Complement: Functions, location and implications.

The complement system, an arm of the innate immune system plays a critical role in both health and disease. The complement system is highly complex with dual possibilities, helping or hurting the host, depending on the location and local microenvironment. The traditionally known functions of complement include surveillance, pathogen recognition, immune complex trafficking, processing and pathogen elimination. The noncanonical functions of the complement system include their roles in development, differentiation, local homeostasis and other cellular functions. Complement proteins are present in both, the plasma and on the membranes. Complement activation occurs both extra- and intracellularly, which leads to considerable pleiotropy in their activity. In order to design more desirable and effective therapies, it is important to understand the different functions of complement, and its location-based and tissue-specific responses. This manuscript will provide a brief overview into the complex nature of the complement cascade, outlining some of their complement-independent functions, their effects at different locale, and their implication in disease settings.

Cohort profile: The PreEclampsia, Angiogenesis, Cardiac dysfunction and Hypertension (PEACH) Study.

BACKGROUND: Hypertensive disorders of pregnancy (HDP) remain a leading cause of maternal morbidity and mortality worldwide, with implications for maternal and neonatal well-being in the short term and for long-term maternal cardiovascular health. Although the mechanisms behind HDP remain incompletely understood, evidence suggests that preeclampsia in particular is a syndrome with more than one distinct subtype. OBJECTIVES: The PEACH (PreEclampsia, Angiogenesis, Cardiac dysfunction, Hypertension) Study was established to identify new HDP subtyping systems reflecting aetiology and prognosis and to find markers of later cardiovascular disease risk associated with preeclampsia. POPULATION: The PEACH Study recruited pregnant women referred to two Copenhagen-area hospitals with suspected preeclampsia (mean gestational age at enrolment: 36.7 weeks) and a group of frequency-matched pregnant women planning delivery at the same hospitals and healthy when enrolled mid-pregnancy. DESIGN: Prospective, longitudinal pregnancy cohort. METHODS: Participants underwent repeated third-trimester blood sample collection, longitudinal cardiac function assessments using the USCOM-1A during the third trimester and at 1 year postpartum and collection of placental samples immediately after delivery. Medical information was abstracted from medical records and hospital databases. PRELIMINARY RESULTS: During 2016-2018, we recruited 1149 pregnant women, of whom 1101 were followed to delivery. Among 691 women enrolled with suspected preeclampsia, 310 and 172 developed preeclampsia and gestational hypertension respectively. Among 410 women with healthy pregnancies when enrolled mid-pregnancy, 37 later developed hypertensive disorders of pregnancy. Of 1089 women still in the cohort 1 year postpartum, 578 (53.1%) participated in the follow-up assessment. CONCLUSIONS: The PEACH Study's rich data from women with and without HDP will enable us to identify new, clinically useful HDP subtypes to aid in decision-making regarding monitoring and treatment. Continued postpartum follow-up will help us develop algorithms to identify women at risk of persistent postpartum cardiac dysfunction and later cardiovascular disease after pregnancies complicated by HDP.

Rebozo and External Cephalic Version in breech presentation (RECEIVE): A randomised controlled study.

OBJECTIVE: To investigate if a hospital-initiated home-based rebozo intervention performed by the pregnant woman and her partner before external cephalic version (ECV) would increase the rate of cephalic presentations at birth. DESIGN: A multicentre randomised controlled trial. SETTING: Three university hospitals in Copenhagen, Denmark. POPULATION: Pregnant women with a breech or transverse presentation at 35 weeks or more of gestation eligible for ECV. METHODS: We compared rebozo before ECV with ECV alone. The randomisation was computer-generated in blocks and stratified by parity. The woman and her partner were instructed in the technique by a project midwife and performed the technique at home three times daily for 3-5 days before the scheduled ECV. Analyses were by intention-to-treat. MAIN OUTCOME MEASURE: The number of cephalic presentations at the time of birth. Odds ratios (OR) and 95% confidence intervals (CI) were calculated. RESULTS: A total of 372 women were randomly assigned (1:1) to either rebozo intervention (n = 187) or control (n = 185). At birth, 95 (51%) in the intervention group versus 112 (62%) in the control group had a fetus in cephalic presentation (OR 0.61; 95% CI 0.40-0.95). No adverse events were observed in relation to the intervention. CONCLUSIONS: In breech or transverse presentation, home-based rebozo exercise before ECV lowered the overall rate of cephalic presentation at birth. TWEETABLE ABSTRACT: Home-based rebozo for breech presentation before external version reduces the rate of cephalic presentation at birth.

