Dietary Lactoferrin Alleviates Age-Related Lacrimal Gland Dysfunction in Mice

BACKGROUND: Decrease in lacrimal gland secretory function is related to age-induced dry eye disease. Lactoferrin, the main glycoprotein component of tears, has multiple functions, including anti-inflammatory effects and the promotion of cell growth. We investigated how oral administration of lactoferrin affects age-related lacrimal dysfunction. METHODS AND FINDINGS: Twelve-month-old male C57BL/6Cr Slc mice were randomly divided into a control fed group and an oral lactoferrin treatment group. Tear function was measured at a 6-month time-point. After euthanasia, the lacrimal glands were subjected to histological examination with 8-hydroxy-2'-deoxyguanosine (8-OHdG) antibodies, and serum concentrations of 8-OHdG and hexanoyl-lysine adduct (HEL) were evaluated. Additionally, monocyte chemotactic protein-1(MCP-1) and tumor necrosis factor-α (TNF-α) gene expression levels were determined by real-time PCR. The volume of tear secretion was significantly larger in the treated group than in the control. Lactoferrin administration reduced inflammatory cell infiltration and the MCP-1 and TNF-α expression levels. Serum concentrations of 8-OHdG and HEL in the lactoferrin group were lower than those in the control group and were associated with attenuated 8-OHdG immunostaining of the lacrimal glands. CONCLUSION: Oral lactoferrin administration preserves lacrimal gland function in aged mice by attenuating oxidative damage and suppressing subsequent gland inflammation

Regulation of Axonal HCN1 Trafficking in Perforant Path Involves Expression of Specific TRIP8b Isoforms

The functions of HCN channels in neurons depend critically on their subcellular localization, requiring fine-tuned machinery that regulates subcellular channel trafficking. Here we provide evidence that regulatory mechanisms governing axonal HCN channel trafficking involve association of the channels with specific isoforms of the auxiliary subunit TRIP8b. In the medial perforant path, which normally contains HCN1 channels in axon terminals in immature but not in adult rodents, we found axonal HCN1 significantly increased in adult mice lacking TRIP8b (TRIP8b−/−). Interestingly, adult mice harboring a mutation that results in expression of only the two most abundant TRIP8b isoforms (TRIP8b[1b/2]−/−) exhibited an HCN1 expression pattern similar to wildtype mice, suggesting that presence of one or both of these isoforms (TRIP8b(1a), TRIP8b(1a-4)) prevents HCN1 from being transported to medial perforant path axons in adult mice. Concordantly, expression analyses demonstrated a strong increase of expression of both TRIP8b isoforms in rat entorhinal cortex with age. However, when overexpressed in cultured entorhinal neurons of rats, TRIP8b(1a), but not TRIP8b(1a-4), altered substantially the subcellular distribution of HCN1 by promoting somatodendritic and reducing axonal expression of the channels. Taken together, we conclude that TRIP8b isoforms are important regulators of HCN1 trafficking in entorhinal neurons and that the alternatively-spliced isoform TRIP8b(1a) could be responsible for the age-dependent redistribution of HCN channels out of perforant path axon terminals

Adenylyl cyclases: Expression in the developing rat thalamus and their role in absence epilepsy

Adenylyl cyclases (ACs) synthesize the second messenger cyclic AMP (cAMP) which influences the function of multiple ion channels. Former studies point to a malfunction of cAMP-dependent ion channel regulation in thalamocortical relay neurons that contribute to the development of the absence epileptic phenotype of a rat genetic model (WAG/Rij). Here, we provide detailed information about the thalamic gene and protein expression of Ca(2+)/calmodulin-activated AC isoforms in rat thalamus. Data from WAG/Rij were compared to those from non-epileptic controls (August-Copenhagen Irish rats) to elucidate whether differential expression of ACs contributes to the dysregulation of thalamocortical activity. At one postnatal stage (P21), we found the gene expression of two specific Ca(2+)-activated AC isoforms (AC-1 and AC-3) to be significantly down-regulated in epileptic tissue, and we identified the isoform AC-1 to be the most prominent one in both strains. However, Western blot data and analysis of enzymatic AC activity revealed no differences between the two strains. While basal AC activity was low, cAMP production was boosted by application of a forskolin derivative up to sevenfold. Despite previous hints pointing to a major contribution of ACs, the presented data show that there is no apparent causality between AC activity and the occurrence of the epileptic phenotype

