Infection of cardiomyocytes and induction of left ventricle dysfunction by neurovirulent polytropic murine retrovirus

Role of TLR4 in lipopolysaccharide-induced acute kidney injury: protection by blueberry

Inflammation has been implicated in the pathophysiology of kidney disorders. Previous studies have documented the contributions of various inflammatory cascades in the development of kidney and other organ dysfunctions. The Toll-like receptor 4 (TLR4) inflammatory pathway is a major contributor of inflammation in the kidney. Interestingly, lipopolysaccharide (LPS), a specific ligand for TLR4, has been shown to induce acute kidney injury (AKI) in animal models. We have previously studied the beneficial effects of nonpharmacological agents, particularly blueberries (BB), in attenuating inflammation and oxidative stress. We hypothesize that BB protect against the LPS-induced AKI by inhibiting TLR4 activation and kidney injury markers. Twelve-week-old male Sprague-Dawley rats received a BB solution or saline intragastric gavage for 2 days. One group of BB and saline-gavaged animals was injected with LPS (10 mg/kg bw). Another group of rats was injected with VIPER (0.1 mg/kg iv), a TLR4-specific inhibitory peptide, 2 h before LPS administration. Compared to LPS-administered rats, the BB-pretreated animals exhibited improved glomerular filtration rate, elevated renal blood flow, and a reduced renal vascular resistance. In addition, a reduction in the rate of production of free radicals, namely total reactive oxygen species (ROS) and superoxide, was observed in the BB-supplemented LPS group. Gene and protein expressions for TLR4, proinflammatory cytokine, and acute kidney injury markers were also attenuated in animals that were pretreated with BB as measured by real time RT-PCR and Western blotting, respectively. These results in the BB-pretreated group were consistent with those in the VIPER-treated rats, and indicate that BB protects against AKI by inhibiting TLR4 and its subsequent effect on inflammatory and oxidative stress pathways.

Analysis of early dengue virus infection in mice as modulated by Aedes aegypti probing

Dengue virus (DENV), the etiologic agent of dengue fever, is transmitted during probing of human skin by infected-mosquito bite. The expectorated viral inoculum also contains an assortment of mosquito salivary proteins that have been shown to modulate host hemostasis and innate immune responses. To examine the potential role of mosquito probing in DENV establishment within the vertebrate host, we inoculated mice intradermally with DENV serotype 2 strain 1232 at sites where Aedes aegypti had or had not probed immediately prior. We assayed these sites 3 h postinoculation with transcript arrays for the Toll-like receptor (TLR), RIG-I-like receptor, and NOD-like receptor signaling pathways of the innate immune system. We then chose TLR7, transcription factor p65 (RelA), gamma interferon (IFN-γ), and IFN-γ-inducible protein 10 (IP-10) from the arrays for further investigation and assayed these transcripts at 10 min, 3 h, and 6 h postinoculation. The transcripts for TLR7, RelA, IFN-γ, and IP-10 were significantly downregulated between 2- and 3-fold in the group subjected to mosquito probing relative to the virus-only inoculation group at 3 h postinoculation. A reduction in these transcripts could indicate reduced DENV recognition and antigen presentation and diminished inhibition of viral replication and spread. Further, mosquito probing resulted in viremia titers significantly higher than those in mice that did not receive probing. A. aegypti probing has a significant effect on the innate immune response to DENV infection and generates an early immune environment more permissive to the establishment of infection.

Beneficial effects of carbon monoxide-releasing molecule-2 (CORM-2) on acute doxorubicin cardiotoxicity in mice: role of oxidative stress and apoptosis

Doxorubicin (DXR) has been used in variety of human malignancies for decades. Despite its efficacy in cancer, clinical usage is limited because of its cardiotoxicity, which has been associated with oxidative stress and apoptosis. Carbon monoxide-releasing molecules (CORMs) have been shown to reduce the oxidative damage and apoptosis. The present study investigated the effects of CORM-2, a fast CO-releaser, against DXR-induced cardiotoxicity in mice using biochemical, histopathological and gene expression approaches. CORM-2 (3, 10 and 30 mg/kg/day) was administered intraperitoneally (i.p.) for 10 days and terminated the study on day 11. DXR (20 mg/kg, i.p.) was injected before 72 h of termination. Mice treated with DXR showed cardiotoxicity as evidenced by elevation of serum creatine kinase (CK) and lactate dehydrogenase (LDH), tissue malondialdehyde (MDA), caspase-3 and decrease the level of total antioxidant status (TAS) in heart tissues. Pre- and post-treatment with CORM-2 (30 mg/kg, i.p.) elicited significant improvement in CK, LDH, MDA, caspase-3 and TAS levels. Histopathological studies showed that cardiac damage with DXR has been reversed with CORM-2+DXR treatment. There was dramatic decrease in hematological count in DXR-treated mice, which has been improved with CORM-2. Furthermore, there was also elevation of mRNA expression of heme oxygenase-1, hypoxia inducible factor-1 alpha, vascular endothelial growth factor and decrease in inducible-nitric oxide synthase expression upon treatment with CORM-2 that might be linked to cardioprotection. These data suggest that CORM-2 treatment provides cardioprotection against acute doxorubicin-induced cardiotoxicity in mice and this effect may be attributed to CORM-2-mediated antioxidant and anti-apoptotic properties.