Local complement factor H protects kidney endothelial cell structure and function.

Factor H (FH) is a critical regulator of the alternative complement pathway and its deficiency or mutation underlie kidney diseases such as dense deposit disease. Since vascular dysfunction is an important facet of kidney disease, maintaining optimal function of the lining endothelial cells is important for vascular health. To investigate the molecular mechanisms that are regulated by FH in endothelial cells, FH deficient and sufficient mouse kidney endothelial cell cultures were established. Endothelial FH deficiency resulted in cytoskeletal remodeling, increased angiogenic potential, loss of cellular layer integrity and increased cell proliferation. FH reconstitution prevented these FH-dependent proliferative changes. Respiratory flux analysis showed reduced basal mitochondrial respiration, ATP production and maximal respiratory capacity in FH deficient endothelial cells, while proton leak remained unaltered. Similar changes were observed in FH deficient human glomerular endothelial cells indicating the translational potential of these studies. Gene expression analysis revealed that the FH-dependent gene changes in mouse kidney endothelial cells include significant upregulation of genes involved in inflammation and the complement system. The transcription factor nuclear factor-kB, that regulates many biological processes, was translocated from the cytoplasm to the nucleus in the absence of FH. Thus, our studies show the functional relevance of intrinsic FH in kidney endothelial cells in man and mouse.

Differentiated timing of induction for women with intrahepatic cholestasis of pregnancy-A historical cohort study.

INTRODUCTION: Intrahepatic cholestasis of pregnancy (ICP) is a pregnancy-specific liver disease characterized by pruritus and abnormal liver function tests and it has been associated with intrauterine fetal distress and stillbirth. We compared two guidelines of the management of ICP: one mandating induction at 38 weeks of gestation (Rigshospitalet and Hvidovre Hospital before 2012) and another separating ICP into mild and severe forms, and only women with severe ICP were recommended for induction at 38 weeks (Hvidovre Hospital after 2012). MATERIAL AND METHODS: We performed a historical cohort study at two Copenhagen Hospitals from 2004 to 2015. We included 62 937 women with singleton deliveries at Rigshospitalet and 71 015 at Hvidovre Hospital, of whom 971 women (1.5%) and 998 women (1.4%) were diagnosed with ICP at Rigshospitalet and Hvidovre Hospital, respectively. Data were retrieved from a local medical database. For the analysis of induction and comparison of obstetrical outcomes we only included pregnancies with an ICP diagnosis and excluded women with other medical conditions that could mandate induction. Main outcome measures were induction and cesarean section rates, asphyxia and stillbirth. RESULTS: We found no changes in the rate of spontaneous labor, cesarean section and induction over the years at Rigshospitalet (P = .17) and Hvidovre Hospital (P = .38). For women with intended vaginal delivery we found no change in the final mode of delivery over the years at Rigshospitalet (P = .28) and Hvidovre Hospital (P = .57). CONCLUSIONS: The two approaches to the management of mild ICP regarding the timing of induction are comparable. Women with mild ICP and their clinicians should be encouraged to engage in shared decision-making when discussing timing of induction.

Efficacy and safety of low-dose IL-2 in the treatment of systemic lupus erythematosus: a randomised, double-blind, placebo-controlled trial.

