Pharmacological antagonism of interleukin-8 receptor CXCR2 inhibits inflammatory reactivity and is neuroprotective in an animal model of Alzheimer’s disease

BACKGROUND: The chemokine interleukin-8 (IL-8) and its receptor CXCR2 contribute to chemotactic responses in Alzheimer’s disease (AD); however, properties of the ligand and receptor have not been characterized in animal models of disease. The primary aim of our study was to examine effects of pharmacological antagonism of CXCR2 as a strategy to inhibit receptor-mediated inflammatory reactivity and enhance neuronal viability in animals receiving intrahippocampal injection of amyloid-beta (Aβ(1–42)). METHODS: In vivo studies used an animal model of Alzheimer’s disease incorporating injection of full-length Aβ(1–42) into rat hippocampus. Immunohistochemical staining of rat brain was used to measure microgliosis, astrogliosis, neuronal viability, and oxidative stress. Western blot and Reverse Transcription PCR (RT-PCR) were used to determine levels of CXCR2 in animal tissue with the latter also used to determine expression of pro-inflammatory mediators. Immunostaining of human AD and non-demented (ND) tissue was also undertaken. RESULTS: We initially determined that in the human brain, AD relative to ND tissue exhibited marked increases in expression of CXCR2 with cell-specific receptor expression prominent in microglia. In Aβ(1–42)-injected rat brain, CXCR2 and IL-8 showed time-dependent increases in expression, concomitant with enhanced gliosis, relative to controls phosphate-buffered saline (PBS) or reverse peptide Aβ(42–1) injection. Administration of the competitive CXCR2 antagonist SB332235 to peptide-injected rats significantly reduced expression of CXCR2 and microgliosis, with astrogliosis unchanged. Double staining studies demonstrated localization of CXCR2 and microglial immunoreactivity nearby deposits of Aβ(1–42) with SB332235 effective in inhibiting receptor expression and microgliosis. The numbers of neurons in granule cell layer (GCL) were reduced in rats receiving Aβ(1–42), compared with PBS, with administration of SB332235 to peptide-injected animals conferring neuroprotection. Oxidative stress was indicated in the animal model since both 4-hydroxynonenal (4-HNE) and hydroethidine (HEt) were markedly elevated in Aβ(1–42) vs PBS-injected rat brain and diminished with SB332235 treatment. CONCLUSION: Overall, the findings suggest critical roles for CXCR2-dependent inflammatory responses in an AD animal model with pharmacological modulation of the receptor effective in inhibiting inflammatory reactivity and conferring neuroprotection against oxidative damage

A comparison of in vitro properties of resting SOD1 transgenic microglia reveals evidence of reduced neuroprotective function

<p>Abstract</p> <p>Background</p> <p>Overexpression of mutant copper/zinc superoxide dismutase (<it>SOD1</it>) in rodents has provided useful models for studying the pathogenesis of amyotrophic lateral sclerosis (ALS). Microglia have been shown to contribute to ALS disease progression in these models, although the mechanism of this contribution remains to be elucidated. Here, we present the first evidence of the effects of overexpression of mutant (TG G93A) and wild type (TG WT) human <it>SOD1 </it>transgenes on a set of functional properties of microglia relevant to ALS progression, including expression of integrin β-1, spreading and migration, phagocytosis of apoptotic neuronal cell debris, and intracellular calcium changes in response to an inflammatory stimulus.</p> <p>Results</p> <p>TG SOD1 G93A but not TG SOD1 WT microglia had lower expression levels of the cell adhesion molecule subunit integrin β-1 than their NTG control cells [NTG (G93A) and NTG (WT), respectively, 92.8 ± 2.8% on TG G93A, 92.0 ± 6.6% on TG WT, 100.0 ± 1.6% on NTG (G93A), and 100.0 ± 2.7% on NTG (WT) cells], resulting in decreased spreading ability, with no effect on ability to migrate. Both TG G93A and TG WT microglia had reduced capacity to phagocytose apoptotic neuronal cell debris (13.0 ± 1.3% for TG G93A, 16.5 ± 1.9% for TG WT, 28.6 ± 1.8% for NTG (G93A), and 26.9 ± 2.8% for NTG (WT) cells). Extracellular stimulation of microglia with ATP resulted in smaller increase in intracellular free calcium in TG G93A and TG WT microglia relative to NTG controls (0.28 ± 0.02 μM for TG G93A, 0.24 ± 0.03 μM for TG WT, 0.39 ± 0.03 μM for NTG (G93A), and 0.37 ± 0.05 μM for NTG (WT) microglia).</p> <p>Conclusions</p> <p>These findings indicate that, under resting conditions, microglia from mutant <it>SOD1 </it>transgenic mice have a reduced capacity to elicit physiological responses following tissue disturbances and that higher levels of stimulatory signals, and/or prolonged stimulation may be necessary to initiate these responses. Overall, resting mutant <it>SOD1</it>-overexpressing microglia may have reduced capacity to function as sensors of disturbed tissue/cellular homeostasis in the CNS and thus have reduced neuroprotective function.</p