Central TNF inhibition results in attenuated neurohumoral excitation in heart failure: a role for superoxide and nitric oxide

This study examined the effect of central tumor necrosis factor-alpha (TNF) blockade on the imbalance between nitric oxide and superoxide production in the paraventricular nucleus (PVN) and ventrolateral medulla (VLM), key autonomic regulators, and their contribution to enhanced sympathetic drive in mice with congestive heart failure (CHF). We also used a TNF gene knockout (KO) mouse model to study the involvement of TNF in body fluid homeostasis and sympathoexcitation in CHF. After implantation of intracerebroventricular (ICV) cannulae, myocardial infarction (MI) was induced in wild-type (WT) and KO mice by coronary artery ligation. Osmotic mini-pumps were implanted into one set of WT + MI/Sham mice for continuous ICV infusion of Etanercept (ETN), a TNF receptor fusion protein, or vehicle (VEH). Gene expressions of neuronal nitric oxide synthase (NOS) and angiotensin receptor-type 2 were reduced, while those of inducible NOS, Nox2 homologs, superoxide, peroxynitrite and angiotensin receptor-type 1 were elevated in the brainstem and hypothalamus of MI + VEH. Plasma norepinephrine levels and the number of Fos-positive neurons were also increased in the PVN and VLM in MI + VEH. MI + ETN and KO + MI mice exhibited reduced oxidative stress, reduced sympathoexcitation and an improved cardiac function. These changes in WT + MI were associated with increased sodium and fluid retention. These results indicate that elevated TNF in these autonomic regulatory regions of the brain alter the production of superoxide and nitric oxide, contributing to fluid imbalance and sympathoexcitation in CHF.

NF-kappaB-induced oxidative stress contributes to mitochondrial and cardiac dysfunction in type II diabetes

AIMS

Inflammatory molecules and their transcription factor, nuclear factor kappa-B (NF-kappaB), are thought to play important roles in diabetes-induced cardiac dysfunction. Here, we investigated the effects of pyrrolidine dithiocarbamate (PDTC), a NF-kappaB inhibitor, in diabetic mice.

METHODS AND RESULTS

Obese db/db mice and heterozygous lean mice (n = 8) were allowed free access to drinking water (control) or water containing PDTC (100 mg/kg) for 20 weeks. Left ventricular (LV) function was measured using echocardiography at baseline and at study end. Mice were sacrificed and LV removed for gene expression, biochemical, immunofluorescence, and mitochondrial assays. LV and mitochondrial reactive oxygen species (ROS), superoxide and peroxynitrite were measured using electron spin resonance spectroscopy. Enhanced NF-kappaB activity in db/db mice was associated with increased oxidative stress as demonstrated by increased ROS, superoxide, and peroxynitrite production, and increased NF-kappaB, gp91phox, and Nox1 expression; PDTC ameliorated these effects. Mitochondrial free radical production and structural damage were higher in the db/db group than in the control, db/db PDTC, and PDTC-treated heterozygous animal groups.

CONCLUSION

This study demonstrates that NF-kappaB blockade with PDTC mitigates oxidative stress and improves mitochondrial structural integrity directly, through down-regulation of increased oxygen-free radicals, thereby increasing ATP synthesis and thus restoring cardiac function in type II diabetes.

Diet-induced renal changes in Zucker rats are ameliorated by the superoxide dismutase mimetic TEMPOL