OBJECTIVES: Open-labelled clinical trials suggested that low-dose IL-2 might be effective in treatment of systemic lupus erythematosus (SLE). A double-blind and placebo-controlled trial is required to formally evaluate the safety and efficacy of low-dose IL-2 therapy. METHODS: A randomised, double-blind and placebo-controlled clinical trial was designed to treat 60 patients with active SLE. These patients received either IL-2 (n=30) or placebo (n=30) with standard treatment for 12 weeks, and were followed up for additional 12 weeks. IL-2 at a dose of 1 million IU or placebo was administered subcutaneously every other day for 2 weeks and followed by a 2-week break as one treatment cycle. The primary endpoint was the SLE Responder Index-4 (SRI-4) at week 12. The secondary endpoints were other clinical responses, safety and dynamics of immune cell subsets. RESULTS: At week 12, the SRI-4 response rates were 55.17% and 30.00% for IL-2 and placebo, respectively (p=0.052). At week 24, the SRI-4 response rate of IL-2 group was 65.52%, compared with 36.67% of the placebo group (p=0.027). The primary endpoint was not met at week 12. Low-dose IL-2 treatment resulted in 53.85% (7/13) complete remission in patients with lupus nephritis, compared with 16.67% (2/12) in the placebo group (p=0.036). No serious infection was observed in the IL-2 group, but two in placebo group. Besides expansion of regulatory T cells, low-dose IL-2 may also sustain cellular immunity with enhanced natural killer cells. CONCLUSIONS: Low-dose IL-2 might be effective and tolerated in treatment of SLE. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov Registries (NCT02465580 and NCT02932137).

The role of neuronal excitability, allocation to an engram and memory linking in the behavioral generation of a false memory in mice.

Memory is a constructive, not reproductive, process that is prone to errors. Errors in memory, though, may originate from normally adaptive memory processes. At the extreme of memory distortion is falsely "remembering" an event that did not occur. False memories are well-studied in cognitive psychology, but have received relatively less attention in neuroscience. Here, we took advantage of mechanistic insights into how neurons are allocated or recruited into an engram (memory trace) to generate a false memory in mice using only behavioral manipulations. At the time of an event, neurons compete for allocation to an engram supporting the memory for this event; neurons with higher excitability win this competition (Han et al., 2007). Even after the event, these allocated "engram neurons" remain temporarily (~6 h) more excitable than neighboring neurons. Should a similar event occur in this 6 h period of heightened engram neuron excitability, an overlapping population of neurons will be co-allocated to this second engram, which serves to functionally link the two memories (Rashid et al., 2016). Here, we applied this principle of co-allocation and found that mice develop a false fear memory to a neutral stimulus if exposed to this stimulus shortly (3 h), but not a longer time (24 h), after cued fear conditioning. Similar to co-allocation, the generation of this false memory depended on the post-training excitability of engram neurons such that these neurons remained more excitable during exposure to the neutral stimulus at 3 h but not 24 h. Optogenetically silencing engram neurons 3 h after cued fear conditioning impaired formation of a false fear memory to the neutral stimulus, while optogenetically activating engram neurons 24 h after cued fear conditioning created a false fear memory. These results suggest that some false memories may originate from normally adaptive mnemonic processes such as neuronal excitability-dependent allocation and memory linking.

Sudden deafness and tuning fork tests: towards optimal utilisation.

The tuning fork tests have been under attack since their first use in clinical examination. However, the tuning fork is small and fits into every white coat, and tuning fork tests for hearing are easy, accurate and inexpensive. They should be used in patients with an acute unilateral hearing loss if an electric audiometer is not available. After more than 100 years, the tuning fork is not obsolete; tuning fork tests are very useful if used correctly and for the appropriate indication.

Dissociable contributions of thalamic nuclei to recognition memory: novel evidence from a case of medial dorsal thalamic damage.

The thalamic nuclei are thought to play a critical role in recognition memory. Specifically, the anterior thalamic nuclei and medial dorsal nuclei may serve as critical output structures in distinct hippocampal and perirhinal cortex systems, respectively. Existing evidence indicates that damage to the anterior thalamic nuclei leads to impairments in hippocampal-dependent tasks. However, evidence for the opposite pattern following medial dorsal nuclei damage has not yet been identified. In the present study, we investigated recognition memory in NC, a patient with relatively selective medial dorsal nuclei damage, using two object recognition tests with similar foils: a yes/no (YN) test that requires the hippocampus, and a forced choice corresponding test (FCC) that is supported by perirhinal cortex. NC performed normally in the YN test, but was impaired in the FCC test. Critically, FCC performance was impaired only when the study-test delay period was filled with interference. We interpret these results in the context of the representational-hierarchical model, which predicts that memory deficits following damage to the perirhinal system arise due to increased vulnerability to interference. These data provide the first evidence for selective deficits in a task that relies on perirhinal output following damage to the medial dorsal nuclei, providing critical evidence for dissociable thalamic contributions to recognition memory.

