Cell cycle S phase markers are expressed in cerebral neuron nuclei of cats infected by the Feline Panleukopenia Virus

Mink enteritis virus infection induced cell cycle arrest and autophagy for its replication

Mink enteritis virus (MEV) is an important pathogen causing mink viral enteritis. The mechanisms of cell cycle arrest induced by MEV infection and the roles of autophagy in MEV replication remain unclear. In this study, the roles of MEV NS1 protein in inducing cell cycle arrest were investigated, using the in vitro CRFK cell models. As a result, MEV infection increased the proportion of the cells in S phase, inducing S phase arrest. MEV NS1 protein also led to cycle arrest in S phase. And the deletions of NLS and TAD significantly weakened the ability of NS1 protein to cause cycle arrest in S phase, and NLS and TAD were the indispensable domains of NS1 protein. Furthermore, proteome profiling of the cells infected with MEV at the early stage demonstrated that the autophagy-related protein TRIM23 was significantly up-regulated during MEV infection. To investigate the effects of TRIM23 on MEV replication, the cell models were established, using siRNAs targeting TRIM23. The knockdown of TRIM23 resulted in the decreases in the levels of TBK1 protein and the phosphorylated p62 protein, and an increase in the level of p62 protein in the cells infected with MEV, indirectly influencing virus replication. The findings implied that S phase arrest and the up-regulated TRIM23 induced by MEV infection played the important roles in MEV replication.

Arthroscopy combined with high tibial osteotomy promotes cartilage regeneration in osteoarthritis

BACKGROUND

To investigate the effect of arthroscopy combined with high tibial osteotomy (HTO) on cartilage regeneration in patients with knee osteoarthritis.

METHODS

A retrospective analysis of 50 patients with varus and medial compartment osteoarthritis of the knee treated by arthroscopy combined with HTO. One year after the operation, a second-look arthroscopy was performed to observe the cartilage regeneration. The regeneration of cartilage was evaluated by different pathological staining of some of the new cartilage. Finally, part of the new cartilages (n = 6) were taken for quantitative real-time PCR and western blotting experiments to display the mechanism of cartilage regeneration.

RESULTS

One year after arthroscopy combined with HTO, the results of arthroscopy revealed the formation of new tissue in the defect area of the medial compartment's cartilage in the knee joint. In addition, different pathological staining results indicated that the new tissue was cartilage-like tissue. Furthermore, HTO potently up-regulated the expression of p-ERK1/2 at the protein level in knee osteoarthritis patients compared with control group. However, there was no significant difference in the relative expression of collagen II at mRNA and protein level between control group and knee osteoarthritis patients.

CONCLUSION

Arthroscopy combined with HTO can promote cartilage regeneration in patients with knee osteoarthritis.

Evidence of cell cycle re-entry in post-mitotic, terminally differentiated feline neurons

Parvovirus infections in dogs and cats are restricted to highly mitotically active tissues, predominantly to the epithelium of the gastrointestinal tract and, in cases of prenatal infections in cats, also to Purkinje cell neuroblasts. The evidence of parvovirus-infected mature feline neurons gave rise to reconsider the dogma of post-mitotically fixed and terminally differentiated neurons in the adult central nervous system. To elucidate the postulated capability of certain terminally differentiated feline neurons to re-enter the cell cycle, immunohistochemical double labeling using the transcription factor Sox2 and the tumor suppressor and cell cycle regulator retinoblastoma protein in its phosphorylated state (pRb) was performed. Formalin-fixed and paraffin-embedded brain tissue negative for parvovirus-antigen from 14 cats was compared to brain tissue from 13 cats with immunohistochemically confirmed cerebral parvovirus infection; the 27 cats were aged between 50 days of gestation (E50) and 5 years. Both groups revealed nuclear Sox2 and pRb immunosignals in numerous neurons, suggesting a more active state than mature neurons should have. Accordingly, parvovirus is not exclusively involved in the reactivation of the cell cycle machinery in those post-mitotic, terminally differentiated feline neurons.

