Increased activity of the insulin-like growth factor system in mesangial cells cultured in high glucose conditions. Relation to glucose-enhanced extracellular matrix production

The Mechanism of Hyperglycemia-Induced Renal Cell Injury in Diabetic Nephropathy Disease: An Update

Diabetic Nephropathy (DN) is a serious complication of type I and II diabetes. It develops from the initial microproteinuria to end-stage renal failure. The main initiator for DN is chronic hyperglycemia. Hyperglycemia (HG) can stimulate the resident and non-resident renal cells to produce humoral mediators and cytokines that can lead to functional and phenotypic changes in renal cells and tissues, interference with cell growth, interacting proteins, advanced glycation end products (AGEs), etc., ultimately resulting in glomerular and tubular damage and the onset of kidney disease. Therefore, poor blood glucose control is a particularly important risk factor for the development of DN. In this paper, the types and mechanisms of DN cell damage are classified and summarized by reviewing the related literature concerning the effect of hyperglycemia on the development of DN. At the cellular level, we summarize the mechanisms and effects of renal damage by hyperglycemia. This is expected to provide therapeutic ideas and inspiration for further studies on the treatment of patients with DN.

Identification of early response to hypertonic dextrose prolotherapy markers in knee osteoarthritis patients by an inflammation-related cytokine array

BACKGROUND

Osteoarthritis (OA) is one of the most common forms of arthritis, and hypertonic dextrose prolotherapy has long been used clinically to treat knee OA. The aim of this study was to investigate the inflammation-related protein-expression profile characterizing the efficacy of the hypertonic dextrose prolotherapy in knee OA as prognostic markers.

METHODS

OA patients over the age of 65 were recruited for Western Ontario McMaster University Osteoarthritis (WOMAC) index, knee X-ray evaluation and knee joint synovial fluid analysis before and after hypertonic dextrose prolotherapy. The expressions of inflammation-related factors were measured using a novel cytokine antibody array methodology. The cytokine levels were quantified by quantitative protein expression and analyzed by ELISA using the patients' knee-joint synovial fluid.

RESULTS

The WOMAC Index and minimum joint space width before receiving the intra-articular injection and at 2-week intervals were compared. Twelve patients who received OA intervention were enrolled and finally a clinical evaluation of 12 knee joints and knee synovial fluid samples were analyzed. In this study, after receiving hypertonic dextrose prolotherapy, the OA patients clearly demonstrated a significant improvement in WOMAC index and increasing tendency in the medial minimum joint space width after intervention. Meanwhile, we observed a significantly associated tendency between hypertonic dextrose treatment of knee OA and the upregulation of MMP2, TIMP-1, EGF, CXCL9 and IL-22.

CONCLUSION

The findings provide knee OA patients receiving hypertonic dextrose prolotherapy, which is accompained by the improvemeny of knee symptoms and associated tendency of upregulation of MMP2, EGF, CXCL 9 and IL-22.

Prolotherapy: Potential for the Treatment of Chronic Wounds?

Significance: Chronic skin ulcers, including venous, diabetic, and pressure ulcers, constitute a major health care burden, affecting 2-6 million people in the United States alone, with projected increases in incidence owing to the aging population and rising epidemic of diabetes. The ulcers are often accompanied by pain. Standard of care fails to heal ∼50% of diabetic foot ulcers and 25% of venous leg ulcers. Even advanced therapies do not heal >60%. Thus there is an unmet need for novel therapies that promote healing and also address the concomitant pain issue. Recent Advances: Prolotherapy involves injection of small amounts of an irritant material to the site of degenerated or painful joints, ligaments, and tendons. Multiple irritants are reported to be efficacious, but the focus here is on dextrose prolotherapy. In vitro and in vivo studies support translation to clinical use. Concentrations as low as 5% dextrose have resulted in production of growth factors that have critical roles in repair. Numerous clinical trials report pro-reparative effects of dextrose prolotherapy in joint diseases, tendon, and ligament damage, and for painful musculoskeletal issues. However, most of the studies have limitations that result in low-quality evidence. Critical Issues: The preclinical data support a role for dextrose prolotherapy in promoting tissue repair that is required for healing chronic wounds and ameliorating the associated pain. Critical issues include provision of evidence of efficacy in human chronic wounds. Another potential obstacle is limitation of reimbursement by third-party payers for a therapy with as yet limited evidence. Future Directions: Preclinical studies in models of chronic wounds would support clinical translation. As dextrose prolotherapy has some mechanistic similarities to already approved honey therapies, it may have a shortened pathway for clinical translation. The gold standard for widespread adoption would be a well-designed clinical trial.

Prospective Evaluation of Intra-Articular Dextrose Prolotherapy for Treatment of Osteoarthritis in Dogs

The objective of this study was to evaluate intra-articular dextrose prolotherapy for osteoarthritis of the elbow or stifle in dogs in a randomized, double-blind, placebo-controlled, prospective pilot study. Seventeen dogs were evaluated with 10 meeting inclusion criteria for this study. Evaluations included orthopedic exam, visual lameness scoring, Canine Brief Pain Inventory (CBPI), goniometry, kinetic gait analysis, and radiography. Initial lameness score, age, body weight, duration of lameness, and CBPI scores did not differ between groups. Change in CBPI pain severity score in the prolotherapy group from wk 6-12 was significantly less improved than in the placebo group, with no other significant differences in pain severity or pain interference scores between groups. Range of motion and radiographic scores did not differ between groups at any time. Mean kinetic forces improved in prolotherapy dogs but were not significantly different between treatment groups at any time. Although easily performed and well-tolerated, there were no statistically significant benefits of dextrose prolotherapy for treatment of osteoarthritis of the elbow and stifle in dogs. Post hoc power analysis of these sample means and standard deviations found that 29-106 animals per group would be necessary to demonstrate significant differences in kinetic forces, providing useful guidance for future studies.