Immunomodulatory Role of Complement Proteins in the Neuropathology Associated with Opiate Abuse and HIV-1 Co-Morbidity.

The complement system which is a critical mediator of innate immunity plays diverse roles in the neuropathogenesis of HIV-1 infection such as clearing HIV-1 and promoting productive HIV-1 replication. In the development of HIV-1 associated neurological disorders (HAND), there may be an imbalance between complement activation and regulation, which may contribute to the neuronal damage as a consequence of HIV-1 infection. It is well recognized that opiate abuse exacerbates HIV-1 neuropathology, however, little is known about the role of complement proteins in opiate induced neuromodulation, specifically in the presence of co-morbidity such as HIV-1 infection. Complement levels are significantly increased in the HIV-1-infected brain, thus HIV-induced complement synthesis may represent an important mechanism for the pathogenesis of AIDS in the brain, but remains underexplored. Anti-HIV-1 antibodies are able to initiate complement activation in HIV-1 infected CNS cells such as microglia and astrocytes during the course of disease progression; however, this complement activation fails to clear and eradicate HIV-1 from infected cells. In addition, the antiretroviral agents used for HIV therapy cause dysregulation of lipid metabolism, endothelial, and adipocyte cell function, and activation of pro-inflammatory cytokines. We speculate that both HIV-1 and opiates trigger a cytokine-mediated pro-inflammatory stimulus that modulates the complement cascade to exacerbate the virus-induced neurological damage. We examined the expression levels of C1q, SC5b-9, C5L2, C5aR, C3aR, and C9 key members of the complement cascade both in vivo in post mortem brain frontal cortex tissue from patients with HAND who used/did not use heroin, and in vitro using human microglial cultures treated with HIV tat and/or heroin. We observed significant expression of C1q and SC5b-9 by immunofluorescence staining in both the brain cortical and hippocampal region in HAND patients who abused heroin. Additionally, we observed increased gene expression of C5aR, C3aR, and C9 in the brain tissue of both HIV-1 infected patients with HAND who abused and did not abuse heroin, as compared to HIV negative controls. Our results show a significant increase in the expression of complement proteins C9, C5L2, C5aR, and C3aR in HIV transfected microglia and an additional increase in the levels of these complement proteins in heroin-treated HIV transfected microglia. This study highlights the a) potential roles of complement proteins in the pathogenesis of HIV-1-related neurodegenerative disorders; b) the combined effect of an opiate, like heroin, and HIV viral protein like HIV tat on complement proteins in normal human microglial cells and HIV transfected microglial cells. In the context of HAND, targeting selective steps in the complement cascade could help ameliorating the HIV burden in the CNS, thus investigations of complement-related therapeutic approaches for the treatment of HAND are warranted.

Hypertensive disorders of pregnancy and subsequent risk of solid cancer--A nationwide cohort study.

Women with hypertensive disorders of pregnancy (HDP) have higher levels of antiangiogenic growth factors during pregnancy than women with normotensive pregnancies. Since angiogenesis is necessary for solid cancer growth and spread, we hypothesized that women with a history of HDP might have a reduced risk of solid cancers (cancers other than lymphomas, hematologic cancers and nonmelanoma skin cancers) later in life. In a register-based cohort study of 1.08 million women giving birth at least once between 1978 and 2011, we used Cox regression to estimate hazard ratios (HRs) comparing solid cancer rates for women with and without a history of HDP. In this cohort, 68,236 women (6.3%) had ≥1 pregnancy complicated by HDP and 42,236 women (3.9%) developed solid tumors during follow-up. A history of HDP was not associated with a clinically meaningful reduction in the overall rate of solid cancer (HR 0.96, 95% confidence interval 0.92-1.00), regardless of HDP severity or time since HDP, nor was there a general tendency toward reduced solid cancer rates across organ sites. A history of HDP was only significantly associated with decreased rates of breast and lung cancers and with increased rates of endometrial and urinary tract cancers. Overall, our results do not support the hypothesis that women with a history of HDP have a reduced overall risk of solid cancer due to a persistent post-HDP antiangiogenic state or an innate tendency toward antiangiogenesis. Observed associations with specific cancers may instead be due to other pregnancy-related mechanisms or to residual/unmeasured confounding.

