Expression of the constitutive and inducible forms of heat shock protein 70 in human proximal tubule cells exposed to heat, sodium arsenite, and CdCl(2).

Abstract

We determined the expression of the constitutive (hsc 70) and inducible (hsp 70) forms of heat shock protein 70 mRNA and protein in human proximal tubule (HPT) cells exposed to lethal and sublethal concentrations of Cd(+2) under both acute and extended conditions of exposure. The HPT cells exhibited the classic heat shock response when subjected to a physical (heat) or chemical stress (sodium arsenite); hsc 70 mRNA and protein levels were constant or slightly increased, whereas hsp 70 mRNA and protein were greatly elevated. Acute exposure to 53.4 microM CdCl(2) for 4 hr failed to increase either hsc 70 mRNA or protein, a finding similar to that observed under classic conditions of stress. However, under identical conditions of acute exposure to Cd(2+), the expected increase in hsp 70 protein level was suppressed as compared to that found under classic conditions of physical or chemical stress. The decrease in hsp 70 protein level correlated to the reduced expression of mRNA from the hsp 70B gene. The expression of mRNA from the hsp 70A and hsp 70C genes was similar to that found when the cells were treated with heat shock or sodium arsenite. We modeled an extended exposure to Cd(2+) by treating the cells continuously with Cd(2+) at both lethal and sublethal levels over a 16-day time course. Chronic exposure to Cd(2+) failed to increase either hsc 70 mRNA or protein levels in the HPT cells at a nonlethal dosage level and decreased hsc 70 mRNA and protein levels late in the time course of lethal exposure. Under identical conditions, the expression of hsp 70 protein remained at basal levels that were only marginally detectable throughout the time course. Hsp 70A and hsp 70C mRNA levels were unaltered by extended exposure to Cd(2+), and hsp 70B mRNA was not detected during the 16-day time course. Cd(2+) is a poor inducer of hsc 70 and hsp 70 in the proximal tubule under both acute and long-term exposure. These results reinforce the fact that the expression of hsp 70 protein does not result from the transcription of a single gene, but is derived from what may be a complex interplay of several underlying genes.ImagesFigure 1Figure 2Figure 3Figure 4Figure 5Figure 6

Expression of hsp 27, hsp 60, hsc 70, and hsp 70 stress response genes in cultured human urothelial cells (UROtsa) exposed to lethal and sublethal concentrations of sodium arsenite.

“…This response was similar to that previously noted by this laboratory when HPT cells were exposed to NaAsO 2 under similar conditions (Somji et al 1999d). The hsp 70 protein is encoded by several genes, three of which (hsp 70A, hsp 70B, and hsp 70C) have been sequenced and identified, and these can be determined using RT-PCR technology (Kim et al 2001;Somji et al 1999d).…”

“…The hsp 70 protein is encoded by several genes, three of which (hsp 70A, hsp 70B, and hsp 70C) have been sequenced and identified, and these can be determined using RT-PCR technology (Somji et al 1999d;Kim et al 2001). Expression of mRNA for all three of these genes was markedly elevated after exposure to 100 µM NaAsO 2 ( Figure 5B).…”

Expression of hsp 27, hsp 60, hsc 70, and hsp 70 stress response genes in cultured human urothelial cells (UROtsa) exposed to lethal and sublethal concentrations of sodium arsenite.

“…This response was similar to that previously noted by this laboratory when HPT cells were exposed to NaAsO 2 under similar conditions (Somji et al 1999d). The hsp 70 protein is encoded by several genes, three of which (hsp 70A, hsp 70B, and hsp 70C) have been sequenced and identified, and these can be determined using RT-PCR technology (Kim et al 2001;Somji et al 1999d).…”

“…The hsp 70 protein is encoded by several genes, three of which (hsp 70A, hsp 70B, and hsp 70C) have been sequenced and identified, and these can be determined using RT-PCR technology (Somji et al 1999d;Kim et al 2001). Expression of mRNA for all three of these genes was markedly elevated after exposure to 100 µM NaAsO 2 ( Figure 5B).…”

A comparison of 60, 70, and 90 kDa stress protein expression in normal rat NRK‐52 and human HK‐2 kidney cell lines following in vitro exposure to arsenite and cadmium alone or in combination

“…Somji and colleagues [21] have observed a down-regulation of 60 kDa from control levels in human proximal tubule cells during the course of chronic Cd 2+ exposures [21]. From these studies they suggest that failure to maintain basal levels and/or to induce the stress protein response is specific to the stress protein [19][20][21]. This may also be a similar case for the HK-2 renal cell line where we observed either no change in 60 and 90 kDa protein levels or a decrease in levels for higher doses of single and combined elements.…”

