Tongqiao Huoxue Decoction ameliorates traumatic brain injury-induced gastrointestinal dysfunction by regulating CD36/15-LO/NR4A1 signaling,which fails when CD36 and CX3CR1 are deficient

Aims

Gastrointestinal (GI) dysfunction, as a common peripheral-organ complication after traumatic brain injury (TBI), is primarily characterized by gut inflammation and damage to the intestinal mucosal barrier (IMB). Previous studies have confirmed that TongQiao HuoXue Decoction (TQHXD) has strong anti-inflammatory properties and protects against gut injury. However, few have reported on the therapeutic effects of TQHXD in a TBI-induced GI dysfunction model. We aimed to explore the effects of TQHXD on TBI-induced GI dysfunction and the underlying mechanism thereof.

Methods

We assessed the protective effects and possible mechanism of TQHXD in treating TBI-induced GI dysfunction via gene engineering, histological staining, immunofluorescence (IF), 16S ribosomal ribonucleic acid (rRNA) sequencing, real-time polymerase chain reaction (RT-PCR), enzyme-linked immunosorbent assay (ELISA), Western blot (WB), and flow cytometry (FCM).

Results

TQHXD administration ameliorated TBI-induced GI dysfunction by modulating the abundance and structure of bacteria; reconstructing the destroyed epithelial and chemical barriers of the IMB; and improving M1/M2 macrophage, T-regulatory cell (Treg)/T helper 1 cell (Th₁), as well as Th₁₇/Treg ratios to preserve homeostasis of the intestinal immune barrier. Notably, Cluster of Differentiation 36 (CD36)/15-lipoxygenase (15-LO)/nuclear receptor subfamily 4 group A member 1 (NR4A1) signaling was markedly stimulated in colonic tissue of TQHXD-treated mice. However, insufficiency of both CD36 and (C-X3-C motif) chemokine receptor 1 (CX3CR1) worsened GI dysfunction induced by TBI, which could not be rescued by TQHXD.

Conclusion

TQHXD exerted therapeutic effects on TBI-induced GI dysfunction by regulating the intestinal biological, chemical, epithelial, and immune barriers of the IMB, and this effect resulted from the stimulation of CD36/NR4A1/15-LO signaling; however, it could not do so when CX3CR1 and CD36 were deficient. TQHXD might therefore be a potential drug candidate for treating TBI-induced GI dysfunction.     

Role of NMDA receptors in the trigeminal pathway,and the modulatory effect of magnesium in a model of rat temporomandibular joint arthritis

Temporomandibular joint (TMJ) arthritis is a common cause of orofacial pain. In the present study, the modulatory effects of N‐methyl‐d ‐aspartate receptors (NMDA‐Rs) and magnesium were investigated in TMJ arthritis hypernociception. Male Wistar rats received an intra‐articular injection of carrageenan (Cg) in the TMJ, and mechanical hypernociception was measured. The NMDA‐R antagonist, MK‐801, and magnesium chloride (MgCl₂) were administered before arthritis induction. Magnesium deficiency was promoted by feeding rats a synthetic magnesium‐free diet for 9 d before injection of Cg. The Cg induced mechanical hypernociception that lasted for 120 h. MK‐801 inhibited this hypernociceptive state. MgCl₂ pretreatment prevented Cg‐induced hypernociception and altered the nociceptive threshold in the absence of Cg. Magnesium deficiency increased hypernociception and induced spontaneous hypernociceptive behavior. TMJ arthritis increased the expression of mRNA for all NMDA‐R subunits and immunostaining of phosphorylated NR1 (phospho‐NR1). MgCl₂ inhibited expression of NR2B mRNA and phospho‐NR1 immunostaining and increased expression of NR3 mRNA. Magnesium deficiency increased expression of both NR1 and NR3 mRNAs and phospho‐NR1 immunostaining in the trigeminal subnucleus caudalis. We found that magnesium modulates nociceptive behavior and induces NMDA‐R subunit rearrangement in the subnucleus caudalis. The present results may lead to a better understanding of central processing in the nociceptive trigeminal pathway and the development of new approaches to treat orofacial pain with a TMJ origin.     

Adolescent brain maturation,the endogenous cannabinoid system and the neurobiology of cannabis-induced schizophrenia

Cannabis use during adolescence increases the risk of developing psychotic disorders later in life. However, the neurobiological processes underlying this relationship are unknown. This review reports the results of a literature search comprising various neurobiological disciplines, ultimately converging into a model that might explain the neurobiology of cannabis-induced schizophrenia. The article briefly reviews current insights into brain development during adolescence. In particular, the role of the excitatory neurotransmitter glutamate in experience-dependent maturation of specific cortical circuitries is examined. The review also covers recent hypotheses regarding disturbances in strengthening and pruning of synaptic connections in the prefrontal cortex, and the link with latent psychotic disorders. In the present model, cannabis-induced schizophrenia is considered to be a distortion of normal late postnatal brain maturation. Distortion of glutamatergic transmission during critical periods may disturb prefrontal neurocircuitry in specific brain areas. Our model postulates that adolescent exposure to Δ9-tetrahydrocannabinol (THC), the primary psychoactive substance in cannabis, transiently disturbs physiological control of the endogenous cannabinoid system over glutamate and GABA release. As a result, THC may adversely affect adolescent experience-dependent maturation of neural circuitries within prefrontal cortical areas. Depending on dose, exact time window and duration of exposure, this may ultimately lead to the development of psychosis or schizophrenia. The proposed model provides testable hypotheses which can be addressed in future studies, including animal experiments, reanalysis of existing epidemiological data, and prospective epidemiological studies in which the role of the dose–time–effect relationship should be central.     