A Systematic Review of Dextrose Prolotherapy for Chronic Musculoskeletal Pain

OBJECTIVE

The aim of this study was to systematically review dextrose (d-glucose) prolotherapy efficacy in the treatment of chronic musculoskeletal pain.

DATA SOURCES

Electronic databases PubMed, Healthline, OmniMedicalSearch, Medscape, and EMBASE were searched from 1990 to January 2016.

STUDY SELECTION

Prospectively designed studies that used dextrose as the sole active prolotherapy constituent were selected.

DATA EXTRACTION

Two independent reviewers rated studies for quality of evidence using the Physiotherapy Evidence Database assessment scale for randomized controlled trials (RCTs) and the Downs and Black evaluation tool for non-RCTs, for level of evidence using a modified Sackett scale, and for clinically relevant pain score difference using minimal clinically important change criteria. Study population, methods, and results data were extracted and tabulated.

DATA SYNTHESIS

Fourteen RCTs, 1 case–control study, and 18 case series studies met the inclusion criteria and were evaluated. Pain conditions were clustered into tendinopathies, osteoarthritis (OA), spinal/pelvic, and myofascial pain. The RCTs were high-quality Level 1 evidence (Physiotherapy Evidence Database ≥8) and found dextrose injection superior to controls in Osgood–Schlatter disease, lateral epicondylitis of the elbow, traumatic rotator cuff injury, knee OA, finger OA, and myofascial pain; in biomechanical but not subjective measures in temporal mandibular joint; and comparable in a short-term RCT but superior in a long-term RCT in low back pain. Many observational studies were of high quality and reported consistent positive evidence in multiple studies of tendinopathies, knee OA, sacroiliac pain, and iliac crest pain that received RCT confirmation in separate studies. Eighteen studies combined patient self-rating (subjective) with psychometric, imaging, and/or biomechanical (objective) outcome measurement and found both positive subjective and objective outcomes in 16 studies and positive objective but not subjective outcomes in two studies. All 15 studies solely using subjective or psychometric measures reported positive findings.

CONCLUSION

Use of dextrose prolotherapy is supported for treatment of tendinopathies, knee and finger joint OA, and spinal/pelvic pain due to ligament dysfunction. Efficacy in acute pain, as first-line therapy, and in myofascial pain cannot be determined from the literature.

Effects of multiple injections of hypertonic dextrose in the rabbit carpal tunnel: a potential model of carpal tunnel syndrome development

BACKGROUND

This study investigated the effects of a series of four hypertonic dextrose injections on the subsynovial connective tissue (SSCT) and median nerve within the carpal tunnel of a rabbit model.

METHODS

Twenty New Zealand white rabbits were used. One forepaw carpal tunnel was randomly injected with 0.1 ml of 10 % dextrose solution. The contralateral forepaw was injected with a similar amount of saline. This injection was made once per week for 4 weeks. The animals were killed at 16 weeks after the initial injection and were evaluated by electrophysiology (EP), SSCT mechanical testing, and histology.

RESULTS

Mechanical testing revealed significantly greater ultimate load and energy absorption in the dextrose injection group compared to the saline injection group (P < 0.05). Histological evaluation revealed SSCT fibrosis and thickening and edema in the median nerve bundles in the dextrose injection group. There was a prolongation in the latency of the EP test in the dextrose injection group (P = 0.08).

CONCLUSIONS

Previous studies had shown that one or two injections of 10 % dextrose could induce moderate SSCT fibrosis and mild EP changes without nerve histology changes. In this study, we have shown that higher doses create more severe fibrosis and, most importantly, more severe neuropathy, suggesting a dose-response effect, and confirming this as a potentially useful animal model for researching the etiology and treatment of carpal tunnel syndrome.

Connective tissue growth factor: structure-function relationships of a mosaic, multifunctional protein

Connective tissue growth factor (CTGF) is a member of the CCN family of six small secreted, cysteine-rich growth factors. The unique modular structure encompasses distinct functional domains which enable CTGF to interact with growth factors, surface receptors and matrix components. Widely expressed, CTGF has critical roles in embryonic development and the maintenance of normal cell and connective tissue function. It is also important for tissue repair following injury, and has been implicated in common diseases including atherosclerosis, pulmonary and renal fibrotic disorders and cancer. Factors that regulate CTGF transcription in response to exogenous stimuli, as well as downstream signalling pathways, have been described. However, only recently have studies begun to unravel how the functional domains within the CTGF modules orchestrate signals and control key biological processes. This article highlights how the structural and functional domains of CTGF and CTGF cleavage fragments integrate multiple extracellular events into cell signals.

Rosiglitazone increases matrix production and quenches inflammation: studies in human cells

BACKGROUND

Type 2 diabetes (T2D) is characterized by an accelerated atherogenesis, a process to which both proliferative and inflammatory responses contribute. Peroxisome proliferator-activated receptors-gamma (PPARgamma) agonists have both anti-proliferative and anti-inflammatory properties. We tested the effect of therapeutic doses of rosiglitazone on proliferative and inflammatory pathways in fibroblasts (HF) from five controls (C) and five T2D patients, and in aortic smooth muscle cells (hSMC).

METHODS

Transforming growth factor-beta (TGFbeta) and interleukin-6 (IL-6) expression, and IL-6, laminin and fibronectin release were measured. To identify the involved intracellular signalling, extracellular signal-regulated kinases (ERK)1/2 phosphorylation and p38 activation were evaluated.

RESULTS

Both phorbol 12-myristate 13-acetate (PMA) [a protein kinase C (PKC) activator] and rosiglitazone increased TGFbeta expression and fibronectin and laminin release in C and T2D patients. Rosiglitazone effect was reversed by its specific inhibitor Sr202. The combination PMA + rosiglitazone was additive in C, but not in T2D patients. IL-6 production was stimulated by PMA in both C and T2D patients; this effect was prevented by rosiglitazone in a Sr202-inhibitable manner. Experiments performed in hSMC yielded the same results. Rosiglitazone increased p38 activation more in C than in T2D patients; PMA-induced phosphorylation of ERK1/2 was similarly reduced in both cells.

