Transport of Phosphatidylserine from Microsomes to the Inner Mitochondrial Membrane in Brain Tissue

Abstract: Phosphatidylserine was labeled by incubating rat brain homogenates with [3-¹⁴C]serine in the presence of Ca²⁺ (base-exchange conditions). Some labeled phosphati-dylethanolamine also forms, in spite of the inhibition of Ca²⁺ on phosphatidylserine decarboxylase. Phosphatidylserine labeling and decarboxylation also occur on incubating a mixture of purified mitochondria and microsomes, suggesting that no soluble factors are necessary for the synthesis and the decarboxylation of phosphatidylserine. Ca²⁺ favors the transfer of phosphatidylserine from microsomes (where it forms) to mitochondria (where it is decarboxylated). The specific radioactivity of the phosphatidylserine transferred to mitochondria is higher than that of microsomal phosphatidylserine. This finding supports the hypothesis that the lipid is compartmentalized in microsomes and that radioactive, newly synthesized phosphatidylserine is much better exported than the bulk of microsomal phospholipid.     

Effect of Desipramine on a Glycoprotein Sialyltransferase Activity in C6 Cultured Glioma Cells

The tricyclic antidepressant desipramine, when added to culture medium, gave rise in C6 rat glioma cells to a decrease of the activity of the enzyme asialofetuin sialyltransferase. The inhibition was dose and time dependent and was observed in both multiplying cells and cells blocked with 2 mM thymidine or depletion of amino acids. This inhibition was rather specific to the sialyltransferase, as under the conditions where this enzyme was inhibited up to 70%, other enzymes such as dolichol phosphate mannose synthetase, glutamine synthetase, and glycerol phosphate dehydrogenase remained unaffected. This inhibition was not reversed after removal of desipramine from the medium and was not observed by direct addition of desipramine to the sialyltransferase incubation assay. Under the same conditions, W-7 [N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide], which is known to be a potent calmodulin antagonist and an inhibitor of calmodulin-dependent kinases, gave the same concentration-dependent inhibition profile of sialyltransferase as desipramine, whereas H-7 [1-(5-isoquinolinylsulfonyl)-2-methylpiperazine], which is an inhibitor of protein kinase C and cyclic nucleotide-dependent kinases, had no effect. So, it is suggested that desipramine inhibits the sialyltransferase activity in C6 glioma cells through a calmodulin-dependent system.     

Decrease of Brain Phospholipid Synthesis in Free-Moving n-3 Fatty Acid Deficient Rats

Abstract: The autoradiographic method with [¹⁴C]-docosahexaenoic acid ([¹⁴C]22:6 n-3) was used to determine whether a diet deficient in n-3 fatty acids, inducing a decrease in 22:6 n-3 circulating level, was associated with changes in local rates of phospholipid synthesis in the rat brain. As compared with rats fed a normal diet (peanut plus rapeseed oil), a n-3 fatty acid deficiency [peanut oil group (P group)] induced a generalized decrease (?35 to ?76%) of 22:6 n-3 incorporation rates into phospholipids in all the regions examined. This effect was confirmed by using [³H]22:6 n-3 infusion by biochemical analysis and quantifications corrected for the contribution of docosahexaenoate derived from lipid store recycling to the unesterified pool, taken as the precursor pool for phospholipid synthesis in the whole brain. In normal or n-3 fatty acid-deficient rats, the values of the brain-to-plasma 22:6 n-3 specific activity ratio (Ψ) were similar (0.03), indicating that a considerable endogenous source of 22:6 n-3 (97%), likely derived from phospholipid degradation, dilutes the specific activity of the tracer coming from plasma. Using the specific activity of 22:6 n-3 in plasma instead of brain would thus lead to a gross underestimation of the rate of phospholipid synthesis. The results also demonstrate that the pattern of ¹⁴C or ³H distribution in brain lipids was not modified by the n-3 fatty acid-deficient diet. The major lipids labeled were phospholipids, particularly phosphatidylethanolamine. Nevertheless, the unesterified 22:6 n-3 concentrations in plasma and brain were significantly reduced (eight- and threefold, respectively) in the P group. In addition, the proportion of 22:6 n-3 in the brain total lipid fraction, total phospholipids, and phosphatidylcholine, -ethanolamine, and -serine was significantly decreased in n-3 fatty acid-deficient rats. This was partially compensated for by an increase in the 22:5 n-6 level. These results are discussed in relation to the limitation of 22:6 n-3 use to quantify, by the quantitative autoradiographic method, changes in local rates of phospholipid synthesis in rat brain.     

