Deoxy-sphingolipids, oxidative stress, and vitamin C correlate with qualitative and quantitative patterns of small fiber dysfunction and degeneration

Defined by dysfunction or degeneration of Aδ and C fibers, small fiber neuropathies (SFNs) entail a relevant health burden. In 50% of cases, the underlying cause cannot be identified or treated. In 100 individuals (70% female individuals; mean age: 44.8 years) with an idiopathic, skin biopsy-confirmed SFN, we characterized the symptomatic spectrum and measured markers of oxidative stress (vitamin C, selenium, and glutathione) and inflammation (transforming growth factor beta, tumor necrosis factor alpha), as well as neurotoxic 1-deoxy-sphingolipids. Neuropathic pain was the most abundant symptom (95%) and cause of daily life impairment (72%). Despite the common use of pain killers (64%), the painDETECT questionnaire revealed scores above 13 points in 80% of patients. In the quantitative sensory testing (QST), a dysfunction of Aδ fibers was observed in 70% and of C fibers in 44%, affecting the face, hands, or feet. Despite normal nerve conduction studies, QST revealed Aβ fiber involvement in 46% of patients' test areas. Despite absence of diabetes mellitus or mutations in SPTLC1 or SPTLC2 , plasma 1-deoxy-sphingolipids were significantly higher in the sensory loss patient cluster when compared with those in patients with thermal hyperalgesia ( P 25 kg/m 2 ), or hyperlipidemia showed significantly lower L-serine (arterial hypertension: P < 0.01) and higher 1-deoxy-sphingolipid levels (arterial hypertension: P < 0.001, overweight: P < 0.001, hyperlipidemia: P < 0.01). Lower vitamin C levels correlated with functional Aβ involvement ( P < 0.05). Reduced glutathione was lower in patients with Aδ dysfunction ( P < 0.05). Idiopathic SFNs are heterogeneous. As a new pathomechanism, plasma 1-deoxy-sphingolipids might link the metabolic syndrome with small fiber degeneration

Pressure oscillation regulates human mesangial cell growth and collagen synthesis

Abstract-Experimental renal disease models establish glomerular hypertension as a crucial determinant in glomerulosclerosis progression and demonstrate that glomerular capillary pressure reduction delays sclerosis development. An oscillating pressure (OP) chamber was constructed as an in vitro model to study human mesangial cells. Cell cultures were grown under atmospheric pressure (AP) and a controlled OP corresponding to intraglomerular capillary pressure. We show that OP significantly decreases mesangial cell proliferation within 24 hours and attenuates DNA synthesis throughout a 7-day period. To explore the effects of OP on cell metabolism, cell-associated and medium-secreted extracellular (CA and EC, respectively) collagen synthesis were measured by [ 3 H]proline incorporation. In subconfluent cultures, total CA and EC collagen synthesis was unaffected by OP, while in confluent cultures total EC collagen [ 3 H]proline incorporation was increased. To determine whether OP influenced mesangial cell growth induction, the effects of increasing glucose in the cell culture media were investigated. Our data show that the high glucose growth stimulatory effect on cell number and DNA synthesis was suppressed by OP. Under high glucose conditions, total CA collagen synthesis was increased in confluent cultures, whereas the EC collagen fraction remained unchanged. In these cultures, OP caused an additional increase in CA collagen synthesis. This study shows that mesangial cell growth and collagen synthesis are influenced by hyperbaric OP, supporting the hypothesis that glomerular capillary pressure plays a role in progressive glomerulosclerosis development. 1-4 Experimental models have shown that changes in intracapillary pressure are accompanied by a loss of afferent arteriole glomerular capillary pressure autoregulation. 5 Furthermore, therapeutic interventions with angiotensin-converting enzyme inhibitors and low protein diets that reduce glomerular intracapillary pressure can attenuate progression of glomerulosclerosis. 6,7 Nevertheless, compelling evidence has not yet been collected about the direct pathophysiologic effects of glomerular intracapillary pressure on intrinsic glomerular cells. A stretch/relaxation model (eg, by cyclic stretch/relaxation of culture plate undersurfaces) has been developed from observations of isolated glomeruli, in which glomerular volume progressively increases with enhanced perfusion pressure. 8 -10 In such studies, shear forces profoundly affect mesangial cell (MC) growth, matrix synthesis, and intermediary filament distribution. Mesangial structures with inherent centripetal forces are maintained by specific MC properties, including a smooth muscle cell phenotype, contractility, and contact points with the capillary basal membrane. 14 Furthermore, the unique central localization of MCs in the glomerular tuft, direct connection to the blood compartment, and absence of an intervening basement membrane support the notion that in addition to shear forces, intraglomerular pressure changes may mediate MC injury. Methods Establishment of Human MC Cultures Human MC isolation and primary cell culture maintenance are described in detail elsewhere