Expression and localization of Inter-alpha Inhibitors in rodent brain

Abstract

Inter-alpha Inhibitor Proteins (IAIPs) are a family of related serine protease inhibitors. IAIPs are important components of the systemic innate immune system. We have identified endogenous IAIPs in the central nervous system (CNS) of sheep during development and shown that treatment with IAIPs reduces neuronal cell death and improves behavioral outcomes in neonatal rats after hypoxic-ischemic brain injury. The presence of IAIPs in CNS along with their exogenous neuroprotective properties suggests that endogenous IAIPs could be part of the innate immune system in CNS. The purpose of this study was to characterize expression and localization of IAIPs in CNS. We examined cellular expressions of IAIPs in vitro in cultured cortical mouse neurons, in cultured rat neurons, microglia, and astrocytes, and in vivo on brain sections by immunohistochemistry from embryonic (E) day-18 mice and postnatal (P) day-10 rats. Cultured cortical mouse neurons expressed the light chain gene Ambp and heavy chain genes Itih-1, 2, 3, 4, and 5 mRNA transcripts and IAIPs proteins. IAIP proteins were detected by immunohistochemistry in cultured cells as well as brain sections from E18 mice and P10 rats. Immunoreactivity was found in neurons, microglia, astrocytes and oligodendroglia in multiple brain regions including cortex and hippocampus, as well as within both the ependyma and choroid plexus. Our findings suggest that IAIPs are endogenous proteins expressed in a wide variety of cell types and regions both in vitro and in vivo in rodent CNS. We speculate that endogenous IAIPs may represent endogenous neuroprotective immunomodulatory proteins within the CNS.

Alterations in inter‐alpha inhibitor protein expression after hypoxic‐ischemic brain injury in neonatal rats

“…However, future investigations would be of interest to determine if there are sex‐related differences in endogenous IAIP expression. In addition, we did not determine differences by Western immunoblot with reference to specific brain regions (Chen et al, 2016).…”

“…Inter‐alpha inhibitor proteins (IAIPs) are a family of endogenous serine protease inhibitors found in blood and numerous fetal, neonatal and adult tissues including the brain (Chen et al, 2016; Salier et al, 1996; Spasova et al, 2014; Takano et al, 1999). Two moieties are found in mammalian plasma: Inter‐alpha Inhibitor ( IαI ) composed of two heavy chains (H1 and H2) and a single light chain also called bikunin, and a Pre‐alpha Inhibitor ( PαI ), composed of one heavy (H3) and one light chain.…”

“…Endogenous IAIPs are expressed in relatively high amounts during development in rodent and ovine brain and are detected in neurons, microglia, astrocytes and oligodendrocytes, and in multiple brain regions including cerebral cortex and hippocampus in both neonatal rats and mice (Chen et al, 2016; Spasova et al, 2014). The ubiquitous presence of endogenous IAIPs in numerous types of brain cells and brain regions in the central nervous system (CNS) of rodents suggests that endogenous IAIPs represent an important, but previously unrecognized constituent of the normal brain composition, and most likely function (Chen et al, 2016; Spasova et al, 2014). In addition, we have previously shown that IAIP expression is reduced shortly after ischemia in the cerebral cortex and cerebellum of fetal sheep and returns toward non‐ischemic levels between 24 and 48 h after an ischemic insult (Spasova et al, 2016).…”

Pentraxin 3 regulates synaptic function by inducing AMPA receptor clustering via ECM remodeling and β1‐integrin

“…Indeed, the N-terminal domain of PTX3 has been found to be fundamental for a proper organization of the HA-rich ECM in the cumulus oophorus through the interaction with the key HA-binding components TSG6 and IaI (Salustri et al, 2004;Scarchilli et al, 2007;Baranova et al, 2014). IaI and TSG-6 are present in the CNS (Bertling et al, 2016;Chen et al, 2016), opening the possibility that the PTX3-dependent regulation of GluA content at the synapse may involve PNN remodeling processes. IaI and TSG-6 are present in the CNS (Bertling et al, 2016;Chen et al, 2016), opening the possibility that the PTX3-dependent regulation of GluA content at the synapse may involve PNN remodeling processes.…”

Immuno-modulator inter-alpha inhibitor proteins ameliorate complex auditory processing deficits in rats with neonatal hypoxic-ischemic brain injury

“…Inter-alpha inhibitor proteins (IAIPs) are a family of structurally related serine protease inhibitors with immune modulating capabilities that have been shown to down-regulate pro-inflammatory cytokines, Interleukin (IL)-1β and Tumor Necrosis Factor (TNF)-α and upregulate anti-inflammatory cytokine IL-10, leading to improved outcomes in several different models of systemic inflammatory disorders (Baek, Brokat et al 2003, Wakahara, Kobayashi et al 2005, Chen, Rivard et al 2016). The major forms if IAIPs are inter-alpha inhibitor (IαI), which consists of two heavy chairs (H1 & H2), and a single light chain (LC), and pre-alpha inhibitor (PαI) consisting of one heavy (H3) chain and one light chain (LC)(Fries and Blom 2000).…”