Direct recognition of the mycobacterial glycolipid,trehalose dimycolate,by C-type lectin Mincle

Tuberculosis remains a fatal disease caused by Mycobacterium tuberculosis, which contains various unique components that affect the host immune system. Trehalose-6,6′-dimycolate (TDM; also called cord factor) is a mycobacterial cell wall glycolipid that is the most studied immunostimulatory component of M. tuberculosis. Despite five decades of research on TDM, its host receptor has not been clearly identified. Here, we demonstrate that macrophage inducible C-type lectin (Mincle) is an essential receptor for TDM. Heat-killed mycobacteria activated Mincle-expressing cells, but the activity was lost upon delipidation of the bacteria; analysis of the lipid extracts identified TDM as a Mincle ligand. TDM activated macrophages to produce inflammatory cytokines and nitric oxide, which are completely suppressed in Mincle-deficient macrophages. In vivo TDM administration induced a robust elevation of inflammatory cytokines in sera and characteristic lung inflammation, such as granuloma formation. However, no TDM-induced lung granuloma was formed in Mincle-deficient mice. Whole mycobacteria were able to activate macrophages even in MyD88-deficient background, but the activation was significantly diminished in Mincle/MyD88 double-deficient macrophages. These results demonstrate that Mincle is an essential receptor for the mycobacterial glycolipid, TDM.Many pathogens are directly recognized by pattern recognition receptors such as Toll-like receptors (TLRs), RIG-I–like helicases, or NOD-like receptors of the host cells (Akira et al., 2006), most of which sense the characteristic signatures of pathogens. Recently, some members of the C-type lectin family have also been identified as pattern recognition receptors for bacteria or fungi; however, the ligands of most C-type lectin receptors remain unidentified (Robinson et al., 2006).Among these C-type lectin receptors is Mincle (macrophage inducible C-type lectin, also called Clec4e or Clecsf9), which is expressed in macrophages subjected to several types of stress (Matsumoto et al., 1999). Mincle possesses carbohydrate recognition domain (CRD) within the extracellular region. We recently reported that Mincle is associated with an immunoreceptor tyrosine-based activation motif –containing Fc receptor γ chain (FcRγ) and functions as an activating receptor for damaged self- and non–self-pathogenic fungi (Yamasaki et al., 2008, 2009).Tuberculosis is caused by Mycobacterium tuberculosis that infects one third of the world''s population (Hunter et al., 2006). M. tuberculosis contains various unique components that affect the host immune system through both identified and unidentified receptors (Jo, 2008). Among these, the cord factor is the first immunostimulatory component to be identified that might elicit pulmonary inflammation, a characteristic feature of mycobacterial infection (Bloch, 1950; Yamaguchi et al., 1955). In 1956, the chemical structure of the cord factor was established as trehalose-6,6′-dimycolate (TDM; Noll et al., 1956), which is the most abundant glycolipid in the mycobacterial cell wall (Hunter et al., 2006). The long-chain lipids of TDM represent a structural component of the hydrophobic cell wall that is critical for the survival of mycobacteria within the phagosome of host cells (Indrigo et al., 2002). TDM has been shown to possess unique immunostimulatory activity, such as granulomagenesis, adjuvant activity for cell-mediated immune responses, humoral responses, and tumor regression (Hunter et al., 2006). Recently, Marco and TLR are proposed as TDM receptor (Bowdish et al., 2009), whereas other group suggested that FcRγ-coupled receptor(s) are candidates (Werninghaus et al., 2009). Thus, the receptor for TDM is still controversial.Some C-type lectins are involved in the recognition of M. tuberculosis (Jo, 2008). Mannose receptor expressed on macrophages is reported to mediate phagocytosis of mycobacteria (Kang et al., 2005). Another C-type lectin receptor, DC-SIGN, is known to recognize mycobacteria (Tailleux et al., 2003), but its binding results in the down-regulation of dendritic cell–mediated immune responses (Geijtenbeek et al., 2003). Dectin-1 is reported to recognize mycobacteria through an unknown ligand (Yadav and Schorey, 2006; Rothfuchs et al., 2007). Other C-type lectins could potentially recognize mycobacteria, but the activating lectin receptors for mycobacteria in macrophages have not been clearly identified.In this study, we show that Mincle is a direct receptor for mycobacterial TDM. We further demonstrate, through Mincle-deficient mice, that Mincle is an essential receptor for TDM-dependent inflammatory responses.     