Effect of In Vivo Modulation of Membrane Docosahexaenoic Acid Levels on the Dopamine-Dependent Adenylate Cyclase Activity in the Rat Retina

Abstract: We have studied the effect of a dietary deprivation of n-3 fatty acids on the activity of the dopamine (DA)-de-pendent adenylate cyclase in the rat retina. Experiments were conducted in 6-month-old rats raised on semipurified diets containing either safflower oil (n-3 deficient diet) or soybean oil (control diet). The levels of docosahexaenoic acid [22:6 (n-3)] in retinal phospholipids were significantly decreased in n-3 deficient rats (35–42% of control levels). This was compensated by a rise in 22:5 (n-6), the total content of poly-unsaturated fatty acids (PUFA) remaining approximately constant. Adenylate cyclase activity was measured in retinal membrane preparations from dark-adapted or light-exposed rats. The enzyme activity was stimulated by DA and SKF 38393 in a light-dependent fashion. The activation was lower in rats exposed to light than in dark-adapted animals, suggesting a down-regulation of the DI DA receptors by light. The activation by guanine nucleotides and forskolin was also decreased in light-exposed rats. There was no significant effect of the dietary regimen on the various adenylate cyclase activities and their response to light. Furthermore, the guanine nucleotide- and DA-dependent adenylate cyclase activities of retinal membranes were found to be relatively resistant to changes in membrane fluidity induced in vitro by benzyl alcohol. The results indicate that in the absence of changes in total PUFA content, a decreased ratio of n-3 to n-6 fatty acids in membrane phospholipids does not significantly affect the properties of adenylate cyclase in the rat retina.     

n-3 Fatty Acid Deficiency Increases Brain Protein Synthesis in the Free-Moving Adult Rat

Abstract: The autoradiographic method with l -[³⁵S]methionine was used to determine the effects of an n-3 fatty acid deficiency on brain protein synthesis. Brain protein synthesis was significantly increased (from 50 to 150%) in 45 of the 52 brain structures studied in n-3 fatty acid-deficient rats as compared with control animals. Biochemical analysis confirmed the increase in overall rate of protein synthesis in brain as a whole.     

Stimulation of Phosphoinositide Hydrolysis by Serotonin in C6 Glioma Cells

5-Hydroxytryptamine (serotonin or 5-HT) stimulated the incorporation of 32Pi into phosphatidylinositol (PI) but not into polyphosphoinositides in C6 glioma cells with an EC50 of 1.2 X 10(-7) M. The phosphoinositide response was blocked by the 5-HT2 antagonists ketanserin and spiperone but inhibited only partly by methysergide and mianserin. Atropine, prazosin, and yohimbine did not block the response, whereas fluphenazine and haloperidol did so partially but also inhibited basal incorporation by approximately 30%. The 5-HT1A agonist 8-hydroxy-2(di-n-propylamino)tetralin did not cause stimulation. Incubation with 5-HT (1 microM) for 1 h increased the incorporation of [2-3H]myoinositol into all phosphoinositides but not into inositol phosphates (IPs). Li+ alone at 10 mM increased labeling in inositol bisphosphate (IP2) and trisphosphate (IP3), whereas labeling in IP and phosphoinositides remained unaltered. Addition of 5-HT had no effect on this increase. Mn2+ at 1 mM enhanced labeling in PI, PI-4-phosphate, lyso-PI, glycerophosphoinositol, and IP, but the presence of 5-HT again did not cause further stimulation. 5-HT also stimulated the release of IPs in cells prelabeled with [2-3H]myo-inositol, incubated with LiCl (10 mM) and inositol (10 mM), and then exposed to 5-HT (1 microM). Radioactivity in IP2 and IP3 was very low, was stimulated approximately 50% as early as 30 s, and remained elevated for at least 20 min. Radioactivity in IP was at least 10 times as high as in IP3 but was increased only from 3 min on with a peak at 20 min, when the elevation was approximately 40 times that in IP3.(ABSTRACT TRUNCATED AT 250 WORDS)     

Direct and Continuous Electrochemical Measurement of Noradrenaline-Induced Nitric Oxide Production in C6 Glioma Cells

1. Nitric oxide (NO) production in C6 glioma cells was directly monitored in real time by electrochemical detection with a NO-specific biosensor.2. We present here the first direct evidence that noradrenaline elicits long-lasting NO production in C6 cells pretreated with lipopolysaccharide and interferon-, an effect blocked by N ^G-monomethyl-L-arginine, a NO synthase inhibitor.3. This direct electrochemical measurement of glia-derived NO should facilitate our understanding of the kinetics of glial signaling in glia-glia and glia-neuron networks in the brain.     

