and increasing the MDA level, and decreased SM level in the hippocampus of 14-month-old rats. Our findings suggest that young adult rats are vulnerable to emotional disturbance and changes in cholesterol levels resulting from melatonin deficiency. In contrast, mature rats with pinealectomy are exposed to an oxidative stress-induced decrease in SM levels in the hippocampus.     

Membrane phospholipids and sterols in microfiltered milk fat globules

Native milk fat globules of various mean diameters, ranging from d₄₃ = 2.3 µm to 8.0 µm, were obtained using microfiltration of raw whole milk. After milk fat globule washing, the milk fat globule membrane (MFGM) was separated by manual churning. After total lipid extraction and separation of polar lipids, their phospholipid (PL) and sterol composition was measured using thin‐layer chromatography, methyl ester analyses by gas chromatography, and gas chromatography coupled to mass spectrometry. The main PL species were phosphatidylethanolamine, phosphatidylcholine and sphingomyelin. The respective fatty acid composition of each PL species was measured. Many different minor bioactive sterols were detected in the MFGM, e.g. lanosterol, lathosterol, desmosterol, stigmasterol and β‐sitosterol. No significant differences in the PL and sterol profile were found between MFGM extracted from small and large milk fat globule fractions.     

Biosynthesis of membrane cholesterol during peripheral nerve development,degeneration and regeneration

Biosynthesis of peripheral nerve cholesterol was investigated by the in vivo and in vitro incorporation of [1-¹⁴C]-acetate into sciatic endoneurium of normal rats during development, degeneration and regeneration. Labeled sterols were rapidly formed (<10 min) within the endoneurial portion of sciatic nerve after [1-¹⁴C]acetate administration by intraneural injection. The majority of labeled sterols were initially found in lanosterol and desmosterol. After six hr, the¹⁴C-labeling in both precursors was decreased to minimum, whereas cholesterol became the major labeled product of sterol. As myelination proceeded, the incorporation of [1-¹⁴C]acetate into endoneurial cholesterol decreased rapidly and reached a minimum after six no. In mature adult nerve, an increased proportion of biosynthesis of lanosterol and desmosterol also was demonstrated. The in vitro incorporation of [1-¹⁴C]acetate into cholesterol was inhibited during Wallerian degeneration. Instead, cholesteryl esters were labeled as the major sterol product. Such inhibition, however, was not observed in the adult Trembler nerve (Brain Res. 325, 21–27, 1985), which is presumed to be due to a primary metabolic disorder of Schwann cells. The cholesterol biosynthesis was gradually resumed in degenerated nerve by either regeneration of crush-injured nerve or reattachment of the transected nerve. These results suggest that cholesterol biosynthesis in peripheral nerve relies on the axon to provide necessary substrates. De novo synthesis appears to be one of the major sources of endoneurial cholesterol that forms and maintains peripheral nerve myelin. A preliminary report of this work was presented at the 17th Annual Meeting of the American Society for Neurochemistry held in Montreal, Quebec, Canada, on March 20, 1985. Part of this work was conducted while the author was associated with Mayo Clinic.     

Chronic pulmonary exposure to traffic-related fine particulate matter causes brain impairment in adult rats

Background

Effects of air pollution on neurotoxicity and behavioral alterations have been reported. The objective of this study was to investigate the pathophysiology caused by particulate matter (PM) in the brain. We examined the effects of traffic-related particulate matter with an aerodynamic diameter of <?1 μm (PM₁), high-efficiency particulate air (HEPA)-filtered air, and clean air on the brain structure, behavioral changes, brainwaves, and bioreactivity of the brain (cortex, cerebellum, and hippocampus), olfactory bulb, and serum after 3 and 6 months of whole-body exposure in 6-month-old Sprague Dawley rats.

Results

The rats were exposed to 16.3?±?8.2 (4.7~?68.8) μg/m³ of PM₁ during the study period. An MRI analysis showed that whole-brain and hippocampal volumes increased with 3 and 6 months of PM₁ exposure. A short-term memory deficiency occurred with 3 months of exposure to PM₁ as determined by a novel object recognition (NOR) task, but there were no significant changes in motor functions. There were no changes in frequency bands or multiscale entropy of brainwaves. Exposure to 3 months of PM₁ increased 8-isoporstance in the cortex, cerebellum, and hippocampus as well as hippocampal inflammation (interleukin (IL)-6), but not in the olfactory bulb. Systemic CCL11 (at 3 and 6 months) and IL-4 (at 6 months) increased after PM₁ exposure. Light chain 3 (LC3) expression increased in the hippocampus after 6 months of exposure. Spongiosis and neuronal shrinkage were observed in the cortex, cerebellum, and hippocampus (neuronal shrinkage) after exposure to air pollution. Additionally, microabscesses were observed in the cortex after 6 months of PM₁ exposure.

Conclusions

Our study first observed cerebral edema and brain impairment in adult rats after chronic exposure to traffic-related air pollution.