A Lipidated Peptide with Mitochondrial Membrane Localization in Human A549 Lung Cells: From Enhanced Cell-Penetrating Properties to Biological Activity Mechanism

Here, a lipidated peptide Pal-pHK-pKV with self-assembly properties and the ability to provoke the disruption of the mitochondrial voltage-dependent anion channel-1 protein (VDAC1)-hexokinase-II (HK-II) complex is reported. The effects of the peptide pHK (N-terminal 15-amino acid fragment of HK-II that specifically binds VDAC1) are compared to those of a designed biomimetic amphiphilic pHK-pKV conjugate (pHK coupled with a cell-penetrating peptide pKV) and Pal-pHK-pKV (a lipidated conjugate modified with a hydrophobic palmitic (Pal) alkyl chain). The Pal-pHK-pKV exhibits a stronger interaction with the membrane as compared to pHK-pKV, which is demonstrated by the Langmuir-Blodgett technique and two-photon excitation microscopy. The amphiphilic peptide derivatives are cytotoxic to the A549 cells, but Pal-pHK-pKV is more cytotoxic. The inhibitory effects of the pHK derivatives on the A549 cells growth are investigated through induced apoptosis pathway, depolarized mitochondrial membrane potential, inhibited glycolysis, and activated caspase. The results of the immunofluorescence evidence the specific mitochondrial targeting by those derivatives.

Effect of cell cycle synchronization on cadmium-induced apoptosis and necrosis in NRK-52E cells

Heavy metal pollution is a problem that cannot be ignored. Due to the prevalence of cadmium in the environment and its harmful effects on humans, cadmium pollution has become a research hotspot recently. The mechanism of cadmium-induced toxicity has also drawn much attention and most studies have been conducted using whole cells, but the toxicological mechanism of cadmium remains unclear. In this study, we aimed to obtain NRK-52E cells at different growth stages by various methods and analyze the differences in cadmium toxicity. The results show that the cadmium sensitivity of cells in each phase was different and the late apoptotic rate was increased significantly after 5 µM Cd treatment. In addition, cadmium easily induces apoptosis of G0- and S-phase cells, as well as necrosis of S- and M-phase cells, but has no significant effect on G1-phase cells. Overall, we first explored the differences in the effects of cadmium on NRK-52E cells at various growth phases. Besides, the findings of this study might provide a theoretical basis for further exploration of the toxicological mechanism of cadmium.Abbreviations Cd: cadmium; CDK: cyclin-dependent kinases; DAPI 2-(4-amidinophenyl)-1H-indole-6-carboxamidine; TBST: Tris-buffered saline with Tween-20; PI: propidium iodide; DMEM: Dulbecco's Modified Eagle Medium; BCA: bicinchoninic acid.

Cloning, Prokaryotic Soluble Expression, and Analysis of Antiviral Activity of Two Novel Feline IFN-ω Proteins

Cats are becoming more popular as household companions and pets, forming close relationships with humans. Although feline viral diseases can pose serious health hazards to pet cats, commercialized preventative vaccines are lacking. Interferons (IFNs), especially type I IFNs (IFN-α, IFN-β, and interferon omega (IFN-ω)), have been explored as effective therapeutic drugs against viral diseases in cats. Nevertheless, there is limited knowledge regarding feline IFN-ω (feIFN-ω), compared to IFN-α and IFN-β. In this study, we cloned the genes encoding feIFN-ωa and feIFN-ωb from cat spleen lymphocytes. Homology and phylogenetic tree analysis revealed that these two genes belonged to new subtypes of feIFN-ω. The recombinant feIFN-ωa and feIFN-ωb proteins were expressed in their soluble forms in Escherichia coli, followed by purification. Both proteins exhibited effective anti-vesicular stomatitis virus (VSV) activity in Vero, F81 (feline kidney cell), Madin-Darby bovine kidney (MDBK), Madin-Darby canine kidney (MDCK), and porcine kidney (PK-15) cells, showing broader cross-species antiviral activity than the INTERCAT IFN antiviral drug. Furthermore, the recombinant feIFN-ωa and feIFN-ωb proteins demonstrated antiviral activity against VSV, feline coronavirus (FCoV), canine parvovirus (CPV), bovine viral diarrhea virus (BVDV), and porcine epidemic diarrhea virus (PEDV), indicating better broad-spectrum antiviral activity than the INTERCAT IFN. The two novel feIFN-ω proteins (feIFN-ωa and feIFN-ωb) described in this study show promising potential to serve as effective therapeutic agents for treating viral infections in pet cats.