A Protective Mechanism against Antibiotic-Induced Ototoxicity: Role of Prestin

Hearing loss or ototoxicity is one of the major side effects associated with the use of the antibiotics, particularly aminoglycosides (AGs), which are the most commonly used antibiotics worldwide. However, the molecular and cellular events involved in the antibiotic-induced ototoxicity remains unclear. In the present study, we test the possibility that prestin, the motor protein specifically expressed in the basolateral membrane of outer hair cells (OHCs) in the cochlea with electromotility responsible for sound amplification, may be involved in the process of AG-induced apoptosis in OHCs. Our results from both mice model and cultured cell line indicate a previously unexpected role of prestin, in mediating antibiotic-induced apoptosis, the effect of which is associated with its anion-transporting capacity. The observed downregulation of prestin mRNA prior to detectable apoptosis in OHCs and hearing loss in the antibiotic-treated mice is interesting, which may serve as a protective mechanism against hearing loss induced by AGs in the early stage

Anti-Prion Activity of Brilliant Blue G

BACKGROUND: Prion diseases are fatal neurodegenerative disorders with no effective therapy currently available. Accumulating evidence has implicated over-activation of P2X7 ionotropic purinergic receptor (P2X7R) in the progression of neuronal loss in several neurodegenerative diseases. This has led to the speculation that simultaneous blockade of this receptor and prion replication can be an effective therapeutic strategy for prion diseases. We have focused on Brilliant Blue G (BBG), a well-known P2X7R antagonist, possessing a chemical structure expected to confer anti-prion activity and examined its inhibitory effect on the accumulation of pathogenic isoforms of prion protein (PrPres) in a cellular and a mouse model of prion disease in order to determine its therapeutic potential. PRINCIPAL FINDINGS: BBG prevented PrPres accumulation in infected MG20 microglial and N2a neural cells at 50% inhibitory concentrations of 14.6 and 3.2 µM, respectively. Administration of BBG in vivo also reduced PrPres accumulation in the brains of mice with prion disease. However, it did not appear to alleviate the disease progression compared to the vehicle-treated controls, implying a complex role of P2X7R on the neuronal degeneration in prion diseases. SIGNIFICANCE: These results provide novel insights into the pathophysiology of prion diseases and have important implications for the treatment

Purinergic modulation of microglial cell activation

Microglial cells are resident macrophages in the brain and their activation is an important part of the brain immune response and the pathology of the major CNS diseases. Microglial activation is triggered by pathological signals and is characterized by morphological changes, proliferation, phagocytosis and the secretion of various cytokines and inflammatory mediators, which could be both destructive and protective for the nervous tissue. Purines are one of the most important mediators which regulate different aspects of microglial function. They could be released to the extracellular space from neurons, astrocytes and from the microglia itself, upon physiological neuronal activity and in response to pathological stimuli and cellular damage. Microglial activation is regulated by various subtypes of nucleotide (P2X, P2Y) and adenosine (A1, A2A and A3) receptors, which control ionic conductances, membrane potential, gene transcription, the production of inflammatory mediators and cell survival. Among them, the role of P2X7 receptors is especially well delineated, but P2X4, various P2Y, A1, A2A and A3 receptors also powerfully participate in the microglial response. The pathological role of microglial purine receptors has also been demonstrated in disease models; e.g., in ischemia, sclerosis multiplex and neuropathic pain. Due to their upregulation and selective activation under pathological conditions, they provide new avenues in the treatment of neurodegenerative and neuroinflammatory illnesses