CONCLUSIONS

In HF and hSMC, rosiglitazone stimulates the synthesis of matrix components via enhanced TGFbeta expression; when combined with PMA, the resulting PKC activation is mediated by enhanced p38 phosphorylation. On the other hand, rosiglitazone quenches inflammation in both cell types, by counteracting PMA-induced phosphorylation of ERK1/2.

Angiotensin II- and glucose-stimulated extracellular matrix production: mediation by the insulin-like growth factor (IGF) axis in a murine mesangial cell line

In diabetic nephropathy, glomerular mesangial cells exhibit aberrant anabolic activity that includes excessive production of extracellular matrix (ECM) proteins, leading to crowding of filtration surface areas and possible renal failure. In the present study, a murine mesangial cell line (MES-13 cells) was studied to determine the roles of the renin-angiotensin system (RAS) and the insulin-like growth factor (IGF) axis in the anabolic response to elevated glucose levels. Culture of MES-13 cells in medium containing supra-physiological glucose concentrations (>5.5 mmol/l) resulted in increased production of ECM proteins including laminin, fibronectin, and heparan sulfate proteoglycan with concurrent increases in IGF-binding protein (IGFBP)-2 production. These responses were blocked by the angiotensin receptor antagonists saralasin and losartan, while exogenous angiotensin II (Ang II) treatment directly stimulated increases in ECM and IGFBP-2. In all experiments, IGFBP-2 levels were correlated with anabolic activity implicating IGFBP-2 as a possible mediator in cellular responses to high glucose and Ang II. Such mediation appears to involve IGFBP-2 modulation of IGF-I signaling, since all responses to high glucose or Ang II were blocked by immuno-neutralization of IGF-I. These data suggest alterations in the IGF axis as key mechanisms underlying nephropathic responses of mesangial cells to Ang II and high glucose.

Mannose-6-phosphate/insulin-Like growth factor-II receptors may represent a target for the selective delivery of mycophenolic acid to fibrogenic cells

PURPOSE

The insulin-like growth factor axis plays an important role in fibrogenesis. However, little is known about mannose-6-phosphate/Insulin-like growth factor-II receptor (M6P/IGF-IIR) expression during fibrosis. When expressed preferentially on fibrogenic cells, this receptor may be used to selectively deliver drugs to these cells.

METHODS

We investigated M6P/IGF-IIR expression in livers of bile duct-ligated (BDL) rats and in renal vascular walls of renin transgenic TGR(mRen2)27 rats. Both models are characterized by fibrogenic processes. Furthermore, we studied whether drug delivery via M6P/IGF-II-receptor-mediated uptake is possible in fibroblasts.

RESULTS

M6P/IGF-IIR mRNA expression was investigated 3, 7 and 10 days after BDL. At all time-points hepatic M6P/IGF-IIR expression was significantly increased compared to healthy controls. Moreover, immunohistochemical staining revealed that alpha-sma-positive cells were M6P/IGF-IIR-positive. In kidneys of TGR(mRen2)27 rats, the number of M6P/IGF-IIR-positive arteries per microscopic field was increased 5.5 fold over healthy controls. To examine whether M6P/IGF-IIRs could be used as a port of entry for drugs, we coupled mycophenolic acid (MPA) to mannose-6-phosphate-modified human serum albumin (M6PHSA). M6PHSA-MPA inhibited 3T3-fibroblast proliferation dose-dependently, which was reversed by co-incubation with excess M6PHSA, but not by HSA.

CONCLUSIONS

M6P/IGF-IIRs are expressed by fibrogenic cells and may be used for receptor-mediated intracellular delivery of the antifibrogenic drug MPA.

Transforming growth factor-β1 regulation of laminin γ1 and fibronectin expression and survival of mouse mesangial cells

The transforming growth factor-beta (TGF-beta) 1 is a mediator of extracellular matrix (ECM) gene expression in mesangial cells and the development of diabetic glomerulopathy. Here, we investigate the effects of TGF-beta1 on laminin gamma1 and fibronectin polypeptide expression and cell survival in mouse mesangial cells (MES-13). TGF-beta1 (10 ng/ml) stimulates laminin-gamma1 and fibronectin expression approximately two-fold in a time-dependent manner (0-48 h). TGF-beta1 treatment also retards laminin-gamma1 mobility on SDS-gels, and tunicamycin, an inhibitor of the N-linked glycosylation, blocks the mobility shift. TGF-beta1 increases the binding of laminin gamma1 to WGA-agarose and the binding is abolished by tunicamycin suggesting that laminin gamma1 is modified by N-linked glycosylation. TGF-beta1 also elevates fibronectin glycosylation but its mobility is not altered. The degradation of laminin gamma1 and fibronectin proteins is reduced by their glycosylation. In addition, TGF-beta1 enhances mesangial cell viability and metabolic activities initially (0-24 h); however, eventually leads to cell death (24-48 h). TGF-beta1 elevates pro-apoptotic caspase-3 activity and decrease cell cycle progression factor cyclin D1 expression, which parallels cell death. These results indicate that TGF-beta1 plays an important role in ECM expression, protein glycosylation and demise of mesangial cells in the diabetic glomerular mesangium.