A Novel Inhibitory Role for Glucocorticoids in the Secretion of Angiotensinogen by C6 Glioma Cells

Abstract: Astrocytes have been identified as the primary source of brain angiotensinogen (Ao), but the regulation of the secretion of this protein from astrocytes is poorly defined. In this study, the rat C6 glioma cell line was used as an astrocyte model to investigate the regulation of Ao secretion. C6 cultures secreted Ao at a rate of 4.05 ± 1.52 (mean ± SD) ng of Ao/10⁶ cells/24 h as determined by a direct radioimmunoassay. This rate was not significantly altered by the hormones thyroxine, estradiol, angiotensin II, growth hormone, and prostaglandins or by increased levels of intracellular cyclic AMP. Treatment with the synthetic glucocorticoid dexamethasone (DEX; 10–⁶M) reduced the rate of Ao secretion to 1.82 ± 0.28 ng of Ao/10⁸ cells/24 h. By comparison, the basal secretion rate for rat H4 hepatoma cells was 142.4 ± 10.0 ng of Ao/10⁶ cells/24 h, and this increased fourfold (572.4 ± 173.1 ng/10⁶ cells/ 24 h) in the presence of 10–⁶M DEX. Both these inhibitory (C6) and stimulatory (H4) actions of DEX were dose related. The inhibition observed in C6 cells was mimicked by RU28362, a pure glucocorticoid agonist, and reversed by the antagonist RU486, demonstrating that DEX was functioning as a true glucocorticoid. The action of DEX was also antagonized by the cyclic AMP analogue N⁶,2′-O- dibutyryladenosine 3′:5′-cyclic monophosphate (dBcAMP) (control, DEX, and DEX + dBcAMP, 3.58 ± 0.73, 1.69 ± 0.82, and 4.93 ± 1.88 ng of Ao/10⁶ cells/24 h, respectively, and by the β-adrenergic agonist isoprenaline, which stimulates cyclic AMP production. It was concluded that glucocorticoids inhibit Ao secretion, possibly by interacting with a cyclic AMP-responsive pathway. The inhibition of Ao production by DEX is a novel observation supporting the view that regulation of Ao is tissue specific.     

Differential Regulation of Intracellular Signaling Systems by Sodium Fluoride in Rat Glioma Cells

Abstract: We investigated the rapid and slow effects of NaF on intracellular signaling systems such as Ca²⁺ homeostasis and cyclic GMP (cGMP) generation in rat glioma C6 cells, using the Ca²⁺-sensitive dye fura-2 and cGMP enzyme immunoassay. We found that the following: (a) NaF enhanced cGMP generation in a concentration-dependent manner. This enhancement was abolished by pretreatment with 100 µ M BAPTA tetraacetoxymethyl ester or in the presence of W-7 in a concentration-dependent manner. N ^G-Monomethyl- l -arginine (NMMA), a competitive inhibitor of nitric oxide synthase (NOS), also inhibited the NaF-induced generation of cGMP. These results suggest that NaF-induced cGMP generation occurs via a calcium/calmodulin- and NOS-dependent pathway. (b) The basal intracellular Ca²⁺ concentration ([Ca²⁺]_i) was transiently greater at 1 and 3 h after pretreatment with NaF. W-7 and W-13 antagonized the increase in [Ca²⁺]_i, whereas NMMA had little effect. This suggests that the NaF-induced change in basal [Ca²⁺]_i was mediated by a calmodulin-dependent pathway but was independent of a NOS-sensitive pathway. (c) The serotonin (5-HT)-induced intracellular mobilization of Ca²⁺ was reduced by pretreating the cells with NaF. The reduction in Ca²⁺ mobilization was antagonized by genistein, a tyrosine kinase inhibitor. W-7, W-5, and H-8 had no effect. Results suggest that NaF differentially regulates the cGMP generation, basal [Ca²⁺]_i, and 5-HT_2A receptor function in C6 glioma cells.     

