Biology subjects

Bajwa, A.

Publications and source records attributed to Bajwa, A..

3 recordsLinked to original sources

bioRxiv2021

Nephrotoxicity of the BRAF-kinase inhibitor Vemurafenib isdriven by off-target Ferrochelatase inhibition

A multitude of disease and therapy related factors drive the frequent development of renal disorders in cancer patients. Along with chemotherapy, the newer targeted therapeutics can also cause renal dysfunction through on and off-target mechanisms. Interestingly, among the small-molecule inhibitors approved for the treatment of cancers that harbor BRAF-kinase activating mutations, vemurafenib can trigger tubular damage and acute kidney injury (AKI). To investigate the underlying mechanisms, here, we have developed cell culture and mouse models of vemurafenib nephrotoxicity. Our studies show that at clinically relevant concentrations vemurafenib induces cell-death in transformed and primary murine and human renal tubular epithelial cells (RTEC). In mice, two weeks of daily vemurafenib treatment causes moderate AKI with histopathological characteristics of RTEC injury. Importantly, RTEC-specific BRAF gene deletion did not influence renal function under normal conditions or alter the severity of vemurafenib-associated renal impairment. Instead, we found that inhibition of ferrochelatase (FECH), an enzyme involved in heme biosynthesis contributes to vemurafenib nephrotoxicity. FECH overexpression protected RTECs and conversely FECH knockdown increased the sensitivity to vemurafenib nephrotoxicity. Collectively, these studies suggest that vemurafenib-associated RTEC dysfunction and nephrotoxicity is BRAF-independent and caused in part by off-target FECH inhibition. Translational StatementBRAF is the most frequently mutated protein kinase and a critical oncogenic driver in human cancers. In melanoma and other cancers with BRAF activating mutations, BRAF targeted small-molecule therapeutics such as vemurafenib, and dabrafenib have shown remarkable clinical benefits. However, recent clinical studies have shown that a significant number of patients that receive vemurafenib develop AKI through mechanisms that remain unknown. The present study describes the development of novel experimental models of vemurafenib nephrotoxicity and reveals the underlying off-target mechanisms that contribute to renal injury.

pharmacology and toxicology↗

bioRxiv2020

SOX9 promotes stress-responsive transcription of VGF nerve growth factor inducible gene in kidney epithelial cells

Acute kidney injury (AKI) is a common clinical condition associated with diverse etiologies and abrupt loss of renal function. In patients with sepsis, rhabdomyolysis, cancer, as well as cardiovascular disorders, the underlying disease or associated therapeutic interventions can cause hypoxic, cytotoxic, and inflammatory insults to renal tubular epithelial cells (RTECs) resulting in the onset of AKI. To uncover stress-responsive disease-modifying genes, here we have carried out renal transcriptome profiling in three distinct murine models of AKI. We find that Vgf nerve growth factor inducible gene upregulation is a common transcriptional stress response in RTECs to ischemia, cisplatin, and rhabdomyolysis-associated renal injury. The Vgf gene encodes a secretory peptide precursor protein that has critical neuro-endocrine functions; however, its role in the kidneys remains unknown. Our functional studies show that RTEC-specific Vgf gene ablation exacerbates ischemia, cisplatin, and rhabdomyolysis-associated AKI in vivo and cisplatin-induced RTEC cell death in vitro. Importantly, addback experiments showed that aggravation of cisplatin-induced renal injury caused by Vgf gene ablation is partly reversed by TLQP-21, a Vgf-derived peptide. Finally, in vitro and in vivo mechanistic studies showed that injury-induced Vgf upregulation in RTECs is driven by the transcriptional regulator Sox9. These findings reveal a crucial downstream target of the Sox9-directed transcriptional program and identify Vgf as a stress-responsive protective gene in kidney epithelial cells.AbbreviationsAKIAcute kidney injuryRTECrenal tubular epithelial cellsBUNblood urea nitrogenChIPchromatin immunoprecipitationSox9SRY-Box transcription factor 9.View Full Text

cell biology↗

bioRxiv2020

The gut mycobiome of healthy mice is shaped by the environment and shapes metabolic outcomes in response to diet

ObjectiveAs an active interface between the host and their diet, the gut bacteriome influences host metabolic adaptation. However, the contribution of gut fungi to host metabolic outcomes is not yet understood. Therefore, we aimed to determine if host metabolic response to an ultraprocessed diet reflects gut fungal community composition. DesignWe compared jejunal fungi and bacteria from 72 healthy mice with the same genetic background but different starting mycobiomes before and after 8 weeks on an ultra-processed or standardized diet using 16S and internal transcribed spacer region 2 ribosomal RNA sequencing. We measured host body composition using magnetic resonance imaging, examined changes in metabolically active host tissues and quantified serum metabolic biomarkers. ResultsGut fungal communities are highly variable between mice, differing by vendor, age and sex. After exposure to an ultra-processed diet for 8 weeks, persistent differences in fungal community composition strongly associate with differential deposition of body mass in male mice compared to mice on standardized diet. Fat deposition in the liver, genomic adaptation of metabolically active tissues and serum metabolic biomarkers are correlated with alterations in fungal diversity and community composition. Variation in fungi from the genera Thermomyces and Saccharomyces most strongly associate with increased weight gain. ConclusionsIn the gut of healthy mice, host-microbe metabolic interactions strongly reflect variability in fungal communities. Our results confirm the importance of luminal fungal communities to host metabolic adaptation to dietary exposure. Gut fungal communities may represent a therapeutic target for the prevention and treatment of metabolic disease. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=169 SRC="FIGDIR/small/158287v1_ufig1.gif" ALT="Figure 1"> View larger version (40K): org.highwire.dtl.DTLVardef@1d80579org.highwire.dtl.DTLVardef@14f5729org.highwire.dtl.DTLVardef@1e379bcorg.highwire.dtl.DTLVardef@14d2ab6_HPS_FORMAT_FIGEXP M_FIG C_FIG In BriefO_LIWhat is already known about this subject? Gut bacterial communities have evolved to influence the metabolic outcomes of the host in mammals. Evidence from across the lifespan suggests that differences in composition of these communities is associated with energy consumption. However, gut microbial communities, while often equated to bacteria, are diverse, multi-kingdom ecologies and limited information is available for the role of other kingdoms of life, such as fungi. C_LIO_LIWhat are the new findings? Gut fungal communities, collectively termed the mycobiome, are less diverse and abundant than bacterial communities in the gastrointestinal tract. This study identifies the considerable influence of the environment and dietary exposure on the composition of jejunal fungal communities in healthy mice with the same genetic background. After exposure to processed diet, differences in fungal community composition in male mice were strongly correlated with persistent differences body composition and markers of metabolic tone. C_LIO_LIHow might it impact on clinical practice in the foreseeable future? These results verify that the baseline metabolic tone of health mice strongly reflects the ecological complexity of the gastrointestinal mycobiome. Variation in the composition of gut fungal communities is likely an underappreciated source of experimental and clinical variability in metabolic studies. Gastrointestinal fungi are likely a target for prevention and treatment of metabolic disease. C_LI

microbiology↗