Adult trkB Signaling in Parvalbumin Interneurons is Essential to Prefrontal Network Dynamics

Inhibitory interneurons expressing parvalbumin (PV) are central to cortical network dynamics, generation of γ oscillations, and cognition. Dysfunction of PV interneurons disrupts cortical information processing and cognitive behavior. Brain-derived neurotrophic factor (BDNF)/tyrosine receptor kinase B (trkB) signaling regulates the maturation of cortical PV interneurons but is also implicated in their adult multidimensional functions. Using a novel viral strategy for cell-type-specific and spatially restricted expression of a dominant-negative trkB (trkB.DN), we show that BDNF/trkB signaling is essential to the integrity and maintenance of prefrontal PV interneurons in adult male and female mice. Reduced BDNF/trkB signaling in PV interneurons in the medial prefrontal cortex (mPFC) resulted in deficient PV inhibition and increased baseline local field potential (LFP) activity in a broad frequency band. The altered network activity was particularly pronounced during increased activation of the prefrontal network and was associated with changed dynamics of local excitatory neurons, as well as decreased modulation of the LFP, abnormalities that appeared to generalize across stimuli and brain states. In addition, our findings link reduced BDNF/trkB signaling in prefrontal PV interneurons to increased aggression. Together our investigations demonstrate that BDNF/trkB signaling in PV interneurons in the adult mPFC is essential to local network dynamics and cognitive behavior. Our data provide direct support for the suggested association between decreased trkB signaling, deficient PV inhibition, and altered prefrontal circuitry.SIGNIFICANCE STATEMENT Brain-derived neurotrophic factor (BDNF)/tyrosine receptor kinase B (trkB) signaling promotes the maturation of inhibitory parvalbumin (PV) interneurons, neurons central to local cortical dynamics, γ rhythms, and cognition. Here, we used a novel viral approach for reduced BDNF/trkB signaling in PV interneurons in the medial prefrontal cortex (mPFC) to establish the role of BDNF/trkB signaling in adult prefrontal network activities. Reduced BDNF/trkB signaling caused pronounced morphologic alterations, reduced PV inhibition, and deficient prefrontal network dynamics. The altered network activity appeared to manifest across stimuli and brain states and was associated with aberrant local field potential (LFP) activities and increased aggression. The results demonstrate that adult BDNF/trkB signaling is essential to PV inhibition and prefrontal circuit function and directly links BDNF/trkB signaling to network integrity in the adult brain.     

Short-term strength training improves muscle quality and functional capacity of elderly women

To assess effects of a short-term strength training (ST) program on muscle quality (MQ) and functional capacity, 36 sedentary elderly women (age = 66.0 ± 8 year, height = 159.1 ± 9.2 cm, body mass = 68.3 ± 12.1 kg, body fat = 37.0 ± 4.2 %) were randomly divided into an experimental group (EG; n = 19) or a control group (CG; n = 17). The EG performed two to three sets of 12–15 repeats of leg press, knee extension, and knee flexion exercises, 2 days/week for 6 weeks. Before and after training, lower body one repetition maximum (1RM), functional performance tests, quadriceps femoris muscle thickness (MT), and muscle quality (MQ) (1RM and quadriceps MT quotient) were assessed. After training, only the EG showed significant improvements in 1RM (p < 0.05), 30-s sit-to-stand (p < 0.001), and 8 foot up-and-go (p < 0.001). In addition, only in the EG, significant increases in all quadriceps femoris MT measurements (vastus lateralis, vastus medialis, vastus intermedius, and rectus femoris) (p ≤ 0.05), and MQ (p < 0.001) were demonstrated. No changes were observed in the CG. Furthermore, there were significant associations between individual changes in MQ and corresponding changes in 30-s sit-to-stand (r = 0.62, p < 0.001), and 8 foot up-and-go (r = −0.71, p < 0.001). In conclusion, a ST program of only 6 weeks was sufficient to enhance MQ of the knee extensors in elderly women, which resulted in beneficial changes in functional capacity.     