Analysis of the microRNA expression profiles in feline kidney cell line infected with feline panleukopenia virus

MicroRNAs (miRNAs) play crucial roles in post-transcriptional regulation of gene expression in many biological processes. Feline panleukopenia virus (FPV) is a highly infectious pathogen that can cause severe disease in pets, economically important animals and wildlife. In this study, miRNAs associated with FPV infection were identified using high-throughput sequencing. Our results showed that 673 known miRNAs and 278 novel miRNAs were identified and 57 significantly differential expression miRNAs were found post-FPV infection in feline kidney cell line. Stem-loop qRT-PCR was applied to validate the expression of the randomly selected miRNAs; the results were consistent with the sequencing data. Furthermore, the target genes of differential expression miRNAs were analyzed and predicated by GO and KEGG pathway. Altogether, our analysis provides a potential link between miRNA expression and the pathogenesis of FPV infection.

Lymphoplasmacytic Meningoencephalitis and Neuronal Necrosis Associated With Parvoviral Infection in Cats

Neurologic manifestations other than cerebellar hypoplasia are rarely associated with feline panleukopenia virus (FPV) infection in cats. Here the authors describe lymphoplasmacytic meningoencephalitis and neuronal necrosis in 2 cats autopsied after exhibiting ataxia and nystagmus. Gross changes consisted of cerebellar herniation through the foramen magnum, with flattening of cerebrocortical gyri and narrowing of sulci. Histologically, lymphoplasmacytic meningoencephalitis, extensive neuronal necrosis, and neuroaxonal degeneration with digestion chambers were present in the telencephalon and brain stem in both cats. Frozen brain tissue of both cats was positive for parvoviral antigen via fluorescent antibody testing, and formalin-fixed, paraffin-embedded tissue sections of brain were immunoreactive for parvovirus antigen and positive for parvoviral DNA on in situ hybridization. Frozen brain tissue from 1 case was positive for parvovirus NS1 and VP2 genes using conventional polymerase chain reaction, and subsequent DNA sequencing and phylogenetic analysis revealed that the viral strain was a FPV. Reverse transcription quantitative polymerase chain reaction on formalin-fixed, paraffin-embedded brain tissue revealed high levels of parvovirus in both cases, supporting an acute and active viral infection. Although rare, FPV infection should be considered in cases of lymphoplasmacytic meningoencephalitis and neuronal necrosis in cats.

Neuronal Vacuolization in Feline Panleukopenia Virus Infection

Feline panleukopenia virus (FPV) infections are typically associated with anorexia, vomiting, diarrhea, neutropenia, and lymphopenia. In cases of late prenatal or early neonatal infections, cerebellar hypoplasia is reported in kittens. In addition, single cases of encephalitis are described. FPV replication was recently identified in neurons, although it is mainly found in cells with high mitotic activity. A female cat, 2 months old, was submitted to necropsy after it died with neurologic deficits. Besides typical FPV intestinal tract changes, multifocal, randomly distributed intracytoplasmic vacuoles within neurons of the thoracic spinal cord were found histologically. Next-generation sequencing identified FPV-specific sequences within the central nervous system. FPV antigen was detected within central nervous system cells, including the vacuolated neurons, via immunohistochemistry. In situ hybridization confirmed the presence of FPV DNA within the vacuolated neurons. Thus, FPV should be considered a cause for neuronal vacuolization in cats presenting with ataxia.

Feline Panleucopenia Virus NS2 Suppresses the Host IFN-β Induction by Disrupting the Interaction between TBK1 and STING

Feline panleucopenia virus (FPV) is a highly infectious pathogen that causes severe diseases in pets, economically important animals and wildlife in China. Although FPV was identified several years ago, little is known about how it overcomes the host innate immunity. In the present study, we demonstrated that infection with the FPV strain Philips-Roxane failed to activate the interferon β (IFN-β) pathway but could antagonize the induction of IFN stimulated by Sendai virus (SeV) in F81 cells. Subsequently, by screening FPV nonstructural and structural proteins, we found that only nonstructural protein 2 (NS2) significantly suppressed IFN expression. We demonstrated that the inhibition of SeV-induced IFN-β production by FPV NS2 depended on the obstruction of the IFN regulatory factor 3 (IRF3) signaling pathway. Further, we verified that NS2 was able to target the serine/threonine-protein kinase TBK1 and prevent it from being recruited by stimulator of interferon genes (STING) protein, which disrupted the phosphorylation of the downstream protein IRF3. Finally, we identified that the C-terminus plus the coiled coil domain are the key domains of NS2 that are required for inhibiting the IFN pathway. Our study has yielded strong evidence for the FPV mechanisms that counteract the host innate immunity.