Effect of the Tricyclic Antidepressant Desipramine on β-Adrenergic Receptors in Cultured Rat Glioma C6 Cells

Rat glioma C6 cells, cultured in the presence of the tricyclic antidepressant desipramine, lost a significant number of beta-adrenergic receptors in a time- and dose-dependent manner. A similar loss was observed whether binding was determined on intact cells with the hydrophilic beta-adrenergic antagonist (+/-)-[3H]4-(3-tert-butylamino-2-hydroxypropoxyl)benzimidazole-2-o n HCl ([3H]CGP-12177) or on cell lysates with the more hydrophobic antagonists [125I]iodocyanopindolol or [3H]dihydroalprenolol. When stimulated with the agonist isoproterenol, desipramine-treated cells accumulated less cyclic AMP than control cells. The affinity of the beta-adrenergic receptors for either antagonist or agonist was unchanged after desipramine treatment. Desipramine interacted only weakly with the receptors and competed for [125I]iodocyanopindolol binding with a Ki of 30 microM. The presence in the culture medium of alprenolol or propranolol, potent beta-adrenergic antagonists, however, did not prevent the reduction in receptors by desipramine. Desipramine also caused a loss of beta-adrenergic receptors from cells maintained in serum-free medium and the cells themselves did not contain or secrete endogenous catecholamines. Although desipramine is a potent inhibitor of catecholamine uptake, it appears unlikely that the observed loss of beta-adrenergic receptors in rat glioma C6 cells exposed to the drug is due to an increase in extracellular catecholamine levels or to a direct interaction with the receptors.     

自噬在声动力疗法抑制C6胶质瘤细胞增殖中的作用

目的:探讨自噬在血卟啉单甲醚(Hematoporphyrin monomethyl ether,HMME)介导的声动力疗法(Sonodynamic therapy,SDT)抑制C6胶质瘤细胞增殖中的作用。方法:选取对数期生长的C6胶质瘤细胞并随机分为四组:对照组(未予处理)、超声组(单独超声照射)、HMME组(单独加入HMME)、SDT组(超声照射+HMME)。透射电镜观察SDT处理的C6胶质瘤细胞中自噬体数量的改变。应用qRT-PCR和免疫印迹分析SDT处理对C6胶质瘤细胞中的LC3、Beclin1、Bcl-2 m RNA及蛋白表达水平的影响。MTT检测C6胶质瘤细胞的活力变化。结果:透射电子显微镜显示SDT组自噬体数量较对照组明显增多。SDT组C6胶质瘤细胞中微管相关蛋白1轻链3 (Microtubule associated protein 1 light chain 3, LC3)、Beclin1 m RNA和蛋白水平高于对照组,B细胞淋巴瘤-2(B cell lymphoma-2, Bcl-2) m RNA和蛋白水平低于对照组。与对照组相比,SDT组C6胶质瘤细胞存活率从0 h至6 h逐渐下降,从12 h至72 h逐渐升高。3-甲基腺嘌呤(3-Methyladenine,3-MA)+SDT、氯喹(Chloroquine,CQ)+SDT处理后C6胶质瘤细胞存活率较SDT组明显降低。结论:SDT可能通过诱导自噬抑制C6胶质瘤细胞增殖。     

Reduction in β-Adrenoceptor Density in Cultured Rat Glioma C6 Cells After Incubation with Antidepressants Is Dependent upon the Culturing Conditions Used

The hydrophilic beta-adrenoceptor ligand (-)-[3H]CGP-12177 binds to intact C6 cells with a high affinity (KD approximately 0.1 nM) and with a high degree of specificity. The binding was inhibited by DL-propranolol (Ki approximately 1 nM). Treatment of cells cultured in Dulbecco's modified Eagle medium (DMEM) without fetal calf serum for 4 days with desipramine reduced the (-)-[3H]CGP-12177 specific binding in a concentration-dependent manner, a reduction from 127 to 102 fmol/mg of protein being found at a ligand concentration of 1 nM after treatment with 10 microM desipramine. Lesser effects were seen after treatment for 1 day. A similar result was found with maprotiline, and reductions in specific binding were seen after 4 days of treatment with amitriptyline, iprindole, and citalopram. The reduction in binding-site density (measured per milligram of protein to compensate for variability in cell density per well), however, was paralleled in all cases by a reduction in the rate of cell proliferation. When C6 glioma cells were cultured in Ham's medium without fetal calf serum during the antidepressant treatment period, a higher specific binding was observed than for the DMEM-cultured cells, and 10 microM desipramine was without effect on either the (-)-[3H]CGP-12177 specific binding or cell proliferation. It is concluded that the effects of the antidepressants tested upon the density of (-)-[3H]CGP-12177 specific binding sites in intact C6 cells may be secondary to the toxicity of the compounds under the conditions used.     