Insulin-like growth factor binding protein-3 mediates cytokine-induced mesangial cell apoptosis

Mesangial cells are critical for glomerular filtration. Mesangial cell dysfunction, the hallmark of diabetic nephropathy, results from disordered mesangial growth induced by cytokines, abnormal hemodynamic influence, and metabolic factors associated with chronic hyperglycemia. Insulin-like growth factors (IGFs) and their high affinity binding proteins (IGFBPs) exert major actions on mesangial cell survival, but their underlying mechanisms remain unclear. In light of emerging IGF-independent roles for IGFBP-3, we investigated IGFBP-3 actions during mesangial cell apoptosis induced by cytokine or high glucose concentration. Quantified by DNA fragmentation ELISA and Annexin V flow cytometry, apoptosis occurred in rat mesangial cells (RMC) exposed to 2 microg/mL IGFBP-3 for 24 h under high ambient or standard glucose. Anti-sense IGFBP-3 oligo at 10 microg/mL significantly inhibited apoptosis induced by 100 ng/mL TNF-alpha, serum-free conditions, or high (25 mM) glucose. Increased IGFBP-3 release associated with high ambient glucose or TNF-alpha was inhibited by pre-treatment with anti-sense oligo. Under serum-free conditions, recombinant human IGFBP-3 blocked Akt phosphorylation at threonine 308 (pThr308), whereas anti-sense oligo treatment was associated with enhanced pThr308 activity. In summary, these data support a novel mechanism for TNF-alpha-induced mesangial cell apoptosis mediated by IGFBP-3 and present regulation of pThr308 activity as a novel mechanism underlying IGFBP-3 action.

Efficacy of dextrose prolotherapy in elite male kicking-sport athletes with chronic groin pain

OBJECTIVE

To determine the efficacy of simple dextrose prolotherapy in elite kicking-sport athletes with chronic groin pain from osteitis pubis and/or adductor tendinopathy.

DESIGN

Consecutive case series.

SETTING

Orthopedic and trauma institute in Argentina.

PARTICIPANTS

Twenty-two rugby and 2 soccer players with chronic groin pain that prevented full sports participation and who were nonresponsive both to therapy and to a graded reintroduction into sports activity.

INTERVENTION

Monthly injection of 12.5% dextrose and 0.5% lidocaine into the thigh adductor origins, suprapubic abdominal insertions, and symphysis pubis, depending on palpation tenderness. Injections were given until complete resolution of pain or lack of improvement for 2 consecutive treatments.

MAIN OUTCOME MEASURES

Visual analog scale (VAS) for pain with sports and the Nirschl Pain Phase Scale (NPPS), a measure of functional impairment from pain.

RESULTS

The final data collection point was 6 to 32 months after treatment (mean, 17 mo). A mean of 2.8 treatments were given. The mean reduction in pain during sports, as measured by the VAS, improved from 6.3+/-1.4 to 1.0+/-2.4 ( P <.001), and the mean reduction in NPPS score improved from 5.3+/-0.7 to 0.8+/-1.9 ( P <.001). Twenty of 24 patients had no pain and 22 of 24 were unrestricted with sports at final data collection.

CONCLUSIONS

Dextrose prolotherapy showed marked efficacy for chronic groin pain in this group of elite rugby and soccer athletes.

High glucose-induced membrane translocation of PKC betaI is associated with Arf6 in glomerular mesangial cells

Protein kinase C (PKC)-induced changes in glomerular mesangial cell (MC) phenotypic behavior has been implicated in diabetes. The activity of diacylglycerol-sensitive PKC isoforms in MCs is altered by ambient changes in glucose, but the regulation of PKC activity and subsequent intracellular signaling events are not yet clearly defined. Small GTP-binding proteins of the ADP-ribosylation factor (Arfs) family, may regulate protein kinase membrane recruitment and hence its activity in signaling events of non-polarized cells. Members of the ARF family may coordinate membrane dynamics and other cellular functions through their interaction with PKC. We studied the activation of Arf, PKC betaI and phospholipase D (PLD) in MCs cultured under normal or high glucose conditions. MCs cultured in high glucose medium exhibited predominantly cytosolic localization of PKC betaI, Arf3 and Arf6. However, phorbol ester (PMA) stimulation of cells cultured in high glucose significantly enhanced membrane association of PKC betaI and Arf6, but not Arf3. Using [3H]choline chloride to prelabel MCs and measuring [3H]choline-containing metabolite release as PLD activity, PMA stimulated a significant increase of PLD activity under high glucose condition. Our data suggest that Arf6 plays a specific role in activation of PKC betaI and PLD under high glucose condition, and may be a significant intracellular event in the change of the mesangial cell phenotype associated with diabetic nephropathy.

Connective tissue growth factor and igf-I are produced by human renal fibroblasts and cooperate in the induction of collagen production by high glucose

Tubulointerstitial fibrosis is an important component in the development of diabetic nephropathy. Various renal cell types, including fibroblasts, contribute to the excessive matrix deposition in the kidney. Although transforming growth factor-beta (TGF-beta) has been thought to play a major role during fibrosis, other growth factors are also involved. Here we examined the effects of connective tissue growth factor (CTGF) and IGF-I on collagen type I and III production by human renal fibroblasts and their involvement in glucose-induced matrix accumulation. We have demonstrated that both CTGF and IGF-I expressions were increased in renal fibroblasts under hyperglycemic conditions, also in the absence of TGF-beta signaling. Although CTGF alone had no effect on collagen secretion, combined stimulation with IGF-I enhanced collagen accumulation. Furthermore, IGF-I also had a synergistic effect with glucose on the induction of collagens. Moreover, we observed a partial inhibition in glucose-induced collagen secretion with neutralizing anti-CTGF antibodies, thereby demonstrating for the first time the involvement of endogenous CTGF in glucose-induced effects in human renal fibroblasts. Therefore, the cooperation between CTGF and IGF-I might be involved in glucose-induced matrix accumulation in tubulointerstitial fibrosis and might contribute to the pathogenesis of diabetic nephropathy.

Biochemical injection treatment for discogenic low back pain: a pilot study

BACKGROUND CONTEXT

Biochemical treatment options including attempts at intervertebral disc restoration are desirable for the physiologic treatment of degenerative disc disease.

PURPOSE

This was a pilot study to test the potential effectiveness of intradiscal injection therapy using agents known to induce proteoglycan synthesis in the treatment of intervertebral disc disease.

STUDY DESIGN

Prospective, within subject, experimental design was applied in the study.

PATIENT SAMPLE

Thirty patients, average age 46.5 years, with chronic intractable low back pain of 8.5 years average duration, took part in the study. All patients had lumbar discography with reproduction of pain.