Cyclic and characteristic expression of phosphorylated Akt in human endometrium and decidual cells in vivo and in vitro

BACKGROUND: Akt is activated by phosphorylation and plays an important role in cell survival and maintenance of structure. METHODS: We investigated whether phosphorylated Akt was characteristically expressed in human endometrium in vivo and whether insulin-like growth factor-I (IGF-I) can activate Akt using cultured decidualized human stromal cells in vitro, using immunohistochemistry and Western blotting analysis. RESULTS: The levels of phosphorylated Akt protein increased markedly in the decidual tissues from ectopic pregnancy. The expression of phosphorylated Akt protein in stromal cells increased with the decidualization. The decidual cells showed strong cytoplasmic staining for phosphorylated Akt. However, cultured decidualized human stromal cells diminished phosphorylated Akt expression compared to control cells. IGF-I administration to decidualized human stromal cells significantly recovered pAkt expression. The effect of IGF-I on decidualized human stromal cells was blocked by an inhibitor of phosphatidylinositol-3 kinase (PI3K) (LY294,002). These results suggest that IGF-I may activate Akt via PI3K in human endometrium and decidua. The expression of phosphorylated Akt in stromal cells was only detected in the functional layer, where tissue remodelling occurs during menstruation or implantation. CONCLUSIONS: Akt activation may be involved in cell survival and extracellular matrix remodelling in human endometrium and decidua.     

Distribution of cerebral cortical lesions in diffuse neurofibrillary tangles with calcification: a clinicopathological study of four autopsy cases showing prominent parietal lobe involvement

We investigated clinicopathologically four Japanese autopsy cases of diffuse neurofibrillary tangles with calcification (DNTC), which has been believed to be characterized by temporal or temporofrontal circumscribed lobar atrophy, and examined the distribution of their cerebral cortical lesions using hemisphere specimens. The lesions were classified into three categories (slight, moderate, and severe). Severe lesions were present in the temporal lobes and insular gyri of all four cases, consistent with the studies reported to date. In contrast, severe lesions were encountered in the parietal lobe of case 1 and moderate lesions were found in the parietal lobes of cases 2–4. Furthermore, moderate lesions of the precentral gyrus were present in cases 2–4, and moderate lesions of the postcentral gyrus were encountered in all four cases. We postulate that the distribution of cerebral cortical lesions in DNTC is more widespread than previously assumed. Our data also indicate that the unusual clinical signs of DNTC reported by several Japanese researchers, including parietal signs such as apraxia and agnosia, are roughly consistent with the topographic distribution of cerebral cortical lesions in DNTC elucidated in this study.     

Effects of olprinone on hepatosplanchnic circulation and mitochondrial oxidation in a porcine model of endotoxemia

Purpose This study was performed in order to assess the effects of olprinone, a phosphodiesterase III inhibitor, on hepatic oxygen delivery (DO₂H), oxygen consumption (VO₂H), and mitochondrial oxidation in the liver of a porcine endotoxemia model. Methods Fourteen pigs received continuous infusion of endotoxin via the portal vein for 240 min. From t = 150 to t = 240 min, animals were randomly divided into two groups to receive saline (control [CONT]; n = 7), or olprinone (OLP; n = 7) via the central vein. Results In the OLP group, prior to olprinone treatment at 150 min, endotoxin induced significant decreases in the cardiac index (CI; from 120 ± 31 to 65 ± 13 ml·kg⁻¹·min⁻¹; P < 0.01) and DO₂H (from 3.58 ± 0.81 to 1.55 ± 0.49 ml·kg⁻¹·min⁻¹; P < 0.01), while VO₂H was maintained. After administration of olprinone (from t = 150 to t = 240 min), CI was unchanged, while DO₂H increased from 1.55 ± 0.49 to 1.93 ± 0.38 ml·kg⁻¹·min⁻¹ (P < 0.01) and VO₂H increased from 0.42 ± 0.28 to 0.69 ± 0.38 ml·kg⁻¹·min⁻¹ (P < 0.01). At t = 240 min, the oxidation level of cytochrome aa3 was significantly higher in the OLP group than in the CONT group (OLP, 66.2 ± 19.3% vs CONT, 26.4 ± 17.3%; P < 0.01). Conclusion Our data for this porcine endotoxemia model suggest that olprinone may have beneficial therapeutic effects in restoring not only systemic and hepatic circulation but also mitochondrial oxidation in the liver.     