Effect of Tenuifoliside A isolated from Polygala tenuifolia on the ERK and PI3K pathways in C6 glioma cells

Tenuifoliside A (TFSA) is a bioactive oligosaccharide ester component of Polygala tenuifolia Wild, a traditional Chinese medicine which was used to manage mental disorders effectively. The neuroprotective and anti-apoptotic effects of TFSA have been demonstrated in our previous studies. The present work was designed to study the molecular mechanism of TFSA on promoting the viability of rat glioma cells C6. We exposed C6 cells to TFSA (or combined with ERK, PI3K and TrkB inhibitors) to examine the effects of TFSA on the cell viability and the expression and phosphorylation of key proteins in the ERK and PI3K signaling pathway. TFSA increased levels of phospho-ERK and phospho-Akt, enhanced release of BDNF, which were blocked by ERK and PI3K inhibitors, respectively (U0126 and LY294002). Moreover, the TFSA caused the enhanced phosphorylation of cyclic AMP response element binding protein (CREB) at Ser133 site, the effect was revoked by U0126, LY294002 and K252a. Furthermore, when C6 cells were pretreated with K252a, a TrkB antagonist, known to significantly inhibit the activity of brain-derived neurotrophic factor (BDNF), blocked the levels of phospho-ERK, phospho-Akt and phosphor-CREB. Taking these results together, we suggested the neuroprotection of TFSA might be mediated through BDNF/TrkB-ERK/PI3K-CREB signaling pathway in C6 glioma cells.     

Calmodulin Antagonist W-7 Inhibits Lysosomal Sphingomyelinase Activity in C6 Glioma Cells

N-(6-Aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7) is known to be a potent calmodulin antagonist and inhibitor of calmodulin-dependent protein kinases. W-7 and 1-(5-isoquinolinyl-sulfonyl)-2-methylpiperazine (H-7) are inhibitors of protein kinase C and cyclic nucleotide-dependent protein kinases. In C6 glioma cells, W-7 and not H-7 inhibited dose-dependently acid sphingomyelinase, a result indicating the modulation of this lysosomal enzyme by a calmodulin-dependent system. Other lysosomal enzymes, such as beta-glucosidase, alpha-galactosidase, and arylsulfatase A, were unaffected by W-7 and H-7, a finding indicating a selective effect of W-7 on sphingomyelinase.     

Heterogeneity of Nucleotide Receptors in NG108-15 Neuroblastoma and C6 Glioma Cells for Mediating Phosphoinositide Turnover

Abstract: We have compared the characteristics of receptors for nucleotide analogues and the involvement of phospholipase C (PLC) in the effector mechanism in NG108-15 neuroblastoma and C6 glioma cells. The relative potency of these analogues to stimulate inositol phosphate (IP) formation is UTP > UDP ? 2-methylthio-ATP (2-MeSATP), GTP > ATP, CTP > ADP > UMP in NG108-15 cells and ATP > UTP > ADP > GTP > UDP ? 2Me-SATP, CTP, UMP in C6 glioma cells. α,β-Methylene-ATP, β,γ-methylene-ATP, AMP, and adenosine had little or no effect in both types of cells. The EC₅₀ values were 3 and 106 µM for UTP in NG108-15 and C6 glioma cells, respectively. The EC₅₀ value for ATP in C6 glioma cells was 43 µM. 2-MeSATP was threefold more potent than ATP in NG108-15 cells but had little effect in C6 glioma cells at 1 mM. In NCB-20 cells, a similar rank order of potency to that found in NG108-15 cells, i.e., UTP ? GTP > ATP > CTP, was observed. In both NG108-15 and C6 glioma cells, preincubation with ATP or UTP caused a pronounced cross-desensitization of subsequent nucleotide-stimulated IP production. ATP and UTP displayed no additivity in terms of IP formation at maximally effective concentrations. In contrast, endothelin-1, bradykinin, and NaF interacted in an additive manner with either nucleotide in stimulating PI hydrolysis. Pretreatment with pertussis toxin did not affect ATP-, UTP-, and GTP-stimulated IP generation in these cells, indicating that nucleotide receptors coupled to PLC by a pertussis toxin-resistant G protein in both cell types. Short-term treatment of the cells with protein kinase C (PKC) activators [phorbol 12-myristate 13-acetate (PMA) and octylindolactam V] produced a dose-dependent inhibition of ATP- and UTP-induced IP formation with a greater extent and higher susceptibility in C6 glioma cells than in NG108-15 cells. Furthermore, a 24-h exposure of the cells to PMA resulted in an obvious attenuation of nucleotide-induced IP formation in C6 glioma cells but failed to change the response in NG108-15 cells. These results suggest that distinct nucleotide receptors that respond to ATP and UTP with different selectivity exist in NG108-15 and C6 glioma cells. These heterogeneous nucleotide receptors coupled to PLC undergo discriminative modulation by PKC. NG108-15 and NCB-20 neuroblastoma are two cell lines that showed the highest specificity to extracellular UTP rather than ATP among the nucleotide receptors so far studied in various cells, suggesting the presence of a pyrimidine receptor in these cells.     