Stress response of heavy metal mixture present in wastewater and leachate on heat-shock protein 47-transfected cells

“…Previously, Somji et al [39] reported that Cd 2þ is a poor stress response inducer of HSP 70 in human proximal tubule cells under both acute and long-term exposure. On the other hand, more recent results by Lui et al [40] have shown the endoplasmic reticulum (ER) stress response in renal epithelial cells following exposure to 10 mM Cd.…”

Expression of hsp 27, hsp 60, hsc 70, and hsp 70 stress response genes in cultured human urothelial cells (UROtsa) exposed to lethal and sublethal concentrations of sodium arsenite.

“…This response was similar to that previously noted by this laboratory when HPT cells were exposed to NaAsO 2 under similar conditions (Somji et al 1999d). The hsp 70 protein is encoded by several genes, three of which (hsp 70A, hsp 70B, and hsp 70C) have been sequenced and identified, and these can be determined using RT-PCR technology (Kim et al 2001;Somji et al 1999d).…”

“…The hsp 70 protein is encoded by several genes, three of which (hsp 70A, hsp 70B, and hsp 70C) have been sequenced and identified, and these can be determined using RT-PCR technology (Somji et al 1999d;Kim et al 2001). Expression of mRNA for all three of these genes was markedly elevated after exposure to 100 µM NaAsO 2 ( Figure 5B).…”

A comparison of 60, 70, and 90 kDa stress protein expression in normal rat NRK‐52 and human HK‐2 kidney cell lines following in vitro exposure to arsenite and cadmium alone or in combination

“…Somji and colleagues [21] have observed a down-regulation of 60 kDa from control levels in human proximal tubule cells during the course of chronic Cd 2+ exposures [21]. From these studies they suggest that failure to maintain basal levels and/or to induce the stress protein response is specific to the stress protein [19][20][21]. This may also be a similar case for the HK-2 renal cell line where we observed either no change in 60 and 90 kDa protein levels or a decrease in levels for higher doses of single and combined elements.…”

Stress response of heavy metal mixture present in wastewater and leachate on heat-shock protein 47-transfected cells

“…Previously, Somji et al [39] reported that Cd 2þ is a poor stress response inducer of HSP 70 in human proximal tubule cells under both acute and long-term exposure. On the other hand, more recent results by Lui et al [40] have shown the endoplasmic reticulum (ER) stress response in renal epithelial cells following exposure to 10 mM Cd.…”

Expression of hsp 27, hsp 60, hsc 70, and hsp 70 stress response genes in cultured human urothelial cells (UROtsa) exposed to lethal and sublethal concentrations of sodium arsenite.

“…This response was similar to that previously noted by this laboratory when HPT cells were exposed to NaAsO 2 under similar conditions (Somji et al 1999d). The hsp 70 protein is encoded by several genes, three of which (hsp 70A, hsp 70B, and hsp 70C) have been sequenced and identified, and these can be determined using RT-PCR technology (Kim et al 2001;Somji et al 1999d).…”

“…The hsp 70 protein is encoded by several genes, three of which (hsp 70A, hsp 70B, and hsp 70C) have been sequenced and identified, and these can be determined using RT-PCR technology (Somji et al 1999d;Kim et al 2001). Expression of mRNA for all three of these genes was markedly elevated after exposure to 100 µM NaAsO 2 ( Figure 5B).…”

A comparison of 60, 70, and 90 kDa stress protein expression in normal rat NRK‐52 and human HK‐2 kidney cell lines following in vitro exposure to arsenite and cadmium alone or in combination

“…Somji and colleagues [21] have observed a down-regulation of 60 kDa from control levels in human proximal tubule cells during the course of chronic Cd 2+ exposures [21]. From these studies they suggest that failure to maintain basal levels and/or to induce the stress protein response is specific to the stress protein [19][20][21]. This may also be a similar case for the HK-2 renal cell line where we observed either no change in 60 and 90 kDa protein levels or a decrease in levels for higher doses of single and combined elements.…”

Stress response of heavy metal mixture present in wastewater and leachate on heat-shock protein 47-transfected cells

“…Previously, Somji et al [39] reported that Cd 2þ is a poor stress response inducer of HSP 70 in human proximal tubule cells under both acute and long-term exposure. On the other hand, more recent results by Lui et al [40] have shown the endoplasmic reticulum (ER) stress response in renal epithelial cells following exposure to 10 mM Cd.…”