Immunohistochemical evaluation of phosphorylated SMAD2/SMAD3 and the co-activator P300 in human glomerulonephritis: correlation with renal injury

TGFβR1 inhibition drives hepatocellular carcinoma proliferation through induction of toll-like-receptor signalling

Transforming growth factor (TGF)-β and toll-like receptors (TLRs) have been shown to independently modulate the proliferation of hepatocellular carcinoma (HCC). Since a direct cross-talk between these two signalling pathways in HCC has not been clearly described before, we aimed here to explore the possibility of such interaction. A human HCC tissue array (n = 20 vs. four control samples), human HCC samples (n = 10) and steatohepatitis-driven murine HCC samples (control, NASH and HCC; n = 6/group) were immunostained for TGFβR1, pSMAD2, TRAF6, IRAK1 and PCNA. The results were confirmed by immunoblotting. Effects of constant activation of the SMAD pathway by constitutive expression of ALK5 or knockdown of mediators of TLR signalling, IRAK1 and MyD88, on HCC proliferation, were investigated in the HCC cell line (HUH-7) after treatment with TGFβ1 cytokine or TGFβR1 kinase inhibitor (LY2157299) using PCNA and MTS assay. TGFβR1 expression is decreased in human and murine HCC and associated with downregulated pSMAD2, but increased IRAK1, TRAF6 and PCNA staining. TGFβR1 kinase inhibition abolished the cytostatic effects of TGFβ1 and led to the induction of IRAK1, pIRAK1 and elevated mRNA levels of TLR-9. Overexpression of ALK5 and knockdown of MyD88 or IRAK1 augmented the cytostatic effects of TGFβ1 on HUH-7. In another epithelial HCC cell line, that is, HepG2, TGFβR1 kinase inhibitor similarly elevated cellular proliferation. There is a balance between the canonical SMAD-driven tumour-suppressing arm and the non-canonical tumour-promoting arm of TGFβ signalling. Disruption of this balance, by inhibition of the canonical pathway, induces HCC proliferation through TLR signalling.

p300 in Cardiac Development and Accelerated Cardiac Aging

The heart is the first functional organ that develops during embryonic development. While a heartbeat indicates life, cessation of a heartbeat signals the end of life. Heart disease, due either to congenital defects or to acquired dysfunctions in adulthood, remains the leading cause of death worldwide. Epigenetics plays a key role in both embryonic heart development and heart disease in adults. Stress-induced vascular injury activates pathways involved in pathogenesis of accelerated cardiac aging that includes cellular dysfunction, pathological cardiac hypertrophy, diabetic cardiomyopathy, cardiac matrix remodeling, cardiac dysfunction and heart failure. Acetyltransferase p300 (p300), a major epigenetic regulator, plays a pivotal role in heart development during embryogenesis, as deficiency or abnormal expression of p300 leads to embryonic death at early gestation periods due to deformation of the heart and neural tube. Acetyltransferase p300 controls heart development through histone acetylation-mediated chromatin remodeling and transcriptional regulation of genes required for cardiac development. In adult hearts, p300 is differentially expressed in different chambers and epigenetically controls cardiac gene expression. Deregulation of p300, in response to prohypertrophic and profibrogenic stress signals, is associated with increased recruitment of p300 to several genes including transcription factors, increased acetylation of specific lysines in histones and transcription factors, altered chromatin organization, and increased hypertrophic and fibrogenic gene expression. Cardiac hypertrophy and myocardial fibrogenesis are common pathological manifestations of several stress-induced accelerated cardiac aging-related pathologies, including high blood pressure-induced or environmentally induced cardiac hypertrophy, myocardial infarction, diabetes-induced cardiomyopathy, and heart failure. Numerous studies using cellular and animal models clearly indicate that pharmacologic or genetic normalization of p300 activity has the potential to prevent or halt the progression of cardiac aging pathologies. Based on these preclinical studies, development of safe, non-toxic, small molecule inhibitors/epidrugs targeting p300 is an ideal approach to control accelerated cardiac aging-related deaths worldwide.

FAT-free p300 is good for scar-free tissue repair

Fibrosis, the deadly pathological manifestation of an abnormal tissue remodeling in any organ due to excessive collagen deposition, is associated with a wide variety of organ failure-related human diseases. Chronic stress or repeated injury in a particular organ induces abnormal molecular signals that lead to super-activation of matrix protein producing fibroblasts, excessive matrix proteins accumulation, loss of physiological tissue architecture or elasticity, and ultimately leading to organ failure. There is no effective therapy for fibrosis. Factor acetyltransferase p300 (FATp300), a major epigenetic regulator that acetylates specific lysines in histones and transcription factors, is essential for elevated collagen synthesis and the levels of FATp300 are significantly elevated in different fibrotic tissues. Pharmacological inhibition of FAT activity of p300 is associated with decreased collagen synthesis by fibroblasts in tissues and amelioration of organ fibrosis. Therefore, FAT-free p300 is superior for physiological tissue repair and must be exploited as a viable therapeutic target against multi-organ fibrosis.

p300 is elevated in systemic sclerosis and its expression is positively regulated by TGF-β: epigenetic feed-forward amplification of fibrosis

