Chemotherapy-induced pain is a dose-limiting condition that affects 30% of patients undergoing chemotherapy. We found that the gut microbiota promotes the development of chemotherapy-induced mechanical hyperalgesia. Oxaliplatin-induced mechnical hyperalgesia was reduced in germ-free mice and in those mice pretreated with antibiotics. Restoration of the microbiota of germ-free mice abrogated this protection. These effects appear to be mediated, in part, by TLR4 expressed on hematopoietic cells, including macrophages.

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The number of studies on trigeminal nerve injury using animal models remains limited. A rodent model of trigeminal neuropathic pain was first developed in the 1994, in which chronic constriction injury is induced by ligation of the infraorbital nerve (IoN-CCI). This animal model has served as a major tool to study trigeminal neuropathic pain. Unfortunately, the surgical procedure in this model is complicated and far more difficult than ligation of peripheral nerves (e.g. sciatic nerve). The aim of this study was to improve on the current surgical procedure of IoN ligation to induce trigeminal neuropathic pain in rats. We demonstrate that the IoN can be readily accessed through a small facial incision. Chronic constriction injury can be induced by ligation of a segment at the distal infraorbital nerve (dIoN-CCI). This dIoN-CCI procedure is simple, minimally invasive and time-saving. Our data show that the dIoN-CCI procedure consistently induced both acute and chronic nociceptive behaviors in rats. Daily gabapentin treatment attenuated mechanical allodynia and reduced face-grooming episodes in dIoN-CCI rats. Perspective The orofacial pain caused by trigeminal nerve damage is severe and perhaps more debilitating than other types of neuropathic pain. However, studies on trigeminal neuropathic pain remain limited. This is largely due to the lack of proper animal models given the complexity of the existing surgical procedure required to induce trigeminal nerve injury. Our improved dIoN-CCI model is likely to make it more accessible to study the cellular and molecular mechanisms of neuropathic pain caused by trigeminal nerve damage.

Protein-tyrosine phosphatases (PTPases) have been implicated in the physiological regulation of the insulin signalling pathway. In cellular and molecular studies, the transmembrane, receptor-type PTPase LAR and the intracellular, non-receptor enzyme PTP1B have been shown to have a direct impact on insulin action in intact cell models. Since insulin signalling can be enhanced by reducing the abundance or activity of specific PTPases, pharmaceutical agents directed at blocking the interaction between individual PTPases and the insulin receptor may have potential clinical relevance to the treatment of insulin-resistant states such as obesity and Type II diabetes mellitus.

In order to define further the mechanisms responsible for tooth amelogenin heterogeneity, seven bovine amelogenin cDNAs were sequenced. On the basis of these sequences, five of the cDNAs could be grouped into one class which differed appreciably in sequence from the second group of two cDNAs. Two overlapping bovine genomic clones were then isolated and shown by sequencing to contain six exons encoding the entire consensus sequence of the class I cDNA. Southern blot analysis of DNA from male and female animals using class I or class II specific oligonucleotide probes suggested that the class I gene sequence was located on the X chromosome while the class II sequence was located on the Y chromosome. Therefore, these results also suggest that the genes on the X and Y chromosomes are both transcribed. Furthermore, the results are consistent with alternative splicing of the class I primary transcript as a potential mechanism for generating amelogenin heterogeneity.

BACKGROUND: Gut microbiota, a consortium of diverse microorganisms residing in the gastrointestinal tract, has emerged as a key player in neuroinflammatory responses, supporting the functional relevance of the “gut–brain axis.” Chronic-constriction injury of the sciatic nerve (CCI) is a commonly used animal model of neuropathic pain with a major input from T cell–mediated immune responses. In this article, we sought to examine whether gut microbiota influences CCI neuropathic pain, and, if so, whether T-cell immune responses are implicated. METHODS: We used a mixture of wide-spectrum oral antibiotics to perturbate gut microbiota in mice and then performed CCI in these animals. Nociceptive behaviors, including mechanical allodynia and thermal hyperalgesia, were examined before and after CCI. Additionally, we characterized the spinal cord infiltrating T cells by examining interferon (IFN)-γ, interleukin (IL)-17, and Foxp3. Using a Foxp3-GFP-DTR “knock-in” mouse model that allows punctual depletion of regulatory T cells, we interrogated the role of these cells in mediating the effects of gut microbiota in the context of CCI neuropathic pain. RESULTS: We found that oral antibiotics induced gut microbiota changes and attenuated the development of CCI neuropathic pain, as demonstrated by dampened mechanical allodynia and thermal hyperalgesia. Percentages of IFN-γ–producing Th1 cells and Foxp3+ regulatory T cells were significantly different between animals that received oral antibiotics (Th1 mean = 1.0, 95% confidence interval [CI], 0.9–1.2; Foxp3 mean = 8.1, 95% CI, 6.8–9.3) and those that received regular water (Th1 mean = 8.4, 95% CI, 7.8–9.0, P < .01 oral antibiotics versus water, Cohen’s d = 18.8; Foxp 3 mean = 2.8, 95% CI, 2.2–3.3, P < .01 oral antibiotics versus water, Cohen’s d = 6.2). These T cells characterized a skewing from a proinflammatory to an anti-inflammatory immune profile induced by gut microbiota changes. Moreover, we depleted Foxp3+ regulatory T cells and found that their depletion reversed the protection of neuropathic pain mediated by gut microbiota changes, along with a dramatic increase of IFN-γ–producing Th1 cell infiltration in the spinal cord (before depletion mean = 2.8%, 95% CI, 2.2–3.5; after depletion mean = 9.1%, 95% CI, 7.2–11.0, p < .01 before versus after, Cohen’s d = 5.0). CONCLUSIONS: Gut microbiota plays a critical role in CCI neuropathic pain. This role is mediated, in part, through modulating proinflammatory and anti-inflammatory T cells.

The amelogenins are the most abundant proteins in developing tooth enamel. Previous analyses have demonstrated that transcriptionally active genes encoding the proteins are located on both the bovine X and the bovine Y chromosomes. We report here the cloning and sequence analysis of the Y-chromosomal gene and corresponding cDNA. The Y-specific mRNA encodes a translation product in which a 21 amino acid domain has been deleted, relative to the X-specific amelogenin, resulting in loss of a structure tentatively described as a beta-spiral. There are also 13 single amino acid differences compared to the X-specific amelogenin. In addition, we have cloned and sequenced an X-chromosomal alternatively spliced amelogenin cDNA that encodes a 43 amino acid amelogenin primary translation product. Hydrophobicity analysis indicates that all analyzed amelogenin proteins have a mean hydrophilic character and the two peptides translated from alternatively spliced messages have significant increases in percentage of hydrophobic amino acids.