Association Between Hypertensive Disorders of Pregnancy and Later Risk of Cardiomyopathy.

IMPORTANCE: Women with hypertensive disorders of pregnancy, preeclampsia in particular, have an increased risk of cardiomyopathy during the peripartum period. Whether hypertensive disorders of pregnancy are also associated with cardiomyopathy later in life is unknown. OBJECTIVE: To determine whether hypertensive disorders of pregnancy are associated with cardiomyopathy beyond the peripartum period. DESIGN, SETTING, AND PARTICIPANTS: Nationwide register-based cohort study using Cox regression to compare rates of cardiomyopathy in women with and without a history of hypertensive disorders of pregnancy in a cohort of 1,075,763 women with at least 1 pregnancy ending in live birth or stillbirth in Denmark, 1978-2012, with follow-up through December 31, 2012. EXPOSURES: A hypertensive disorder of pregnancy (severe or moderate preeclampsia or gestational hypertension) registered in the National Patient Register. MAIN OUTCOMES AND MEASURES: Cardiomyopathy more than 5 months after delivery (outside the peripartum period) up to 34 years 7 months. RESULT: The women in the primary cohort had 2,067,633 eligible pregnancies during the study period, 76,108 of which were complicated by a hypertensive disorder of pregnancy. During follow-up, 1577 women (mean age, 48.5 years at cardiomyopathy diagnosis; 2.6% with multiple pregnancies) developed cardiomyopathy. Compared with women with normotensive pregnancies (18,211,603 person-years of follow-up; n = 1408 cardiomyopathy events, 7.7/100,000 person-years [95% CI, 7.3-8.2]), women with a history of hypertensive disorders of pregnancy had significantly increased rates of cardiomyopathy (in 173,062 person-years of follow-up among women with severe preeclampsia, n = 27 cardiomyopathy events; 15.6/100,000 person-years [95% CI, 10.7-22.7]; adjusted hazard ratio [HR], 2.20 [95% CI, 1.50-3.23]; in 697,447 person-years of follow-up among women with moderate preeclampsia, n = 102 cardiomyopathy events; 14.6/100,000 person-years [95% CI, 12.0-17.8]; adjusted HR, 1.89 [95% CI, 1.55-2.23]; in 213,197 person-years of follow-up among women with gestational hypertension, n = 40 cardiomyopathy events; 17.3/100,000 person-years [95% CI, 12.7-23.6]; adjusted HR, 2.06 [95% CI, 1.50-2.82]). These increases persisted more than 5 years after the latest pregnancy. Mediation analyses suggested that only about 50% of the association was an indirect association through postpregnancy chronic hypertension. In this cohort, 11% of all cardiomyopathy events occurred in women with a history of hypertensive disorders of pregnancy. CONCLUSIONS AND RELEVANCE: Women with a history of hypertensive disorders of pregnancy, compared with women without such a history, had a small but statistically significant increased risk of cardiomyopathy more than 5 months after delivery. Further research is necessary to understand whether there is a causal mechanism behind this association.

CD11b is protective in complement-mediated immune complex glomerulonephritis.

In chronic serum sickness, glomerular immune complexes form, yet C57BL/6 mice do not develop glomerulonephritis unless complement factor H (CfH) is absent, indicating the relevance of complement regulation. Complement receptor 3 (CD11b) and Fcγ receptors on leukocytes, and CfH on platelets, can bind immune complexes. Here we induced immune complex-mediated glomerulonephritis in CfH(-/-) mice chimeric for wild-type, CfH(-/-), CD11b(-/-), or FcRγ(-/-) bone marrow stem cells. Glomerulonephritis was worse in CD11b(-/-) chimeras compared with all others, whereas disease in FcRγ(-/-) and wild-type chimeras was comparable. Disease tracked strongly with humoral immune responses, but not glomerular immune complex deposits. Interstitial inflammation with M1 macrophages strongly correlated with glomerulonephritis scores. CD11b(-/-) chimeras had significantly more M1 macrophages and CD4(+) T cells. The renal dendritic cell populations originating from bone marrow-derived CD11c(+) cells were similar in all experimental groups. CD11b(+) cells bearing colony-stimulating factor 1 receptor were present in kidneys, including CD11b(-/-) chimeras; these cells correlated negatively with glomerulonephritis scores. Thus, experimental immune complex-mediated glomerulonephritis is associated with accumulation of M1 macrophages and CD4(+) T cells in kidneys and functional renal insufficiency. Hence, CD11b on mononuclear cells is instrumental in generating an anti-inflammatory response in the inflamed kidney.