Recovery of Altered Fatty Acid Composition Induced by a Diet Devoid of n-3 Fatty Acids in Myelin, Synaptosomes, Mitochondria, and Microsomes of Developing Rat Brain

Rats were fed a semisynthetic diet containing either sunflower oil or soya oil. Half the litter fed with sunflower oil diet was changed to a soya oil diet when the pups were 15 days old (during active myelination). Fatty acid analysis was then performed on subcellular fractions of the animals fed (a) soya oil, (b) sunflower oil, and (c) soya oil replacing sunflower oil from the 15th day, to determine the speed of the recovery. All material from animals fed sunflower oil showed an important reduction in docosahexaenoic acid (22:6 n-3), compensated by an increase in docosapentaenoic acid (22:5 n-6), whereas arachidonic acid (20:4 n-6) was not affected. In all fractions examined, when sunflower oil was replaced by soya oil in 15-day-old pups the recovery started from the very first day but lasted more than 2 months (this recovery was determined by the increase of 22:6 n-3 up to the normal value and decrease of the 22:5 n-6). In addition a delay was found for myelin recovery, starting only from the 25th day.     

Determination of a Potential Role of the CCN Family of Growth Regulators in Connexin43 Transfected C6 Glioma Cells

Tumour cells often exhibit erratic cell growth, as well as decreased gap junctional intercellular communication (GJIC). C6 glioma cells are characterized by low levels of gap junction mRNA and protein, and decreased amounts of GJIC when compared with astrocytes. Previous work has shown that C6 glioma cells transfected with connexin43 (C6-Cx43) exhibit decreased proliferation in vivo and in vitro, as well as genes that are differentially expressed between these cells. In this study, RNA levels of two CCN (connective tissue growth factor [CTGF], Cyr61/Cef-10, nephroblastoma overexpressed [NOV]) gene family members are shown to be upregulated in C6-Cx43 cells: Cyr61 and Nov. Cyr61 has previously been shown to increase adhesion, migration and growth in many cell types, whereas NOV has growth suppressive capacities. Cyr61 RNA expression is shown here to respond to serum in quiescent cells in an immediate early gene fashion, independent of Cx43 expression. In contrast, Nov RNA levels remain constant, reflective of transfected Cx43 expression. Furthermore, confocal microscopy indicates that NOV colocalizes with Cx43 plaques at the cell membrane. These findings provide insight into the possible role of Nov and Cyr61 in tumour cells.     

Kainic Acid and Decorticating Lesions Stimulate the Synthesis of C1q Protein in Adult Rat Brain

Abstract: The first component of the classic complement cascade, C1q, was increased in whole rat brain after lesioning by intraperitoneally injected kainic acid (KA) (20-fold, 3 days after KA) and in the striatum ipsilateral to unilateral decortication (fivefold, 10 days after decortication). C1q was measured after purification by chromatography and electrophoresis. De novo biosynthesis of C1q 3 days after KA was increased >10-fold, as measured by the incorporation of [³⁵S]methionine into C1q after incubation of brain slices from KA-treated rats for 2 h. In parallel with these responses, KA induced fivefold increase of C1q bioactivity, as evaluated with C1q-dependent hemolysis. The contribution of C1q from entrapped cerebrovascular blood was evaluated by the effects of perfusion and was minor relative to the increases of C1q in response to KA lesioning. These findings support the hypothesis that the C1q protein detected by immunocytochemistry in senile plaques of Alzheimer brains and in the hippocampus after deafferenting lesions is synthesized by resident brain cells.