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Chemotherapy-induced peripheral neuropathy (CIPN) is a disruptive and persistent side-effect of cancer treatment with paclitaxel. Recent reports showed that paclitaxel treatment results in the activation of Toll-like receptor 4 (TLR4) signaling and increased expression of monocyte chemotactic protein 1 (MCP-1) in dorsal root ganglion cells. In this study, we sought to determine whether an important consequence of this signaling and also a key step in the CIPN phenotype was the recruitment and infiltration of macrophages into dorsal root ganglia (DRG). Here, we show that macrophage infiltration does indeed occur in a time course that matches the onset of the behavioral CIPN phenotype in Sprague-Dawley rats. Moreover, depletion of macrophages by systemic administration of liposome-encapsulated clodronate (clophosome) partially reversed behavioral signs of paclitaxel-induced CIPN as well as reduced TNFα expression in DRG. Intrathecal injection of MCP-1 neutralizing antibodies reduced paclitaxel-induced macrophage recruitment into the DRG and also blocked the behavioral signs of CIPN. Intrathecal treatment with the TLR4 antagonist LPS-RS blocked mechanical hypersensitivity, reduced MCP-1 expression, and blocked the infiltration of macrophages into the DRG in paclitaxel treated rats. Finally, the inhibition of macrophage infiltration into DRG following paclitaxel treatment with clodronate or LPS-RS prevented the loss of intra-epidermal nerve fibers (IENFs) observed following paclitaxel treatment alone. Taken altogether, these results are the first to indicate a mechanistic link such that activation of TLR4 by paclitaxel leads to increased expression of MCP-1 by DRG neurons resulting in macrophage infiltration to the DRG that express inflammatory cytokines and the combination of these events results in IENF loss and the development of behavioral signs of CIPN.

Successful implantation is an absolute requirement for the reproduction of species, including humans. The process by which a foreign blastocyst is accepted by the maternal endometrium is complex and requires interplay of many systems. Implantation occurs during the putative implantation window, in which the maternal endometrium is ready to accept the blastocyst, which on the other hand, also plays a specific role. It produces cytokines and chemokines and expresses adhesion molecules and certain classes of MHC molecules. We review the most important players in implantation. Concerning the cytokines, the establishment of controlled aggression is key; an excess of pro- or anti-inflammation is detrimental to pregnancy outcome. Chemokines control the orientation of the embryo. The adhesion molecules are necessary to establish the required physical interaction between mother and blastocyst. Finally, immune cells and in particular, uterine NK and regulatory T cells are pivotal in inducing tolerance to the blastocyst. The aim of this review is to discuss mechanisms at play and their relative importance to the establishment of pregnancy.