Diabetic nephropathy is the leading cause of renal failure in the United States. The obese Zucker rat (OZR; fa/fa) is a commonly used model of type 2 diabetes and metabolic syndrome (MetS), and of the nephropathy and renal oxidative stress commonly seen in these disorders. Heterozygous lean Zucker rats (LZRs; fa/+) are susceptible to high-fat diet (HFD)-induced obesity and MetS. The present study was designed to investigate whether 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPOL), a membrane-permeable radical scavenger, could alleviate the renal effects of MetS in OZR and LZR fed a HFD, which resembles the typical "Western" diet. OZR and LZR were fed a HFD (OZR-HFD and LZR-HFD) or regular diet (OZR-RD and LZR-RD) and allowed free access to drinking water or water containing 1 mmol/l TEMPOL for 10 weeks. When compared to OZR-RD animals, OZR-HFD animals exhibited significantly higher levels of total renal cortical reactive oxygen species (ROS) production, plasma lipids, insulin, C-reactive protein, blood urea nitrogen (BUN), creatinine (Cr), and urinary albumin excretion (P < 0.05); these changes were accompanied by a significant decrease in plasma high-density lipoprotein levels (P < 0.05). The mRNA expression levels of desmin, tumor necrosis factor-alpha (TNF-alpha), nuclear factor kappaB (NFkappaB), and NAD(P)H oxidase-1 (NOX-1) were significantly higher in the renal cortical tissues of OZR-HFD animals; NFkappaB p65 DNA binding activity as determined by electrophoretic mobility shift assay was also significantly higher in these animals. The same trends were noted in LZR-HFD animals. Our data demonstrate that TEMPOL may prove beneficial in treating the early stages of the nephropathy often associated with MetS.

Effect of the HMG-CoA reductase inhibitor rosuvastatin on early chronic kidney injury in obese zucker rats fed with an atherogenic diet

The obese Zucker rat (OZR) spontaneously develops hyperlipidemia, insulin resistance, and microalbuminuria. In this study, the initial metabolic, functional, and glomerular pathology in young OZR fed with an atherogenic diet resembles the characteristics of metabolic syndrome. Hyperlipidemia and other metabolic derangement cause early glomerular damage in OZR by 10 weeks of age, before overt diabetes is developed. Consequently, the effects of potential interventions should also be evaluated at the young age. In OZR fed with an atherogenic high-fat diet, low (5 mg/kg) and high (20 mg/kg) dosages of rosuvastatin started at 5 weeks and maintained for 10 weeks induced a significant improvement in metabolic abnormalities, blood pressure, and renal function, including microalbuminuria. The low dose of rosuvastatin significantly decreased mesangial expansion, and the high dose exerted a marked protective effect on the development of both glomerular hypertrophy and mesangial expansion. The statin also attenuated the inflammatory expression in the kidney cortex.

Analysis of protein levels of 24 cytokines in scrapie agent-infected brain and glial cell cultures from mice differing in prion protein expression levels

Activation of microglia and astroglia is seen in many neurodegenerative diseases including prion diseases. Activated glial cells produce cytokines as a protective response against certain pathogens and as part of the host inflammatory response to brain damage. In addition, cytokines might also exacerbate tissue damage initiated by other processes. In the present work using multiplex assays to analyze protein levels of 24 cytokines in scrapie agent-infected C57BL/10 mouse brains, we observed elevation of CCL2, CCL5, CXCL1, CXCL10, granulocyte-macrophage colony-stimulating factor (GM-CSF), gamma interferon (IFN-gamma), interleukin 1alpha (IL-1alpha), IL-1beta, IL-6, and IL-12p40. Scrapie agent-infected wild-type mice and transgenic mice expressing anchorless prion protein (PrP) had similar cytokine responses in spite of extensive differences in neuropathology. Therefore, these responses may be primarily a reaction to brain damage induced by prion infection rather than specific inducers of a particular type of pathology. To study the roles of astroglia and microglia in these cytokine responses, primary glial cultures were exposed to scrapie agent-infected brain homogenates. Microglia produced only IL-12p40 and CXCL10, whereas astroglia produced these cytokines plus CCL2, CCL3, CCL5, CXCL1, G-CSF, IL-1beta, IL-6, IL-12p70, and IL-13. Glial cytokine responses from wild-type mice and transgenic mice expressing anchorless PrP differed only slightly, but glia from PrP-null mice produced only IL-12p40, indicating that PrP expression was required for scrapie agent induction of other cytokines detected. The difference in cytokine response between microglia and astroglia correlated with 20-fold-higher levels of PrP expression in astroglia versus microglia, suggesting that high-level PrP expression on astroglia might be important for induction of certain cytokines.

Effects of pyrrolidine dithiocarbamate on high-fat diet-induced metabolic and renal alterations in rats

AIMS

We investigated the effects of the nuclear factor kappa B (NFkappaB) blocker pyrrolidine dithiocarbamate (PDTC) on high-fat diet (HFD)-induced metabolic and renal alterations in obese and lean Zucker rats (OZR and LZR, respectively).

MAIN METHODS

Rats were fed a HFD resembling the typical "Western" diet or a regular diet (RD) and allowed free access to tap water or tap water containing PDTC (150 mg/kg body weight) for 10 weeks; rats were then sacrificed. Total ROS production rates were measured using electron paramagnetic resonance spectroscopy, and superoxide production was measured with lucigenin assay. Blood, plasma, and urine were analyzed. Semi-quantitative reverse transcriptase-polymerase chain reaction and electrophoretic mobility shift assay were conducted to assess NFkappaB mRNA levels and DNA binding activities, respectively; immunofluorescence was performed to assess protein levels.