Fibrosis, the hallmark of systemic sclerosis (SSc), is characterized by persistent fibroblast activation triggered by transforming growth factor-β (TGF-β). As the acetyltransferase p300 has a key role in fibrosis and its availability governs the intensity of fibrotic responses, we investigated p300 expression in SSc and the molecular basis of its regulation. We found that expression of p300 was markedly elevated in SSc skin biopsies and was induced by TGF-β in explanted normal skin fibroblasts. Stimulation of p300 by TGF-β was independent of Smads and involved the early-immediate transcription factor Egr-1 (early growth response 1), a key regulator of profibrotic TGF-β signaling. Indeed, Egr-1 was both sufficient and necessary for p300 regulation in vitro and in vivo. Increased p300 accumulation in TGF-β-treated fibroblasts was associated with histone hyperacetylation, whereas p300 depletion, or selective pharmacological blockade of its acetyltransferase activity, attenuated TGF-β-induced responses. Moreover, TGF-β enhanced both p300 recruitment and in vivo histone H4 acetylation at the COL1A2 (collagen, type I, α2) locus. These findings implicate p300-mediated histone acetylation as a fundamental epigenetic mechanism in fibrogenesis and place Egr-1 upstream in TGF-β-driven stimulation of p300 gene expression. The results establish a firm link between fibrosis with aberrant p300 expression and epigenetic activity that, to our knowledge, is previously unreported. Targeted disruption of p300-mediated histone acetylation might therefore represent a viable antifibrotic strategy.

Transcription factor Sp1 expression is upregulated in human glomerulonephritis: correlation with pSmad2/3 and p300 expression and renal injury

BACKGROUND

Sp1 is a ubiquitous transcription factor that mediates the fibrogenic factor transforming growth factor beta (TGF-beta) signals through cooperation with Smad proteins. The transcriptional coactivator p300 is also suggested to play a role in Smad signal transduction.

METHODS

We investigated the immunohistochemical expression of Sp1 as well as the expression of pSmad2/3 and the coactivator p300 in 157 renal biopsy specimens from patients with various types of glomerulonephritis (GN). Correlations between immunohistochemical, clinical, and histologic parameters were performed.

RESULTS

Sp1 exhibited an increased glomerular and proximal tubular expression in all forms of GN compared to controls. The proximal tubular expression of Sp1 was significantly increased in proliferative GNs (p = 0.025), whereas in secondary GNs, there was a significant increase in the molecule's glomerular expression (p = 0.008). Sp1 correlated positively with pSmad2/3 and p300 expression in proximal tubules (r = 0.241, p = 0.018 and r = 0.244, p = 0.014, respectively), while in proliferative GNs, its expression correlated positively with pSmad2/3 expression in glomeruli (r = 0.32, p = 0.028). Sp1 glomerular and proximal tubular immunostaining correlated positively with serum creatinine levels (r = 0.265, p = 0.02 and r = 0.306, p = 0.006, respectively), while its proximal tubular expression showed a similar correlation with interstitial fibrosis (r = 0.213, p = 0.025). Sp1 was constantly detected in hyperplastic lesions and cellular crescents (each 100%), and very often in micro adhesions (94%) and segmentally or globally sclerotic areas (each 83%).

CONCLUSIONS

This study documents the upregulation of Sp1 expression in glomeruli and proximal tubules of GN specimens. Our findings suggest a possible cooperation of Sp1 with pSmad2/3 and p300 in mediating renal injury as well as a possible role for this molecule in the pathogenesis and the progression of human GN.

Histopathologic findings in ascending aortas from individuals with Loeys-Dietz syndrome (LDS)

Loeys-Dietz syndrome (LDS) is an autosomal dominant connective tissue disorder resulting from genetic mutations in the transforming growth factor beta receptors 1 and 2 (TGFBR1 and TGFBR2). The syndrome is characterized phenotypically by hypertelorism, bifid uvula, and/or cleft palate, and arterial tortuosity with aneurysms and dissections. LDS has a much more rapid clinical course than Marfan syndrome (MFS) and thus those diagnosed with LDS are currently being recommended for prophylactic aortic root replacement at younger ages and with smaller aortic dimensions. Aortic root tissue obtained at surgery was compared between 15 patients carrying a diagnosis of LDS, 11 patients with MFS and 11 control aortas to evaluate the range of histopathologic changes in LDS. Standard hematoxylin and eosin and Movat pentachrome stains were performed. LDS samples had increased medial collagen and a subtle but diffuse form of elastic fiber fragmentation and extracellular matrix deposition, referred to as diffuse medial degeneration. LDS samples had significantly more diffuse medial degeneration compared with MFS and control samples (P<0.05), significantly less medial degeneration of the "cystic" variety compared with MFS (P<0.01) and significantly more collagen deposition than control samples (P<0.01). Additionally, an immunohistochemical stain for pSmad2, a marker of TGFbeta activity, was significantly increased in LDS patients compared with controls (P<0.001). Overall, the histologic findings of LDS are best appreciated with special stains to evaluate fibrosis and elastic fiber fragmentation. The changes described, although not entirely specific for LDS, help differentiate this entity from other vascular diseases in the appropriate clinicopathologic setting.