OUTCOME MEASURES

Pretreatment Roland-Morris disability scores and visual analogue scores were compared with 1-year follow-up posttest values of these scores.

METHODS

Lumbar intervertebral discs were injected with a solution of glucosamine and chondroitin sulfate combined with hypertonic dextrose and dimethlysulfoxide (DMSO). Assessment of pain and disability was completed before treatment and an average of 12 months after the last treatment.

RESULTS

Posttreatment Roland-Morris scores for the entire group of 30 patients of 6.4+/-.994 were significantly (p<.001) lower than pretreatment scores of 12.0+/-.92 (mean+/-SE). The posttreatment visual analogue scores of 3.00+/-.44 were also significantly less than the pretreatment of 6.11+/-.33 (mean+/-SE). Although the results were statistically significant for the 30 patients as a whole, 17 of the 30 patients (57%) improved markedly with an average of 72% improvement in disability scores and 76% in visual analogue scores. The other 13 patients (43%) had little or no improvement. Patients who did poorly included those with failed spinal surgery, spinal stenosis and long-term disability. There were no complications or serious side effects, although postinjection pain was moderate to severe for 48 to 72 hours and required epidural steroids in five cases.

CONCLUSIONS

The results of this pilot study suggest that intradiscal injection therapy with glucosamine, chondroitin sulfate, hypertonic dextrose and DMSO warrants further evaluation with randomized controlled trials.

Interactions of human mesangial cells with IgA and IgA-containing immune complexes

BACKGROUND

IgA nephropathy (IgAN) is characterized by IgA1-containing immune complexes in mesangial deposits and in the circulation. The circulating immune complexes (CIC) are composed of galactose- (Gal) deficient IgA1 and IgG or IgA1 antibodies specific for the Gal-deficient IgA1; interactions of these CIC with mesangial cells (MC) were studied.

METHODS

Binding, internalization, and catabolic degradation of myeloma IgA1 protein as a standard control and the isolated CIC were studied using human MC, hepatoma cell line HepG2 expressing the asialoglycoprotein receptor (ASGP-R), and monocyte-like cell line U937 expressing the Fc(alpha)-R (CD89). Biochemical and molecular approaches were used to assess expression of CD89 and ASGP-R by MC.

RESULTS

At 4 degrees C, radiolabeled IgA1 bound to MC and HepG2 cells in a dose-dependent and saturable manner. The binding was inhibited by IgA-containing CIC or excess IgA1 or its Fc fragment but not by the Fab fragment of IgA1. At 37 degrees C, the cell-bound IgA1 was internalized and catabolized. In addition to IgA1, HepG2 cells also bound (in a Ca2+-dependent manner), internalized, and catabolized asialoorosomucoid (ASOR), other asialo-(AS)-glycoproteins, and secretory component (SC). The binding by MC appeared to be restricted to IgA1 or AS-IgA1 and was not Ca2+-dependent. Furthermore, MC and HepG2 cells internalized and catabolized IgA1-containing CIC. Using RT-PCR with ASGP-R- or CD89-specific primers, mRNAs of the two respective genes were not detected in MC.

CONCLUSIONS

The data showed that the ability of MC to bind IgA1 and IgA1-containing CIC in vitro was mediated by an IgA receptor that was different from CD89 or ASGP-R and had a higher affinity for IgA-CIC than for uncomplexed IgA.

Direct measurement of IGF-I and IGFBP-3 in bronchoalveolar lavage fluid from idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is characterized by the rearrangement of extracellular matrix and progressive increase in the amount of fibrotic tissue in the lung. IGF-I is a potent profibrogenic molecule and its bioavailability is dependent on at least 6 binding proteins called IGFBPs. Among these, IGFBP-3 is the most represented in serum and in different connective tissues. The purpose of this study was to identify and characterize IGFBP-3 in bronchoalveolar lavage (BAL) fluids. We studied 11 patients with IPF and 6 normal subjects by performing baseline pulmonary function test and BAL. IGF-I and IGFBP-3 were measured by RIA in BAL and serum. No significant differences were observed between serum IGF-I and IGFBP-3 from IPF patients and normal subjects. Instead, the direct measurement in BAL revealed a significant increase of IGF-I and IGFBP-3 in IPF patients compared to normal subjects. BAL IGF-I and IGFBP-3 concentrations were significantly related to inspiratory vital capacity (IVC) and carbon dioxide partial pressure (PaCO2): the higher the value of IVC and the lower the value of PaCO2, the higher the level of IGF-I and IGFBP-3. In conclusion, IGFBP3 and IGF-I could be important local mediators of IPF. Their direct measurement in BAL in IPF patients could be used as a clinical marker of the disease, since high levels of IGFBP-3 and IGF-I in BAL are associated to the initial phase of the disease.

Activation of PKC-beta(I) in glomerular mesangial cells is associated with specific NF-kappaB subunit translocation

Changes in expression and activity of protein kinase C (PKC) isoforms and early transcription factors may account for alterations in cell behavior seen in diabetes. We studied the expression of PKC-beta(I) in rat glomerular mesangial cells (MCs) cultured in normal or high glucose and compared it with the temporal and spatial expression of dimeric transcription factor (NF-kappaB) p50 and p65. The results show that in unstimulated cells PKC-beta(I) and NF-kappaB p50 are distributed in the cytosol and, on stimulation, their distribution is perinuclear and they are localized to the membrane. Serum-starved MCs cultured in high-glucose medium exhibit a predominantly cytosolic localization of PKC-beta(I) and both p50 and p65 NF-kappaB. However, phorbol 12-myristate 13-acetate (PMA) stimulation of cells grown in the presence of high glucose resulted in membrane translocation of PKC-beta(I) that was associated with nuclear translocation of NF-kappaB p65, but not NF-kappaB p50. Moreover, the translocation to the nucleus for NF-kappaB p65 was significantly higher in MCs exposed to high glucose compared with those exposed to normal glucose. These observations indicate that the NF-kappaB p65, but not NF-kappaB p50, expression and translocation pattern mirrors that of PKC-beta(I), which may be one important pathway by which signaling is enhanced in the high-glucose state.

