CXCR3 mediates chondrocyte injury through regulating nitric oxide.

OBJECTIVE: As a common joint disease, osteoarthritis exhibits increasing trend in recent years. C-X-C motif chemokine receptor 3 (CXCR3) is a kind of chemokine with the characteristic of recruiting inflammatory cells. Its function in osteoarthritis has not been clarified. This study aims to explore the role of CXCR3 in cartilage injury by affecting unfolded protein response (UPR) pathway. PATIENTS AND METHODS: The sample was obtained from osteoarthritis patients to test CXCR3 expression by Real-time polymerase chain reaction (PCR). Chondrocyte apoptosis model was established in vitro induced by interleukin 1ß (IL-1ß) and sodium nitroprusside (SNP). CXCR3 level was downregulated by using siRNA. Cell apoptosis was determined by using transferase-mediated deoxyuridine triphosphate-biotin nick end labeling (TUNEL) assay. UPR pathway related factors C/EBP homology protein (CHOP) and glucose regulated protein 78 (GRP78) protein expressions were tested by using Western blot. RESULTS: CXCR3 protein level significantly increased in osteoarthritis patients (2.66 ± 0.25 vs. 1.00 ± 0.05, p<0.05). CXCR3 siRNA significantly reduced nitrate level in chondrocytes induced by IL-ß (35.22 ± 1.76 vs. 17.82 ± 0.89, p<0.05) without affecting cell apoptosis (1.13 ± 0.05 vs. 0.859 ± 0.04, p>0.05). CXCR3 siRNA markedly downregulated nitrate level in chondrocytes (50.63 ± 2.53 vs. 30.63 ± 1.63, p<0.05) and alleviated cell apoptosis induced by SNP (1.98 ± 0.10 vs. 1.25 ± 0.06, p<0.05). UPR pathway C/EBP homology protein (CHOP) and glucose regulated protein 78 (GRP78) participated in the process of chondrocyte apoptosis. CONCLUSIONS: Endoplasmic reticulum (ER) stress signaling pathway CHOP and GRP78 are involved in CXCR3 receptor attenuating chondrocyte apoptosis induced by SNP.

Association of p53 Arg72Pro and MDM2 SNP309 polymorphisms with glioma.

Epidemiological studies of the association of variants p53 Arg72Pro and MDM2 single-nucleotide polymorphism 309 (SNP309) with glioma risk have produced inconsistent results. The aim of the current study was to evaluate the association of these 2 variants with glioma susceptibility using a meta-analysis approach. For p53 Arg72Pro, 10 case-control studies including 2587 glioma patients and 4061 unrelated controls were identified. The pooled odds ratios (ORs) for Arg/Pro heterozygotes and Pro/Pro homozygotes were 1.08 [95% confidence interval (95%CI) = 0.85-1.37] and 1.08 (95%CI = 0.85-1.36), respectively, when compared to Arg/Arg carriers. Under the dominant effect model, Pro allele carriers also showed no significantly elevated glioma risk (pooled OR = 1.11, 95%CI = 0.90-1.38), and similar results were found under the recessive-effect model (pooled OR = 1.17, 95%CI = 0.85-1.61). For variant MDM2 SNP309, 3 case-control studies including 606 cases and 309 controls were identified. A marginal association with glioma risk was found for heterozygous G/T carriers (pooled OR = 1.95, 95%CI = 1.00- 3.81), whereas homozygous G/G carriers showed an increased but not significantly elevated risk of glioma (pooled OR = 2.14, 95%CI = 0.71-6.45) compared with that of T/T homozygotes. We also found no significant association between the MDM2 SNP309 polymorphism and glioma risk (pooled OR = 1.86, 95%CI = 0.94-3.67 and pooled OR = 1.25, 95%CI = 0.62-2.56, respectively) under the dominant and recessive models. Taken together, the current data suggested that the 2 polymorphisms may not contribute to glioma susceptibility.

Normal light response, photoreceptor integrity, and rhodopsin dephosphorylation in mice lacking both protein phosphatases with EF hands (PPEF-1 and PPEF-2).