PEST family phosphatases in immunity, autoimmunity, and autoinflammatory disorders

Summary:  The proline-, glutamic acid-, serine- and threonine-rich (PEST) family of protein tyrosine phosphatases (PTPs) includes proline-enriched phosphatase (PEP)/lymphoid tyrosine phosphatase (LYP), PTP-PEST, and PTP-hematopoietic stem cell fraction (HSCF). PEP/LYP is a potent inhibitor of T-cell activation, principally by suppressing the activity of Src family protein tyrosine kinases (PTKs). This function seems to be dependent, at least in part, on the ability of PEP to bind C-terminal Src kinase (Csk), a PTK also involved in inactivating Src kinases. Interestingly, a polymorphism of LYP in humans (R620W) is a significant risk factor for autoimmune diseases including type 1 diabetes, rheumatoid arthritis, and lupus. The R620W mutation may be a 'gain-of-function' mutation. In non-hematopoietic cells, PTP-PEST is a critical regulator of adhesion and migration. This effect correlates with the aptitude of PTP-PEST to dephosphorylate cytoskeletal proteins such as Cas, focal adhesion associated-kinase (FAK), Pyk2, and PSTPIP. While not established, a similar function may also exist in immune cells. Additionally, overexpression studies provided an indication that PTP-PEST may be a negative regulator of lymphocyte activation. Interestingly, mutations in a PTP-PEST- and PTP-HSCF-interacting protein, PSTPIP1, were identified in humans with pyogenic sterile arthritis, pyoderma gangrenosum, and acne (PAPA) syndrome and familial recurrent arthritis, two autoinflammatory diseases. These mutations abrogate the ability of PSTPIP1 to bind PTP-PEST and PTP-HSCF, suggesting that these two PTPs may be negative regulators of inflammation.     

Effect of chronic treatment with new benzylidene-thiazolidine-2,4-dione (LPSF/GQ-06) with potential hypoglycemic on rat Leydig cell steroidogenesis

Thiazolidinediones work by sensitizing the action of insulin by acting as ligands for the PPAR receptor. This study describes the effects of chronic treatment with new benzylidene-thiazolidine-2,4-dione (LPSF/GQ-06) on Leydig cell steroidogenic capacity, and expression of the steroidogenic acute regulatory protein (StAR) and cholesterol side-chain cleavage enzyme (P450scc) in normal rats. Twelve adult male Wistar rats were treated with LPSF/GQ-06 (5 mg/kg) administered by gavage for 15 days. Testosterone in plasma and incubation medium was measured by radioimmunoassay. The StAR and P450scc expression was detected by immunocytochemistry. The levels of total circulating testosterone were increased by LPSF/GQ-06 treatment. The ability of LPSF/GQ-06 to affect the production of testosterone by Leydig cells was examined using an ex vivo model. The production of testosterone was induced by activators of the cAMP/PKA pathway (hCG and dbcAMP) or substrates of steroidogenesis (22(R)-hydroxycholesterol, substrate for the P450scc enzyme, and pregnenolone, the product of the P450scc-catalyzed step). An increase in basal or induced testosterone production was observed in Leydig cells from LPSF/GQ-06-treated rats. The ultrastructural and immunocytochemical analysis showed that LPSF/GQ-06-treated Leydig cells presented morphological characteristics similar to those of control cells as well as similar labeling to StAR and P450scc throughout the cytoplasm of control and treated cells. We can therefore conclude that the stimulatory action of the LPSF/GQ-06 on testosterone production is not due to an increase of the quantity of StAR or P450scc. These results suggest that the activity of these two proteins as well as of other steroidogenic enzymes is augmented by LPSF/GQ-06.     

GSTP1 and ABCB1 Polymorphisms Predicting Toxicities and Clinical Management on Carboplatin and Paclitaxel‐Based Chemotherapy in Ovarian Cancer