Tetrahydrobiopterin reverses the inhibition of nitric oxide by high glucose in cultured murine mesangial cells

Alterations of intrarenal nitric oxide (NO) synthesis play an important role in the pathogenesis and progression of diabetic nephropathy. We tested the hypothesis that hyperglycemia modulates intrarenal NO synthesis, which might mediate the mesangial cell proliferation and matrix production. Murine mesangial cells were grown in media containing varying glucose concentrations, and cytokine-induced NO synthesis was assayed by chemiluminescence using an NO analyzer. High media glucose (25 mM) inhibited NO synthesis in a time-dependent fashion. This inhibition was posttranslational as revealed by analysis of inducible nitric oxide synthase (iNOS) gene and protein expression. L-Arginine supplementation partially reversed the inhibition whereas addition of tetrahydrobiopterin (BH4), a cofactor for NOS, restored the inducibility of NO synthesis. The in vitro [3H]citrulline assay for iNOS activity indicated that high glucose decreased BH4 availability whereas examination of the BH4 synthetic pathway suggested decreased BH4 stability rather than synthesis, a defect that was corrected by ascorbic acid. We conclude that hyperglycemia inhibits NO synthesis in mesangial cells by a posttranslational defect that might involve the stability and hence availability of BH4.

Altered nephrogenesis due to maternal diabetes is associated with increased expression of IGF-II/mannose-6-phosphate receptor in the fetal kidney

We have recently demonstrated that the exposure to hyperglycemia in utero impairs nephrogenesis in rat fetuses (Amri K et al., Diabetes 48:2240-2245, 1999). Diabetic pregnancy is commonly associated with alterations in the IGF system in fetal tissues. It has also been shown that both IGF-I and IGF-II are produced within developing metanephros and promote renal organogenesis. Therefore, we investigated the effect of maternal diabetes on IGFs and their receptors in developing fetal rat kidney. Diabetes was induced in pregnant rats by a single injection of streptozotocin on day 0 of gestation. We measured the amounts of IGF and their receptors, both proteins and mRNAs, in the metanephroi of fetuses issued from diabetic subjects and in age-matched fetuses from control subjects (14-20 days of gestation). IGF-II was produced throughout fetal nephrogenesis, whereas IGF-I protein was not detected, suggesting a critical role of IGF-II in kidney development. Fetal exposure to maternal diabetes caused no change in IGF production in the early stages of nephrogenesis. Similarly, the amounts of IGF-I receptor and insulin receptor were not altered. By contrast, there was an increase in production of IGF-II/mannose-6-phosphate receptor throughout nephrogenesis. Because this receptor plays an essential role in regulating the action of IGF-II, the altered nephrogenesis in fetuses exposed to maternal diabetes may be linked to a decrease in IGF-II bioavailability.

Regulation of B(2)-kinin receptors by glucose in vascular smooth muscle cells

The development of vascular disease is accelerated in hyperglycemic states. Vascular injury plays a pivotal role in the progression of atherosclerotic vascular disease in diabetes, which is characterized by increased vascular smooth muscle cell (VSMC) proliferation and extracellular matrix accumulation. We previously reported that diabetes alters the activity of the kallikrein-kinin system and results in the upregulation of kinin receptors in the vessel wall. To determine whether glucose can directly influence the regulation of kinin receptors, the independent effect of high glucose (25 mM) on B(2)-kinin receptors (B2KR) in VSMC was examined. A threefold increase in B2KR protein levels and a 40% increase in B2KR surface receptors were observed after treatment with high glucose after 24 h. The mRNA levels of B2KR were also significantly increased by high glucose as early as 4 h later. To elucidate the cellular mechanisms by which glucose regulates B2KR, we examined the role of protein kinase C (PKC). High glucose increased total PKC activity and resulted in the translocation of conventional PKC isoforms (beta(1) and beta(2)), novel (epsilon), and atypical (zeta) PKC isoforms into the membrane. Inhibition of PKC activity prevented the increase in B2KR levels induced by ambient high glucose. These findings provide the first evidence that glucose regulates the expression of B(2) receptors in VSMC and provide a rationale to further study the interaction between glucose and kinins on the pathogenesis of atherosclerotic vascular disease in diabetes.

Randomized, prospective, placebo-controlled double-blind study of dextrose prolotherapy for osteoarthritic thumb and finger (DIP, PIP, and trapeziometacarpal) joints: evidence of clinical efficacy

OBJECTIVES

To determine the clinical benefit of dextrose prolotherapy (injection of growth factors or growth factor stimulators) in osteoarthritic finger joints.

DESIGN

Prospective randomized double-blind placebo-controlled trial.

SETTINGS/LOCATION

Outpatient physical medicine clinic.

SUBJECTS

Six months of pain history was required in each joint studied as well as one of the following: grade 2 or 3 osteophyte, grade 2 or 3 joint narrowing, or grade 1 osteophyte plus grade 1 joint narrowing. Distal interphalangeal (DIP), proximal interphalangeal (PIP), and trapeziometacarpal (thumb CMC) joints were eligible. Thirteen patients (with seventy-four symptomatic osteoarthitic joints) received active treatment, and fourteen patients (with seventy-six symptomatic osteoarthritic joints) served as controls.

INTERVENTION

One half milliliter (0.5 mL) of either 10% dextrose and 0.075% xylocaine in bacteriostatic water (active solution) or 0.075% xylocaine in bacteriostatic water (control solution) was injected on medial and lateral aspects of each affected joint. This was done at 0, 2, and 4 months with assessment at 6 months after first injection.

OUTCOME MEASURES

One-hundred millimeter (100 mm) Visual Analogue Scale (VAS) for pain at rest, pain with joint movement and pain with grip, and goniometrically-measured joint flexion.