Activity Modes in Thalamocortical Relay Neurons are Modulated by G(q)/G(11) Family G-proteins - Serotonergic and Glutamatergic Signaling

In thalamocortical relay (TC) neurons, G-protein-coupled receptors play an important part in the control of activity modes. A conditional Galpha(q) knockout on the background of a constitutive Galpha(11) knockout (Galpha(q)/Galpha(11) (-/-)) was used to determine the contribution of Gq/G11 family G-proteins to metabotropic serotonin (5-HT) and glutamate (Glu) function in the dorsal part of the lateral geniculate nucleus (dLGN). In control mice, current clamp recordings showed that alpha-m-5-HT induced a depolarization of V(rest) which was sufficient to suppress burst firing. This depolarization was concentration-dependent (100 muM: +6 +/- 1 mV, n = 10; 200 muM: +10 +/- 1 mV, n = 7) and had a conditioning effect on the activation of other Galpha(q)-mediated pathways. The depolarization was significantly reduced in Galpha(q)/Galpha(11) (-/-) (100 muM: 3 +/- 1 mV, n = 11; 200 muM: 5 +/- 1 mV, n = 6) and was apparently insufficient to suppress burst firing. Activating Galpha(q)-coupled muscarinic receptors affected the magnitude of alpha-m-5-HT-induced effects in a reciprocal manner. Furthermore, the depolarizing effect of mGluR1 agonists was significantly reduced in Galpha(q)/Galpha(11) (-/-) mice. Immunohistochemical stainings revealed binding of 5-HT(2C)R- and mGluR1alpha-, but not of 5-HT(2A)R-specific antibodies in the dLGN of Galpha(q)/Galpha(11) (-/-) mice. In conclusion, these findings demonstrate that transmitters of ascending brainstem fibers and corticofugal fibers both signal via a central element in the form of Gq/G11-mediated pathways to control activity modes in the TC system

Postnatal expression pattern of HCN channel isoforms in thalamic neurons: Relationship to maturation of thalamocortical oscillations

Hyperpolarization-activated cyclic nucleotide-gated cation (HCN) channels are the molecular substrate of the hyperpolarization-activated inward current (I(h)). Because the developmental profile of HCN channels in the thalamus is not well understood, we combined electrophysiological, molecular, immunohistochemical, EEG recordings in vivo, and computer modeling techniques to examine HCN gene expression and I(h) properties in rat thalamocortical relay (TC) neurons in the dorsal part of the lateral geniculate nucleus and the functional consequence of this maturation. Recordings of TC neurons revealed an approximate sixfold increase in I(h) density between postnatal day 3 (P3) and P106, which was accompanied by significantly altered current kinetics, cAMP sensitivity, and steady-state activation properties. Quantification on tissue levels revealed a significant developmental decrease in cAMP. Consequently the block of basal adenylyl cyclase activity was accompanied by a hyperpolarizing shift of the I(h) activation curve in young but not adult rats. Quantitative analyses of HCN channel isoforms revealed a steady increase of mRNA and protein expression levels of HCN1, HCN2, and HCN4 with reduced relative abundance of HCN4. Computer modeling in a simplified thalamic network indicated that the occurrence of rhythmic delta activity, which was present in the EEG at P12, differentially depended on I(h) conductance and modulation by cAMP at different developmental states. These data indicate that the developmental increase in I(h) density results from increased expression of three HCN channel isoforms and that isoform composition and intracellular cAMP levels interact in determining I(h) properties to enable progressive maturation of rhythmic slow-wave sleep activity patterns