Intraperitoneal drain placement and outcomes after elective colorectal surgery: international matched, prospective, cohort study

Despite current guidelines, intraperitoneal drain placement after elective colorectal surgery remains widespread. Drains were not associated with earlier detection of intraperitoneal collections, but were associated with prolonged hospital stay and increased risk of surgical-site infections.Background Many surgeons routinely place intraperitoneal drains after elective colorectal surgery. However, enhanced recovery after surgery guidelines recommend against their routine use owing to a lack of clear clinical benefit. This study aimed to describe international variation in intraperitoneal drain placement and the safety of this practice. Methods COMPASS (COMPlicAted intra-abdominal collectionS after colorectal Surgery) was a prospective, international, cohort study which enrolled consecutive adults undergoing elective colorectal surgery (February to March 2020). The primary outcome was the rate of intraperitoneal drain placement. Secondary outcomes included: rate and time to diagnosis of postoperative intraperitoneal collections; rate of surgical site infections (SSIs); time to discharge; and 30-day major postoperative complications (Clavien-Dindo grade at least III). After propensity score matching, multivariable logistic regression and Cox proportional hazards regression were used to estimate the independent association of the secondary outcomes with drain placement. Results Overall, 1805 patients from 22 countries were included (798 women, 44.2 per cent; median age 67.0 years). The drain insertion rate was 51.9 per cent (937 patients). After matching, drains were not associated with reduced rates (odds ratio (OR) 1.33, 95 per cent c.i. 0.79 to 2.23; P = 0.287) or earlier detection (hazard ratio (HR) 0.87, 0.33 to 2.31; P = 0.780) of collections. Although not associated with worse major postoperative complications (OR 1.09, 0.68 to 1.75; P = 0.709), drains were associated with delayed hospital discharge (HR 0.58, 0.52 to 0.66; P &lt; 0.001) and an increased risk of SSIs (OR 2.47, 1.50 to 4.05; P &lt; 0.001). Conclusion Intraperitoneal drain placement after elective colorectal surgery is not associated with earlier detection of postoperative collections, but prolongs hospital stay and increases SSI risk

ATP release via anion channels

ATP serves not only as an energy source for all cell types but as an ‘extracellular messenger-for autocrine and paracrine signalling. It is released from the cell via several different purinergic signal efflux pathways. ATP and its Mg2+ and/or H+ salts exist in anionic forms at physiological pH and may exit cells via some anion channel if the pore physically permits this. In this review we survey experimental data providing evidence for and against the release of ATP through anion channels. CFTR has long been considered a probable pathway for ATP release in airway epithelium and other types of cells expressing this protein, although non-CFTR ATP currents have also been observed. Volume-sensitive outwardly rectifying (VSOR) chloride channels are found in virtually all cell types and can physically accommodate or even permeate ATP4- in certain experimental conditions. However, pharmacological studies are controversial and argue against the actual involvement of the VSOR channel in significant release of ATP. A large-conductance anion channel whose open probability exhibits a bell-shaped voltage dependence is also ubiquitously expressed and represents a putative pathway for ATP release. This channel, called a maxi-anion channel, has a wide nanoscopic pore suitable for nucleotide transport and possesses an ATP-binding site in the middle of the pore lumen to facilitate the passage of the nucleotide. The maxi-anion channel conducts ATP and displays a pharmacological profile similar to that of ATP release in response to osmotic, ischemic, hypoxic and salt stresses. The relation of some other channels and transporters to the regulated release of ATP is also discussed