RESULTS

Pain at rest and with grip improved more in the dextrose group but not significantly. Improvement in pain with movement of fingers improved significantly more in the dextrose group (42% versus 15% with a p value of .027). Flexion range of motion improved more in the dextrose group (p = .003). Side effects were minimal.

CONCLUSION

Dextrose prolotherapy was clinically effective and safe in the treatment of pain with joint movement and range limitation in osteoarthritic finger joints.

High glucose induces the activity and expression of Na(+)/H(+) exchange in glomerular mesangial cells

Changes in activity or expression of transporters may account for alterations in cell behavior in diabetes. We sought to ascertain if mesangial cells (MC) grown in different glucose concentrations exhibit changes in activity and expression of acid-extruding transporters, the Na(+)/H(+) and Na(+)-dependent Cl(-)/HCO(-)(3) exchanger. pH(i) was determined by the use of the fluorescent pH-sensitive dye BCECF. In MCs grown in 5 mM glucose (control), the Na(+)/H(+) exchanger was responsible for 31.8 +/- 5.1% of steady-state pH(i), whereas Na(+)-dependent Cl(-)/HCO(-)(3) contributed 62.9 +/- 4.0% (n = 11). In MCs grown in high glucose for 2 wk, Na(+)/H(+) exchange contribution to acid-extrusion increased as follows: 42.3 +/- 4.6% [n = 8, 10 mM, not significant (NS)], 51.1 +/- 5.1% (n = 8, 20 mM, P < 0.01), and 64.8 +/- 5.5% (n = 7, 30 mM, P < 0.001). The Na(+)-dependent Cl(-)/HCO(-)(3) exchanger contributed less [47.0 +/- 4.6, 38.6 +/- 5.8, and 21.1 +/- 3.8%, for 10, 20, and 30 mM glucose, respectively (n > 7)]. We sought to ascertain if the magnitude of the acute stimulated response to ANG II by the Na(+)/H(+) and Na(+)-dependent Cl(-)/HCO(-)(3) exchanger is changed. Na(+)/H(+) exchanger (1.89-fold increase in 30 vs. 5 mM, P < 0.002), but not Na(+)-dependent Cl(-)/HCO(-)(3) exchange (0. 17-fold, NS), exhibited an enhanced response to ANG II (1 microM). Na(+)/H(+) exchange (NHE1) expression was significantly different (1. 72-fold) after prolonged exposure to high glucose. These results suggest that the Na(+)/H(+) exchanger, but not Na(+)-dependent Cl(-)/HCO(-)(3) exchanger, may play an early role in the response to hyperglycemia in the diabetic state.

Human glomerular endothelial cells IGFBPs are regulated by IGF-I and TGF-beta1

The release of insulin-like growth factor binding proteins (IGFBPs) and their regulation in human glomerular endothelial cells (GENC) was characterised. GENC produce IGFBP-4, IGFBP-2 and IGFBP-3 and express mRNA for IGFBP-2 to IGFBP-5. Due to the fact that IGF-I and TGF-beta1 modulate glomerular hypertrophy, their action on IGFBP release and GENC growth was studied. IGF-I increased IGFBP-3, IGFBP-2 and decreased IGFBP-4, while TGF-beta1 decreased IGFBP-3 and apparently increased IGFBP-4. All of the IGFBPs, except the TGF-beta1-regulated IGFBP-4, were modulated at mRNA level. IGF-I stimulated GENC proliferation, while TGF-beta1 inhibited their growth. It was demonstrated that an IGFBP-3 antibody reduced GENC proliferation. However, rhIGFBP-3 alone had no effect on GENC, but after 48 h pre-incubation the IGF-I stimulated GENC growth was increased, suggesting that IGFBP-3 could modulate the IGF-I induced GENC proliferation. It was concluded that the stimulatory IGFBP-3 and the inhibitory IGFBP-4 could regulate GENC growth, although the IGFBP-3 seems to have a predominant effect in this control.

The circulating insulin-like growth factor system in children with coeliac disease: an additional marker for disease activity

BACKGROUND

Chronic undernutrition resulting from coeliac disease (CD) could be associated with changes in the circulating insulin-like growth factor (IGF) system, which may participate in the pathogenesis of growth retardation occurring in these patients.

METHODS

We performed a cross-sectional study in CD subjects attempting to (1) document the pattern of serum IGF-I and IGF binding protein (IGFBP) 1 and 3 at diagnosis and (2) assess the response of circulating IGF system to dietary treatments, in comparison with the response of clinical and laboratory findings utilized for the diagnosis of CD. Thirty-two prepubertal CD children were divided into three groups based on the dietetic treatment: at diagnosis (D, n=18); on gluten-free diet for at least 6 months (GFD, n=7); and on gluten challenge for at least 3 months (CH, n=7). Six postpubertal CD patients were also studied at diagnosis.

RESULTS

In prepubertal children IGF-I levels were significantly reduced (by 29%) in D vs sex- and age-matched normal control (NC) subjects, with reductions being more pronounced before 3 years of age. Likewise, serum IGFBP-3 concentrations were decreased by 22%, whereas circulating IGFBP-1 levels were increased by 60%, compared with NC, with more marked IGFBP changes in older children. Similar alterations were observed in postpubertal patients. Changes in the circulating IGF system disappeared in GFD subjects and reappeared in CH children, as positivity of disease-specific antibodies. Body mass index (BMI) also improved in GFD subjects, but did not decrease in CH children. Changes in IGF-I and IGFBPs did not correlate with each other. Levels of IGF-I, but not of IGFBPs, maintained the relation with age and correlated significantly with BMI and positivity of antibodies.

CONCLUSIONS

These results demonstrate that CD patients show significant changes in serum IGF-I, in younger children, and IGFBPs (particularly IGFBP-1), in older children and adolescents, correlating with clinical course and response to dietary treatments. The alteration in the circulating IGF system could be implicated in the pathogenesis of growth retardation occurring in CD and may provide an additional tool in monitoring of the disease.