Transcriptional profiling reveals that C5a alters microRNA in brain endothelial cells.

Blood-brain barrier (BBB) disturbance is a crucial occurrence in many neurological diseases, including systemic lupus erythematosus (SLE). Our previous studies showed that experimental lupus serum altered the integrity of the mouse brain endothelial layer, an important constituent of the BBB. Complement activation occurs in lupus with increased circulating complement components. Using a genomics approach, we identified the microRNA (miRNA) altered in mouse brain endothelial cells (bEnd3) by lupus serum and the complement protein, C5a. Of the 318 miRNA evaluated, 23 miRNAs were altered by lupus serum and 32 were altered by C5a alone compared with controls. Seven miRNAs (P < 0 · 05) were differentially expressed by both treatments: mmu-miR-133a*, mmu-miR-193*, mmu-miR-26b, mmu-miR-28*, mmu-miR-320a, mmu-miR-423-3p and mmu-miR-509-5p. The microarray results were validated by quantitative RT-PCR. In line with the in vitro results, expression of miR-26b and miR-28* were also significantly up-regulated in lupus mouse brain which was reduced by C5a receptor inhibition. Target prediction analysis revealed miR gene targets encoding components involved in inflammation, matrix arrangement, and apoptosis, pathways known to play important roles in central nervous system lupus. Our findings suggest that the miRNAs reported in this study may represent novel therapeutic targets in central nervous system lupus and other similar neuroinflammatory settings.

Transcriptional regulation of dentin matrix protein 1 (DMP1) in odontoblasts and osteoblasts.

Dentin matrix protein 1 (DMP1) is a noncollagenous protein important for the mineralization of bones and teeth. Examination of the transcription factor binding sites within the 6.24 kb upstream sequence of rat DMP1 promoter by Matinspector software revealed that TCF11 had the highest number (six) of binding sites with 100% matrix similarity. Four of these sites are conserved in the mouse DMP1 promoter. TCF11 is a member of the Cap-n-Collar (cnc) family of basic leucine zipper transcription factors. Results from this study showed that TCF11 can bind specifically to the DMP1 promoter and activate its transcription in odontoblasts and osteoblasts. This could be attributed to both direct and indirect effects of TCF11. Electrophoretic mobility shift (EMSA) assay showed differential interaction between TCF11 and its binding sites on the DMP1 promoter. 21 bp oligos spanning the TCF11 matrix were used as probes in EMSA, and the results showed that the binding was specific to the sequence of the TCF11 matrix as well as the flanking sequences and this is typical of a heterodimer binding site. Results also showed changes in the binding pattern when cells were differentiated in osteogenic medium for 2 d. Thus, TCF11 may play an important role in the transcriptional regulation of DMP1 gene.

Higher-order interactions between hippocampal CA1 neurons are disrupted in amnestic mice.

Across systems, higher-order interactions between components govern emergent dynamics. Here we tested whether contextual threat memory retrieval in mice relies on higher-order interactions between dorsal CA1 hippocampal neurons requiring learning-induced dendritic spine plasticity. We compared population-level Ca2+ transients as wild-type mice (with intact learning-induced spine plasticity and memory) and amnestic mice (TgCRND8 mice with high levels of amyloid-ß and deficits in learning-induced spine plasticity and memory) were tested for memory. Using machine-learning classifiers with different capacities to use input data with complex interactions, our findings indicate complex neuronal interactions in the memory representation of wild-type, but not amnestic, mice. Moreover, a peptide that partially restored learning-induced spine plasticity also restored the statistical complexity of the memory representation and memory behavior in Tg mice. These findings provide a previously missing bridge between levels of analysis in memory research, linking receptors, spines, higher-order neuronal dynamics and behavior.

Excitability mediates allocation of pre-configured ensembles to a hippocampal engram supporting contextual conditioned threat in mice.