KEY FINDINGS

OZR-HFD rats exhibited significantly higher levels of total renal cortical reactive oxygen species production, plasma lipids, insulin, C-reactive protein, blood urea nitrogen, creatinine, and urinary albumin excretion than all other groups (p<0.05); these changes were accompanied by a significant decrease in plasma high density lipoprotein levels (p<0.05). Gene expression levels of desmin, cytokine and oxidative stress genes were significantly higher in the renal cortical tissues of OZR-HFD; NFkappaB p65 DNA binding activity was also significantly higher in these animals. PDTC attenuated these changes.

SIGNIFICANCE

Our data suggest that NFkappaB blockade may prove beneficial in treating the nephropathy often associated with metabolic syndrome.

Chronic NF-{kappa}B blockade reduces cytosolic and mitochondrial oxidative stress and attenuates renal injury and hypertension in SHR

Nuclear factor-kappaB (NF-kappaB) plays an important role in hypertensive renal injury; however, its roles in perpetuating mitochondrial oxidative stress and renal dysfunction remain unclear. In this study, we assessed the effects of chronic NF-kappaB blockade with pyrrolidine dithiocarbamate (PDTC) on renal dysfunction and mitochondrial redox status in spontaneously hypertensive rats (SHR). PDTC (150 mg.kg body wt(-1).day(-1)) or vehicle was administered orally to 8-wk-old SHR and their respective controls for 15 wk. Systolic blood pressure (SBP) was measured by tail-cuff plethysmography at the start of and at every third week throughout the study. After 15 wk of treatment, anesthetized rats underwent acute renal experiments to determine renal blood flow and glomerular filtration rate using PAH and inulin clearance techniques, respectively. Following renal experiments, kidneys were excised from killed rats, and cortical mitochondria were isolated for reactive oxygen species (ROS) measurements using electron paramagnetic resonance. Tissue mRNA and protein levels of NF-kappaB and oxidative stress genes were determined using real-time PCR and immunofluorescence or Western blotting, respectively. PDTC treatment partially attenuated the increase in SBP (196.4 +/- 9.76 vs. 151.4 +/- 2.12; P < 0.05) and normalized renal hemodynamic and excretory parameters and ATP production rates in SHR. PDTC treatment also attenuated the higher levels of cytosolic and mitochondrial ROS generation and tissue mRNA and protein expression levels of NF-kappaB and oxidative stress genes in SHR without any comparable responses in control rats. These findings suggest that NF-kappaB activation by ROS induces the cytosolic and mitochondrial oxidative stress and tissue injury that contribute to renal dysfunction observed in SHR.

Toll-like receptor 2 recognition of the microsporidia Encephalitozoon spp. induces nuclear translocation of NF-kappaB and subsequent inflammatory responses

Microsporidia are obligate intracellular parasites that are ubiquitous in nature and have been recognized as causing an important emerging disease among immunocompromised individuals. Limited knowledge exists about the immune response against these organisms, and virtually nothing is known about the receptors involved in host recognition. Toll-like receptors (TLR) are pattern recognition receptors that bind to specific molecules found on pathogens and signal a variety of inflammatory responses. In this study, we show that both Encephalitozoon cuniculi and Encephalitozoon intestinalis are preferentially recognized by TLR2 and not by TLR4 in primary human macrophages. This is the first demonstration of host receptor recognition of any microsporidian species. TLR2 ligation is known to activate NF-kappaB, resulting in inflammatory cytokines, such as tumor necrosis factor alpha (TNF-alpha) and interleukin-8 (IL-8). We found that the infection of primary human macrophages leads to the nuclear translocation of NF-kappaB in as early as 1 h and the subsequent production of TNF-alpha and IL-8. To verify the direct role of TLR2 parasite recognition in the production of these cytokines, the receptor was knocked down in primary human macrophages using small interfering RNA. This knockdown resulted in decreases in both the nuclear translocation of NF-kappaB and the levels of TNF-alpha and IL-8 after challenge with spores. Taken together, these experiments directly link the initial inflammatory response induced by Encephalitozoon spp. to TLR2 stimulation in human macrophages.

Neurovirulence of polytropic murine retrovirus is influenced by two separate regions on opposite sides of the envelope protein receptor binding domain

Changes in the envelope proteins of retroviruses can alter the ability of these viruses to infect the central nervous system (CNS) and induce neurological disease. In the present study, nine envelope residues were found to influence neurovirulence of the Friend murine polytropic retrovirus Fr98. When projected on a three-dimensional model, these residues were clustered in two spatially separated groups, one in variable region B of the receptor binding site and the other on the opposite side of the envelope. Further studies indicated a role for these residues in virus replication in the CNS, although the residues did not affect viral entry.