Variation in drug disposition genes might contribute to susceptibility to toxicities and interindividual differences in clinical management on chemotherapy for epithelial ovarian cancer (EOC). This study was designed to explore the association of GST and ABCB1 genetic variation with hematologic and neurologic toxicity, changes in chemotherapy, and disease prognosis in Brazilian women with EOC. A total of 112 women with a confirmed histological diagnosis of EOC treated with carboplatin/paclitaxel were enrolled (2014–2019). The samples were analyzed by multiplex polymerase chain reaction (PCR) for the deletion of GSTM1 and GSTT1 genes. GSTP1 (c.313A>G/rs1695) and ABCB1 (c.1236C>T/rs1128503; c.3435C>T/rs1045642; c.2677G>T>A/rs2032582) single nucleotide polymorphisms (SNPs) were detected by real‐time PCR. Subjects with the GSTP1 c.313A>G had reduced risk of anemia (odds ratio (OR): 0.17, 95% confidence interval (CI): 0.04–0.69, P = 0.01, dominant model) and for thrombocytopenia (OR: 0.27, 95% CI: 0.12–0.64, P < 0.01; OR 0.18, 95% CI 0.03–0.85, P = 0.03, either dominant or recessive model), respectively. The GSTP1 c.313A>G AG genotype was associated with a lower risk of dose delay (OR: 0.35, 95% CI: 0.13–0.90, P = 0.03). The ABCB1 c.1236C>T was associated with increased risk of thrombocytopenia (OR: 0.15, 95% CI: 0.03–0.82, P = 0.03), whereas ABCB1 c.3435C>T had increased risk of grade 2 and 3 neurotoxicity (OR: 3.61, 95% CI: 1.08–121.01, P = 0.03) in recessive model (CC + CT vs. TT). This study suggests that GSTP1 c.313A>G, ABCB1 c.1236C>T, and c.3435C>T SNP detection is a potential predictor of hematological toxicity and neurotoxicity and could help predict the clinical management of women with EOC.

Study Highlights

• WHAT IS THE CURRENT KNOWLEDGE ON THE TOPIC?

Variation in drug disposition genes encoding drug‐metabolizing enzymes and transporters might contribute to susceptibility to toxicities and interindividual differences in clinical management such as the need to delay, reduce, or discontinue treatment.

• WHAT QUESTION DID THIS STUDY ADDRESS?

We studied the association of GST and ABCB1 genetic variation with hematologic and neurologic toxicity, clinical management, and disease prognosis in Brazilian women with epithelial ovarian carcinoma (EOC) who undergo carboplatin and paclitaxel‐based chemotherapy.

• WHAT DOES THIS STUDY ADD TO OUR KNOWLEDGE?

GSTP1 c.313A>G is a potential predictor of anemia and thrombocytopenia and associated with a lower risk of dose delay during chemotherapy. In addition, ABCB1 c.1236C>T and c.3435C>T is associated with a higher risk of thrombocytopenia and neurotoxicity.

• HOW MIGHT THIS CHANGE CLINICAL PHARMACOLOGY OR TRANSLATIONAL SCIENCE?

The polymorphism detection could be a strategy to careful monitoring of patients at increased risk of toxicity and appropriate supportive therapy could decrease the need for changes in treatment, thus improving the likelihood of a beneficial treatment response in women with EOC.