Effect of NMDA NR2B antagonist on neuropathic pain in two spinal cord injury models

N-Methyl-d-aspartate (NMDA) receptors are thought to play an important role in the processes of central sensitization and pathogenesis of neuropathic pain, particularly after spinal cord injury (SCI). NMDA antagonists effectively reduce neuropathic pain, but serious side effects prevent their use as therapeutic drugs. NMDA NR2B antagonists have been reported to effectively reduce inflammatory and neuropathic pain. In this study, we investigated the effects of NR2B antagonists on neuropathic pain and the expression of NR2B in the spinal cord in 2 SCI models. SCI was induced at T12 by a New York University impactor (contusion) or by sectioning of the lateral half of the spinal cord (hemisection). Ifenprodil (100, 200, 500, 1000nmol) and Ro25-6981 (20, 50, 100, 200nmol) were intrathecally injected and behavioral tests were conducted. Ifenprodil increased the paw withdrawal threshold in both models but also produced mild motor depression at higher doses. Ro25-6981 increased the mechanical nociceptive threshold in a dose-dependent manner without motor depression. NR2B expression was significantly increased on both sides at the spinal segments of L1-2 and L4-5 in the hemisection model but did not change in the contusion model. Increased expression of NR2B in the hemisection model was reduced by intrathecal ifenprodil. These results suggest that intrathecal NMDA NR2B antagonist increased the mechanical nociceptive threshold after SCI without motor depression. A selective subtype of NMDA receptor, such as NR2B, may be a more selective target for pain control because NMDA receptors play a crucial role in the development and maintenance of chronic pain.     

Improved short-term memory and increased expression of NR2B observed in senescence-accelerated mouse (SAM) P6

The increased dopamine and serotonin were suggested [Niimi et al., 2008. Emotional behavior and expression pattern of tyrosine hydroxylase and tryptophan hydroxylase in senescence-accelerated mouse (SAM) P6 mice. Behav. Brain Res. 188, 329-336], and as these monoamines are well known to influence working memory processes, SAMP6 may show improved working memory. We found that spatial Y-maze memory and non-spatial novel object recognition memory of SAMP6 were improved compared with those of senescence-accelerated mouse resistant 1 (SAMR1). Among molecules known to be related with memory processes other than dopamine and serotonin, we focused on N-methyl-d-aspartate (NMDA) receptors. Animals treated with (+/-)-3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP), a NMDA receptor antagonist, were subjected to the Y-maze and novel object recognition tests to examine whether NMDA receptors are associated with the improved short-term memory of SAMP6. CPP (10mg/kg) significantly impaired the spontaneous alternation behavior and the exploratory preference of SAMR1, whereas no significant effect was seen in SAMP6 in either of these behavioral tests. Western blot analyses revealed increased expression of NMDA receptor (NR) subunit 2B in forebrain of SAMP6 compared with SAMR1, while there was no difference in the levels of NR1 and NR2A between SAMR1 and SAMP6. Our results indicate that increased expression of NR2B in forebrain of SAMP6 is one of the causes of the improved short-term memory of SAMP6.     

氯胺酮对脂多糖诱导的大鼠肺泡巨噬细胞氧化应激的影响

目的研究氯胺酮对脂多糖(LPS)刺激的大鼠肺泡巨噬细胞氧化应激的影响。方法体外培养的大鼠肺泡巨噬细胞株NR8383经氯胺酮(10、100和1000μmol/L)预处理,LPS刺激24 h后,应用试剂盒检测细胞培养上清液中丙二醛(MDA)及超氧化物岐化酶(SOD)的水平。结果与PBS组比较,LPS组培养上清液中MDA水平均明显增加,而SOD水平显著下降,而氯胺酮预处理组(100和1000μmol/L)对此具有抑制作用。结论氯胺酮对LPS所致的NR8383细胞的氧化应激损伤具有一定的保护作用。     

氯胺酮鞘内注射对慢性坐骨神经损伤大鼠脊髓 NMDA-2B mRNA表达的影响

目的：探讨氯胺酮连续鞘内注射对慢性坐骨神经损伤大鼠脊髓背角N-甲基-D天冬氨酸亚基（NR2B）mRNA表达的影响。方法：雄性SD大鼠18只，随机分为假手术组、CCI组和氯胺酮组。按Bennett等法制作CCI模型，测von-Frey丝触痛及冷水阈值，采用原位杂交技术检测各组脊髓背角NR2B mRNA表达的变化。结果：CCI组痛阈显著下降，冷水阈显著升高，脊髓背角有大量NR2B mRNA阳性表达（P＜0．01）；氯胺酮组仅出现轻度痛敏症状，NR2B mRNA表达受到明显抑制（P＜0．01）。结论：NR2B mRNA表达上调可能是神经损伤后慢性疼痛的发病机制之一，氯胺酮可抑制其表达从而发挥一定程度的镇痛作用。