Little is understood about how engrams, sparse groups of neurons that store memories, are formed endogenously. Here, we combined calcium imaging, activity tagging, and optogenetics to examine the role of neuronal excitability and pre-existing functional connectivity on the allocation of mouse cornu ammonis area 1 (CA1) hippocampal neurons to an engram ensemble supporting a contextual threat memory. Engram neurons (high activity during recall or TRAP2-tagged during training) were more active than non-engram neurons 3 h (but not 24 h to 5 days) before training. Consistent with this, optogenetically inhibiting scFLARE2-tagged neurons active in homecage 3 h, but not 24 h, before conditioning disrupted memory retrieval, indicating that neurons with higher pre-training excitability were allocated to the engram. We also observed stable pre-configured functionally connected sub-ensembles of neurons whose activity cycled over days. Sub-ensembles that were more active before training were allocated to the engram, and their functional connectivity increased at training. Therefore, both neuronal excitability and pre-configured functional connectivity mediate allocation to an engram ensemble.

Curcumin alleviates immune-complex-mediated glomerulonephritis in factor-H-deficient mice.

Complement factor H (Cfh) is a key regulator of the complement cascade and protects C57BL/6 mice from immune complex-mediated complement-dependent glomerulonephritis. In chronic serum sickness (CSS) there are increased deposits of immune complexes in the glomeruli with inflammation and a scarring phenotype. As cucurmin is an effective anti-inflammatory agent and reduces complement activation, we hypothesized that it should alleviate renal disease in this setting. To determine the effectiveness of curcumin, an apoferritin-induced CSS model in Cfh-deficient (Cfh(-/-)) mice was used. Curcumin treatment (30 mg/kg) given every day in parallel with apoferritin reduced glomerulonephritis and enhanced kidney function (blood urea nitrogen, 45·4 ± 7·5 versus 35·6 ± 5·1; albuminuria, 50·1 ± 7·1 versus 15·7 ± 7·1; glomerulonephritis, 2·62 + 0·25 versus 2 + 0·3, P < 0·05). In line with reduced IgG deposits in mice with CSS given curcumin, C9 deposits were reduced indicating reduced complement activation. Mice treated with curcumin had a significant reduction in the number of splenic CD19(+) B cells and the ratio of CD19 : CD3 cells (P < 0·05) with no change in the T-cell population. Myeloperoxidase assay showed reduced macrophages in the kidney. However, a significant reduction in the M2 subset of splenic macrophages by apoferritin was prevented by curcumin, suggesting a protective function. Curcumin treatment reduced mRNA expression of inflammatory proteins monocyte chemoattractant protein-1 and transforming growth factor-ß and matrix proteins, fibronectin, laminin and collagen. Our results clearly illustrate that curcumin reduces glomerulosclerosis, improves kidney function and could serve as a therapeutic agent during serum sickness.

Formation and fate of an engram in the lateral amygdala supporting a rewarding memory in mice.

Memories allow past experiences to guide future decision making and behavior. Sparse ensembles of neurons, known as engrams, are thought to store memories in the brain. Most previous research has focused on engrams supporting threatening or fearful memories where results show that neurons involved in a particular engram ("engram neurons") are both necessary and sufficient for memory expression. Far less is understood about engrams supporting appetitive or rewarding memories. As circumstances and environments are dynamic, the fate of a previously acquired engram with changing circumstances is unknown. Here we examined how engrams supporting a rewarding cue-cocaine memory are formed and whether this original engram is important in reinstatement of memory-guided behavior following extinction. Using a variety of techniques, we show that neurons in the lateral amygdala are allocated to an engram based on relative neuronal excitability at training. Furthermore, once allocated, these neurons become both necessary and sufficient for behavior consistent with recall of that rewarding memory. Allocated neurons are also critical for cocaine-primed reinstatement of memory-guided behavior following extinction. Moreover, artificial reactivation of initially allocated neurons supports reinstatement-like behavior following extinction even in the absence of cocaine-priming. Together, these findings suggest that cocaine priming after extinction reactivates the original engram, and that memory-guided reinstatement behavior does not occur in the absence of this reactivation. Although we focused on neurons in one brain region only, our findings that manipulations of lateral amygdala engram neurons alone were sufficient to impact memory-guided behavior indicate that the lateral amygdala is a critical hub region in what may be a larger brain-wide engram.