Potentiating effects of hyper-osmolality and epidermal growth factor on the release of arachidonic acid in human glomerular mesangial cells

Studies were performed to determine the interactive effects of high concentrations of glucose (HG) and epidermal growth factor (EGF) on the release of arachidonic acid (3H-AA) in human glomerular mesangial cells (MC) in culture. Since high glucose has been reported to increase the mass of diacylglycerol (DAG) in MC, the HG-induced release of 3H-AA was compared to that initiated by the phorbol ester, PMA. It was found that when media contained high levels (25 mM) of glucose, the release of 3H-AA was increased significantly by 8.4% (change from control) after 1 h of exposure and was maintained at values not significantly different from this level for the next 2 h. After 3-h exposure, there was no significant difference between 25 and 50 mM glucose, suggesting that the effects of glucose are saturating at 25 mM. After 1-h exposure, 3H-AA release was also increased by PMA; however, the increase was larger and the peak increase was delayed until after 1 h. 3H-AA release was significantly increased by epidermal growth factor (EGF) by 8.5% after 1 h and was maintained at this level after 2 and 3 h of exposure. In the presence of HG, EGF increased 3H-AA release by 24.6% after the 1st hour and by 20.4 and 19.4%, after the 2nd and 3rd hours, respectively. Mannitol (20 mM), added as an osmotic control, increased 3H-AA release by 6.2% and also significantly enhanced the effects of EGF after 3 h. The experimental values (19.0%) for the release of 3H-AA after 3-h exposure to EGF in combination with either high glucose or mannitol were significantly greater than the expected (added) values (12.1%). These results demonstrate that as a result of an elevated solution osmolality, high glucose acts synergistically with EGF to increase the release of 3H-AA in human mesangial cells.

Elevated glucose increases mesangial cell sensitivity to insulin-like growth factor I

To determine the effects of glucose on insulin-like growth factor I (IGF-I)-induced mesangial cell (MC) proliferation, we have examined the relationships between IGF binding protein 2 (IGFBP-2) secretion and proliferation in murine MCs (MMCs). MMCs incubated in high glucose (HG, 25 mM) exhibited a 25-30% reduction in IGFBP-2 secretion compared with cells in normal glucose (NG, 5.6 mM). This loss was not due to cell surface binding; it correlated with a 3.1-fold decrease in IGFBP-2 mRNA. IGFBP-2 secretion was stimulated by IGF-I in NG but was unaltered in HG. Insulin treatment yielded similar results at 10-fold higher doses, indicating that this response is IGF-I receptor dependent. MMCs in HG displayed increased IGF-I-stimulated insulin receptor substrate-1/2 phosphorylation and activator protein-1 transcriptional activity compared with NG controls. Accordingly, although IGF-I was not proliferative in NG, it increased [3H]thymidine incorporation and cell number in HG to an extent proportional to the decrease in IGFBP-2. Thus hyperglycemia, as seen in diabetes, may increase MC IGF-I sensitivity by reducing IGFBP-2 expression, in turn increasing its proliferative and secretory responses and contributing to the development of diabetic glomerulosclerosis.

Growth factors and the kidney in diabetes mellitus

Nephromegaly and mesangial matrix expansion observed in the diabetic kidney are all clues of a role of growth factors in the pathogenesis of these lesions. A growing body of evidence shows that changes in (1) insulin-like growth factor I regulation, and (2) the transforming growth factor beta loop exist in the kidney in the diabetic hypertrophic kidney and in diabetic glomerulosclerosis. However, other growth factors may be involved in some diabetic renal changes. The abnormalities in growth factor content and regulation, the role of growth factors in the diabetic kidney, and the effect of hyperglycemia and advanced glycosylation end products on growth factors in the kidney are reviewed.

Regulatory role of eicosanoids in extracellular matrix overproduction induced by long-term exposure to high glucose in cultured rat mesangial cells

Accumulation of extracellular matrix in the mesangium and altered renal eicosanoid synthesis are two prominent features of diabetic glomerular disease. We investigated the relationship between eicosanoid and extracellular matrix production in rat mesangial cells cultured under high glucose vs normal glucose conditions. Long-term exposure of rat mesangial cells to high glucose, but not to iso-osmolar mannitol, significantly increased extracellular matrix accumulation and gene expression and transforming growth factor-beta (TGF-beta) mRNA levels, and decreased prostaglandin (PG) E2 synthesis without affecting production of either thromboxane (TX) B2 or PGF2 alpha, with respect to cells incubated in normal glucose. Addition of exogenous PGE2 resulted in a dose-dependent reduction of matrix protein and mRNA levels and TGF-beta gene expression in cells cultured in either normal or high glucose conditions, whereas exposure to exogenous PGF2 alpha produced a significant increment in matrix production and matrix and TGF-beta gene expression in cells grown in normal glucose, but only a slight increase in those cultured in high glucose. Stimulation of endogenous endoperoxide metabolism towards PGE2 and PGF2 alpha synthesis with FCE-22,178, a drug originally developed as TXA2 synthase inhibitor, resulted in a dose-dependent decrease in matrix accumulation and matrix and TGF-beta gene expression which was suppressed by coincubation with the cyclo-oxygenase inhibitor fenoprofen blocking the FCE-22,178-enhanced PG production. In both cell lines, the rate of synthesis of TXA2 was very low and the selective blockade of its synthesis (by two other TXA2 synthase inhibitors, OKY-046 and Ridogrel) or action (by the TXA2 receptor antagonist BM-13,177) did not alter matrix production or TGF-beta mRNA levels. These results suggest that the cyclo-oxygenase pathway is involved in the regulation of matrix changes induced by high glucose in rat mesangial cells; the reduced production of PGE2 may enhance the synthesis or potentiate the effect of stimulators of ECM formation such as TGF-beta, whereas TXA2 does not appear to be involved. These data also indicate that glucose-enhanced mesangial matrix accumulation may be prevented by exogenous PGE2 or by drugs capable of increasing endogenous PGE2 synthesis.