Rhodopsin dephosphorylation in Drosophila is a calcium-dependent process that appears to be catalyzed by the protein product of the rdgC gene. Two vertebrate rdgC homologs, PPEF-1 and PPEF-2, have been identified. PPEF-1 transcripts are present at low levels in the retina, while PPEF-2 transcripts and PPEF-2 protein are abundant in photoreceptors. To determine if PPEF-2 alone or in combination with PPEF-1 plays a role in rhodopsin dephosphorylation and to determine if retinal degeneration accompanies mutation of PPEF-1 and/or PPEF-2, we have produced mice carrying targeted disruptions in the PPEF-1 and PPEF-2 genes. Loss of either or both PPEFs has little or no effect on rod function, as mice lacking both PPEF-1 and PPEF-2 show little or no changes in the electroretinogram and PPEF-2-/- mice show normal single-cell responses to light in suction pipette recordings. Light-dependent rhodopsin phosphorylation and dephosphorylation are also normal or nearly normal as determined by (i) immunostaining of PPEF-2-/- retinas with the phosphorhodopsin-specific antibody RT-97 and (ii) mass spectrometry of C-terminal rhodopsin peptides from mice lacking both PPEF-1 and PPEF-2. Finally, PPEF-2-/- retinas show normal histology at 1 year of age, and retinas from mice lacking both PPEF-1 and PPEF-2 show normal histology at 3 months of age, the latest time examined. These data indicate that, in contrast to loss of rdgC function in Drosophila, elimination of PPEF function does not cause retinal degeneration in vertebrates.

Disruption of a retinal guanylyl cyclase gene leads to cone-specific dystrophy and paradoxical rod behavior.

One of two orphan photoreceptor guanylyl cyclases that are highly conserved from fish to mammals, GC-E (or retGC1) was eliminated by gene disruption. Expression of the second retinal cyclase (GC-F) as well as the numbers and morphology of rods remained unchanged in GC-E null mice. However, rods isolated from such mice, despite having a normal dark current, recovered from a light flash markedly faster. Unexpectedly, the a- and b-waves of electroretinograms (ERG) from dark-adapted null mice were suppressed markedly. Cones, initially present in normal numbers in the retina, disappeared by 5 weeks, based on ERG and histology. Thus, the GC-E-deficient mouse defines a model for cone dystrophy, but it also demonstrates that morphologically normal rods display paradoxical behavior in their responses to light.

A cGMP-gated cation channel and phototransduction in depolarizing photoreceptors of the lizard parietal eye.

Photoreceptors of the lizard parietal eye, unlike rods and cones but like most invertebrate photoreceptors, respond to light under dark-adapted conditions with a depolarization. Using excised-patch recordings, we have nonetheless found a cGMP-gated, non-selective cation channel present at high density at the presumptive light-sensitive part (the outer segment) of these cells. This channel resembles the rod cGMP-gated channel in its activation characteristics, and by showing a relative non-selectivity among alkali monovalent cations, a high permeability to Ca2+, a high sensitivity to L-cis-diltiazem, as well as a negative modulation by Ca(2+)-calmodulin. This channel appears to mediate phototransduction by opening in the light to produce the depolarizing response.

An unusual cGMP pathway underlying depolarizing light response of the vertebrate parietal-eye photoreceptor.

All cellular signaling pathways currently known to elevate cGMP involve the activation of a guanylyl cyclase to synthesize cGMP. Here we describe an exception to this rule. In the vertebrate parietal eye, the photoreceptors depolarize to light under dark-adapted conditions, unlike rods and cones but like most invertebrate photoreceptors. We report that the signaling pathway for this response involves a rise in intracellular cGMP resulting from an inhibition of the phosphodiesterase that hydrolyzes cGMP. Furthermore, this phosphodiesterase is driven by an active G protein in darkness. These results indicate an antagonistic control of the phosphodiesterase by two G proteins, analogous to the Gs/Gi control of adenylyl cyclase. Our findings demonstrate an unusual phototransduction mechanism and at the same time indicate that signaling involving cyclic nucleotides is more elaborate than previously known.