Clinicopathological study of two subtypes of Pick's disease in Japan

We examined the clinical and neuropathological findings in 3 cases of Pick's disease with Pick bodies (PiD) and 7 cases of atypical Pick's disease without Pick bodies (aPiD). PiD and aPiD cases corresponded clinically to frontotemporal dementia and semantic dementia, respectively, based on the clinical diagnostic criteria of frontotemporal lobar degeneration. Brain CT showed that cerebral atrophy was accentuated at an early stage of the illness in the anterior portion of the frontal lobes in PiD cases and in the anterior portion of the temporal lobes in aPiD cases. Neuropathologically, PiD cases showed more circumscribed lobar atrophy than aPiD cases. Both PiD and aPiD cases revealed moderate to severe degeneration with neuronal loss and gliosis in the affected cerebral cortex and subcortical nuclei, but only aPiD cases had pyramidal tract degeneration. Immunohistochemical analyses demonstrated that tauopathy with phosphorylated tau accumulation in the Pick bodies in PiD cases, while aPiD cases showed ubiquitinopathy with ubiquitin accumulation in the intraneuronal and dendritic inclusions. These findings suggested that two subtypes of Pick's disease in Japan can be distinguished not only neuropathologically but also clinically based on differences in pathogenesis.     

4-repeat tauopathy sharing pathological and biochemical features of corticobasal degeneration and progressive supranuclear palsy

We report a 67-year-old man with 4-repeat (4R) tauopathy sharing both features of corticobasal degeneration (CBD) and progressive supranuclear palsy (PSP). Although CBD and PSP have a common pathological feature that 4R tau accumulates in neurons and glia, recent pathological studies have confirmed differences between the two disorders. Clinical features of the present case were asymmetrical apraxia, parkinsonism, memory disturbance, disorientation and left limb myoclonus with a 5-year history. Pathological features were the widespread occurrence of 4R tau-positive structures including pre-tangles, neurofibrillary tangles, astrocytic plaques, tufted astrocytes, coiled bodies and argyrophilic threads. Biochemically, immunoblotting of insoluble tau demonstrated the low molecular fragments of 37 kDa and 33 kDa observed in typical CBD and PSP, respectively, in addition to the presence of 4R tau isoforms. The present case shared tau-related pathological and biochemical features of CBD and PSP. These findings support that CBD and PSP are closely associated disorders having a pathogenesis common to 4R tauopathy.     

Timing of neural excitation in relation to basilar membrane motion in the basal region of the guinea pig cochlea during the presentation of low-frequency acoustic stimulation

In spite of many studies concerning auditory nerve action potentials, the timing of neural excitation in relation to basilar membrane (BM) motion is still not well understood. In this study, therefore, BM vibrations in the basal region of the guinea pig cochlea were measured using a laser Doppler velocimeter, and action potentials in auditory nerve fibers were recorded by a conventional microelectrode technique. An attempt was then made to determine the relationship between BM motion and neural excitation in auditory nerve fibers. To obtain BM responses in the high-characteristic frequency (CF) region (18-22 kHz) and responses of auditory nerve fibers with high CFs (14-22 kHz), low-frequency stimuli (50-2000 Hz), frequencies of which were well below CFs, were presented at 60-100 dB SPL. The results indicated that neural excitation occurred when the BM was displaced toward the scala vestibuli. Moreover, the neural excitatory phase did not significantly vary with the fiber's CF between 14 and 22 kHz nor with the stimulus level between 60 and 100 dB SPL.     

Astrocytic pathology in progressive supranuclear palsy: significance for neuropathological diagnosis

Progressive supranuclear palsy (PSP) is known to have tau-positive cytoskeletal abnormalities in astrocytes and oligodendroglia as well as neurons. Astrocytic tau-positive structures (tuft-shaped astrocytes; Tu-SA) were studied to elucidate their proper significance in the neuropathological diagnosis of PSP. The distribution and incidence of Tu-SA were examined in 26 cases of PSP. The disease specificity of Tu-SA was demonstrated by comparison with diseases accompanied by neurofibrillary tangles (NFTs) and those with or without cytoskeletal abnormalities other than NFTs. In PSP, Tu-SA appeared prominently in the precentral and premotor cortex (areas 4 and 6) of the superior and middle frontal gyri, but were quite scare in the temporal lobe and limbic area. In the subcortical nuclei, they appeared preferentially in the putamen and were also scattered in other degenerating regions. In the cerebrum the Tu-SA and NFTs were distributed in quite different regions. The assessment of the incidence of Tu-SA in area 6 revealed that only 5 of 26 PSP cases lacked Tu-SA in the examined fields. In contrast, in the control diseases, Tu-SA were found only rarely in cases of corticobasal degeneration in the cerebral cortex among other frequent tau-positive structures. One case of Pick’s disease showed occasional Tu-SA but only in the hippocampal region and not in the frontal lobe or putamen. In summary, although the absence of Tu-SA does not necessarily exclude the possibility of PSP, Tu-SA in the frontal lobe and putamen is highly suggestive for PSP. Thus, detection of Tu-SA and the ranking of the characteristic distribution of NFTs contribute to the neuropathological diagnosis of PSP. Received: 22 September 1997 / Revised, accepted: 2 March 1998