Epithelial ovarian cancer (EOC) is the most common cause of gynecological cancer death, largely due to the advanced stage of the disease at the time of diagnosis. ¹ Standard first‐line treatment is cytoreductive surgery and subsequent chemotherapy using a combination of carboplatin and paclitaxel or neoadjuvant chemotherapy and residual tumor resection. ² Despite a high response rate to chemotherapy, ~ 70% of the women have a relapse within the subsequent 3 years. ³ Platinum and taxane‐based chemotherapy are often associated with severe hematological toxicities, such as anemia, neutropenia, leukopenia, and thrombocytopenia. ⁴ In addition, neuropathy is a dose‐limiting side effect of paclitaxel. ⁵ , ⁶ Interindividual differences in carboplatin and paclitaxel toxicity may be associated with polymorphisms in genes encoding drug‐metabolizing enzymes and transporters, including GSTs and ATP‐binding cassette (ABC) efflux transporters like ABCB1. ⁴ , ⁷ , ⁸ , ⁹ The GSTs are a family of phase II enzymes involved in detoxification of xenobiotics by conjugation reactions between glutathione and endogenous and exogenous electrophilic compounds, such as chemotherapeutic drugs, including the platinum agents. The GST family consists of several gene subfamilies of which GSTM1, GSTT1, and GSTP1 are the most relevant for drug metabolism. ¹⁰ , ¹¹ Functional GSTM1 and GSTT1 enzymes are directly related with the presence of the intact genes, because the absence of activity is the result of a 15 kb and 54 kb deletions that span the entire GSTM1 and GSTT1 genes (GSTM1‐null and GSTT1‐null genotypes), respectively. Consequently, individuals homozygous for the GSTM1 or GSTT1‐null allele have a complete absence of GSTM1 and GSTT1 activity, whereas individuals with two copies of the GSTM1 or GSTT1 genes have reference protein levels. ¹² , ¹³ There is some evidence that these deletion genotypes may play a role in toxicity, response to treatment, and survival in some cancers, ¹⁴ , ¹⁵ , ¹⁶ including cancer of the ovary. ⁸ In contrast to the commonly studied GSTM1 and GSTT1 genotypes, the GSTP1 c.313A>G (rs1695) is an exonic single nucleotide polymorphism (SNP) that causes an amino acid substitution and results in an isoleucine to valine (Ile > Val) change at codon 105 of the enzyme. The highest level of GSTP1 activity is seen in individuals with the AA genotype (Ile/Ile) and is associated with increased toxicity in different carcinomas, but there are discordant results regarding the effect of GSTP1 c.313A>G on treatment outcomes. ⁹ , ¹⁷ , ¹⁸ , ¹⁹ , ²⁰ Polymorphisms in ABCB1 or multidrug resistance 1 may affect the function of P‐glycoprotein, a critical transporter for efflux of paclitaxel from cells. ²¹ , ²² Three SNPs in the coding region of ABCB1 (c.1236C>T, rs1128503; c.3435C>T, rs1045642; and c.2677G>T>A, rs2032582) have been extensively studied. ²³ , ²⁴ These common ABCB1 SNPs have been associated with toxicity during carboplatin and paclitaxel‐based chemotherapy, including increased risk of anemia in carriers of the c.1236C>T SNP, a more pronounced neutrophil decrease in patients carrying the c.3435C>T and c.2677G>T>A SNPs and increased risk of peripheral neuropathy associated with the c.3435C>T SNP. ¹⁸ , ²⁵ , ²⁶ Similar to studies of GST polymorphisms, the associations of ABCB1 genetic variation with treatment outcomes is inconsistent across studies. ²⁷ , ²⁸ Patients developing severe toxicities often require dose reduction, dose delay, or treatment interruption that require clinical interventions and may affect the disease prognosis. ⁴ However, no study has been found so far focus on regarding the utility of polymorphisms in the management of chemotherapy and toxicities for ovarian cancer. The current study was designed to examine the association of GST and ABCB1 genetic variants with hematologic and neurologic toxicities, clinical management on chemotherapy, and disease prognosis in Brazilian women with EOC.     

Targeted mutagenesis in pathogenic Leptospira species: disruption of the LigB gene does not affect virulence in animal models of leptospirosis

The pathogenic mechanisms of Leptospira interrogans, the causal agent of leptospirosis, remain largely unknown. This is mainly due to the lack of tools for genetically manipulating pathogenic Leptospira species. Thus, homologous recombination between introduced DNA and the corresponding chromosomal locus has never been demonstrated for this pathogen. Leptospiral immunoglobulin-like repeat (Lig) proteins were previously identified as putative Leptospira virulence factors. In this study, a ligB mutant was constructed by allelic exchange in L. interrogans; in this mutant a spectinomycin resistance (Spc^r) gene replaced a portion of the ligB coding sequence. Gene disruption was confirmed by PCR, immunoblot analysis, and immunofluorescence studies. The ligB mutant did not show decrease virulence compared to the wild-type strain in the hamster model of leptospirosis. In addition, inoculation of rats with the ligB mutant induced persistent colonization of the kidneys. Finally, LigB was not required to mediate bacterial adherence to cultured cells. Taken together, our data provide the first evidence of site-directed homologous recombination in pathogenic Leptospira species. Furthermore, our data suggest that LigB does not play a major role in dissemination of the pathogen in the host and in the development of acute disease manifestations or persistent renal colonization.